The effects of soil temperature and moisture and certain biological factors on the pathogenicity of
Rhizoctonia Solani Kuhn to sugar beet seedlings
by Harry S Fenwick
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Botany
Montana State University
© Copyright by Harry S Fenwick (1952)
Abstract:
The effect of temperature and moisture and of certain biological factors on the pathogenicity of several
isolates of Rhizoctonia solani to sugar beet seedlings tbs studied.
Pathogenicity of six isolates of Rhizoctonia solani obtained from seedling and matured sugar beets was
established on sugar beet seedlings in the greenhouse. Four of the six isolates were selected for further
study on the basis of their virulence and total per cent disease produced on the beets. Two of the
isolates were obtained from beet seedlings, the other two were obtained from matured beets.
The minimum temperature for growth of these isolates in culture was, found to be near 10° C. The
optimum growth for these cultures was at 29° C, and the maximum was near 40° C.
Rhizoctonia disease was produced at both temperatures used (15° and 25° C) and at all moisture levels
(55, 70, and 85 per cent of the total moisture holding capacity). More disease occurred at 25° C than at
15° C. Moisture level of the soil appeared to have less effect on the incidence of the disease than did
temperature. The total per cent disease was greater with isolates obtained from seedling beets, also the
average weight per plant and the average length of tops were smaller with these isolates than with
isolates from matured beets.
A test of the effect of inoculum of varying ages on beet seedlings In different stages of growth revealed
that beets are subject to attack by Rhizoctonia at any stage of growth and that the age of the beet is
more important than the age of the inoculum in total incidence of disease.
Antagonistic action was exhibited by Trichoderma lignorum toward Rhizoctonia in soil and culture
tests.
Penicillium notatum did not appear to have any effect on Rhizoctonia in soil or culture tests.
Streptomyces griseus appeared to increase the pathogenicity of Rhizoctonia in soil tests, but no
conclusive results could be obtained in culture tests. THE EFFECTS OF SOIL TEMPERATURE MD MOISTURE AND CERTAIN
BIOLOGICAL FACTORS ON THE PATHOGENICITY OF
RHIZOCTONIA SOLANI KUHN TO SUGAR BEET SEEDLINGS
*
HARRY S. FENWICK
A THESIS
S u b m itted t o th e G rad u ate F a c u lty
r
in
■ p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e d eg ree o f
M aster o f S c ie n ce i n B otany
at
Montana S ta te C o lle g e ■
Approved:
Head, M ajor D epartm ent
Chairm an,
Examining Committee
Bozeman, Montana
A u g u st, 1952; Vtitit,
«7/il'.7:-r C-JU
Z-I-J/;. •/ ,
N i? !
N 2L ,2z.
—2 —
(U--US1 5 -
ACKNOWLEDGI'fflNT
G r a te f u l acknowledgment i s mad.e t o D r. M. M. A fa n a sie v , who
d i r e c t e d t h i s s tu d y and was most h e lp f u l i n a l l o f i t s p h a s e s . The
a s s is ta n c e o f P r o fe s s o r H. E. M orris and o th e r s t a f f members o f th e
D epartm ent o f B otany and B a c te rio lo g y i s a ls o g r e a t l y a p p r e c ia te d .
105517
-3 -
TABLE OF COETENTS
ACKKTOWIiEDG-MEET
2
ABSTRACT
4-
IETRODUCTIOE
5
REVIEW OF LITERATURE
•
7
MATERIALS ABD METHODS
13
EXPERIMENTAL PROCEDURE AED RESULTS
l6
T e s ts o f P a th o g e n ic i t y o f th e I s o l a t e s
o f R h iz o c to n ia
17
E f f e c t o f T em perature on R a d ia l Growth in C u ltu re
21
E f f e c t o f T em perature and M o istu re on th e Amount o f
R h iz o c to n ia D isea se
24
E f f e c t o f Inoculum o f V arying Ages on Sugar B eet
S e e d lin g s a t D if f e r e n t S ta g e s o f Growth -
3%
The A n ta g o n is tic E f f e c t o f O ther F u n g i
P a th o g e n ic i t y o f R h iz o c to n ia i n S o i l
on th e
40
The A n ta g o n is tic E f f e c t o f O ther F u n g i
i n C u ltu re
on R h iz o c to n ia
4$
GENERAL DISCUSSION AND. CONCLUSIONS
4t
SUMMARY-
53
LITERATURE CITED
56
■ABSTRACT"
The e f f e c t o f te m p e ra tu re and m o is tu re and o f c e r t a i n b i o l o g i c a l
f a c t o r s on th e p a th o g e n ic ity o f s e v e r a l i s o l a t e s o f R h iz o c to n ia s o la n i
t o su g a r b e e t s e e d lin g s was s tu d ie d .
P a th o g e n ic ity o f s i x i s o l a t e s o f R h iz o c to n ia s o la n i o b ta in e d from
s e e d lin g and m atured s u g a r b e e ts was e s ta b lis h e d - o n s u g a r b e e t s e e d lin g s
i n th e g re e n h o u se . F our o f th e ,six i s o l a t e s were s e le c te d f o r f u r t h e r
s tu d y on th e b a s is o f t h e i r v iru le n c e and t o t a l p e r c e n t d is e a s e
produced on th e b e e t s . Two o f th e i s o l a t e s were o b ta in e d from b e e t
s e e d lin g s , th e o th e r two w ere o b ta in e d from m atured b e e t s .
The minimum te m p e ra tu re f o r grow th o f th e s e i s o l a t e s i n c u ltu r e was,
found t o be n e a r IO0 -C. The optimum grow th f o r th e s e c u ltu r e s was a t
29° C, and th e maximum was n e a r 40° C.
R h iz o c to n ia d is e a s e was produced a t b o th te m p e ra tu re s u sed (1 5 ° and
25° C) and a t a l l m o istu re le v e l s (55? "70, and 85 p e r c e n t o f th e t o t a l
■m o is tu r e . h o ld in g c a p a c i t y ) . More d is e a s e o c c u rre d a t 25° C t h a n - a t 1 5® C.
M o istu re l e v e l o f th e s o i l ap p eared to .h a v e le s s e f f e c t on th e in c id e n c e
o f th e d is e a s e th a n d id te m p e ra tu re . The t o t a l p e r c e n t d is e a s e was
g r e a t e r w ith i s o l a t e s o b ta in e d from s e e d lin g b e e t s , a ls o th e average
w eig h t p e r p l a n t and th e av erag e le n g th o f to p s were s m a lle r w ith th e s e
i s o l a t e s th a n w ith i s o l a t e s from m atured b e e ts-.
A t e s t o f 'th e e f f e c t o f inoculum o f v a ry in g ages on b e e t s e e d lin g s in
d i f f e r e n t s ta g e s o f grow th re v e a le d t h a t b e e ts a re s u b je c t t o a t t a c k b y ..
R h iz o c to n ia a t any s ta g e o f grow th and t h a t th e age o f th e b e e t i s more
im p o rta n t th a n th e age o f th e inoculum i n t o t a l in c id e n c e o f d is e a s e .
A n ta g o n is tic a c t i o n was e x h ib ite d b y Trichoderm a lig n o ru m tow ard
R h iz o c to n ia i n s o i l and c u ltu r e t e s t s .
P e n ic illiu m notatum d id n o t a p p e a r t o have any e f f e c t on R h iz o c to n ia ■
i n s o i l o r c u ltu r e t e s t s .
S treptom yces g r is e u s ap p eared t o in c r e a s e th e p a th o g e n ic ity o f
R h iz o c to n ia i n s o i l t e s t s , b u t no c o n c lu s iv e r e s u l t s c o u ld b e o b ta in e d
i n c u ltu r e t e s t s . .
,
.
..
-
-5 -
THE EFFECTS OF SOIL TEMPERATURE' MD' MOISTURE' AHD CERTAIN
BIOLOGICAL FACTORS OH THE PATHOGEHICITY OF
REIZOCTOHIA SOLAHI EUHH TO SUGAR BEET SEEDLINGS
INTRODUCTION
One o f th e m ost s e r io u s and tro u b leso m e d is e a s e s o f su g a r b e e ts
• (B e ta v u lg a r is L .) i s t h e s o - c a l l e d r o o t r o t due t o th e fungus R h iz o c to n ia
s o la n i Kuhn (P e l l i c u l a r i a fila m e n to s a ( P a t . ) R o g e rs ).
T h is fu n g u s is
r e s p o n s ib le f o r damping o f f o f see d in g s a s ,w e ll a s d ecay and d e a th o f
o ld e r su g a r b e e t s .
I n th e heavy s o i l s t y p i c a l o f many o f th e s u g a r b e e t
grow ing a r e a s o f M ontana, th e o c cu rren c e o f R h iz o c to n ia d is e a s e v a r ie s
from a t r a c e t o s e v e r e , r e s u l t i n g i n re d u c e d s ta n d s and many b e e ts o f
p o o r m arket v a lu e .
Coons and S te w a rt ( 5 ) showed t h a t th e c o l o r . o f t h e young su g ar
b e e t le a v e s g iv e s th e f i r s t in d ic a tio n o f R h iz o c to n ia d is e a s e o n ,s e e d ­
lin g s .
The le a v e s may b e m e re ly d e ep e r g re e n i n c o lo r , b u t o c c a s io n a lly
th e y a r e b lu e g r e e n .
A s s o c ia te d w ith t h i s s ig n , one o f te n f in d s a ,le m o n -
y e llo w c o lo r o f th e stem .
L a te r , t h e p o in t o f a t t a c k a p p e a rs t o be a t
th e ground l e v e l o r j u s t below th e s o i l s u r f a c e ,
O th er p o in ts o f a t t a c k
a re a t th e b a se o f th e l e a f p e t i o l e s o r on th e main t a p r o o t .
On th e stem
i t p ro d u ces d ry l o c a l le s i o n s t h a t e x te n d upward and downward a lo n g i t
and o f te n .c o m p le te ly g i r d l e
th e stem , k i l l i n g th e b e e t .
O ften in f e c te d
s e e d lin g s a p p e a r s tu n te d a n d , in g e n e r a l, show ev id en ce o f m a ln u tr it io n .
On rem o v al o f su ch a s e e d lin g from th e s o i l , t h e ta p r o o t i s fo u n d decayed
a t th e low er en d , b u t -t h e r o o t l e t s have d ev elo p ed above th e decayed r e g io n
g iv in g th e a p p e a ra n c e t h a t th e p rim a ry r o o t i s b e in g r e p la c e d b y them .
-6 -
Som stlm ss t h e p l a n t s may a p p e a r norm al and h e a lth y up t o th e . tim e o f t h i n ­
n in g , h u t when th e s e b e e ts a r e dug and exam ined, s m a ll b la c k le s io n s may
b e p r e s e n t n e a r th e end o f th e main t a p r o o t .
These le s io n s may g iv e r i s e
t o th e symptoms found on b e e ts , h a l f grown o r o ld e r .
The f i r s t v i s i b l e e v id en c e o f th e d is e a s e on o ld e r ;b e e t s i s a
s l i g h t w i l t i n g o f t h e p l a n t , w hich a p p e a rs t o re c o v e r te m p o r a r ily in t h e
c o o l p a r t o f th e d a y .
T h is s ig n i s c l o s e l y fo llo w e d b y a d a rk e n in g o f th e
b a s e s o f th e p e t i o l e s aru| b y th e r o t t i n g o f th e crown.
The le a v e s may
r e t a i n t h e i r c o lo r f o r seme tim e , o r u n t i l th e l e a f p e t i o l e s r o t o f f
c o m p le te ly .
W ith th e r o t t i n g o f th e crown, th e le a v e s t u r n y e llo w , b e g in
t o w i l t , and th e p l a n t d i e s .
Upon c lo s e r e x a m in a tio n , th e r o o t may be
found t o b e r o t t e d o f f a t th e b a s a l end and la r g e c ra c k s may e x ten d h a l f
way th ro u g h th e r o o t .
O fte n t h e e n t i r e r o o t may ap p ear t o be r o t t e d ,
b u t when c u t r a d i a l l y , th e r e may b e a s m a ll p o r tio n o f f i r m , h e a lth y a p p e a rin g t i s s u e w ith in .
A b e e t may b e b a d ly in f e c te d and show l i t t l e o r
n o symptoms above g round, and when c o n d itio n s become u n fa v o ra b le t o th e
fu n g u s , th e r o t t i n g and c ra c k in g slow down and th e p la n t u s u a l l y s u rv iv e s
u n t i l th e h a r v e s t .
A c o n s id e ra b le amount o f r o o t r o t o f su g ar b e e ts o c c u rre d in 19^8
and 19k9 i n s e v e r a l o n e -q u a rte r a c r e p l o t s i n F i e l d 0-11' a t th e H u n tley
B ranch S t a t i o n , H u n tle y , M ontana.
I n 19^-9 more th a n 90 p e r c e n t o f a l l
th e s u g a r b e e ts i n th e s e p l o t s were dead o r d is e a s e d a t h a r v e s t tim e .
S u c c e s s iv e cro p s o f su g a r b e e ts w ere grown i n th e s e p l o t s d u rin g th e y e a r s
1950, 1951, and 1952.
The amount o f d is e a s e .h a s s u b s e q u e n tly d e c re a se d
and v a r ie d each y e a r .
Epidem ics o f R h iz o c to n ia d is e a s e su ch a s th e one
-7 -
i n 19^9 a r e a p p a r e n tly th e r e s u l t o f a com b in atio n o f f a c t o r s , such a s th e
p re s e n c e o f a v i r u l e n t s t r a i n o f th e fu n g u s , a s u s c e p tib le v a r i e t y o f
p l a n t , and optimum te m p e ra tu re , m o is tu re and o th e r c o n d itio n s fa v o ra b le
f o r i n f e c t i o n and developm ent o f th e d i s e a s e .
The p r e s e n t s tu d y was u n d e rta k e n t o in v e s t ig a te th e e f f e c t o f
s e v e r a l e n v iro n m e n ta l and b i o l o g i c a l f a c t o r s on th e p a th o g e n ic ity o f
E h iz o e to n ia c u ltu r e s t o s u g a r b e e t s , and t o a tte m p t t o e x p la in th e
o c c u rre n c e and v a r i a t i o n i n t h i s d is e a s e a t th e H u n tley S t a t i o n .
REVIEW OF LITEEATnREr
S e e d lin g d is e a s e o f su g a r b e e ts may b e cau sed b y s e v e r a l f u n g i.
Those f u n g i m ost p r e v a le n t as s e e d lin g p ath o g en s a re o f th e g e n e ra
R h iz o c to n ia , P ythium , Aphanomyces,. and Phoma.
A fa n a sie v ( l ) is o la te d
th e s e f o u r g e n e ra a s w e ll a s F usariu m and M acrosporium fro m d is e a s e d
s e e d lin g s .
Leach ( l 4 ) r e p o r te d t h a t th e th r e e most common f u n g i t o
cause damping o f f o f su g a r b e e ts
i n C a l if o r n ia were R h iz o c to n ia s o l a n ! ,
P ythium ultim um Trow, and Phoma b e ta e F r .
The f i r s t two a r e common i n
f i e l d s o i l s , w h ile Phoma a p p e a rs t o o r ig i n a te o n ly from im p o rted s e e d .
T i l f o r d and Young ( 31) s t a t e d t h a t Aphanomyces c o c h lio id e s D rechs isr e s p o n s ib le f o r th e m ajor p a r t o f lo s s e s in Ohio from s e e d lin g d is e a s e s ,
b u t t h a t R l s o l a n i , a lth o u g h l e s s common, may cause s e v e re damage.
Edson (8 ) r e p o r te d th e d i s t r i b u t i o n o f th e fungus R h iz o c to n ia t o be v e ry
g e n e r a l, b u t under f i e l d c o n d itio n s , damping o f f o f su g a r b e e ts d u e . t o
!
R h iz o c to n ia was f a r more g e n e r a l . in th e s o i l s o f th e s e m i- a r id W est. He
s t a t e d t h a t th e fungus was a cau se o f a v e ry d e s tr u c ti v e crown r o t i n th e
-8 -
W est, where i t f r e q u e n tly "became e p id e m ic .
I t was n o t uncommon t o see
e n t i r e f i e l d s o f 50 o r 100 a c r e s p r a c t i c a l l y d e s tro y e d i n A ugust b y r o o t
r o t o f w hich th e r e was no ev id en ce e a r l i e r i n th e s e a s o n .
T h is form o f
r o t i s se e n o n ly o c c a s io n a lly i n th e more e a s te r n b e e t grow ing d i s t r i c t s
w here i t a p p e a rs t o be o f l e s s economic im p o rtan c e .
The a c t u a l c o n tr o l o f R h iz o c to n ia d is e a s e i s a p ro b lem o f g r e a t
d i f f i c u l t y , s in c e th e su g a r b e e t i s s u s c e p tib le t o th e ra v a g e s o f
R h iz o c to n ia a t any s ta g e o f grow th and b e ca u se o f th e h ig h d eg ree o f
v ir u le n c e o f th e fungus u n d er v a rio u s e n v iro n m e n ta l c o n d itio n s .
Sugar b e e t s , a s a r u l e , a re grown in th e West i n i r r i g a t e d a re a s
where a crop r o t a t i o n i s p r a c t i c e d .
The e x tre m e ly wide h o s t ra n g e o f
R h iz o c to n ia e n a b le s th e fungus t o l i v e from y e a r t o y e a r i n th e s e f i e l d s
on many o f th e cro p s u s e d i n th e r o t a t i o n sy stem .
P e l t i e r (22) i n 1916
r e p o r te d ab o u t 165 s p e c ie s o f p la n ts w ere s u b je c t t o a tta c k s b y R h iz o c to n ia .
In c lu d e d i n th e s e s p e c ie s w ere a l l th e more im p o rtan t f a m ilie s of
d ic o ty le d o n s a s w e ll a s a number o f m onocotyledons, a n d .s e v e r a l gymnosp erm s.
He r e p o r te d t h a t m ost o f th e f l o r ! c u l t u r a l p l a n t s , v e g e ta b le
and f i e l d c ro p s , h erb aceo u s p l a n t s , and many weeds were s u s c e p tib le t o
a tta c k s o f R h iz o c tb n ia .
I n a d d itio n t o i t s o ccu rren c e on
many d i f f e r e n t
h o s t s , R h iz o c to n ia a ls o form s s p e c ia liz e d r a c e s o r s t r a i n s , some o f w hich
d i f f e r , m o rp h o lo g ic a lly a s s tu d ie d b y Matsumoto ( 19) and L eC lerg ( 15) .
They have shown t h a t t h e r e may b e a s l i g h t o r o c c a s io n a lly somewhat more
pronounced m orphologic d if f e r e n c e betw een i s o l a t e s .
More r e c e n t l y , Exner
and C h ilto n ( 9 ) found as many a s 29 d i s t i n c t c u l t u r a l ty p e s d i f f e r i n g in
-9 - .
r a t e o f g ro w th , c o lo r , s i z e , and p o s itio n , o f s c l e r o t i a o c c u rrin g among
i s o l a t e s from a s in g le h a s ! d i a l m at.
■The c r i t e r i a m ost o f te n employed i n s t r a i n o r r a c i a l d i f f e r e n t i a ­
t i o n have been d if f e r e n c e s i n p a th o g e n ic i t y o r grow th form i n a r t i f i c i a l
■
c u l t u r e .. I n v e s tig a t io n s on r a c i a l s p e c i a l i z a t i o n have b e en u n d e rta k e n
b y s e v e r a l w o rk ers in c lu d in g Buggar ( 7 ) , L eC lerg ( 16, 17, 1 8 ),
S a n fo rd ( 27, 2 8 ) , S to re y ( 30) , and more r e c e n t l y , H ouston ( 1 2) .
LeClerg
( 15) t e s t e d l l 6 i s o l a t e s o b ta in e d c h i e f l y from s c le r o tia ,f o r m e d on p o ta to
tu b e r s and from th e le s io n s on stem s o f o ld e r p l a n t s .
Among th e s e i s o l a t e s
he d id n o t f i n d an y t h a t w ere p a th o g e n ic t o h a lf-g ro w n o r m atu re s u g a r
b e e ts .
On th e o th e r h a n d , E h iz o c to n ia i s o l a t e s o b ta in e d fro m s u g a r b e e ts
w ere p a th o g e n ic on p o ta to e s .
However, he l a t e r found t h a t some p o ta to
i s o l a t e s w ere p a th o g e n ic t o su g a r b e e t s .
S to r e y ( 30) r e p o r te d t h a t some
s t r a i n s had a wide h o s t ra n g e , w hereas o th e rs e x h ib ite d a more s e le c tiv e
p a r a s iti s m .
B u ch h o ltz (b) r e p o r te d a s e v e re c ase o f E h iz o c to n ia r o o t
r o t o f su g a r b e e ts on la n d p r e v io u s ly p la n te d t o p o t a t o e s .
A d jo in in g la n d
t h a t had b een p r e v io u s ly p la n te d t o b a r l e y showed v e ry l i t t l e -to o t r o t .
On th e p o ta to g round, 50 p e r c e n t ,o f th e s ta n d o f b e e ts .w a s r o t t e d ; o n ly
1 .6 p e r c e n t was r o t t e d on th e b a r l e y g ro u n d .
H ouston (12) made a d d i t i o n a l
s tu d ie s on 260 i s o l a t e s o f E h iz o c to n ia from 15 d i f f e r e n t c ro p p l a n t s .
c l a s s i f i e d th e i s o l a t e s in to c u l t u r a l t y p e s .
He
D iffe re n c e s i n grow th h a b it
on n u t r i e n t m edia such as p re s e n c e o r ab sen ce o f stro m a , n a t u r e , s i z e , and
abundance o f s c l e r o t i a and absence o r p re s e n c e o f su b sta n c e s t h a t d ark en
th e medium w ere c r i t e r i a f o r d i f f e r e n t i a t i o n .
A lthough in te r g r a d e s
-1 0 -
o c c u rre d , he s t a t e d t h a t m ost i s o l a t e s c o u ld r e a d i l y h e a s s ig n e d t o t h e i r
a p p r o p r ia te t y p e s .
Type A -was o b ta in e d .from many h o s ts and was a p o ly -
phagus ty p e , w hereas ty p e B and C were h ig h ly s p e c i f i c a s t o h o s t s .
Type C
was e s s e n t i a l l y non -p a th o g e n ic t o s u g a r "beet r o o t s , and Type B w as, from
a p r a c t i c a l s ta n d p o in t, n o n -p a th o g e n ic on s u g a r b e e t s e e d lin g s b u t was
h ig h ly p a th o g e n ic on o ld e r b e e t r o o t s .
K o tila ( 13) r e p o r te d f in d in g a
s t r a i n o f R h iz o c to n ia t h a t a tta c k e d o n ly th e f o li a g e o f s u g a r b e e ts an d .
d id n o t cause any damage t o th e o ld e r r o o ts b u t was c a p a b le o f cau sin g
b o th p r e -em ergence and po st-em erg en ce damping o f f o f su g a r b e e t s e e d lin g s ,
o f te n k i l l i n g 100 p e r c e n t.
I n a d d itio n , th e s t r a i n was p a th o g e n ic to
b e a n s , a l f a l f a , b ro m e g ra ss, and p o t a t o .
The o b s e r v a tio n t h a t R h iz o c to n ia d is e a s e d ev elo p s b e s t i n w et s o i l
and under r e l a t i v e l y w et c o n d itio n s h as b e e n re c o rd e d b y s e v e r a l
in v e s tig a to rs .
H a rte r ( l l ) r e p o r te d R h iz o c to n ia d is e a s e o f sw eet p o ta to e s
t o b e more p r e v a le n t in beds t h a t had b e e n to o f r e q u e n tly w a te re d .
R oth
and R ik e r ( 27) , w h ile w orking w ith damping o f f o f r e d p in e s e e d lin g s i n
t h e g re e n h o u se , found s o i l m o is tu re s somewhat l e s s th a n 70 p e r c e n t o f th e
s o i l m o is tu re h o ld in g c a p a c ity were f a v o ra b le t o R h iz o c to n ia and th o s e
above JO p e r c e n t w ere fa v o r a b le t o P y th iu m .
A lexander e t a l . ( 2 )
r e p o r te d d ry s o i l was found t o be u n fa v o ra b le t o th e R h iz o e to n ia damping
o f f d is e a s e o f tom ato s e e d lin g s .
M o rris and A fa n asie v ( 2 l ) r e p o r te d th e. ■
d is e a s e t o b e m ost p r e v a le n t i n Montana i n h eav y , w et s o i l s r i c h in
■o rg a n ic m a t t e r .
'
numerous i n v e s t ig a ti o n s show t h a t th e developm ent o f c e r t a i n s o i l -
—1 1 —
. "borne d is e a s e s o f p l a n t s a ls o depends on a s p e c i f i c ra n g e o f s o i l te m p e ra t u r e s ^ w hich i n co m b in atio n w ith th e o th e r s o i l f a c t o r s , c r e a te s fa v o ra b le
c o n d itio n s f o r th e developm ent o f d is e a s e . .R ich ard s (2 4 ) fo u n d t h a t
R h iz o e to n ia was m ost v i r u l e n t t o p o ta to e s a t s o i l te m p e ra tu re s o f
15° t o 21° Go He a ls o c o n clu d ed t h a t th e g r e a t e s t damage t o p e as was
"between 12° and 27° C w ith th e maximum, i n j u r y n e a r 18° G, and 15° t o 18°. C
was th e optimum te m p e ra tu re .f o r maximum i n j u r y t o "beans.
h an d , P e l t i e r (2 2 ) fo u n d t h a t h ig h te m p e ra tu re
On t h e o th e r
(3 0 °) to g e th e r w ith to o
l i t t l e o r to o much m o is tu re d e term in e d t o a la r g e d e g r e e ;th e v ir u le n c e o f
v a rio u s s t r a i n s o f R h iz o e to n ia .
LeG lerg ( l$ ) r e p o r te d s o i l te m p e ra tu re s ,
o f 25° t o 33° t o be th e m ost fa v o ra b le f o r developm ent o f R h iz o c to n ia
ro o t r o t of sugar b e e ts .
D e f in ite e x p e rim e n ta l e v id en c e on th e combined e f f e c t s o f s o i l
te m p e ra tu re and s o i l m o is tu re on p a r a s i t i s m o f R h iz o c tb n ia i s a p p a r e n tly
v e r y m eagre.
S a n fo rd ( 2 9 ) s tu d ie d th e e f f e c t s o f s o i l te m p e ra tu re s
betw een l6 ° C and 25° C and o f s o i l m o is tu re c o n te n t betw een 19 and 40
p e r c e n t o f th e ■m o is tu re h o ld in g c a p a c ity on th e v ir u le n c e and ty p e o f
x
a t t a c k o f R h iz o c to n ia on young p o ta to s p r o u t s ..
He fo u n d th e p ath o g en
t o be e q u a lly v i r u l e n t th ro u g h o u t th e ra n g e o f s o i l m o is tu re betw een th e
te m p e ra tu re s o f l6 ° and 23° C, b u t h e was u n a b le t o - o b ta in any c o n c lu siv e
r e s u l t s t h a t th e v ir u le n c e o f R h iz o e to n ia was g r e a t e r a t l 6 ° C th a n a t
23° C, o r .t h a t a d ry s o i l was more o r l e s s f a v o ra b le f o r th e developm ent
o f R h iz o c to n ia d is e a s e th a n a w et s o i l .
S e p a r a te ly co nducted' te m p e ra tu re
and m o is tu re s tu d ie s w ere 'u n d e rta k e n on th e p a th o g e n ic ity o f R h iz o c to n ia
-1 2 -
on beans b y P e rs o n ( 2 3 )»
He t e s t e d th e p a th o g e n ic ity o f B h iz o e to n ia
a t te m p e ra tu re s o f 15° t o 28° C, and a t m o is tu re le v e ls o f 4 0 , 60, and 80
p e r c e n t, he s tu d ie d th e e f f e c t o f s o i l m o is tu re on th e em ergence o f b ean
s e e d lin g s .
H is r e s u l t s showed t h a t B h iz o c to n ia was p a th o g e n ic o n .b ean s
from 150 t o 28° C, and t h a t i t was m ost p a th o g e n ic a t th e low er tem p era­
tu re .
I n "the m o istu re s t u d i e s , t h e s ta n d s w ere red u ced a b o u t e q u a lly
a t a l l th r e e s o i l m o is tu re l e v e l s , b u t th e a v erag e d eg ree o f in f e c tio n
was more s e v e re a t 60 and 80 p e r c e n t s o i l m o is tu re .
U n fo rtu n a te ly ,
n e i t h e r o f th e above named a u th o rs s t a t e d th e t o t a l m o istu re h o ld in g
c a p a c ity o f th e s o i l w ith w hich th e y w orked.
As f a r a s i t i s known, no
s tu d y h as b e en made on th e combined e f f e c t s o f te m p e ra tu re and m o istu re
on th e p a th o g e n ic ity o f B h iz o c to n ia i s o l a t e s on su g a r b e e t s e e d lin g s .
I n r e c e n t y e a r s , c o n s id e ra b le e v id en c e h as b een accu m u lated t o
b r in g o u t th e im portance o f an tag o n ism among m icro o rg an ism s.
W eindling (3 ^ )
i n 1932 o b serv ed T richoderm a lign o ru m (Tode) H arz, c o i l i n g around th e
hyphae o f B h iz o c to n ia , d e s tro y in g th e c o lo n ie s, and su g g e s te d t h a t
T . lig n o ru m m ight b e u se d f o r th e b i o l o g i c a l c o n tr o l o f B h iz o e to n ia
and o th e r fungus d i s e a s e s .
L a te r he r e p o r te d v a rio u s f u n g i grown on
c u ltu r e m edia w ith B h iz o e to n ia a tta c k e d th e l a t t e r i n a manner re sem b lin g
th e p a r a s i t i c a c ti o n o f T richoderm a.
G lio e la d iu m fim b ria tu m G and A .
was a ls o r e p o r te d (3 4 ) c a p a b le o f a tta c k in g and d e s tr o y in g 't h e hyphae
o f B h iz o e td n ia and o th e r f u n g i when grown i n c o n ju n c tio n on n u t r i e n t
m ed ia.
A S trep to m y ce te a n ta g o n i s tic t o a Pybhiuia r o o t p a r a s i t e o f su g a r
cane was r e p o r te d b y Tims ( 32) .
H is t e s t s showed th e S trep to m y ce te
-1 3 -
produced a to x ic p r i n c i p l e l e t h a l t o th e P ythinm r a t h e r , th a n e x h a u s tio n
Qf th e n u t r i e n t s ' i n th e medium, w hich w ould s ta r v e ,th e Pythium .,
D iachun
(6 ) r e p o r te d P e n ic illiu m notatu m W e s tl. o f f e r e d some p r o t e c t i o n a g a in s t
i n f e c t i o n Dy P e n ie illiu m oxalicum C u rrie and Thom.
MATERIA1S MD BETEODS
A m ix tu re o f s u g a r b e e t se e d o f U .S , 22 and 266 o f th e G reat
W estern. S ugar Company was u sed th ro u g h o u t t h e c o u rse o f th e e x p e rim e n ts .
T h is see d was t r e a t e d w ith Wew Improved C eresan on a b a s i s o f one ounce
p e r 20 pounds o f s e e d , o r 0 .3 1 grams p e r 100 grams o f s e e d .
The s o i l u sed i n a l l th e e x p erim en ts was o b ta in e d from F i e l d 0 - H ,
p lo ts I to 3
a t th e H u n tley B ranch S t a t i o n , H u n tley , M ontana, and was
n a t u r a l l y i n f e s t e d w ith B h iz o e to n ia .
T h is s o i l i s c l a s s i f i e d a s a heavy
c la y s o i l , c h a r a c t e r i s t i c of. much o f t h e i r r i g a t e d la n d p la n te d t o su g a r
b e e ts in t h i s a r e a .
P r i o r t o any e x p e rim e n t, th e s o i l was s i f t e d th ro u g h
a No. 16 mesh s c r e e n and a i r d r i e d .
A l l s o i l d i s i n f e c t i n g was done i n an
a u to c la v e (15 pounds p r e s s u r e f o r 3 h o u r s ) .
I n e x p erim en ts c a r r i e d o u t u n d er o r d in a r y e n v iro n m e n ta l c o n d itio n s
i n th e greenhouse,' 6 -in c h c la y p o ts f i l l e d w ith th e above m entioned s o i l
w ere e m p lo y e d .. I n th e m ain t e s t s i n w hich th e e f f e c t o f s o i l m o istu re
and te m p e ra tu re was s tu d ie d on th e developm ent o f B h iz o c to n ia d is e a s e o f
su g a r b e e t s , th e p l a n t s w ere grown in ' s o i l u n d er c o n tr o lle d c o n d itio n s
i n th e c o n t r o l c a g e , i n m e ta l f l a t s 9 in c h e s b y seven and- t h r e e - e ig h th s
in c h es b y f o u r and o n e -h a lf in c h e s , and sto n e j a r s 5 in c h e s in d ia m e ter
and th r e e and t h r e e - e ig h th s in c h e s h ig h .
-3.4 -
The c o n tr o l cage was a sim p ly c o n s tr u c te d chamber e n c lo s e d on
th re e , s id e s and b o tto m , and w ith a sw in g in g d o o r on th e f o u r t h s i d e .
Double g la s s c o n s t i t u t e d th e r o o f o f th e cham ber.
12 f lu o r e s c e n t tu b e s w ere i n s t a l l e d .
Above th e g l a s s ,
W ith in t h e cham ber, l 4 c o i l s
w ere f a s te n e d t o th e t h r e e e n c lo s e d w a lls f o r u n ifo rm r e f r i g e r a t i o n .
A th e rm o s ta t was i n s t a l l e d w ith in th e chamber f o r c o n s ta n t te m p e ra tu re '
c o n tr o l.
A r e f r i g e r a t i o n u n i t was i n s t a l l e d on. th e f l o o r b e n e a th th e
e n t i r e cham ber.
F o r th e d e te rm in a tio n o f th e t o t a l m o istu re h o ld in g c a p a c ity
(TMHC) o f H u n tle y s o i l , a method d e s c rib e d b y Goss (lO ) was em ployed.
T hree m e ta l tu b e s 25 cm lo n g and 5 cm w ide w ere f i l l e d w ith th e a i r d r ie d s o i l and ta p p e d 10 tim e s fro m a h e ig h t o f 3 in c h e s .
The tu b e s
o f s o i l w ere p la c e d i n w a te r f o r 6 h o u rs u n t i l th e s o i l was- th o ro u g h ly
s a t u r a t e d , th e n d ra in e d f o r 3 h o u rs and w eighed.
The tu b e s o f s o i l were
th e n p la c e d i n a d ry in g oven f o r th r e e days a t a c o n s ta n t te m p e ra tu re o f
105° C.
S im u lta n e o u s ly , 2 s m a ll s o i l cans c o n ta in in g a i r - d r i e d s o i l ,
b o th o f w hich had b e en w eighed, w ere a l s o p la c e d i n th e d ry in g oven t o
d e term in e th e h y d ro sc o p ic m o is tu re i n a i r - d r i e d H u n tley s o i l .
A fte r th e
th r e e - d a y p e r io d o f oven d ry in g , th e tu b e s and cans o f s o i l were w eig h ed ,
r e - h e a t e d , and re -w e ig h ed u n t i l a c o n s ta n t w eig h t was m a in ta in e d .
The
TMHC o f t h i s s o i l was th e n computed and fo u n d t o b e e q u a l t o 3 8 .3 p e r c e n t
b y w e ig h t.
The h y d ro sc o p ic m o istu re was fo u n d t o be e q u a l t o 2 .1 2 p e r
cent
The medium u sed in i s o l a t i o n s , la b o r a to r y t e s t s , and f o r ; growing
-1 5 -
.c u ltu r e s v a s p o ta to d e x tro s e a g a r p re p a re d b y adding I J grams o f d e x tr o s e , ■
20 grams o f a g a r a g a r , and 200 grams o f s l i c e d p o ta to e s t o 1000 cc o f ta p
w a te r.
S e v e ra l c u ltu r e s o f R M z o e to n ia w ere i s o l a t e d fro m m a tu re d , in f e c te d
s u g a r b e e t r o o ts c o lle c te d a t th e H u n tle y S t a t i o n d u rin g th e f a l l o f 1950.
The b e e ts w ere w ashed i n t a p w a te r and b ro k e n b y h a n d .
S m all p ie c e s o f
f ir m , in f e c te d t i s s u e ta k e n a s n e a r a s p o s s ib le t o th e h e a lt h y " tis s u e w ere
imbedded i n th e m edia i n s t e r i l e P e t r i d i s h e s .
R h iz b e to n ia c u ltu r e s were
a l s o i s o l a t e d from in f e c te d b e e t s e e d lin g s grown i n th e H u n tle y s o i l i n th e
greenhouse d u rin g th e f a l l o f 1950.
I n making i s o l a t i o n s from th e s e s e e d ­
l i n g s , th e fo llo w in g p ro c e d u re was u se d :
th e s e e d lin g s w ere p la c e d i n a
b e a k e r; cheese c l o t h was p la c e d o v er th e mouth o f th e b e a k e r and h e ld in
p la c e b y a ru b b e r b a n d .
The s e e d lin g s w ere washed w ith ru n n in g ta p w a te r
f o r f o u r h o u rs , and th e n w ashed s e v e r a l tim e s w ith s t e r i l e d i s t i l l e d
w a te r .
S m all p ie c e s o f th e d is e a s e d r o o ts w ere imbedded in '" th e m edia.
A l l c u ltu r e s were grown a t room te m p e ra tu re .
S e v e ra l c o n ta m in a tin g organism s w ere e n co u n te re d i n e ac h i s o l a t i o n
m ethod.
Those m ost p r e v a le n t w ere P u sariu m s p p , Phoma sp p , R hisbgus sp p , ’
P e n n c lliiu m s p p , and b a c t e r i a l c o n ta m in a te s .
R h iz o e to n ia c u ltu r e s were
s e p a r a te d from c o n ta m in a tin g f u n g i b y th e d i l u t i o n method and from "the
c o n ta m in a tin g b a c t e r i a b y th e fo llo w in g m ethod, w hich was d e s c rib e d b y
A rk and D ickey ( 3 ) .
o f Van Tiegham r i n g s .
to u c h in g th e g l a s s .
T hree s m a ll p e l l e t s o f c la y were- p la c e d on one edge
The r in g s w ere p la c e d i n P e t r i d is h e s w ith th e c la y
The P e t r i d is h c o v ers were re p la c e d and th e e n t i r e
—
i6 —
■
a p p a ra tu s s t e r i l i z e d in a n a u to c la v e (15 pounds, p r e s s u r e f o r 30 m in u te s )»
M elted p o ta to d e x tro s e a g a r o f pH 3 .8 was p o u re d i n t o th e p l a t e s .
A f te r
th e a g a r was s o l i d i f i e d , th e c o n tam in ate d m a te r ia l was p la c e d i n th e r i n g .
The fungus hypha te n d t o grow in to th e a g a r and come o u t fro m u n d er th e
r i n g t o th e s u r f a c e o f th e a g a r o u ts id e th e r i n g , f r e e fro m any b a c t e r i a .
The a c i d i f i e d a g a r was p re p a re d b y a d d in g 10 dro p s o f 25 p e r c e n t l a c t i c
a c id t o 1000 cc xsf p o ta to d e x tro s e a g a r .
As a r e s u l t o f th e s e i s o l a t i o n s , s i x c u ltu r e s o f E h iz o c to n ia were
o b ta in e d .
They w ere numbered I , 2 , 3 , 595, 596, and 599.
2 , and 3 w ere i s o l a t e d from m ature su g a r b e e t s .
C u ltu re s I ,
C u ltu re s 595? 596, and
599 w ere i s o l a t e d from s e e d lin g s .
EXPERIMEEfTAL PROCEDURE' AMT RESULTS"
I n a n a tte m p t t o e x p la in th e re a s o n s f o r th e sudden in c re a s e and
su b seq u en t v a r i a t i o n in . i n t e n s i t y o f B h iz o c to n ia d is e a s e o f s u g a r b e e ts,
a t th e H u n tle y S t a t i o n , a s e r i e s o f e x p erim en ts were co n d u cted i n which
v a rio u s e n v iro n m e n ta l and b i o l o g i c a l f a c t o r s w ere in v e s t i g a t e d .
These
s t u d i e s w ere a s fo llo w s :
(1 )
A t e s t o f p a th o g e n ic ity o f th e i s o l a t e s o f R h iz o c to n ia .
(2)
The e f f e c t s o f te m p e ra tu re on th e grow th o f th e i s o l a t e s i n
c u ltu re .
( 3)
~
The e f f e c t s of- te m p e ra tu re an d m o istu re on t h e amount o f
d is e a s e cau sed b y th e i s o l a t e s o f B h iz o c to n ia .
(4 )
The e f f e c t s o f inoculum o f v a ry in g ag es on b e e t s e e d lin g s a t
,th e d i f f e r e n t s ta g e s o f g ro w th .
-1 7 (5 )
,
A n ta g o n is tic e f f e c t s o f o th e r fu n g i on B h iz o c to n ia .
T e s ts o f P a th o g e n ic ity o f th e I s o l a t e s o f B h iz o c to n ia
These t e s t s "were con d u cted i n t h e g reenhouse d u rin g th e w in te r
o f 1950» In, th e s e e x p e rim e n ts, th e p a th o g e n ic ity o f th e t h r e e c u ltu r e s
( l , 2 , 3 ) o f B h iz o c to n ia i s o l a t e d from m atured "beets, and o f th e th r e e
c u ltu r e s (595> 596, 599) i s o l a t e d from s e e d lin g s , w ere t e s t e d .
Twelve
6 -in c h c la y p o ts c o n ta in in g s t e r i l e s o i l w ere in o c u la te d w ith th e s i x
is o la te s .
Two p o ts w ere u sed f o r e ac h i s o l a t e .
on th e m edia m entioned a b o v e.
The inoculum was grown
Two p l a t e s o f inoculum w ere th o ro u g h ly
mixed i n t o th e to p la y e r o f th e s o i l i n e ac h p o t .
Twenty segm ented
b e e t seed s w ere p la n te d a t a d e p th o f o n e - h a lf in c h i n e ac h p o t .
The
b e e ts p la n te d i n th e in o c u la te d s o i l emerged i n ab o u t f i v e d a y s .
The
f i r s t re a d in g f o r h e a lth y and d is e a s e d b e e ts was made one day l a t e r , an d
a t t h r e e - t o f o u r - d a y i n t e r v a l s t h e r e a f t e r u n t i l h a r v e s t.
grown 38 days a f t e r em ergence and h a r v e s te d .
The b e e ts w ere
F i n a l re a d in g s f o r h e a lth y ,
d is e a s e d , and th e t o t a l number o f dead b e e ts w ere re c o rd e d a t th e tim e o f
h a rv e s t.
The p e rc e n ta g e s o f d is e a s e d b e e ts re c o rd e d d u rin g th e 38-day
grow ing p e r io d a r e compared i n f i g u r e I and t a b l e I .
The c u ltu r e s
( 595, 596, 599) i s o l a t e d from s e e d lin g b e e ts d eveloped th e g r e a t e s t
amount o f d is e a s e (lOO per c e n t, 95 p e r c e n t, and 95 p e r c e n t r e s p e c t i v e l y ,
w ith an a v erag e o f 9 6 . T p e r c e n t ) .
The c u ltu r e s i s o l a t e d fro m m ature
b e e ts ( l , 2 , 3 )? a lth o u g h c a u sin g s l i g h t l y l e s s i n f e c t i o n , a ls o produced
a c o n s id e ra b le amount o f d is e a s e
(9^ p e r c e n t, 88 p e r c e n t, and 91 p e r
c e n t, r e s p e c t i v e l y , w ith a n a v erag e o f 91 p e r c e n t ) .
-1 8 -
L im ita tio n s o f equipm ent and tim e f o r th e te m p e ra tu re and m o istu re
s tu d ie s p la n n e d made i t n e c e s s a ry t o s e l e c t o n ly h o f th e 6 i s o l a t e s f o r
u s e i n t h e te m p e ra tu re and m o istu re s tu d ie s and su b seq u en t e x p e rim e n ts.
The. i s o l a t e s ( l , 2 , 595» 599) w ere s e le c te d on th e b a s i s o f ( l ) e a r l y
v ir u le n c e and (2 ) t o t a l number o f b e e ts k i l l e d .
I s o l a t e I k i l l e d 38 b e e t s ,
o r 65 p e r c e n t o f th e t o t a l number o f emerged p l a n t s .
Is o la te 2 k ille d
36 , o r 62 p e r c e n t o f th e p l a n t s , and a ls o showed a r e l a t i v e l y h ig h d eg ree
of e a r ly v iru le n c e .
I s o l a t e 595 k i l l e d A l , o r 89 p e r c e n t o f th e p l a n t s ,
and i s o l a t e 599» a lth o u g h c a u sin g th e l e a s t k i l l i n g p e rc e n ta g e (48 p e r c e n t ) ,
was s e le c te d on t h e b a s i s o f e a r l y v ir u l e n c e .
Ho p r e -em ergence damping o f f
was o b se rv e d , b u t' i t i s s u sp e c te d t h a t some d id o c c u r, e s p e c i a l l y w ith
i s o l a t e 599» s in c e th e number o f p l a n t s t h a t emerged i n th e p o ts in o c u la te d
w ith t h i s c u ltu r e was c o n s id e ra b ly l e s s th a n w ith th e o th e r i s o l a t e s . •A l­
th o u g h th e t o t a l p e r c e n t o f d is e a s e a s p ro duced b y th e 6 i s o l a t e s was
p r a c t i c a l l y th e same, th e s e r e s u l t s show t h a t i s o l a t e s from th e same h o s t
d i f f e r e d i n v ir u l e n c e .
The e x is te n c e o f d i f f e r e n t s t r a i n s o f B h iz o c to n ia
w hich v a ry i n t h e i r p a th o g e n ic ity on th e same o r d i f f e r e n t h o s ts i s a w e l l known f a c t , a s r e p o r te d b y L eC lerg (1% ), K o tila ( 13) , and H ouston (1 2 ) .
•
—1 9 —
T ab le I .
,1
P a th o g e n ic ity - t e s t i n th e g re e n h o u se <, showing th e
m o r t a l i t y and t o t a l d is e a s e p e r c e n t p ro d u c e d "by
e a c h i s o l a t e o f R M so c to n ia on s u g a r "beet s e e d lin g s »
Is o la te
Number
P la n ts
Emerged
Number
..,P lants
H a rv este d
Number
I
58
20
65
58
22
62
6l ■
30
51.
2
3
'
595
k6 .
596
ko
599
31
Check
57
C-
5-
■
M o r ta lity
a t H arv est
P er cent
89
19
52
16
48.
57
-
T o ta l
D isea sed
"Per c e n t
94
-
88
91
100
.
.
95
95
-
-2 0 -
_______________ I
________________2
________ ______ 3
— . -----------------596
------------------------599
Days a f t e r g e rm in a tio n
F ig u re I .
The p ro g re s s o f R h iz o c to n ia d is e a s e o f su g a r
b e e t s e e d lin g s a s cau sed by each i s o l a t e in
th e g re e n h o u se .
-2 1 -
The E f f e c t o f Tenrperatiare on R a d ia l Growth in C u ltu re
D iffe re n c e s i n grow th h a b it on m edia i s o f te n u sed a s a c r i t e r i o n
f o r s t r a i n d i f f e r e n t i a t i o n o f R h iz o c to n ia i s o l a t e s .
The p r e s e n t t e s t o f
th e e f f e c t o f te m p e ra tu re on th e r a d i a l g ro w th o f th e 4 i s o l a t e s was u n d e r­
ta k e n t o d e term in e i f any o f t h e . i s o l a t e s c o u ld b e p la c e d i n c u l t u r a l ty p e s
a s s u g g e s te d b y H ouston ( 1 2 ) .
P u re c u ltu r e s o f each i s o l a t e o f R h iz o c to n ia were grown on
p o ta to d e x tro s e a g a r a t room te m p e ra tu re . When th e m ycelium f i l l e d th e
>:
■
'
p l a t e s , d is c s 1»5 ram i n d ia m e te r were c u t from th e m argins o f th e c o lo n ie s
and p la c e d u p s id e .down i n f r e s h l y p o u red a g a r i n P e t r i d is h e s .
d is h e s w ere u sed f o r e ac h i s o l a t e .
Four
These w ere th e n im m ed iately p la c e d in,
c o n tr o l chambers a t te m p e ra tu re s o f 1 0 °, 1 5% 2 0 °, 2 5 °, 2 9° , 3 4 °, and
39° C.
M easurem ents o f th e g r e a t e s t and s m a lle s t d ia m e te rs w ere made e a c h
24 h o u r s .
A t th e end o f 72 h o u rs , th e av erag e d ia m e te r o f th e i s o l a t e s
was d eterm in ed and r e c o rd e d .
i n f ig u r e 2 .
The r e s u l t s o f th e ex p erim en t a re summarized
The optimum te m p e ra tu re f o r th e 4 i s o l a t e s was fo u n d t o l i e
betw een 25° and 29° C.
The grow th r a t e o f a l l th e i s o l a t e s was p r a c t i c a l l y
}
th e same th ro u g h o u t e x c e p t a t te m p e ra tu re s o f IO0 and 15°G. At 10°C,
i s o l a t e I made some g ro w th , w hereas i s o l a t e s 2 , 595, and 599 showed o n ly
a t r a c e o f grow th o r none a t a l l .
I t i s th e r e f o r e assumed t h a t th e
minimum te m p e ra tu re r e q u ir e d f o r grow th on t h i s c u ltu r e medium f o r
i s o l a t e I l i e s betw een 5° and 10° C, and th e minimum te m p e ra tu re f o r th e
o th e r i s o l a t e s l i e s betw een 8° and 10° C.
A t 15° C, i s o l a t e s I and 599
showed a s l i g h t l y g r e a t e r r a t e o f grow th th a n i s o l a t e s 2 and 595»
-2 2 -
The maximum te m p e ra tu re f o r a l l i s o l a t e s was found t o "be n e a r 40° C.
These r e s u l t s ■g e n e r a lly a g re e w ith p re v io u s work t h a t has been
done on d i f f e r e n t i s o l a t e s o f R h iz o c to n ia .
L eC lerg ( l 8 ) r e p o r te d th e
optimum te m p e ra tu re f o r su g a r b e e t i s o l a t e s a s 25° t o 30° C, and f o r
p o ta to i s o l a t e s , 20° t o 25° C.
W alker (33)» w h ile w orking w ith an
i s o l a t e o f R h lz o e to n ia from c o tto n , found t h a t th e optimum te m p e ra tu re
f o r i t s grow th was betw een 27° and 2 9 ° C, w ith no grow th above 38° C,
and a minimum te m p e ra tu re betw een rJ0 and 11* C.
M o n tieth and B ahl (20)
w orking w ith g r a s s and p o ta to s t r a i n s o f R h iz o c to n ia * fo u n d wide v a r i a ­
t i o n s i n grow th r a t e s betw een th e p o ta to i s o l a t e s w ith th e optimum
grow th betw een 2 5 ° and 30° C, and i n m o st-c a se s n e a r e r t o 2 5 ° th a n 30°
H ouston (12) r e p o r te d a s t r a i n o f ty p e B. o b ta in e d from s u g a r b e e ts t o
a c h ie v e maximum grow th a t 28° —29° G.
On th e b a s i s o f th e s e r e s u l t s , i t i s b e lie v e d t h a t th e c u l t u r a l
ty p e o f a l l th e i s o l a t e s u sed i n t h i s t e s t was s i m i l a r .
-2 3 -
______________ I
------------------- 595
-------------
»
■■ »
■
F ig u re 2 . The av erag e grow th on p o ta to d e x tro s e a g a r o f fo u r i s o l a t e s
o f R h iz o c to n ia s o la n i a f t e r 72 h o u rs a t sev en d i f f e r e n t
te m p e r a tu r e s .
-2kThe E f f e c t o f Temperatizre and Moi s t u r e on th e
Amount o f E h iz o c to n ia D isea se '
The e f f e c t o f te m p e ra tu re and m o istu re on th e p a th o g e n ic i t y o f
B h iz o c to n ia t o "beet s e e d lin g s was s tu d ie d in a p a r a l l e l s e r i e s .
Tempera­
tu r e s o f 15° and 25° C and m o istu re l e v e l s o f 55> '70, and 80 p e r c e n t o f
t h e t o t a l m o istu re h o ld in g c a p a c ity were s e l e c t e d .
The m o is tu re l e v e l o f
70 p e r c e n t was c o n s id e re d a s optimum, th e l e v e l o f 55 p e r c e n t minimum,
and th e 85 p e r c e n t l e v e l was c o n sid e re d a s maximum m o is tu r e .
and one j a r w ere u sed f o r each m o is tu re l e v e l .
Two f l a t s
A ll f l a t s and j a r s were
w eighed s e p a r a te ly , f i l l e d w ith a i r - d r i e d s o i l , and re -w e ig h e d .
Tap
w a te r was added t o e a c h ; th e n th e y w ere s t e r i l i z e d i n th e a u to c la v e as
m entioned ab o v e.
A ll th e f l a t s w ere in o c u la te d w ith a 7 -day-old. c u ltu r e
n f R h iz o c to n ia grown on p o ta to d e x tro s e a g a r i n P e t r i d i s h e s .
Four P e tp i
d is h e s o f inoculum w ere added t o each f l a t , and th e inoculum was th o ro u g h ly
m ixed w ith th e to p th r e e in c h e s o f s o i l .
tro ls .
The .jars, w ere r e t a i n e d a s con­
I n each f l a t two rows o f su g a r b e e t seed s w ith tw e n ty seed s p e r
row were p la n te d a t a d e p th o f o n e -h a lf in c h .
i n each j a r .
Twenty see d s w ere p la n te d
The amount o f w a te r t o b e added t o each f l a t and j a r t o
b rin g , th e s o i l up t o i t s r e s p e c tiv e m o is tu re le v e l was com puted.
F la ts I
and 2 and j a r I w ere k e p t a t 55 p e r c e n t TMEC, f l a t s 3 and U and j a r 2
w ere k e p t a t 70 p e r c e n t TMHC', and f l a t s 5 and 6 and. j a r 3 were k e p t a t
85 p e r c e n t TMHC.
A ll f l a t s and j a r s w ere p la c e d i n th e c o n tr o l c ag e .
The. s e e d lin g s w ere s u b je c te d t o a f i f t e e n - h o u r l i g h t p e r io d b y tu rn in g
on th e l i g h t s a t 5 :00 p .m . and tu r n in g them o f f a t 8 :0 0 a .m .
Throughout
-2 5 -
th e s e t e s t s t h e ite m p e ra tu re i n th e cage was c o n tr o lle d w ith in I 0 C.
The
m o is tu re l e v e l s w ere m a in ta in e d d a i l y "by w eighing each f l a t and j a r and
adding th e r e q u ir e d amount o f ta p w a te r t o r e s t o r e th e o r i g i n a l w e ig h t.
The f l a t s and j a r s w ere r o t a t e d d a i l y i n th e cham ber.
The h u m id ity o f
th e i n t e r i o r o f th e cage was n e a r s a t u r a t i o n a t a l l tim e s .
The p ro c e d u re
d e s c rib e d above was re p e a te d f o r each i s o l a t e a t te m p e ra tu re s o f 15° C
and 25° C ,
The b e e ts em erged i n ab o u t 7 t o 9 days a f t e r p la n tin g a t
15° C and i n ab o u t 5 days a t 25° C.
R eadings began 4 days a f t e r emergence
The b e e ts w ere grown f i v e weeks a f t e r em ergence, and' re a d in g s o f h e a lth y
and d is e a s e d s e e d lin g s were ta k e n a t f r e q u e n t in t e r v a l s d u rin g t h i s p e r io d
The l a s t re a d in g o f h e a lth y and d is e a s e d b e e ts was ta k e n a t th e tim e o f
h a rv e s t.
The b e e ts w ere w ashed and c lo s e ly exam ined f o r symptoms o f th e
d is e a s e a t t h i s tim e .
The number o f b e e ts dead a t h a r v e s t , th e w eig h ts
o f to p s and r o o t s , th e av erag e w eig h t p e r b e e t , and th e a v erag e le n g th
o f to p s w ere a l l re c o rd e d a t th e tim e o f h a r v e s t.
The symptoms of th e d is e a s e d s e e d lin g s w ere v e ry s im ila r t o th o s e
p r e v io u s ly d e s c r ib e d .
o r j u s t b elo w .
p e tio le s .
lin g .
The p o in t o f a t t a c k was m o stly a t th e s o i l l e v e l
O c c a s io n a lly a b e e t was a tta c k e d a t th e b a se o f th e
T h is ty p e o f a t t a c k in v a r ia b ly r e s u lte d , i n d e a th t o th e se e d ­
Many o f th e p la n ts a t b o th te m p e ra tu re s and a t a l l m o istu re l e v e l s
n e v er p ro g re s s e d beyond th e eoty led o n o u s l e a f s ta g e .
When th e s e b e e ts
w ere exam ined a t th e tim e o f h a r v e s t, th e r e was alw ays a d i s t i n c t absence
o f r o o t l e t s and r o o t h a i r s a s a r e s u l t o f R h iz o c to n ia d is e a s e .
Coons and
S te w a rt ( 5 ) have r e p o r te d a c o n d itio n v e ry s im ila r t o t h i s i n t h e i r work
-2 6 -
w ith E h iz o e to n ia danrping o f f d is e a s e o f s u g a r "beets.
Sometimes th e p l a n t
m a in ta in e d i t s e l f in t h i s s tu n te d c o n d itio n alm o st th e e n t i r e 5 weeks o f
grow ing p e r io d .
T h is c o n d itio n was most common when i s o l a t e s "595 and 599
w ere u sed a s th e so u rc e s o f i n f e c t i o n .
O c c a s io n a lly a p l a n t a p p e a rin g t o "be h e a lth y and v ig o ro u s , and as
la r g e o r l a r g e r th a n m ost o f th e "beets i n th e f l a t , , would su d d en ly develop
th e symptoms o f R h iz o c to n ia d is e a s e and b e dead i n a few d a y s .
c o n d itio n o f t h e p la n ts u s u a ll y o c c u rre d a t 25° C.
T his
The le n g th o f tim e
from i n f e c t i o n t i l l d e a th was c o n s id e ra b ly lo n g e r a t 15° C th a n a t 25° C.
I s o l a t e s 2 and 599 cau sed a c o n s id e ra b le amount o f e a r l y i n f e c t i o n a t
25® C, a s was th e c ase in th e green h o u se t e s t s .
21 p e r c e n t o f th e b e e ts 3 days a f t e r em ergence.
I s o l a t e 2 in f e c te d up t o
A f te r t h i s i n i t i a l
a t t a c k , new i n f e c t i o n was slo w er t o d e v e lo p , and as th e b e e ts grew l a r g e r ,
th e amount o f new i n f e c t i o n decreased ."
I s o l a t e 599 cau sed some e a r l y
i n f e c t i o n , b u t i t was 5 t o J days a f t e r emergence b e fo re th e d is e a s e
showed up t o any e x t e n t .
I s o l a t e s I and 595 n ev er cau sed an y deg ree o f
sudden i n f e c t i o n o r k i l l i n g .
W ith i s o l a t e I , many o f th e b e e ts ap p eared
t o be h e a lth y a t th e tim e o f h a r v e s t, b u t had sm a ll le s i o n s on th e ta p r o o t
when exam ined.
I s o l a t e 595 ap p eared t o b e slow in causing, in f e c tio n ,
b u t most o f th e s e e d lin g s t h a t became in f e c te d d ie d .
Ho p r e -emergence
damping o f f was o b serv ed th ro u g h o u t t h e e x p erim en t.
I s o la t io n s from d ise a se d b e e t s e e d lin g s were made a t frequent
in t e r v a ls throughout th e t e s t s .
r e s u lt e d from, th e s e i s o l a t i o n s .
In v a r ia b ly c u ltu re s o f B h izo eto n ia
-2 7 -
The amount o f d is e a s e t h a t o c c u rre d d u rin g th e 5 weeks p e rio d a t th e
d i f f e r e n t te m p e ra tu re s and m o is tu re l e v e l s a r e compared i n t a b l e 2 and
f ig u r e 3«
I t was i n t e r e s t i n g t o n o te t h a t w h ile i s o l a t e
I e x h ib ite d
a h ig h d e g re e o f p a th o g e n ic ity in p r e lim in a r y t r i a l s i n th e g re e n h o u se .
(94 p e r c e n t) th ro u g h o u t th e s tu d y u n d er c o n tr o lle d c o n d itio n s , i t
cau sed th e l e a s t amount o f d is e a s e .
A t 25° P and .85 p e r c e n t TMHC,
„
how ever, i s o l a t e s I and 2 produced th e same amount o f d is e a s e w ith a
d is e a s e p e rc e n ta g e o f 6 2 .
A p p a re n tly th e in c re a s e i n m o is tu re l e v e l o f
th e s o i l had l i t t l e e f f e c t upon in c re a s in g th e in c id e n c e o f d is e a s e a t
15° C „ W ith i s o l a t e I , th e amount o f d is e a s e rem ained n e a r ly c o n s ta n t
r e g a r d le s s o f th e m o istu re l e v e l , w ith d is e a s e p e rc e n ta g e s o f 2 5, 2 4 , and
2 3 , r e s p e c t i v e l y , a t 55, 7 0, and 85 p e r c e n t ' rTMHC.
I s o l a t e 2 , a lth o u g h
c a u sin g s l i g h t l y more in f e c tio n ) a ls o rem ain ed f a i r l y c o n s ta n t w ith
d is e a s e p e rc e n ta g e s o f 36, 4 0, and 39-
I t was d i f f i c u l t t o d eterm in e
e x a c tly how much i n f e c t i o n i s o l a t e 595 cau sed a t 15® C, b e c a u se a l l th e
v
p l a n t s were d e f o l i a t e d 7 days a f t e r emergence d u e ' t o th e s p ra y u sed i n
th e b u ild in g (s e e fo o tn o te on t a b l e 2 ) .
The p la n ts w ere n o t k i l l e d o u t­
r i g h t , b u t most o f them f a i l e d t o re p ro d u c e le a v e s .
E x am in atio n o f
s e v e r a l o f th e r o o ts showed no symptoms o f d is e a s e .
The f ig u r e s u sed i n
t a b l e 2 and f ig u r e 3 a r e b a se d upon th e number o f b e e ts h a r v e s te d .
There
was no way t o d e term in e how many b e e ts d ie d b e fo re h a r v e s t a s a r e s u l t o f
i n f e c t i o n w ith B h iz o e to n ia .
The in c id e n c e o f th e d is e a s e a p p ea re d t o b e somewhat a f f e c t e d b y
.
m o is tu re when th e s o i l was in o c u la te d w ith i s o l a t e 599«
A t each in c re a s e d
-2 8 -
m o is tu re l e v e l , t h e . amount o f d is e a s e in c re a s e d s l i g h t l y fro m 33 p e r c e n t
d is e a s e d p l a n t s a t 55 p e r c e n t TrMHC, t o 38 p e r cent, d is e a s e d a t 70 p e r c e n t
TMHC, t o b2 p e r c e n t d is e a s e d a t 85 p e r c e n t TMHC. A t 25° C, a marked in c re a s e i n amount o f d is e a s e o c c u rre d w ith a l l
is o la te s " e x c e p t i s o l a t e I , a s compared t o th e t e s t s a t 15° C.
Is o la te I
a g a in cau sed th e l e a s t amount o f i n f e c t i o n w ith d is e a s e p e rc e n ta g e s o f
4 l , 33, and 6 2 , r e s p e c t i v e l y , a t 55, 7 0 , and 85 p e r c e n t TMHC „ When th e
te m p e ra tu re was h e ld a t 15° C, i s o l a t e 2 , a s a r u l e , c au se d a s much o r
more d is e a s e th a n d id i s o l a t e s 595 and 599, h u t a t 2 5 ° C, i s o l a t e s 595
and 599 cau sed c o n s id e ra b ly more d is e a s e th a n i s o l a t e 2 .
Is o la te 2 '
caused 6 6 , 68, and 62 p e r c e n t, b e in g p r a c t i c a l l y th e same th ro u g h o u t
r e g a r d le s s o f m o is tu re l e v e l m a in ta in e d i n th e s o i l .
I s o l a t e 595 caused
d is e a s e p e rc e n ta g e s o f 7 9 , 9&, and 9 6 , an d i s o l a t e 599 cau sed d is e a s e
p e rc e n ta g e s o f 78, 89, and 97«
B oth i s o l a t e s th e n , (595 and 599) more o r
l e s s r e p e a te d th e p a th o g e n ic ity t e s t s i n th e greenhouse when th e y w ere u sed
a s th e so u rc e o f i n f e c t i o n .
c e n t TMHC.
T his was e s p e c i a l l y t r u e a t 70 and 80 p e r
As i n th e f i r s t p a r t o f t h i s t e s t , s o i l te m p e ra tu re ap p eared
t o be more o f a d e c id in g f a c t o r a s a c a u s a l a g e n t f o r p ro d u cin g i n f e c t i o n
th a n was ■m o is tu r e .
Y et w ith a g ra d u a l in c r e a s e i n m o is tu re , more d is e a s e
was shown b y th e b e e ts grown a t 25° C th a n a t 15° C.
T h is was e s p e c ia ll y
t r u e f o r i s o l a t e s I , 595, and 599« •
I t i s o f i n t e r e s t t o n o te th e b e h a v io r o f th e d i f f e r e n t i s o l a t e s
o f B h iz o c to n ia re g a rd in g t h e amounts o f b e e ts k i l l e d d u rin g th e growing
p e r io d u n d er c o n tr o lle d c o n d itio n s i n com parison t o th e amounts k i l l e d
-2 9 -
i n th e p r e lim in a r y t e s t s in th e greenhouse ( ta b le s I and 2 ) .
I n th e
greenhouse t e s t s , a l l i s o l a t e s ( l , 2 , 595> and 599) cau sed a r e l a t i v e l y
h ig h p e rc e n ta g e o f dead "beets h y h a r v e s t tim e , 6 5, 6 2 , 8 9 , and 48 p e r
c e n t r e s p e c t i v e l y , "but under c o n tr o lle d c o n d itio n s a t 25° C, is o la te " I
caused an av erag e p e r c e n t m o r t a lit y o f 2 9, o r o f 36 p e r c e n t l e s s th a n
i t d id under th e greenhouse c o n d itio n s .
I s o l a t e 2 caused an av erag e
p e r c e n t m o r t a l i t y o f 32, w hich i s 30 p e r c e n t l e s s .
I s o l a t e 595 caused an
av erag e p e r c e n t m o r t a lit y o f 58, w hich i s 31 p e r c e n t l e s s ; and
i s o l a t e 599 caused an av erag e p e rc e n t m o r t a lit y o f 44, w hich i s 4 p e r c e n t
l e s s th a n t h a t under greenhouse c o n d itio n s .
These r e s u l t s show t h a t
i s o l a t e 599 was th e o n ly i s o l a t e t o approxim ate o r exceed th e greenhouse
t e s t in th e amount o f "beets k i l l e d "before h a r v e s t.
In each case when th e s o i l was .in ocu lated w ith a c u ltu r e o f
R h izocton ia obtained from mature sugar b e e t s , fo r exam ple, w ith is o la t e s
I and 2 , th e average .weight per p la n t and th e average le n g th o f top s was
g r ea ter than when is o la t e s from seed lin g s' were used as inoculum (Figure
4 ).
Between is o la t e s from th e same so u rce, th e averages o f w eight and
le n g th o f to p s v a ried somewhat.
.For example, a t 15° 'C, u sin g is o la t e I ,
th e two averages o f b e e ts showed a g r e a te r w eight and lon ger tops than
w ith is o la t e 2 , but a t 25° C, th e rev e r se occurred.
The com parison betw een i s o l a t e s 595 and 599 when in o c u la te d in
s o i l a t 15° C w i l l n o t be d is c u s s e d s in c e th e b e e ts grown w ith i s o l a t e
595 were d e f o l i a t e d by th e s p ra y .
A t 25* C, how ever, th e s e i s o l a t e s were
s im ila r as t o deg ree o f p a th o g e n ic ity co n cern ed , b u t a s a r u l e th e y were
-3 0 -
more p a th o g e n ic th a n i s o l a t e s I and 2 ,
The w eig h t and le n g th o f to p s o f
"beets in o c u la te d w ith i s o l a t e s 595 and 599 were s i m i l a r , "but a w ide d i f ­
fe re n c e e x is t e d when th e w e ig h ts and to p s o f th e s e b e e ts w ere compared
w ith th o s e o b ta in e d u s in g i s o l a t e s I and 2 ( t a b l e 2 and f i g u r e k ) ,
These
d a ta show a tr e n d in d ic a tin g t h a t th e amount o f d e tr im e n ta l e f f e c t p r o ­
duced on th e ’ h o s t i s c lo s e ly c o r r e la te d w ith th e deg ree o f p a th o g e n ic i t y
o f th e i s o l a t e .
T h is was m a n ife ste d c h i e f l y i n r e d u c tio n o f v ig o r and
s tu n tin g o f th e p l a n t s , and was e s p e c i a l l y n o tic e a b le when R h iz o c to n ia
c u ltu r e s i s o l a t e d from d is e a s e d s e e d lin g s were u sed as inoculum .
These
r e s u l t s a ls o show v e ry d e f i n i t e l y t h a t th e c u ltu r e s i s o l a t e d from
s e e d lin g s w ere more pathogenic, t o b e e t s e e d lin g s th a n were th o s e c u ltu r e s
i s o l a t e d from m atured b e e t r o o t s .
A comparison o f th e e f f e c t s o f each is o la t e a t tem peratures o f 15° and 25° C, and a t
each m oisture l e v e l , on m o r ta lity , t o t a l per cen t d is e a s e , average w eight per p la n t,
and average le n g th o f tops o f th e b e e t s e e d lin g s .
55#
°
I
2
595
599
Ck.
I
70#
2
595
599
Ck.
I
85#
2
595
599
Ck .
84
75 84
94 89
96
*68-31 109 *31
82 102
102
77
85 77
57
75 7 -3
39 * _
50 85 -
#
15°
25°
25°
!2 5 .8 25
4 2 .5 36
38.2 *35
4 2 .9 33
41
66
79
78
5
-
_
2 4 .0 24
2 0 .2 4o
6 4 .2 *36
39 .0 38
-
-
112
76 109 45 2 .7 38.2 23
96 84 64 7 -7 33.3 39
91
*70-34 70 *34 20 * . 7 1 .4 *38
117
85 H 7 36 - 57.6 42
2
95 108 95 108 -
0 .1 8 0 .1 6
0.1 5 0 .0 6
*0 .0 8 PO.02
0 .1 0 0 .0 3
0 .1 1
0 .4 9
0.7 3
0.1 8
0 .1 9
0.25
0 .2 1
0 .5 7
0 .1 0
0 .0 9
33
0 .3 9 0 .4 5
68
0 .2 5 0 .10
96 *0 .0 6 *0.02
0 .l 4 0.0 5
89
0
.2 8
5
O.58
0 .9 3
0.1 3
0 .22
0 .3 7
0.7 3
0 .3 3
0 .1 5
0 .H
0 .4 5 0 .5 9
0 .3 0 0 .1 0
*0 .06 *0 .0 3
0 .1 8 o .o 4
—
0 .2 7
0.8 0
0.8 5
0.2 0
0.3 3
0 .4 7
0 .6 0
0 .6 7
0 .0 9
0 .1 5
62
62
96
97
20
-
-
I:
Mm.
D isea sed
H e alth y
D isea sed
G r.
2;S0
G r.
Or.,.
H e alth y
D isea sed
I
No.
No.
#
1T.~ PT ~ 1T 2-7 I T
I
I
66 85 i 4 9 :1 .2
86
96
73 9 0 I 42 6 .2
1*62-23 68 *23 42 * 96
77 96 44 —
HO
91 110 91 -
H -
H e a lth y
I
0)
D isea sed
$ %
B U
0)
Average Length
o f Tcps
Average W eight
p e r P la n t
H e a lth y
-P ch
to O
U
T o ta l
P la n ts
D isea sed
§1
M o r ta lity o f
P la n ts a t
H a rv est
Sl
Ii
P la n ts Emerged
35
P la n ts H a rv este d
Table 2 .
250
Mm.
Mm,
Mm.
4 2 .1 4 3 .1
37.6 25.8
*20.4 *17.0
34 .4 18.7
—
31 .0
7 3 .4
8 5 .7
33-8
38.4
4 6 .2
54.6
6 9 .8
24 .0
27 .8
58.0 57.5
4 7 .7 2 6 .1
* 1 9 .9 *13.3
39 .9 20 .0
4 0 .5
7 6 .1
8 9 .9
39-0
4 2 .8
53.2
58.2
7 9 .6
32.6
33-2
6 0 .5 50.5
51 .7 27 .8
* 2 3 .3 *15.2
4 2 .8 2 4 .1
4 l.4
83 .2
8 9 .5
37.0
4 5 .0
56.8
75-1
8 0 .0
24.3
36.0
*The b u ild in g i n w hich th e s e t e s t s were conducted was sp ray ed w ith c h lo rd a n e _
7 days a ft e r emergence• A ll th e b e e ts v ere d e fo lia te d and most o f them k i l l e d .
a re b a se d on th e number o f b e e ts h a rv e s te d (2 3 , 31, 3*0»_________________________
-
-
A ll fig u r e s
-3 2 -
P e r c e n t D isease
Is o la te
'
1
5%
TMHC*
XV
C X f
IV
4 -V
)V
UV
I V
^iiiliiiiniiiiIIiiiIm
U V
^ V
XVV
15o c
2
595
miiriTirimiimmvmfJi
599
1
70#
TMHC*
8#
TMHC*
w /////////////«
y //////////////m w /W M ^
2
595 ///////////M z y y ///////////^
599 v ///////y y y y y /y y y /y y /y # # ^
1 . v//////////yyy///////%
^ y y ^ y y /y y /y W y /y ///^
2
5 9 5 . yyyyyyyymyzy/yyyyyy/y/y/y/y4
599 y y y / y /y y y /y > W /w ^ /y / y ^
1
2
TMHC*
595
599
1
70#
TMHC*
2
T jlliv illIillliclMllkilIlMA
iiiiiiiiiiiiiiliiiiiiiiiiiiiiiiiiiiiinniiiiiiiiiiliillWJi
25° C
y /y y //y /y /y y y y /M //w /////y /y y ^ /y /} y y //y /y y //^
/////////////////////////y ////////////y y y y /////////////////y ///y /y //<
y ///////////////y ////y //^
/y y y y y y y y y y y y y y y /y y /////y ///////y ////w /w //y /^ ^
595
yyyy/yyyyy/yyy//yy/yy/wyyyyy/vy/% /yyyyyy/77/////////////////i/77}]
y /y /W /y y /y /Z /w /^
1
^ //////// / / / / / / / / / / '/ / / / / / / / / / / / / / / / / / / y y y y y y y
2
5 9 5 1Z / / / / / / / / / / / / v // / y / 7 X / / y / / y / / / / / / / / / / / ////////////////////X zZ yzzyyy///!
599 'y y y y y y y y y y y ///////y / / / / y / / / / / / / / / / / / / / / / / / y / ^ y y y y / % ^ % y y y ^
599
8$#
TMCH*
L
F ig u re 3 . Top t o bottom : th e t o t a l p e r c e n t o f d is e a s e d su g ar
b e e t s e e d lin g s a s p ro duced b y each i s o l a t e o f R h iz o c t o n i a a t 15° and 25° C r e s p e c t i v e l y , and a t each
m o istu re l e v e l ,
* T o ta l M o istu re H olding C a p a c ity
Length o f to p s i n m illim e te rs
•33
F ig u re b. (L e f t t o r i g h t ) . Average le n g th o f to p s o f su g ar "beets
i n m illim e te r s a t 1 5 ° and 2 5 ° C, r e s p e c t i v e l y , and a t
each m o istu re l e v e l . The u n lin e d p o r tio n s r e p r e s e n t
h e a lth y b e e t to p s ; th e lin e d p o r tio n s r e p r e s e n t d is e a s e d
b e e t to p s .
-3bThe E f f e c t o f Inoculum, o f V arying Ages on S u g ar B eet
S e e d lin g s a t D if f e r e n t S ta g e s o f Growth .
.
'■
B h iz o c to n ia d is e a s e o f su g a r "beets o f te n does n o t m a n ife st I t s e l f
i n s e v e re fo rm . i n th e f i e l d u n t i l l a t e i n th e s p rin g o r e a r l y i n summer
d e s p ite a heavy c o n c e n tra tio n o f inoculum in th e s o i l th ro u g h o u t th e
y ear,
i n o rd e r t o have a "b e tte r u n d e rs ta n d in g o f th e d e la y e d appearance
o f R h iz o e to n ia d is e a s e o f "beets, t e s t s w ere conducted t o d eterm in e th e
e f f e c t o f th e age o f inoculum and th e age o f p la n ts on th e appearance and
developm ent o f t h i s d is e a s e .
These t e s t s w ere ru n i n 2 s e r i e s i n th e
g re e n h o u se , u s in g I ^ s i x - in c h c la y p o ts i n e ac h s e r i e s .
The p o ts were
f i l l e d w ith s o i l and s t e r i l i z e d in th e a u to c la v e . I n s e r i e s I , th e s o i l
i n each p o t was in o c u la te d w ith 100 cc o f a su sp e n sio n o f a m ix tu re o f
th e 4 i s o l a t e s o f B h iz o c to n ia m ycelium .
The su sp e n sio n was p re p a re d "by
s c ra p in g 7 -d a y -o ld mycelium o f f 7 p l a t e s o f each i s o l a t e .
w a te r was added t o make up 1400 cc o f inoculum .
Enough ta p
The su sp e n sio n was p u t
i n a Waring "blender f o r 10 seconds and th e n e v e n ly d i s t r i b u t e d t o th e
to p o f th e s o i l i n th e l k p o t s .
Two p o ts were p la n te d im m ed iately w ith
15 segm ented b e e t seed s a t a d e p th o f o n e -h a lf in c h a t th e tim e o f
in o c u la tio n .
Each 5 days a f t e r th e f i r s t p l a n t i n g , 2 more p o ts were
p la n te d i n th e same m anner.
T h i r t y - f i v e days a f t e r th e p la n tin g o f each
s e t o f 2 p o t s , th e b e e ts w ere h a rv e s te d and examined f o r d is e a s e .
s e rie s 2 ,
In
th e p la n tin g method was th e same and to o k p la c e on th e same
days as, in s e r i e s I , b u t th e inoculum was n o t added u n t i l th e b e e ts in
th e f i r s t 2 p o ts w ere 30 days o ld .
The b e e t s in s e r i e s 2 were, h a rv e s te d
-3 5 -
35 days a f t e r th e inoculum had "been ad d ed .
I n s e r i e s I , th e age o f th e inoculum p la c e d i n th e s o i l v a r ie d
a t th e tim e o f p l a n t i n g 'o f the. d i f f e r e n t s e t s from z ero t o 30 d a y s, and
th e age o f th e p la n ts i n a l l s e t s was 35 days a t th e tim e o f h a r v e s t .
I n s e r i e s 2 , th e age o f th e p la n ts when th e inoculum was added t o th e
s o i l v a r ie d from z ero t o 30 d a y s, and th e age o f th e h a r v e s te d p la n ts
■'
"
v a r ie d from 35 t o 65 d a y s ,
The "beets i n a l l th e p o ts emerged f o u r t o f i v e days a f t e r p la n tin g ,
and re a d in g s o f th e number o f h e a lth y and d is e a s e d b e e ts b eg an on th e
day o f emergence and c o n tin u e d a t f iv e - d a y i n t e r v a l s u n t i l h a r v e s t .
At
th e tim e o f h a r v e s t, th e t o t a l number o f .h e a l t h y and d is e a s e d b e e ts was
re c o rd e d .
The r e s u l t s o b ta in e d i n th e s e t e s t s a re g iv e n i n t a b l e 3«
■ The f i r s t v i s i b l e symptoms o f th e d is e a s e ap p eared i n s e r i e s I
;
when th e b e e ts were a p p ro x im a te ly in th e same s ta g e o f g ro w th , r e g a r d le s s
o f th e age o f th e inoculum .
I t i s assumed t h a t th e te m p e ra tu re in th e
greenhouse p la y e d a v e ry im p o rtan t r o l e i n th e p a th o g e n ic ity o f E h izo c t o n i a in th e s e t e s t s .
The e x p erim en ts w ere begun May 15, 1952, and
te rm in a te d J u ly 19, 1952.
A c o a t o f w hitew ash had b een a p p lie d , t o th e .
greenhouse g la s s e a r l i e r i n May, b u t i t had b een washed o f f b y r a i n
ab o u t th e tim e th e e x p erim en ts were s t a r t e d .
W hitewash was sp ray ed on
th e greenhouse a g a in th e l a t t e r p a r t o f J u n e .
The te m p e ra tu re in th e
greenhouse d u rin g th e day th ro u g h o u t th e month o f May and e a r l y June
u s u a ll y exceeded 32® C and was o f te n above Ij-Oe C.
The te m p e ra tu re
d u rin g th e l a t t e r p a r t o f June and e a r l y p a r t o f J u ly .was somewhat l e s s
-3 6 -
th a n 32° C.
The grow th o f th e mycelium d e c re a se d v e ry r a p i d l y i n . c u l t u r e a t
te m p e ra tu re s above 29° C (F ig u re 2 ) .
I f th e e f f e c t s o f te m p e ra tu re on
th e grow th o f R h iz o c to n ia in c u ltu r e a re c o r r e la te d w ith th e grow th and
p a th o g e n ic i t y o f R h iz o c to n ia in th e s o i l , th e n i n s e r i e s I , when th e
g reen h o u se te m p e ra tu re was 32° C o r ab o v e, th e p ath o g en may have b e en in
a more o r l e s s dorm ant s t a t e and u n ab le t o i n f e c t th e s e e d lin g s t o any
g re a t e x te n t.
However, i t a p p e a rs t h a t th e fungus made some grow th, which-'
i s in d ic a te d b y th e t o t a l p e r c e n t o f d is e a s e d b e e ts shown i n t a b l e 3 «
T h is t o t a l p e r c e n t o f d is e a s e in s e r i e s I in d ic a te s t h a t on th o s e days
and n ig h ts when th e te m p e ra tu re o f th e g reen h o u se was 29° C o r l e s s , th e
fungus was a b le t o grow and i n f e c t th e b e e t r o o t s .
I n th e p re v io u s t e s t s in w hich th e s o i l was in o c u la te d w ith ■
R h iz o e to n ia , th e inoculum was mixed w ith t h e to p la y e r,- e n a b lin g th e
fungus t o grow i n a l l d i r e c t i o n s .
I n t h e p r e s e n t t e s t s , th e inoculum
was added t o th e s o i l s u r f a c e , and n o t mixed
w ith th e s o i l , e n a b lin g
th e fungus t o g r b w o n ly downward i n th e s o i l .
I n s e r i e s I , th e b e e ts
em erged th ro u g h th e inoculum , and i n s e r i e s 2 , w ith th e e x c e p tio n o f p o t
7 , th e inoculum was p o u red around t h e b e e t s .
I t was o f i n t e r e s t t o
n o te t h a t th e symptoms o f th e d is e a s e on th e b e e ts i n b o t h - s e r i e s was
n o t a t th e p o in t o f c o n ta c t betw een th e inoculum and th e b e e t s , b u t
s l i g h t l y below th e p o in t o f c o n ta c t.
I n s e r i e s I , many b e e ts showed
no v i s i b l e symptoms o f d is e a s e u n t i l h a r v e s te d , and o f te n th e le s io n s
were s e v e r a l m illim e te r s below th e s u rfa c e o f th e s o i l .
-3 7 -
I n s e r i e s 2 , i n w hich th e "beets v a r ie d in age from 0 t o 30 days a t
th e tim e th e s o i l was in o c u la te d , th e symptoms o f th e d is e a s e ap p eared
f i r s t on th e younger "b eets,
T his no doubt was in flu e n c e d "by th e c o o le r
greenhouse te m p e ra tu re s d u rin g th e l a t t e r p a r t o f June and e a r l y p a r t o f
J u l y , e n a b lin g th e fungus t o p e n e tr a te "below th e s o i l s u rfa c e and in c re a s e
e x te n s iv e ly "by v e g e ta tiv e g ro w th .
I t i s o f i n t e r e s t t o compare p o t I i n
s e r i e s I , and p o t 7 i n s e r i e s 2 .
I n each c a s e , th e inoculum was added a t
th e tim e o f p l a n t i n g , and th e "beets emerged th ro u g h th e inoculum .
The
d is e a s e symptoms a p p ea re d 12 days e a r l i e r i n p o t 7 , s e r i e s 2 , th a n i n
p o t I , s e r i e s I , g iv in g f u r t h e r in d ic a tio n t h a t te m p e ra tu re i s one of
th e m ain f a c t o r s t o c o n s id e r i n t e s t i n g th e p a th o g e n ic ity a n d .v iru le n c e
o f in d iv id u a l i s o l a t e s o f R h iz o c to n ia .
I n m ost c a se s i n w hich
th e b e e ts had n o t d ev elo p ed beyond th e
6 - l e a f s ta g e o f g row th, th e y , were more s u b je c t t o a t t a c k b y R h iz o c to n ia
th a n when th e y w ere beyond th e 6 - l e a f s t a g e .
When younger b e e ts a re
a tta c k e d and k i l l e d , th e f u r t h e r grow th o f R h iz o c to n ia i n t h e s o i l i s
a p p a r e n tly enhanced b y th e n u t r i e n t su p p ly fu r n is h e d b y th e dead s e e d lin g s .
The t o t a l p e r c e n t o f d is e a s e d b e e ts i n s e r i e s 2 a t th e tim e o f
h a r v e s t showed- t h a t th e b e e ts became somewhat r e s i s t a n t t o R h iz o c to n ia .
I n n e a r ly a l l in s ta n c e s , t h e o ld e r th e b e e ts a t th e tim e o f in o c u la tio n ,
t h e l e s s was th e t o t a l p e rc e n t o f d i s e a s e .
The age o f th e inoculum in"
th e s e t e s t s ap p eared t o have v e ry l i t t l e e f f e c t on th e tim e o f in f e c t i o n ,'
a s d if f e r e n c e i n age o f th e inoculum was o n ly 2 days when th e f i r s t
p la n te d i n s e r i e s 2 (p o t
l ) showed v i s i b l e symptoms o f i n f e c t i o n
b e e ts
-3 8 -
and when th e l a s t b e e ts p la n te d i n s e r i e s 2 (p o t 7 ) showed th e same '
symptoms o f damping o f f .
The r e s u l t s o f t h i s e x p e rim e n t, on -th e
w hole, show t h a t su g ar
b e e t s e e d lin g s a re s u b je c t t o a t t a c k a t an y "stage o f grow th and t h a t
in th e developm ent o f R h iz o c to n ia d is e a s e , th e age o f th e inoculum is
n o t as im p o rta n t as th e s ta g e o f grow th o f th e b e e ts in t h a t th e younger
b e e ts were more s u s c e p tib le t o d is e a s e th a n th e o ld e r o n e s .
T able 3«
Pot
Number ■
The e f f e c t s o f K h iz o e to n ia inoculum -of v a ry in g ag es oh h e e t s e e d lin g s ■in- d i f f e r e n t •'s ta g e s
o f g row th.
Age' o f Inoculum
a t P la n tin g
Days
. Number o f Days
A fte r Emergence
f o r A ppearance
o f Symptoms ■
Days
Age o f Inoculum
' a t A ppearance o f
F i r s t Symptom
Days
S e rie s I
I
2
3
4
5
6 7
O
5
10
15
20
25
30
30
26 .
30
28
30
30
24
35
36
45
48
55
60
.59
S e r ie s 2
I
. 2
3
4
' 5
6
7*
0
0
0
0
0
0
0
50
52 v
34
25
24
23
18
• 25
32
19
15
19
. 23
23
.
•
*The p o ts i n S e r ie s I. were in o c u la te d when p o t I was p la n te d .
- in o c u la te d when p o t 7 was p la n te d .
H arv est
Age o f
Age o f
Inoculum P l a n t s ■ D isease
Days
Days
Per cent
35
40
45
50
55
6o
65
35
35
35
• 35
35
35
35
35
35
35
35
35
35
35
65
60 •
55
50
45
4o
• 35
I n S e r ie s 2 , th e s o i l was
4 .3
1 2 .1
1 3 .0
1 3 .2
2 4 .0
1 7 .9
. 2 2 .5
7 -1
4 .7
2 0 .4
55 .9
79*4
5 8 .9 .
• 6l . l
—
I^O-
The A n ta g o n is tic E f f e c t o f O ther F u n g i on th e
P a th o g e n ic ity o f R h iz o c to n ia i n S o il
I t i s known t h a t p a th o g e n ic ity o f a c e r t a i n o rganism can he
m o d ifie d and d e c re a se d "by th e i n t e r a c t i o n o f v a rio u s o th e r o rg a n ism s.
To in v e s t ig a te th e p o s s i b i l i t i e s o f a n ta g o n i s tic a c tio n on th e p a th o ­
g e n i c i t y o f R h iz o c to n ia t o su g a r b e e t s e e d lin g s , s e v e r a l e x p erim en ts •
w ere c o n d u cte d .
Two a n tib io tic - p r o d u c in g f u n g i, S trep to m y ces g f ls g u s K fa in and
P e n ic illiu m notatum W e s tl., and
a l s o T richoderm a lig n o ru m (Tode) H a rz .,
w hich i s known t o be a n ta g o n is tic t o R . s o l a n i ( 3 4 ) , w ere t e s t e d a g a in s t
' th e v a rio u s i s o l a t e s o f R h iz o c to n la .i n
o f 1951- 5 2 .
th e g reenhouse d u rin g th e w in te r ,
F ifty " 6 -in c h c la y p o ts were f i l l e d w ith a i r - d r i e d s o i l and
s t e r i l i z e d a s m entioned above.. S u sp en sio n s o f each i s o l a t e o f R h iz o c to n ia
and o f each o f th e o th e r f u n g i t o b e t e s t e d f q r an tag o n ism t o R h iz o c to n ia
• « ••
w ere p re p a re d .
^•
.•
1
« .
,
.
.
1
.
1 *'
■
*. '
1
Each i s o l a t e o f R h iz o c to n la was th o ro u g h ly mixed w ith th e
to p la y e r o f s o i l i n
8 p o ts .
I n e ac h s e t o f 8 p o ts , i n a d d itio n t o
b e in g . in o c u la te d w ith th e p a r t i c u l a r i s o l a t e o f R h iz o c to n ia . 2 p o ts o f
s o i l w ere in o c u la te d w ith
w ith T l lig n o ru m .
gffilgbus ; 2 p o ts o f Pjl n o tatu m , and 2 p o ts
A s e t o f 8 s o i l p o ts was "also in o c u la te d w ith a s u s ­
p e n s io n o f m ixed c u ltu r e s o f R h iz o c to n ia and was t r e a t e d i n th e same manner
as ab o v e.
C o n tro ls c o n s is te d o f 2 p o ts o f s o i l in o c u la te d w ith o n ly
S l grfs& ns » 2 p o ts w ith P l notatu m , and 2 p o ts w ith T l lig n o ru m .
a d d itio n t o
In
th e s e c o n t r o l s , 2 p o ts o f s t e r i l e , n o n -in o c u la te d s o i l and
2 p o ts o f n o n - s t e r i l i z e d , n o n -in o c u la te d s o i l were u s e d .
Twenty segm ented
—
4 lse e d s w ere p la n te d , i n each p o t o f s o i l .
P e r io d ic re a d in g s o f th e number .
o f h e a lt h y and d is e a s e d s e e d lin g s were made o v er a p e r io d o f 6 w eeks,
a f t e r w hich tim e th e "beets w ere h a r v e s te d .
F in a l.r e a d in g s o f th e t o t a l
number o f b e e ts d is e a s e d w ere made a t th e tim e o f h a r v e s t.
As shown i n t a b l e 4 , a n ta g o n is tic e f f e c t t o R h iz o c to n ia was
e x h ib ite d b y T richoderm a i n a l l i n s ta n c e s .
The amount o f d is e a s e i n
th e
p o ts in o c u la te d o n ly w ith R h iz o c to n ia was S i , 8 2, 4 8 , 6 0, and $6 p e r c e n t,
r e s p e c t i v e l y , f o r i s o l a t e s I , 2 , 595> and 599/ and th e mixed inoculum .
When T , lig n o ru m was added i n a d d itio n t o th e c u ltu r e s o f R h iz o c to n ia ,
'
th e amount o f . d is e a s e d e c re a se d f o r e ac h i s o l a t e and th e m ixed c u ltu r e
b y 2 5 , 1 5 , l 6 , 8 , and 17 p e r c e n t r e s p e c t i v e l y .
The amount o f d is e a s e
was d e c re a se d more when T . lig n o ru m was added t o the. s o i l w ith i s o l a t e s
I , 599, and th e m ixed c u ltu r e o f R h iz o c to n ia th a n when i t was added w ith
i s o l a t e s 2 and 599*
I t would seem t h a t when a mixed .c u ltu re o f i s o l a t e s
o f R h iz o c to n ia was added t o th e s o i l t h a t th e combined p a th o g e n ic i t y o f
t h e i s o l a t e s w ould r e s u l t i n a n in c r e a s e i n t o t a l d is e a s e . T h i s , how ever,
was n o t th e c a se i n th e s e t e s t s . When i s o l a t e s I , 2 , and 599 were u sed
1
a s inoculum , th e t o t a l d is e a s e p e rc e n ta g e s were 6l , 82, and 60 r e s p e c t i v e 1
I y . The mixed c u ltu r e s produced s l i g h t l y l e s s d is e a s e th a n th e th r e e
above m entioned i s o l a t e s u sed s in g ly .
T h is i n d i c a t e s , th e n , t h a t a num•
b e r o f d i f f e r e n t s t r a i n s o f R h iz o c to n ia p r e s e n t i n th e s o i l c o u ld cause
1
l e s s R h iz o c to h ia d is e a s e o f s u g a r b e e ts th a n one s t r a i n t h a t w as.
h ig h ly v i r u l e n t and p a th o g e n ic .
I t was o b serv ed t h a t th e d eg ree o f an tag o n ism e x h ib ite d b y
T , lig n o ru m t o R h Iz o e to n ia i s o l a t e s 2 , 59 5 , and th e m ixed c u ltu r e s was
■- 4 2 -
n e a r ly th e same, ’o u t th e amount o f an tag o n ism e x e r te d to w a rd i s o l a t e
599 "was a b o u t o n e -h a lf t h a t o f th e above m entioned i s o l a t e s .
. a n ta g o n i s tic e f f e c t s o f T 0 lig n o ru m
The
to w ard i s o l a t e I was th r e e tim es
g r e a t e r th a n t h a t e x e r te d tow ard i s o l a t e 599, and ab o u t o n e - th ir d more
th a n th e a n ta g o n i s tic a c ti o n tow ard i s o l a t e s 2 , 595, and th e mixed
c u ltu re s e
I n p re v io u s t e s t s , i s o l a t e I was c o n s i s t e n t l y low i n v iru le n c e
a s compared t o th e o th e r i s o l a t e s , and i s o l a t e 599 was u s u a l l y h ig h i n
v ir u le n c e when compared t o th e o th e r i s o l a t e s »
T h e re fo re , th e s e r e s u l t s in d ic a te t h a t T . lig n o ru m e x e r ts a
s t r o n g e r . d e p re s s in g e f f e c t on R h iz o c to n ia i s o l a t e s o f low v ir u le n c e
th a n on i s o l a t e s w ith h ig h e r v ir u l e n c e .
The e f f e c t s o f P e n ic illiu m n o tatu m on th e developm ent o f R h iz o c to n ia
d is e a s e w ere v e ry e r r a t i c ,
P 0 notatum d e c re a se d th e amount o f d is e a s e
when in o c u la te d i n th e s o i l w ith i s o l a t e s I , 2 , and 595 b y p e rc e n ta g e s
o f 16, l 4 , and 10, r e s p e c t i v e l y , b u t w ith i s o l a t e 599? t h e amount o f
d is e a s e was in c re a s e d b y 12 p e r c e n t.
W ith th e mixed c u ltu r e o f
B h iz o c to n ia , P . notatum in c re a s e d th e amount o f d is e a s e o n ly 3 p e r c e n t.
I n th e c o n tr o l p o ts o f s o i l i n which, o n ly P . notatum was ad d ed , 3 p e r c e n t
o f th e b e e ts shewed symptoms o f some ty p e o f s e e d lin g d is e a s e somewhat
d i f f e r e n t fro m th e symptoms d e s c rib e d f o r R h iz o c to n ia d is e a s e = T h e re fo re
no c o n c lu s iv e r e s u l t s w ere o b ta in e d i n t h i s p a r t o f t h e . t e s t 0
The e f f e c t s o f S treptom yees g r i s e u s on th e in c id e n c e o f R h izo cto n ia^ .
d is e a s e w ere d i r e c t l y o p p o s ite t o th o s e o b ta in e d w ith Te lig n o ru m and
R h iz o e to n ia c u ltu re ,,
'The r e s u l t s o b ta in e d when S 0 g r is e u s and R h izo cto n ia-
-b3w ere in o c u la te d to g e th e r i n th e s o i l showed t h a t S„ g r is e u s in c re a s e d
th e amount o f d is e a s e o f th e . h e e ts b y p e rc e n ta g e s o f Il)., 13, 5, 12, and 9,
r e s p e c t i v e l y , f o r i s o l a t e s I , 2, 595; 599; and th e m ixed c u ltu r e o f
K h iz o c to n ia 0
A lthough t h i s t e s t i s to o r e s t r i c t e d t o a llo w an y c o n c lu s iv e
r e s u l t s so f a r a s P e n ic illiu m no tatu m and S trep to m y ees g r is e u s a re
c o n ce rn e d , i t in d ic a te s t h a t S 0 g r is e u s e s p e c i a l l y may i n some way
a i d th e p a th o g e n .
•4 4 -
The e f f e c t o f o th e r fu n g i on th e p a th o g e n ic ity o f
R h iz o c to n ia i n th e g re e n h o u se .
Es
T ab le 4 .
D iseased
T. i.a /
P. n >
S , g .s
—
56
42 .
49
4l .
36
23
12
16
20
19
37
25
6 4 .3
5 4.8
2 4 .5
3 9 .0
3 5 .7
4 5 .2
7 5 .5
6 1 .0
T. I .
P« n .
3 „; g »
49
47
58
56
16
15
3
10
33
32
55
46
3 2 .7
3 1 .9
5 .2
1 7 .9
6 7 .3
6 8 .1
9 4 .8
8 2 .1
T. I .
P. n.
S .* g 4
-
53
55
46
52
36
34
26
27
17
21
20
25
6 7 .9
6 1 .8
56.5
5 1 .9
32 .1
38 .2
4 3 .5
4 8 .1
T. I .
P . n.
S g»
56.
64
46
55
29
27
46
18
13 ■ 33
22
33
4 8 .2
2 8 .1
2 8 .3
4 o .o
51.8
7 1 .9 '
7 1 .7
6 0 .0
T. I ,
Po n .
So go
55
50
52
53
34 . 21
27
23
18
34
30
23
6 1 .8
4 6 .0
34.6
4 3 .4
38 .2
5 4 .d
6 5 .4
56.6
To Io
P. n.
Sg g «
-
54
.62
53
4?
54
60
52
47
57
19
T re a tinent
—
595
599
'Maximum1
S tan d
•
I
*
-
Mixed
c u ltu r e s
Check
Hon s t e r i l e
a / T richoderm a lignorum
b / P e n ic illlu m notatum
c / S treptom yees g r ie s u s
100.0
9 6 .8
2
I
98,. 1
-= 1 0 0 .0
38
3 3 .3
tie
3 .2
1 .9
6 6 .7
Per cent
D ecrease
H ealth y
2
D iseased
I
H ealth y
Is o la te
Humber
fieri+,
In c re a s e
P rt
oer
1
E tl
2 5 .3
1 5 .8
1 4 .5
l4 .8
,1 4 .0
1 2 .7
4 .6
1 6.0
9 .9
\
8 .2
1 1 .9
1 1 .7
18 .4
2 .6
8 .8
-4 5 -
The A n ta g o n is tic E f f e c t o f O ther F u n g i on B h iz o c to n ia i n O n ltn re
I n a d d itio n t o th e greenho u se t e s t s on th e a n ta g o n i s tic e f f e c t s
o f T richoderm a lig n o ru m , P e n ic illiu m n o tatu m , and S trep to m y ees g r is e u s
on th e p a th o g e n ic ity o f B h iz o c to n ia i n s o i l , lim ite d s tu d ie s o f s im ila r
n a tu r e w ere conducted i n th e la b o r a to r y , w here th e organism s w ere grown
on p o ta to d e x tro s e a g a r i n P e t r i d i s h e s .
On one s id e o f th e P e t r i d is h
c o n ta in in g th e a g a r , s m a ll p ie c e s of" B h iz o c to n ia mycelium w ere p la c e d .
S m all drops o f a s u sp e n sio n o f each o f th e o th e r fu n g i w ere p la c e d a t
o n e -h a lf in c h i n t e r v a l s a c r o s s th e c e n te r o f th e p l a t e .
O b se rv a tio n s
beg an a s soon a s th e B h iz o c to n ia mycelium came in to c o n ta c t w ith each
o f th e o th e r f u n g i.
I n th e p l a t e s c o n ta in in g mycelium o f B h iz o c to n ia and T l lig n o ru m ,
a n i n h i b i t o r y e f f e c t o f T^ lig n o ru m was e x h ib ite d tow ard th e
B h iz o c to n ia .
When th e hyphae o f th e two c u ltu r e s w ere a few m illim e te r s a p a r t , grow th
o f B h lz o e to n ia was sto p p e d . ' The mycelium o f ."T. lig n o ru m th e n grew over
th e mycelium o f th e B h iz o c to n ia and c o m p le te ly covered, th e a g a r in th e
P e t r i d is h .
The c u ltu r e s o f B h iz o c to n ia form ed a few s m a ll s c l e r o t i a ,
b u t a f t e r a few d a y s, th e s e s c l e r o t i a w ere a ls o co v ered w ith
mycelium and sp o re s o f T ^ lig n o ru m .
th e
A f te r t h e f i r s t c o n ta c t o f th e
mycelium o f T l lig n o ru m and B h iz o c to n ia , th e B h iz o c to n ia c o lo n y f a i l e d
t o a t t a i n f u r t h e r r a d i a l grow th i n th e a g a r .
I n th e p l a t e s o f a g a r c o n ta in in g P l notatum and B h iz o c to n ia , no
i n h i b i t o r y e f f e c t such as was m entioned above was o b se rv e d .
In s te a d
th e B h iz o c to n ia c u ltu r e a p p ea re d t o slow down th e grow th o f th e
P . Etotatum-
T his was soon fo llo w e d "by an in te rm in g lin g o f th e hypha o f
t h e two c u l t u r e s .
A few d ay s a f t e r th e f i r s t c o n ta c t, th e R h iz o c to n ia
c u ltu r e ap p eared t o grow ov er th e m ycelium o f th e P*_ n o tatu m e x ce p t where
a dense c o n c e n tr a tio n o f P i notatu m sp o re s was a cc u m u la te d .
The r e s u l t s
o f t h i s p a r t o f th e t e s t in d ic a te d t h a t so f a r as a n tag o n ism t o R h izo ct o n i a i s c o n ce rn e d ,
P . notatu m i s more o r l e s s n e u t r a l , • showing n e ith e r
a n ta g o n i s tic n o r " b e n e fic ia l e f f e c t s .
When th e R h iz o c to n ia mycelium came
i n t o c o n ta c t w ith th e c u ltu r e s
o f S treptom yces g r 'i s . e u s th e r e s u l t s w ere d i f f e r e n t from th e two above
m entioned t e s t s .
The R h iz o c to n ia c u ltu r e s p ro duced d en se a e r i a l hypha
a t th e f i r s t c o n ta c t.
c u ltu r e s o f Si gffi.is'eus.
T h is a e r i a l hypha a p p ea re d t o su rro u n d th e
T h is was q u ic k ly fo llo w ed , "by th e p ro d u c tio n o f
s m a ll R h iz o c to n la s c l e r o t i a a t
Two t o
th e p e rim e te r o f th e Si g r ls e u s c u l t u r e s .
th r e e days l a t e r , R h lz o c to n ia mycelium was o b serv ed growing over
th e c u ltu r e s o f
Si gftffigjgMSo ■
■■ "•
I
These r e s u l t s in d ic a te d t h a t a s tim u la tin g e f f e c t was a t f i r s t
p ro d u ced b y th e
g ro w th .
Si j ^ l s e u s tow ard R h iz o c to n ia , c a u sin g th e r a p i d a e r i a l
Yet th e fb rm atio n o f s c l e r o t i a b y th e R h iz o c to n ia c u ltu r e s
in d ic a te s t h a t S . gli-lsep-S produces a c o n d itio n u n fa v o ra b le t o ■R h iz o c to n ia .
The grow th o f th e R h iz o c to n ia m ycelium o v er t h e S_. g r ts o u s c u l t u r e s ,
how ever, showed t h a t Si g r l s e u s , i f a n ta g o n i s tic t o R h iz o c to n ia a t a l l ,
d id n o t rem ain a n ta g o n i s tic a f t e r a few d a y s.
.
-h j-
GEHERAL DISCUSSION AND CONCLUSIONS
The s e r i e s o f ex p erim en ts w ith s e v e r a l c u ltu r e s o f E h iz o c to n ia
s o la n i were u n d e rta k e n i n an a tte m p t t o o b ta in a c l e a r e r p i c t u r e o f th e
c au se s o f v a r i a t i o n s o f R h iz o c to n ia d is e a s e o f b e e ts i n th e f i e l d .
. The m icroorganism s t h a t in h a b it th e s o i l a re e x tre m e ly numerous
and d iv e r s e , and any s tu d y t h a t in c lu d e s th e s o i l and any o r a l l o f i t s
in h a b ita n ts in c re a s e s th e c o m p le x ity 'o f t h a t s tu d y .
Predom inate d e v elo p ­
ment o f p a r a s i t i c o r s a p ro p h y tic groups o f m icroorganism s i s l a r g e ly
dependent upon th e p re d is p o s in g c o n d itio n s w hich f a v o r grow th o f one or
a n o th e r group of m ic ro o rg a n ism s.
The o ccu rren c e o f s t r a i n s o f R h iz o c to n ia d i f f e r i n g i n v iru le n c e
and p a th o g e n ic ity
on th e same o r on d i f f e r e n t h o s ts te n d s t o c o m p licate
th e s tu d y of th e e f f e c t s o f th e p re d is p o s in g f a c t o r s on th e p a th o g e n ic ity
o f th e o rg an ism .
Any one p a th o g en may c r e a te ep idem ics i n a g iv e n a r e a ,
o r c o m p e titio n from th e o th e r m icroorganism s m ig h t’re d u c e " th e p ath o g en
co ncerned t o a s t a t e o f l i t t l e economic im p o rtan c e .
The p o s s i b i l i t y o f
s e lf -a n ta g o n is m o f a p a th o g en a f t e r th e p ro d u c tio n o f an epidem ic can
h a r d ly be o v e rlo o k e d .
T h is s e lf -a n ta g o n is m may e x p re ss i t s e l f i n the.
form o f a s t a l l i n g e f f e c t o r a d e p le tio n o f th e n u t r i e n t s i n th e ' s o i l
f■
.
. .
r e s u l t i n g i n s t a r v a t i o n o f th e p a th o g en and th e r e f o r e a d e c re a se in i t s
num bers.
F lu c tu a tio n s o f environm ental- f a c t o r s , f o r exam ple, te m p e ra tu re
and m o is tu re , a r e e x tre m e ly im p o rta n t i n d e te rm in in g th e predom inance
o f any one m icroorganism a t any tim e .
I
-4 8 -
I n a l l th e e x p erim en ts conducted i n t h i s s tu d y , th e s o i l was
d is i n f e c t e d "by steam s t e r i l i z a t i o n , and presum ably a l l o r n e a r ly a l l
th e s o i l m icroorganism s w ere d e stro y e d i n th e s t e r i l i z a t i o n p r o c e s s ,
th e r e b y e lim in a tin g th e c o m p e titiv e f a c t o r o f s o i l organism s from th e
p ic tu re .
T h e re fo re , te m p e ra tu re and m o is tu re and c e r t a i n s e le c te d
b i o l o g i c a l t e s t s were employed as th e v a r ia b le f a c t o r s w hich co u ld
in flu e n c e th e amount o f R h iz o c to n ia d is e a s e on
su g a r b e e t, s e e d lin g s ,
s in c e th e amount o f inoculum o f R h iz o c to n ia added, t o each f l a t was th e
sam e.
V ery d e f i n i t e r e s u l t s were o b ta in e d when th e b e e ts w ere grown
u n der c o n tr o lle d c o n d itio n s a t te m p e ra tu re s o f 15° and 25° C and m o istu re
l e v e l s o f 55> 70, and 85 p e r c e n t TMHC« At 15° C th e p e r c e n t d is e a s e
f o r th e i n d i v i d u a l - i s o l a t e s rem ained n e a r ly c o n s ta n t, r e g a r d le s s o f - th e
m o is tu re l e v e l m a in ta in e d i n th e s o i l .
The
amount o f d is e a s e as caused
b y i s o l a t e I d e c re a se d I p e r c e n t each tim e th e m o istu re l e v e l was
in c re a s e d b y 15 p e r c e n t TMHC.
The a v e ra g e amount o f d is e a s e a s caused
b y i s o l a t e s 2 , 595; and 599; computed c o l l e c t i v e l y , in c r e a s e d ab o u t 3
p e r . c e n t i n each case when th e m o is tu re l e v e l was in c re a s e d b y 15 p e r c e n t
TMHC.
When i s o l a t e s 595 and 599 w ere u sed as" inoculum , th e amount o f
d is e a s e a t 25° C was o v er two tim e s t h a t produced a t 15° C.
T his
p r o p o r tio n a te in c re a s e i n th e amount o f d is e a s e o c c u rre d a t a l l m o istu re
le v e ls .
W ith i s o l a t e s I and 2 , th e in c r e a s e o f d is e a s e a t 25° C as
compared w ith t h a t a t 15® C was c o n s id e ra b ly l e s s th a n th e above
p r o p o r tio n w ith i s o l a t e s 595 and 599«
When th e "beets were grown i n s o i l in o c u la te d w ith i s o l a t e I o r 2,
th e a v erag e w eig h t p e r p l a n t and th e a v erag e le n g th o f th e to p s o f th e
"beets were much l e s s th a n when i s o l a t e s 595 o r 599 "were u sed as th e
inoculum i n th e s o i l .
Whenever th e i s o l a t e s o b ta in e d fro m s e e d lin g "beets w ere u sed i n
th e s e t e s t s , th e p e r c e n t o f m o r t a l i t y o f b e e ts a t th e tim e o f h a rv e s t
was more th a n when i s o l a t e s I and 2 , w hich were o b ta in e d from m atured
b e e t s , w ere u sed a s th e inoculum .
On th e b a s i s o f th e r e s u l t s o b ta in e d i n th e s e te m p e ra tu re and
m o is tu re s t u d i e s , i t seems p l a u s i b l e t o assume t h a t some s t r a i n d i f ­
f e r e n t i a t i o n may e x i s t betw een th e i s o l a t e s o b ta in e d from s e e d lin g
b e e ts and th o s e o b ta in e d from m atu re b e e t s , and t h a t i s o l a t e s from th e
s e e d lin g s a re more a p t t o a t t a c k o th e r b e e t s e e d lin g s i n a manner more
s e v e re
th a n w i l l i s o l a t e s o b ta in e d fro m m ature b e e t s .
The f ig u r e s o b ta in e d i n th e s e t e s t s have a ls o in d ic a te d t h a t
s o i l te m p e ra tu re was more o f a d e c id in g f a c t o r i n c r e a tin g c o n d itio n s
\
*.
f a v o ra b le t o R h iz o c to n ia d is e a s e o f b e e ts th a n was m o is tu r e .
I n th e ex p erim en t d e a lin g w ith th e e f f e c t o f inoculum o f v a ry in g
a g es on b e e ts i n d i f f e r e n t s ta g e s o f g ro w th , th e r e s u l t s ' o f th e e x p e r i­
ment sh o w e d .th a t b e e ts a r e s u b je c t t o a t t a c k b y R h iz o e to n ia a t any s ta g e
o f g ro w th .
These r e s u l t s a ls o in d ic a te d t h a t th e o ld e r th e b e e ts a t th e
tim e o f in o c u la tio n , th e l e s s was th e t o t a l p e rc e n ta g e o f d is e a s e d b e e ts
I n t h i s t e s t a s w e ll a s i n th e p re v io u s t e s t w ith te m p e ra tu re and
-5 0 -
m oisture.., th e r e l a t i o n o f te m p e ra tu re t o th e fungus i n c u ltu r e
c lo s e ly
p a r a l l e l e d t h a t i n s o i l e i t h e r i n th e g reen h o u se o r i n th e c o n tr o l
cage.
'
C o n clu siv e e v id en c e was o b ta in e d t h a t a n ta g o n is tic e f f e c t s
e x h ib ite d tow ard R h iz o c to n ia b y T richoderm a lig n o ru m .
a re
T_. Iisn o ru m d e ­
c re a s e d th e amount o f R h iz o c td n ia d isea se i n a l l th e t e s t s
b y an
o v e r - a l l a v erag e o f 1 6 .5 p e r c e n t.
Ho c o n c lu s iv e r e s u l t s were o b ta in e d when P e n ic illiu m notatum
and R h iz o c to n ia c u ltu r e s were in o c u la te d i n th e same p o ts o f s o i l .
W ith
some i s o l a t e s o f R h iz o c to n ia , th e a d d itio n o f P_. n o tatu m in c re a s e d th e
amount o f d is e a s e , and w ith th e o th e r i s o l a t e s , th e amount was d e c re a se d .
I n no way d id S treptom yces g r i s e u s show any a n ta g o n i s tic e f f e c t
to w ard R h iz o c to n ia i n th e greenh o u se t e s t s .
I t seems t h a t th e a d d itio n
o f §_. g r is e u s t o s o i l in o c u la te d w ith R h iz o c to n ia c u ltu r e s had some
te n d e n c y t o in c r e a s e th e in c id e n c e o f th e d is e a s e .
la b o r a t o r y t e s t s showed t h a t T . Iig norum e x h ib ite d a n t a g o n i s t i c '
e f f e c t s to w ard R h iz o c to n ia c u l t u r e s .
P a n o tatu m ap p eared t o b e n e u tr a l
So f a r a s antagonism to w ard R h iz o e to n ia was co n cern ed .
The t e s t s w ith
R h iz o c to n ia and S_. g r is e u s i n c u ltu r e a t f i r s t showed a s l i g h t s tim u la ­
t i o n , b u t l a t e r no b e n e f i c i a l o r a n ta g o n i s tic e f f e c t s w ere n o te d .
The o c cu rren c e o f R h iz o c to n ia d is e a s e o f su g ar b e e t s i n F ie ld
O -II a t th e H u n tle y S t a t i o n d u rin g th e y e a rs 1948 t o 1952 g iv e s conr
e lu s iv e e v id en c e t h a t s u f f i c i e n t amounts o f R h iz o c to n ia inoculum t o
produce epidem ics o f th e d is e a s e h as b e e n p r e s e n t i n th e s o i l d u rin g
'
-5 1 -
th e s e y e a r s .
D uring 19^9 t h i s d is e a s e was so s e v e re t h a t th e "beets were
n o t h a rv e s te d i n th e f a l l .
The u s u a l tr e n d o f te m p e ra tu re d u rin g th e grow ing se a s o n a t th e
H u n tle y S t a t i o n i s a c o o l s p r in g , a h o t summer, and a warm f a l l . A ccord♦
in g t o th e s o i l te m p e ra tu re re c o rd s o b ta in e d from th e H u n tle y S t a t i o n ,
th e summer o f 19^9 was c o n sid e re d a c o o l one i n
com parison t o th e summers
p re v io u s t o 1949# and th e summers fo llo w in g 1949«
These re c o rd s showed
t h a t th e n o rm a lly " h o t" p e rio d d id n o t d e v e lo p , a lth o u g h warm w e ath e r d id
o ccu r d u rin g th e m id d le o f th e summer.
The s e e d lin g "beets in t h a t a re a seldom e x h ib it any v i s i b l e symptoms
o f E h iz o c to n ia d is e a s e from th e tim e o f emergence up t o th e tim e o f
V -V
th i n n i n g .
F ig u re 2 showed t h a t a t 10° t o 15° G, th e grow th o f th e fungus
'
i n c u ltu r e was slo w .
I n t a b l e 2 i t was shown t h a t th e amount o f I n f e c t i o n
i s c o n s id e ra b ly l e s s a t 15^ G th a n a t 2 5 ° G.
"T herefore, la c k o f d is e a s e
symptoms on t i e s e e d lin g s i n th e f i e l d i n th e s p rin g i s p ro b a b ly due t o
th e low te m p e ra tu re s a t t h a t tim e .
The t e s t s in! th e c o n tr o l cage a t
150 c showed, how ever, t h a t many ,o f th e b e e ts t h a t a p p ea re d h e a lth y had
s m a ll d a rk le s io n s n e a r th e b a se o f th e m ain t a p r o o t , and some
s m a ll r o o t l e t s a ls o showed s ig n s o f i n f e c t i o n .
of th e
I t seems p la u s i b le to
assum e, th e n , t h a t i n s p i t e o f c o o l w e a th e r e a r l y in th e s e a s o n , in f e c t i o n
may ta k e p la c e d u rin g t h i s p e r io d o f g ro w th .
As s p rin g e x te n d s in to e a r l y summer,
th e days become lo n g e r and
:;
t h e te m p e ra tu re becomes c o n s i s t e n t l y h ig h e r th a n i t was e a r l y i n .th e
season.
As in d ic a te d i n
f ig u r e 2 , th e r a t e o f grow th o f th e fungus
Iv .
.
•- 5 2 -
i n c u ltu r e in c re a s e d r a p i d l y when th e te m p e ra tu re was in c re a s e d above
15° G.
A h ig h e r te m p e ra tu re ra n g e i s a ls o more fa v o ra b le f o r e x te n s iv e
v e g e ta tiv e grow th o f th e fungus in th e s o i l .
T able 2 showed t h a t an
in c re a s e i n te m p e ra tu re r e s u l t e d i n a marked in c re a s e i n th e in c id e n c e
o f d is e a s e , b u t t a b l e 3 showed t h a t when inoculum comes i n t o c o n ta c t
w ith b e e ts beyond th e 6 - l e a f s ta g e o f g ro w th , .p a r a s itis m o f R h iz o e to n ia
t o th e b e e ts became in c r e a s in g ly more d i f f i c u l t and th e b e e ts were a b le
t o s u s t a i n th em selv es c o n s id e ra b ly lo n g e r , even th ough th e y w ere in f e c te d
w ith R h iz o c to n ia .
I t i s th o u g h t t h a t th e m ajor p a r t o f R h iz o e to n ia i n ­
f e c t i o n p ro b a b ly occurs d u rin g t h i s p e r io d o f e a r l y summer.
th e b e e ts may w i l t and d ie a t t h i s tim e , how ever.
o f . t h i s d is e a s e depends l a r g e l y on
A few o f
A f u r t h e r p ro g re s s
a co m b in atio n o f e n v iro n m e n ta l
c o n d itio n s fa v o ra b le t o t h i s d i s e a s e .
As th e summer becomes more p ronounced, more, o f th e b e e ts in th e
f i e l d b e g in t o show th e symptoms o f R h iz o c to n ia . d i s e a s e T h e te m p e ra ­
t u r e s a t th is - tim e o f y e a r o f te n become v e ry h o t, and w ith th e s h o r t
n ig h ts th e r e i s o n ly a b r i e f c o o lin g o f f p e r io d .
The e x tre m e ly h o t
te m p e ra tu re s a t t h i s tim e may a id somewhat i n keeping th e fungus in
c h ec k .
F ig u re 2 showed t h a t th e grow th o f th e fungus d e c re a se d s h a rp ly
when th e te m p e ra tu re was above 29° C.
S e r ie s I in t a b l e 3 in d ic a te d
t h a t e x c e e d in g ly h o t g reenhouse te m p e ra tu re s d e c re a se d th e tim e o f
i n f e c t i o n as w e ll as th e t o t a l amount o f d is e a s e oh b e e t s .
A lthough th e s o i l te m p e ra tu re a few in c h es below t h e s u rfa c e may
be c o n s id e ra b ly l e s s than- t h a t a t th e s u r f a c e , t h i s in te n s e h e a t i n th e
-5 3 -
m iddle o f th e swmier may i n h i b i t th e fu n g u s fro m a tta c k in g t h e l e a f
p e t i o l e s and crown o f th e b e e t s .
As. th e t r e n d o f w e ath e r c o n d itio n s e x ten d s in to l a t e summer and
e a r l y f a l l , re d u c e d te m p e ra tu re s and s h o r te r days o c c u r„ The in c id e n c e
o f w i l t i n g and dying o f b e e ts d u rin g t h i s p e r io d a p p ea rs t o in c r e a s e .
A t th e tim e o f .h a r v e s t , some o f th e b e e ts may b e dead and many o f them
■
a re p a r t i a l l y in fe c te d .
The c o o l.te m p e ra tu re s d u rin g th e grow ing se a so n o f 19^9 su g g e st
t h a t environm ental, c o n d itio n s t h a t y e a r w ere fa v o ra b le f o r th e develop^
ment o f a s e v e re o u tb re a k o f E h iz o c to n ia
H u n tle y S t a t i o n .
d is e a s e o f s u g a r b e e ts a t th e
The s e v e re case o f r o t t i n g and
dying o f b e e ts d u rin g
th e l a t t e r p a r t o f A ugust in d ic a te s t h a t th e e n v iro n m e n ta l c o n d itio n s
t h a t fa v o re d th e o u tb re a k o f th e d is e a s e rem ained so th ro u g h o u t most, o f
th e grow ing s e a s o n .
These e n v iro n m e n ta l c o n d itio n s t h a t a p p ea re d to
f a v o r th e grow th o f R h iz o c to n ia and th e developm ent of t h i s d is e a s e
on s u g a r b e e ts p ro b a b ly w ere u n fa v o ra b le t o th e developm ent o f a n ta g o n is tic
m irco o rg an ism s, w hich u n d er d i f f e r e n t e n v iro n m e n ta l c o n d itio n s , may h o ld
t h i s d is e a s e i n check.
SUMMARY
The e f f e c t o f te m p e ra tu re and m o istu re , and o f c e r t a i n b io lo g ic a l
f a c t o r s on th e p a th o g e n ic ity o f R h iz o c to n ia s o la n i Kuhn t o su g a r b e e t
s e e d lin g s was s tu d ie d .
These t e s t s w ere co n d u cted i n a c o n tr o l cage
and i n the g re e n h o u se , u s in g a r t i f i c i a l l y in o c u la te d h eav y c la y loam
s o i l o b ta in e d from th e H u n tley B ranch S t a t i o n , H u n tle y , M ontana.
T h is seal
-5 k -
had a t o t a l m o is tu re h o ld in g c a p a c ity o f 3 8 .3 p e r c e n t.
A s ta n d a rd i s o l a t i o n p ro c e d u re was employed t o o b ta in s i x
R h iz o c to n ia i s o l a t e s from m atured and s e e d lin g b e e t s .
P a th o g e n ic i t y
o f th e s i x i s o l a t e s was e s ta b lis h e d on su g a r b e e t s e e d lin g s i n th e
g re e n h o u se .
On th e b a s i s o f v ir u le n c e and t o t a l p e r c e n t d is e a s e
p ro d u c e d .o n th e b e e t s , fo u r o f th e s i x i s o l a t e s w ere s e le c te d f o r f u r t h e r
s tu d ie s .
Two. o f th e i s o l a t e s were o b ta in e d from m atured b e e t s ; th e o th e r
two w ere 'o b ta in e d from b e e t s e e d lin g s .
Minimum grow th o f th e i s o l a t e s i n c u ltu r e o c c u rre d n e a r IO0 C.
The optimum te m p e ra tu re f o r grow th o f th e s e i s o l a t e s was a t 29° C, and
grow th c e a se d a t a te m p e ra tu re n e a r 40° C »
■ S o i l te m p e ra tu re s o f 15° and 2. 5 °. C and m o is tu re l e v e l s o f 55> 70*
and 85 per. c e n t o f th e t o t a l m o istu re h o ld in g c a p a c ity w ere u sed t o t e s t
th e p a th o g e n ic i t y o f th e i s o l a t e s i n a c o n tr o l c ag e .
R h iz o c to n ia d is e a s e was pro d u ced on th e b e e ts a t b o th te m p e r a tu r e s ,
and a t a l l m o istu re l e v e l s , b u t more d is e a s e was p ro d u ced a t 25° th a n
a t 15® C.
The m o istu re l e v e l o f th e s o i l had l e s s e f f e c t On th e in c id e n c e
o f R h iz o c to n ia d is e a s e th a n d id te m p e r a tu r e .
I s o l a t e s o b ta in e d from s e e d lin g b e e ts p ro d u ced more d is e a s e a t
b o th te m p e ra tu re s and a t a l l m o istu re le v e l s th a n d id i s o l a t e s o b ta in e d
from m atured b e e t s .
The a v erag e w eig h t p e r p la n t and t h e av erag e le n g th o f to p s were
s m a lle r when th e i s o l a t e s o b ta in e d fro m s e e d lin g b e e fs w ere u sed as
inoculum , th a n w ith i s o l a t e s , o b ta in e d from m atu red b e e t s .
-5 5 -
Yoxmg b e e ts w ere more s u s c e p tib le t o a t t a c k b y R h iz o c to n ia th a n
w ere b e e ts a t th e 6 - l e a f s ta g e o f grow th o r beyond.
' The age o f th e inoculum had no e f f e c t on th e tim e r e q u ir e d f o r
R h iz o e to n ia t o i n f e c t th e " b e e ts .
T richoderm a lig n o ru m d e c re a se d th e amount o f d is e a s e on b e e ts
when in c o rp o ra te d i n th e s o i l w ith th e i s o l a t e s o f
R h iz o c to n ia .
In
c u l t u r e , T^ lig n o ru m e x h ib ite d a n ta g o n i s tic e f f e c t s to w ard R h iz o e to n ia
c u ltu re s .
P e n ic illiu m notatum was n o t o b serv ed t o have any e f f e c t on
th e p a th o g e n ic ity o f R h iz o e to n ia in
s o il te s ts .
Ho a n ta g o n is tic a c ti o n
t o R h iz o c to n ia was shown b y I\_ n o tatu m i n c u ltu r e t e s t s .
The p a th o g e n ic ity
o f R h iz o c to n ia i s o l a t e s t o su g a r b e e ts a p p ea re d t o be in c re a s e d when
th e s o i l was in o c u la te d w ith th e R h iz o c to n ia i s o l a t e s and S treptom yces
g ris .e u s «, Ho c o n c lu s iv e r e s u l t s w ere o b ta in e d in c u ltu r e t e s t s w ith
R h iz o c to n ia and S ^ g r i s e u s *
-5 6 -
LITEEATURE CITED,
I.
A fa n a sie v , M. M= 1948 The r e la t io n o f s i x groups o f fu n g i to
s e e d lin g d is e a s e s o f sugar b e e ts in Montana. Phytopath. 38,
205-2 1 2 .
2=
A lexander, L. J . , H. C. Young, and C= M= Kiger= 1932 Causes
and c o n tr o l o f damping o f f o f tomato s e e d lin g s . Phytopath. 22,
3.
■
3 = A rk, P e te r A. and R o b ert S . D ick ey . 1950 A m o d if ic a tio n o f th e
Van Tiegham c e l l f o r p u r i f i c a t i o n o f c o n tam in ated fu n g u s c u l t u r e s .
Phyfcopath. 4 0, 389-399•
•4«
B u c h h o ltz , W. F . 1937 A s e v e re c ase o f R h iz o c to n ia r o o t r o t o f
su g a r b e e ts a f t e r p o ta to e s . P h y to p a th . 2 7 , I l 8 0 - l l 8l=
5,
Coons, G-. H= and Dewey S te w a rt 1927 P re v e n tio n o f s e e d lin g d is e a s e s
o f su g a r b e e t s . Phyfcopath= r £ , 259-296.
.6 .
D iachun,. S te p h e n 1939, The e f f e c t o f some s o i l f a c t o r s on P e n i c i l Iium in j u r y o f c o rn s e e d lin g s . Phyfcopath. 2 9 , 231-241.
7.
D uggar, B . M. 1915 R h iz o c to n ia crocorum (P e rs ) DC and R_^ s o la n i
Kuhn ( Corticum vagum B and Cj w ith n o tes on other s p e c ie s .
Ann. Mo. B o t. Gard= 2 , 4 0 3-458. ■
8.
E dson, H. A= 1915 S e e d lin g d is e a s e s o f s u g a r b e e ts and t h e i r
r e l a t i o n t o r o o t r o t and crown r o t . J o u r . A gr. R e s. 4 , 135-168 =
9.
E x n er, B e a tr ic e and S . J= P= C h ilto n 1943 V a r ia tio n i n s in g le
B a s id io s p o re c u ltu r e s o f R h iz o c to n ia s o l a n i . Phyfcopath. 33; 3«
10.
G oss, R= W= 1923 R e la tio n o f environm ent and o th e r f a c t o r s to
p o ta to w i l t cau sed b y F u sariu m oxysporum. Keb = A g r. E xp.
S t a . R e s . B u l. 23=
11.
H a r te r , L . L . 1916 R h iz o e to n ia and S c le ro tiu m r o l f s i i on sweet
p o ta to e s = Phyfcopath= 6 , 305-306.
12=
H ouston, B. R= 1945 C u ltu re ty p e s and p a th o g e n ic ity o f i s o l a t e s
o f C orticum s o l a n i . Phybopath= 35 ; 371-393*
13.
K oti l a , John E„ 1947 R h iz o c to n ia f o l i a g e b l i g h t o f s u g a r b e e ts '.
Jour= A g r. R es. %4, 289-314.
14.
L each, L= D= 1940 In flu e n c e o f t h e p a th o g e n , e n v iro n m en t, and
h o s t re s p o n se on th e e f f i c a c y o f s e e d tre a tm e n t w ith su g ar
-5T "beets and some v e g e ta b le c r o p s .
P h y to p a th - 30, 7 8 8 .
15-
L eC lerg , E„ L« 193^ P a r a s itis m o f R h iz o c to n ia s o la n i on su g ar
b e e t s . J o u r . A gr. R es. h-9, 407-431*
16 .
L eC Ierg , E . L . 1938 F u r th e r s tu d ie s on th e p a r a s i t i s m o f
R h iz o c to n ia s o la n i on s u g a r b e e t s . P h y to p a th . 2 8 , 152-153«
17.
L eC Ierg, E . L . 1941 P a th o g e n ic i t y s tu d ie s w ith i s o l a t e s o f
R h iz o e to n ia s o la n i o b ta in e d from p o ta to and s u g a r b e e t .
P h y tq p a th . 31, 4 9 -6 1 . .
18.
L eC Ierg, E . L . 1941 Com parative, s tu d ie s o f s u g a r b e e t and
p o ta to i s o l a t e s o f R h iz o c to n ia s o l a n i . P h y to p a th . 31» 274-278.
19.
M atsumoto, T a k a sh i 1921 S tu d ie s i n th e p h y s io lo g y o f th e
f u n g i X II P h y s io lo g ic a l s p e c i a l i z a t i o n i n R h iz o c to n ia s o la n i
Kuhn. Ann. Mo. B o t. C ard . 8 , 1 -6 2 .
2 0.
M o n te ith , John J . and A rnold 8 . D ahl 1928 A com parison o f some
s t r a i n s o f R h iz o e to n ia s o la n i i n c u l t u r e . J o u r...Agr.. R es.
36, 897-903.
21.
M o rris , H. E . and M. M. A fa n a sie v 1945 Sugar b e e t d is e a s e s and
t h e i r c o n tr o l i n M ontana. Mont. A g r. Exp. S t a . B u i. 427*
22.
P e l t i e r , George L . 1916 P a r a s i t i c R h iz o e to n ia s i n A m erica.
111. A g r. Exp. S t a . B u i. 1 8 9 .
23.
P e rs o n , L . H. 1944 P a r a s itis m o f R h iz o c to n ia s o l a n i ' o h b e a n s .
P h y tq p a th . 34, IO56-IO6 8 .
24.
R ic h a rd s , B . L . 1921 P a th o g e n ic ity o f C orticum vagum on th e
p o ta to a s a f f e c t e d b y s o i l te m p e ra tu re . J o u r . A g r. R es. 21,
459-482.
25.
R ic h a rd s , B . L . 1923 S o i l te m p e ra tu re a s a f a c t o r a f f e c t i n g
th e p a th o g e n ic i t y o f C ortieum vagum on th e p e a and th e b e a n .
Jour. A g r. R e s . 2 £, 431-450.
26.
R o th , L . F . and A. J . R ik e r 1942 The in flu e n c e o f te m p e ra tu re ,
m o is tu re , and s o i l r e a c t i o n on damping o f f . o f r e d p in e by
P vthium and R h iz o c to n ia . P h y to p a th . 32j 15- 1 6.
27.
S a n fo rd , G. B . 1938 S tu d ie s on R h lz o c to n ia s o la n i Kuhn. I l l •
R a c ia l d if f e r e n c e s i n p a th o g e n i c ity . Can. J o u r . R e s. S e c . C. l 6 ,
53-64.
-JjS28.
S a n fo rd , G „ B . 1941 S tu d ie s on R iiiz o c to n ia s o la n i Kuhn. V
V iru le n c e i n steam s t e r i l i z e d and n a tu r a l s o i l . Can. J o u r.
R e s. S e c . C 1 9, 1^8.
29.
S a n fo rd , G. B . 1938 S tu d ie s on R M z o c to n ia s o la n i Kuhn. IV E f f e c t
o f s o i l te m p e ra tu re and m o is tu re oh v ir u l e n c e . Can. J o u r . R e s.
S e c . C l £ , 203-213.
30.
S to r e y , I . F . 1941 A com p arativ e s tu d y o f s t r a i n s o f R h iz o c to n ia
s o la n i w ith s p e c i a l r e f e r e n c e t o t h e i r p a r a s iti s m . Ann. A p p l.
B i o l . 28, 219- 2 2 8 . 1
31.
T i l f o rd , P a u l E , . and H. C. Young 1944 S e e d lin g d is e a s e s o f su g ar
"beets i n O hio. P h y to p a th . 34, 1012.
3 2.
T im s, E.. C. 1932 An A ctinom ycete a n ta g o n is tic t o a Pyfchium r o o t
p a r a s i t e o f s u g a r c a n e . Phyfcopath. 2 2 , 2 7 .
33»
W alker, M. H. 1928 S o i l te m p e ra tu re s tu d ie s w ith c o tto n I I I '
R e la tio n o f s o i l te m p e ra tu re and s o i l m o istu re t o th e s o re s h in
d is e a s e o f c o tto n . F l a . A g r. Exp. S t a . B u i. 197«
34.
W ein d lin g , R . 1932 T richoderm a lig n o ru m a s a p a r a s i t e o f
o th e r s o i l f u n g i. P hyb o p ath . 22, 837-84$.
3$.
W ein d lin g , R. 1934 V a rio u s f u n g i r e c e n t l y fo u n d t o h e p a r a s i t i c
on R h iz o c to n ia s o l a n i . Phyfcopath. 24, l l 4 l .
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