Effect of sterol-biosythesis inhibiting fungicides on take-all of spring wheat caused by
Gaeumannomyces graminis var. tritici
by Celsa Garcia
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Plant
Pathology
Montana State University
© Copyright by Celsa Garcia (1986)
Abstract:
Take-all of wheat caused by Gaeumannomyces graminisis var. tritici (Ggt) is a very important root rot
disease of wheat around the world. In Montana it is prevalent in irrigated spring wheat. Eight
sterol-biosynthesis inhibiting fungicides (triadimenol, bitertanol, propi conazol, etaconazol, imazalil,
prochloraz, nuarimol, and XE-779) were tested for their in vitro effect on mycelial growth of Ggt. Only
five of the fungicides (triadimenol, propiconazol, XE-779, prochloraz, and imazalil) were tested in the
field under artificial inoculation (infested oat kernels). Effect of soil fumigation, inoculum rate, and
inoculum placement on disease level were also tested in the field. In the greenhouse, the efficacy of
triadimenol as a seed treatment was evaluated as influenced by Inoculum level, inoculum location, soil
fumigation, soil reaction, and wheat and barley cultivars. All 8 fungicides at 1000, 100, and 10 uM
inhibited mycelial growth on PDA. At the lowest concentration tested, 0.01uM, prochloraz and imazalil
inhibited growth by 70% while the remaining compounds were only minimally inhibitory. At 1 000
uM, nuarimol, imazalil, and prochloraz were fungicidal. The other compounds were only fungistatic
but caused abnormal and restricted growth. None of the fungicides affected the virulence of Ggt. In the
field, with 2g of inoculum/3m of row, the lowest disease index for 6 week old plants was obtained
where seed was treated with triadimenol at 0.31 and 0.47 6 a.i./kg, with imazalil at 0.1 g a.i./kg, with
XE-779 at 0.22 g a.i./kg, and with prochloraz at 0.2 and 0.4 g a.i./kg. At 5 g of inoculum/row, only
triadimenol lowered significantly the disease index. At 2 g of inoculum/row only triadimenol had grain
yield comparable to the non-inoculated check, but at 5 g of inoculum/row, none of the fungicides
significantly increased yield. Fumigation of the soil had a marked effect on disease severity. Grain
yield of the inoculated untreated fumigated check was reduced more than 90$. Seed treatment wwith
triadimenol or propiconazol in this experiment failed to provide a protective effect in fumigated plots.
Level of infection in plots in which the inoculum was rototilled into the soil was not as high as when it
was placed in close contact with the seed. Inoculum location had a differential effect on the
performance of triadimenol. The disease index of triadimenol seed treated seedlings when the inoculum
was above the seed was 3.0 in a scale from 1 to 5. With inoculum below the seed, the DI was 1.1.
Infection severity of seedlings grown in the greenhouse was not affected by reaction of the soils with
pHs varying from 5.0 to 7.2. Barley cultivars had a lower infection than wheat cultivars. Triadimenol
seed treatment significantly reduced infection level for all cultivars of wheat and barley. main lib,
.(//AS
(Lop,
EFFECT
OF
STEROL-BIOS YN THESIS
INHIBITING
FUNGICIDES
ON TAKE-ALL OF SPRING WHEAT
CAUSED BY
fiaeumannom^es K r aminis van.
tritici
by
Celsa Garcia
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Master of Science
in
Plant Pathology
MONTANA STATE UNIVERSITY
Bozeman, Montana
October I 9 86
ii
APPROVAL
of a thesis submitted
by
Celsa Garcia
This t hesis has been read by each m e m b e r of the thesis
committee and has been found to be satisfactory regarding
content, E n g l i s h usage, format, citation, b i b l i o g r a p h i c
st y l e and c o n sistency, and is ready i or s u b m i s s i o n to the
College of Graduate Studies.
Date
Chairperson,
^
Graduate
Committee
Approved for the Major Department
(Pc±-3,l 19%L
Date
Approved for the College of Graduate Studies
Date
Graduate Dean
iii
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/9idV
iv
TABLE OF CONTENTS
Page
APPROVAL P A G E .......
STATEMENT OF PERMISSION TO USE. . .......!! I !!!!! !
LIST OF TABLES.................i
LIST OF FIGURES..... ....... ...... ............... ..!!!'
ABSTRACT. ... . .................................
ii
*.! iii
i /i
Vi
x
INTRODUCTION..... ........................
LITERATURE REVIEW. ...... ..... ... . ... ............ .............
Infection P r o cess.... ............
Field Symptoms. ...... . . ... . . . . ... . . . . ................
Chemical Control....... ........
Sterol-Biosynthesis Inhibiting Fungicides............
MATERIALS AND METHODS...,................... ..............
Poison Food Tests............
........... .
In Vitro Mycelial Growth Tests. ...................... ... ... ..
Fungicidal/Fungi static Activity T e s t s ......
Virulence Tests ....... ..............
Field Trials... ....... . ... . . .... ....... .
. . ... . . ... . ,
Inoculum Preparation....................... ... ............. . .
Seed Treatments ... ..........
..........
.....
Planting....... ......... ... ......... .................
Evaluation of Fungicides.........................
Effect of Soil Fumigation. ... ....................... ... . ... .....
Effect of Inoculum Placement........... ......... .
Greenhouse Te s t s ........................................
Inoculum Location.
. . ........ . ...
....... . . . .
Soil P H .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... ..
Host Species and Cultivars.. ........ ..............
x±
i
4
c
g
q
12
1 Ii
14
14
16
16
1g
1g
20
20
21
22
24
26
26
28
30
RESULTS..... ...... ....... .... ........... ..................... ' g2
Poison Food Tests. ... ..... ... . ... . ... . ... ... ....... . ....... 32
Field Trials... ..... .................................
36
Evaluation of Fungicides. ... . ... . . . . . ....... .
36
Effect of Soil Fumigation.,........................................... .. 4?
Effect of Inoculum Placement. ........ .
... .... ... 53
Greenhouse Tests.......................................
58
Inoculum L ocation........ ........ .
58
Soil pH.,. ...... ..................................
6I
Host Species and Cultivars. . . . ... ... ... ... ... ........
62
V
TABLE OF CONTENTS
(cont..)
Page
DISCUSSION. .,. ..... ...... ... ..... ..............................
LITERATURE
CITED.,......................
63
vi
-LIST OF TABLES
Table
1
2
3
4
5
6
7
8
Title
Page
Sterol-biosynthesis i n h i b i t i n g f u n g i c i d e s
tested for activity against G a e u m a n n o m vces
-gram i ni s var.
t r i t i ^ i ........................
I5
Scale
used
to
assess
infection
by
G a e u m a n n o m v c es g r a m i n is var. t r i tici on
wheat
p l a n t s ...................... ;...........
19
Sterol-biosynthesis i n h i b i t i n g f u n g i c i d e s
tested
as
seed
treatments
against
G a e u m a n n o m y c e s gr a m i n i s var. t r i t i c i ........
20
E f f e c t of v a r i o u s
sterol-biosynthesis
i n h i biting fungicides on in vitro mycelial
g r o w t h of G a e u m a n n o m y c e s g r a m i n i s var.
_tr ijt i.^i on p otato d e x t r o s e a g a r .............
33
P r o p e n s i t y of v a r i o u s sterol-biosynthesis
i n h i b i t i n g c o m p o u n d s to be f u n g i c i d a l or
fungistatic to G aeumannomvces graminis var.
tr i t i c i ................................. ...........
34
E ffect of p r e v i o u s m y c e l i u m e x p o s u r e to
v a r i o u s s t e r o l - b i o s y n t h e sis i n h i b i t i n g
fungicides on virulence of Ga e u m annomyces
g r a m i nis var. t r i tici to P o n d e r a s p r i n g
w h e a t .................. ............................
35
E f f e c t of v a r i o u s s t e r o l - b i o s y n t h e s i s
inhibiting fungicides on in vitro mycelial
g r o w t h of G a e u m a n n p m y c e s g r a m i n i s var.
t,r i_t a.£ i on C z a p e k ts a g a r .....................
36
Effect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
P o n d e r a s p r i n g w h e a t o n . s e v e r i t y of takeall d i s e a s e after 6 w e e k s in the f i e l d .......
38
vii
LIST OF TABLES (cent.)
Table
9
10
11
12
13
14
Title
Page
Effect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
Pondera spring wheat on shoot dry weight of
6 week old plants in the field artificially
infested with Q aeumannomvces graminis var.
trit i c i ............................................
39
E ffect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
P o n d e r a s p r i n g w h e a t on n u m b e r of t i l l e r s
per plant of 6 w e e k old p l a n t s in the field
artificially infested w i t h G a e u m a n n o m y c e s
a m i.ni s var. . t r i t i c i ............... ........
41
Effect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
P o n d e r a s p r i n g w h e a t on s e v e r i t y of takeall after 8 and 12 w e e k s in the f i e l d ........
43
Effect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as
seed t r e a t m e n t s to
P o n d e r a s p r i n g w h e a t on n u m b e r of live
p l a n t s / m in plots a r t i f i c i a l l y i n f e s t e d
with Gaeu m a n n o m vces graminis var. tritici....
44
E ffect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
Pondera spring wheat on number of tillers/m
in
plots
artificially
infested
with
G a u m a n n o m y c es g r a m i n is var. t r i t i c i .........
46
Effect of s t e r o l - b i o s y n t h e s i s i n h i b i t i n g
f u n g i c i d e s a p p l i e d as seed t r e a t m e n t s to
P o n d e r a s p r i n g w h e a t on g r a i n y i e l d of
plants in field plots artificially infested ■
wi t h Guamannomvces gram inis var. tritici....
47
viii
LIST OF TABLES (cont.)
Table
15
16
17
18
19
20
21
22
Title
Page
A n a l y s e s of v a r i a n c e of seven p a r a m e t e r s
that m e a s u r e i n f e c t i o n by G a e u m a n n o m y c e s
g r a m i n is var. trijtici on P o n dera s p r i n g
wheat in artificially infested field plots...
49
E f f e c t of s o i l f u m i g a t i o n on t a k e - a l l
d i s e a s e in d e x and p e r f o r m a n c e of sterolbiosynthesis inhibiting fungicides applied
as seed treatments to Pondera spring w h e a t ...
50
E ffect of soil f u m i g a t i o n w i t h m e t h y l
b r o m i d e b n g r a i n y i e l d in f i e l d p l o t s
artificially infested w i t h G a e u m a n n o m y c e s
^ remind. S1 a nd
performance
of s t e r o l biosynthesis inhibiting fungicides applied
as seed treatments to Pondera spring w h e a t ...
52
Effect of i n o c u l u m level and p l a c e m e n t on
severity of take-all of 6 week old Pondera
s p r i n g w h e a t in the f i e l d ....................
54
E ffect of i n o c u l u m level and p l a c e m e n t on
dry w e i g h t of t a k e - a l l of 6 w e e k old
P o n d e r a s p r i n g w h e a t in the f i e l d ...........
55
Effect of i n o c u l u m level and p l a c e m e n t on
severity of take-all of 12 week old Pondera
s p r i n g w h e a t in the f i e l d ....................
56
Interaction of seed treatment and inoculum
rate and Ggt p l a c e m e n t on grain y i e l d of
P o n d e r a s p r i n g w h e a t .........................
57
Effect
of
amount
of
broadcast
G a e u m a n n o m y j j e s .gr a m i n_i.s i n o c u l u m
on
percentage of white heads of Pondera spring
w h e a t as a f f e c t e d by seed t r e a t m e n t .....
58
ix
LIST OF TABLES (cent.)
Table
23
24
25
Title
Effect of triadimenol on severity of takeall of seedlings of Pondera spring wheat in
the g r e e n h o u s e as a f f e c t e d by i n o c u l u m
p o s i t i o n ..........................................
E ffect of soil pH and t r i a d i m e n o l seed
t r e a t m e n t on s e v e r i t y of t a k e - a l l of
artificially in oculated Pondera s p r i n g
w h e a t s e e d l i n g s in the g r e e n h o u s e ...........
E ffect of t r i a d i m e n o l seed t r e a t m e n t of
w h e a t and barley c u l t i v a r s on s e v e r i t y of
take- a l l ........... ........... ...............
Page
59
61
62
X
LIST OF FIGURES
Figure
1
2
Title
Page
Flow sheet showing sequence of tests to
determine
the
effect
of
sterolbiosynthesis fungicides on virulence of
Gae u m a n n o m vces graminis var. tritici on
wheat
s e e d l i n g s ......................... ..
17
Location of Ggt inoculum with respect to
Pondera wheat seed used to test activity
of t r i a d i m e n o l .............................
27
xi
Abstract
T a k e - a l l of w h e a t caused by £ a e u m a n no m.y_£ e s ^ r a m i n i s
van. t r i t i ^ i (Ggt) is a very i m p o r t a n t root rot disease of
w h e a t a r o u n d the world.
In M o n t a n a it is p r e v a l e n t in
i r r i g a t e d s p r i n g wheat.
Eight s t e r o l - b i o s y n t h e s i s
inhibiting
fungicides
(triadimenol,
bitertanol,
propi conaz ol, etaconazol, imazalil,
pro chi or az, nuarimol,
and X E - 7 7 9) wer e tested for their in v i t r o effect on
m y c e l i a l g r o w t h of Ggt.
Only five of the f u n g i c i d e s
( t r i a d i m e n o l , p r o p i c o n a z o l , X E - 7 7 9 , p r o c h l o r a z , and
i m a z a l i l ) w e r e t e s t e d in t he f i e l d u n d e r a r t i f i c i a l
i n o c u l a t i o n (i n f e s t e d o a t k e r n e l s ) .
E f f e c t of soil
fumigation,
i n o c u l u m rate,
and i n o c u l u m p l a c e m e n t on
d i s e a s e level w e r e also tested in the field.
In the
greenhouse, the efficacy of triadimenol as a seed treatment
w as e v a l u a t e d as i n f l u e n c e d by i n o c u l u m level, i n o c u l u m
location, soil f u m i g a t i o n , soil reaction, and w h e a t and
barley cultivars.
Al I 8 fungicides at 1 000, 1 00, and 10 uM
inhibited
mycelial
g r o w t h on PDA.
At the l o w e s t
c o n c e n t r a t i o n tested,
O.OluM,
p r o c h l o r a z and i m a z a l i l
inhibited growth by 7 0 $ while the remaining compounds were
only minimally inhibitory.
At 1 000 uM, nuarimol, imazalil,
and prochloraz were fungicidal.
The other compounds were
only fungistatic but caused abnormal and restricted growth.
None of the f u n g i c i d e s a f f e c t e d the v i r u l e n c e of Ggt.
In
the field,
wi t h 2 g of i n o c u l u m / 3 m or row,
the l o w e s t
disease index for 6 week old plants was obtained where seed
was t r e a t e d w i t h t r i a d i m e n o l at 0 . 3 1 and 0.47 g a.i./kg,
w i t h i m a z a l i l at 0 . 1 g a.i./kg, w i t h XE-7 7 9 at 0 . 2 2 g
a.i./kg, and w i t h p r o c h l o r a z at 0.2 and 0.4 g a.i./kg.
At
5 g of inoculum/row, only triadimenol lowered significantly
the disease index.
At 2 g of inoculum/row only triadimenol
had grain yield comparable to the non-inoculated check, but
at 5 g of i n o c u l u m / r o w ,
none
of t h e f u n g i c i d e s
significantly increased yield.
Fumigation of the soil had
a m a r k e d effect on d i s ease severity.
Grain yield of the
inoculated untreated fumigated check was reduced
more than
90$.
Seed treatment wwith triadimenol or propiconazol in
this experiment
failed to provide a protective effect in
fumigated plots. Level of infection in plots in which the
i n o c u l u m was r o t o t i l l e d into the soil was not as high as
w h e n it w a s p l a c e d in c l o s e c o n t a c t w i t h the seed.
I n o c u l u m l o c a t i o n h a d a d i f f e r e n t i a l e f f e c t on the
performance
of t r i a d i m e n o l .
T h e d i s e a s e i n d e x of
t r i a d i m e n o l seed t r e ated s e e d l i n g s w h e n the i n o c u l u m was
above the seed w a s 3*0 in a scale from I to 5.
With
i n o c u l u m b e l o w the seed, the DI w a s 1.1.
Infection
s e v e r i t y of s e e d l i n g s g r o w n in the g r e e n h o u s e w as not
affected by reaction of the soils with pHs varying from 5.0
to 7 .2 . Barley cultivars had a lower infection than wheat
cultivars.
Triadimenol
seed
treatment
significantly
r e d u c e d i n f e c t i o n level for all c u l t i v a r s of w h e a t and
barley.
I
INTRODUCTION
Take-all is an old problem in the production of wheat.
It has a worldwide
distribution and has been reported from
all temperate climates and tropical regions where wheat can
be grown.
Take-all
is a serious problem in winter wheat in
Australia, Europe, So u t h Africa, Japan, North A m e r i c a and
So u t h A m e r i c a
(Garrett,
1981).
The d i s ease is caused by
G a e u m a n n o m v c e s .graminis. (Saco.)
i r ij; d._c_i.
The
f ungus
causes
f a v ored by high l e v e l s of
extensive
l osses
root
Arx and
and
Olivier
crown
soil moisture.
rot
In the United States,
and
is
and yield
1 977) and s o m e t i m e s
Wo r l d w h e a t p r o d u c t i o n in general,
A m e r i c a in particular,
v ar.
Crop d a m a g e is
in i r r i g a t e d or high r a i n f a l l areas,
can be as high as 5 0% (Wiese,
greater.
wheat
v.
and in North
c o n s i s t s l a r g e l y of w i n t e r wheat.
winter
production (Reitz,
wheat
I 96 7).
represents 70% of total
Thus,
most of the reports
of t a k e - a l l are from w i n t e r w h e a t areas,
and most of the
w o r k d e a l i n g w i t h take- all has been done on w i n t e r wheat.
In Montana,
however,
take - a l l
is p r i m a r i l y
s p r i n g w h e a t p r o d u c e d under i r r i g ation,
are very
conducive
for the disease.
a disease
where
Juhnke
of
conditions
(1983) rated
take-all as the second most important yield limiting factor
for
irrigated wheat.
The irrigated acreage
in Montana has
2
increased
considerably
ha in 1984
(Montana Agricultural
Control
cultural
ea r l y
take-all
practices,
1 9 0 0 ‘s,
common
crop
recent
has
to
more
rotation
for
r o t a t i o n of i r r i g a t e d
through
crop rotation.
In the
take-all
Australia
on
1985).
accomplished
rotation has
constraints
46,378
totalling
Statistics,
particularly
recently,
economic
years,
been
p r a c t i c e in E u r o p e and
However,
due
of
in
control
was
(Yarham,
been less
growers.
a
1981).
attractive
In
Montana,
areas is r e s t r i c t e d due to lack of
s u i t a b l e a l t e r n a t i v e crops w h i c h
can provide an e c o n o m i c
return to the grower.
In O r e g o n and Idaho,
take- a l l have
s o m e r e d u c t i o n in l o s s e s due to
been o b t a i n e d
through
the use
of a m m o n i u m
based f e r t i l i z e r s ( S m i l e y and Cook, 1973) a n d / o r chloride
fertilizers
disease
by
associated
(Christensen et al., 1981).
ammonium
with
and
c h a nges
chloride
in
the
emphasis
cropping
in
the
fertilizers
rhizosphere
This phenomenon and the occurrence
continuous
Suppression of
sam e
in research on biological
the
may
be
microflora.
of disease decline with
soil
ha v e
led
to
the
control.
To allow m a x i m u m development of the decline phenomenon
(zdisease
suppression),
it
would
be
useful
a v a i l a b l e other control m e a s u r e s for take-all
reduce
include
the losses that a grower
the
use
of
fungicides
suffers.
as
soil
Such
to
have
that wo u l d
control
drenches
or
may
seed
3
treatments.
Bockus
(1983)»
by using triadimenol
as a seed
t r e a t m e n t , o b s e r v e d a r e d u c t i o n of 60-75% in yield losses
due to take-all
The
in winter wheat.
purpose
of
sterol-biosynthesis
potential
in
this
study
inhibiting
controlling
treatments on spring wheat.
was
to
evaluate
fungicides
take-all
when
for
used
as
eight
their
se e d
4
LITERATURE REVIEW
Gaum annom vces gram inis (Saco.) v. Arx & Olivier
root
r ot
in
several
grasses
G a_e Umannomj; ce. s .graminis
and
(Sacc.)
a v e n a e (Turner) D e n n i s (Gga)
cultivated
v.
Arx
&
graminis
(Ggg)
is
a
cereals.
O l i vier
var.
is c o m m o n l y a s s o c i a t e d w i t h
oats and turf grasses; CL. gram inis (Sacc.)
var.
causes
weak
v. Arx & Olivier
pathogen
that
has
been
r e p o r t e d f r o m rice c a u s i n g c r o w n and sheath rot, and fr o m
several
grasses; G . g r a m i n is (Sacc.) v. Arx & O l i v i e r var.
tritici (Walker)
(Ggt) is primarily a pathogen of wheat and
barley,
has
but
it
gramineae
(Scott,
characteristically
runner
The
hyphae,
runner
infectious
lobed
hyphae
Gga
forms
tissue
and
mycelial
root
to
man y
produce
hyphopodia,
and
Walker
Ggt
produce
lighter
are
morphological
(19 81).
simple
finer
Simple
produced
hyphopodia.
description of
I 93 4).
and
s o m e t i m e s in culture
only
called
(Garret,
the root.
other
graminis
strands,
surface
penetrate
called
attack
Gaeumannomgces
da r k
b ranch
to
and
on
(Fellows,
Ggg p r o d u c e s s i m p l e and lobed hyphopodia,
detailed
by
1981).
h yphae w h i c h
i n f e c t e d host
reported
on the host
swellings,
1928).
been
whereas
A more
gram inis is given
5
Ggt
causes
the disease known as Take-all
both barley and wheat.
As a rule, however,
that affects
w h e a t is mor e
s u s c e p t i b l e than barley, and e x t e n s i v e d a m a g e to the root
system of wheat
plants is reported from many wheat growing
ar e a s a r o u n d the w o r l d (Cook,
et a l . , 1 9 6 8 ; Diehl,
G o r s k a - P o czop ko , !971;
1 977;
Heyne,
1 925; L e s c a r and Caron,
1984;
Suzuki,
et
al.,
1957).
1 9 8 I ; Kirby,
Jarham,
1 9 80 ; Lester,
The
et al.,
1 967;
Scott,
pathogen
1 97 8;
survives
s a p r o p h y t i c a l Iy in the soil as m y c e l i u m in i n f e s t e d crop
debris (H o r n b y , 1975;
Shipton,
infested
tropically
debris
grows
1981). ' M y c e l i u m
growing plants (Brown and Hornby,
1 982).
Once
the mycelium
any part of the plant
toward
1971;
roots
the
of actively
W ildermuth,
reaches the roots,
below
from
et al.,
it can grow
on
ground.
Infection Process
In
noncompatible
and G g t , the fungus
surface
host
without
such
as
host-parasite
will grow
establishing
wheat,
systems,
such
as
oats
as runner hyphae on the root
infection.
runner
In
hyphae
a susceptible
usually
grow
l o n g i t u d i n a l l y over the root surface, and f r o m the r unner
h y p h a e i n f e c t i o n h y p h a e d e v e l o p that p e n e t r a t e e p i d e r m a l
cells.
Once the i n f e c t i o n hyphae are in c o n t a c t w i t h the
cell wall of epidermal
cells,
Penetration
largely
is
they form a penetration peg.
d i s i n t e g r a t i o n due to e n z y m e s
the
result
of
cell
wall
exuded fr o m the peg (S k o u,
6
1981).
The
host
cell
responds
s u b s t a n c e s in the i n n e r m o s t
part
point of i n f e c t i o n (Fellows,
and Fulcher,
1971).
stain
1928; Russell,
at the
1934; H o l l a n d
an inner tube of ligneous material
give a positive reaction with safranin,
but do
is
new
lengthening
the
hyphae
indicating
from
that
of
that
the
h e a lthy
matter
to
compensate
lignituber.
to p r e v e n t
for
Eventually,
that
the
ligneous
cell
So l o n g as the root cell r e m a i n s
the
are not able
around
fuchsin,
different
(Sko u , 1981).
produces
of the cell wall
I 92 8 ).
is formed
with
material
ligneous
(Fellows,
(Iignitubers)
not
depositing
As the h yphae a d v a n c e d i s i n t e g r a t i n g
the deposited materials,
Lignitubers
by
wa l l s
alive,
it
decomposed,
root
tissues
the h y p h a e from penetrating,
and
die (Skou, I 97 5).
Cell
the
contents
rapidly
pathogen resulting
then either
or fill
grow
in cell
forward
the invaded
disintegrate
death.
to attack
following entry
Infection
the opposite
cell with mycelium.
hyphae
cell
wall
This mycelium
d e v e l o p into c r u s t - s h a p e d s c l e r o t i u m - l i k e structures,
into
small
spherical
bodies
of
like
m i c r o s c l e r o t i a (Fellows,
tightly
interw ovum
of'
may
or
hyphae,
1928; H o l l a n d and Fulcher,
I 971) .
Hyphae. spre ad
infection.
into
t he
In weak attacks,
cortex
several
from
the
lignitubers
site
of
are found
7
in
t he
epidermis
constitute
a
a nd
outer
palisade.
cell
In
layers
severe
lignitubers are found in these layers
in the
tissue,
ligni tubers
lignitubers
are,
again,
constitutes a barrier,
(Fellows,
1 928;
Skou,
are
common
fewer
(Skou,. I 97 5).
Deeper
Palisades
of
endoderm is where
it
and the rate of infection slows down
1 975).
According to Skou (1 975),
d e v e l o p m e n t of l i g n i t u b e r s is
resistance
th e y
attacks,
scattered.
in the
where
mechanism,
but
a
the
not c o n s i d e r e d a deci s i v e
general
protective
mechanism
against weak or moderate attacks.
Once
the
the stele,
endodermis is crossed and the fungus reaches
the hyphae grow rapidly.
xy Iem vessels,
r u p t u r e of cell w a l l s and b r e a k d o w n of all
s telar
tissues
1976).
The
that
5
only
pathogen.
occurs
phloem
other s t e l a r
usually
tissues.
to
(Clarkson
10%
of
the
All
xylem
enlongation
compounds
are
of
of
the
is
the
cessation
transportation in the xylem
metabolic
a I. ,
1 97 5;
occupied
phloem
of phloem
infected
can continue,
consumed
but
s u r f a c e m ay be a t t a c k e d by Ggt.
in the
same
way
than
estimated
by
the
leads
to
translocation
root.
Ion
ceases after
(Clarkson et al., 1 97 5).
parts of susceptible plants at and below
is a t t a c k e d
Holden,
disintegrates more rapidly
Disintegration
root
et
C l a r k s o n et al. (1975),
restriction and eventual
and
W i t h i n v a s i o n of the
the soil
The s u b c o r o n a l inter node
as s e m i n a l
and a d v e n t i t i o u s
8
roots
but is probably
h igher
c o n tent
Robertson,
subcoronal
of
more resistant, perhaps
ligneous
substances
1932).
T he
crown
internode
and
the
is
because
1928;
(Fellows,
invaded
adventitious
of a
through
roots
the
(Fellows,
I 938).
I n f e c t i o n and d e s t r u c t i o n of s e m i n a l roots p r o m o t e s
growth
of
Clarkson
additional
et
adventitious
a l . , 1974).
resistance
of
barley
to
additional
adventitious
Skou
Ggt
(1975)
to
roots
roots
the
1 975 ;
attributes
ability
during
conditions this is an important
(Sko u ,
to
attack.
the
produce
In field
survival mechanism,
but if
i n f e c t i o n o c c u r s in very, yo u n g plants, n u t r i e n t and w a t e r
s u pply to the shoot w i l l
additional
adventitious
be i n a d e q u a t e and p r o d u c t i o n of
roots
may
be inadequate
to sustain
growth of the plant.
Zieid Symptoms
The n ature and s e v e r i t y of s y m p t o m s o b s e r v e d in
field will
depend on the virulence
the
of the pathogen and the
ability of the host to produce
new
the f u n g u s
In severe a t t a c k s on young
plants,
can d e s t r o y
there
plant dies.
is
no
effective
will
root
replacement
and
than
the
This is the 'take-all' phase and goes largely
u n n o t i c e d in the field.
stage
them.
roots more quickly
r e sult
in
The death
patches
of plants
sparsely
at an early
populated
with
9
stunted
plants.
In
older
plants,
the
most
conspicuous
symptom of take-all is the prematurely ripened white heads.
At
this
stage,
the
straw
always brown to black,
mycelial
crusts
base
and l o w e r
leaf
sheath
are
which is caused by runner hyphae and
(Fellows,
1 928)..
Chemical
Control
The control of the take-all d i s e a s e of w h e a t is a hard
problem..
The first approach and best known control measure
is crop rotation..
during
problem
the last
on
certainly
less
Although take-all
century,
wheat.,
caused
trouble
This may have
of the day".
it w as
Yarham
not r e c o g n i z e d
(1981)
states
that
as a big
"take-all
nineteenth-century British farmers
than
it
did
their
Australian
To this day,
far
counterparts.
been due in part to the rotational
practices
crop rotation is by far the most
common (if not the only one in some
for
was present in Britain
areas) control
measure
this disease..
Use of. ammoniacal
sources of N (Smiley and Cook,
1 973)
are r e p o r t e d to d e c r e a s e the effect of take- all on yield.
This e f f e c t , however,
soil
pH
and
soil
is not u n i v e r s a l and w i l l vary with
type.
Continuous
cropping
of
wheat
promotes build-up of Ggt antagonistic microorganisms in the
soil
that
several
this
results
in
years of wheat..
take-all
decline
a
decrease
For many
of
the
disease
wheat producers,
is not e c o n o m i c a l l y
after
however,
feasible
as a
control
measure.
Until
recently,
cnemical
control
of
the
take-all
was
of l i m i t e d value b ecause of the lack of p e r s i s t e n c e or lack
of efficacy
of fungicides available..
of systemic fungicides,
take-all
was
With
the development
a new perspective on the control of
available..
Benomyl
was
one
of
the
first
systemic fungicides tested as a seed treatment against Ggt..
Gorska-Paczapko
vitro
mycelial
several
other
(1971)»
growth
found
inhibitor
(2g a. i/kg. seed)..
observe
naturally
(I
s y s t e m i c fungicides..
against Ggt in greenhouse
not
be no m yI to be the best in-
tests,
of
i n f e s t e d fields..
of
a.i.)
among
It also had acti v i t y
applied as a seed dressing
Pre n and M c I n t o s h
activity
ppm.
benomyl
( 1 975), however,
against
M o r e recently,
Kollmorgen (1986) found that benomyl
take-all
did
in
B a l l i n g e r and
significantly
reduced
the disease when tested in the greenhouse with doses as low
as O .Sg
a.i./kg seed,
but
not
when
Bateman (1980) also found benomyl,
compounds,
chose
soil
greenhouse
1984b,
tested
as well
in
as several
to be toxic to Ggt on agar plates..
drenching
for
and
(Bateman,
field
testing
the
the
He,
field..
other
however,
fungicides
in the
I 9 80 , 1 9 81 , 1 9 82,
1 9 84 a,
1985; B a t e m a n and N i c h o l l s, 1982)..
Soil d r e n c h i n g
does not have a p r a c t i c a l use in the field since b e n omyl is
effective only in the area where it is applied..
This means
that
surfactants
or
large
amounts
to be used to o b t a i n a better
the
of fungicide
would
have
c o v e r a g e and p r o t e c t i o n
of
roots.
Several
against
systemic
take-all,
compared
1980).
to
In
treatment
inhibiting
losses
other
but,
benomyl
fungicides
with
less
Dolezal
with
triadimefon,
of w i n t e r
Triadimenol,
and
fungicide,
wheat
another
been tested
successful
(Gor s k a - P r o c z opho,
1981,
systemic
have
Jo n e s
a
results
1971;
reported
as
Bateman,
that
seed
sterol-biosynthesis
significantly
in a r t i f i c i a l l y
reduced yield
infested
sterol-biosynthesis
fields.
inhibiting
f u n g i c i d e used a g a i n s t bunts and early i n f e c t i o n of rusts
in cereals, was r e p o r t e d (Bockus, 1982) to p r o t e c t w i n t e r
wheat
seedlings
yield
by 3 8 %
found
that
yield
of
in the greenhouse
in
field.
triadimenol
spring
infested
the
Mathre
reduced
wheat
in
for 8
et
weeks
al. , (1 9 8 6 ),
infection
naturally
and increase
and
and
also
increased
artificially
fields.
E r g o s t e r o l is the m a i n sterol in most f u n g i , and is an
important
however,
component
of
mycelial
the m a i n sterol
membranes.
It is
not,
in.the U r i d i n a l e s and.it is not
p r e s e n t at all in the O o m y c e t e s P v t h ium and P h.yj;ojdh_th 0 r a
(Mercer,
The
1 984).
starting point
acetyl-CoA.
Squalene
in the synthesis of all
is
the
leading
sterols is
compound
in
the
synthesis
of ergosterol,
and is f o r m e d
biosynthetic
reactions..
c y c l ization.
In
fungi,
the
I a n a sterol,
lighter
but
plants
conversion
of
Squalene
non-photosynthetic
product
in
of
algae,
lanasterol
it
into
m u l t i s t e p process..
The s e q u e n c e
certain
of
but
the first
in
step
followed
most
the
of
ergosterol
organisms
of
such
squalene
such
cycloasterol.,
ergosterol
is
a
as
is
as
The
complex
of the r e a c t i o n s is not
ergosterol-synthesizing
can be m e t h y l a t i o n of C-24.,
reactions
undergoes
organisms,
is
by d i m e t h y l a t i o n at C-I 4,
sequence
then
cyclization
photosynthetic
and
after a series of
leading
fungi,
This is then
C- 4 a , and C - 4 3.,
from
in photosynthetic organism,
cycloasterol
The
to
the 4a-methyl group,
is n o r m a l l y r e m o v e d first, then f o l l o w e d by C-4g and C - 1 4
(Mercer,
1 984).,
Sterol-Biosvnthesis Inhibiting Fungicides
A large number
for the control
biosynthesis
control
inhibiting
a large
This
caused
group
of
demethylation
developed
in recent years
of fungal p a t h o g e n s of plants are sterol-
number
Ba s i d i o m y c e t e s , and
diseases
of compounds
fungicides..
of diseases
These
caused
Deuteromycetes,
but
fungicides
by Ascomycetes,
do
not
control
by Pvthium and Phvtophthora (Siegel,
fungicides
process
in
inhibits
the
the
ergosterol
sterol
1981).
14-
.biosynthesis
13
pathway
causing
(Siegel,
19 81;
the
accumulation
Ragsdale
and
of' sterol
S i s l er,
intermediates
1 97 3 ;
Bu che n a u e r ,
1977).
There is a considerable diversity in the structures of
compounds which inhibit
C-I4 demethylation.
The ones with
agricultural
use are included in three classes.
the l a r g e s t
group,
t riadimenol,
imazalil
includes
bitertanol,
and
the f u n g i c i d e s
diclobutrazol,
prochloraz
are
pyrimidines include fenarimol
triademefon,
and
propiconozal;
imidazoles,
and nuarimol
defined,
believed
(N e s ,
but
their
principal
to be as a r c h i t e c t u r a l
I 974).
Reduction
in
role
has
is
components
the
amount
of
while
the
(Siegel, 1 9 8 1 ).
The precise function of sterols in fungi
well
Triazoles,
not
been
generally
of m e m b r a n e s
ergosterol
or
qualitative change in sterol
composition results in altered
membrane
as
activity
properties
(Sancholle
patterns,
such
et
swollen
al., 1 984),
hyphae,
branching.
AlI
of these
germination
but
can
Propiconazol,
fungicidal
though,
(Sancholle
permeability
be
causing abnormal
and/or
compounds
fungicidal
and
excessive
do not
at high
inhibit
enzyme
growth
hyphal
spore
concentrations.
appears to be fungistatic rather than
et al,
1 9 8 4 ).
MATERIALS AND METHODS
To
determine
inhibiting
the
fungicides
development,
several
in the laboratory,
activity
of
on G g t , and
different
sterol
therefore
experiments
greenhouse,
biosynthesis
on
were
disease
conducted
and field.
Poison Food Tests
Jn Vitro Mycelial Growth Tests
Eight
t e sted
for
sterol-biosynthesis
their
effect
determine
the
field
greenhouse
and
materials
are
mos t
also
Each f u n g i c i d e w a s
0.01 p M of
active
toxic
mycelial
compounds
tests
reported
to later
(Table
to
growth
I).
have
ingredient
and PDA-2)
of
be
Many
systemic
tested at 1 000 , 1 00,
or C z apek agar (CA).
PDA (PDA-1
on
i n h i b i t i n g chemicals were
in potato
Ggt
to
used
in
of
these
activity.
1 0 , 1.0 , 0.1 , and
dextrose
agar
(PDA)
Two e x p e r i m e n t s were c o n d u c t e d w i t h
and one w i t h
CA.
T r i a d i m e no I was
not included in. the CA test.
Czapek agar was
used
because
it does not c o n t a i n sterols.
D i l u t i o n s of the f u n g i c i d e s
were prepared in sterile water except for bitertanol,
was diluted with 95%
added
to
poured
m o l t e n aga r
into
solidification,
4
100
ethanol.
medium
x
which
The solution/suspension was
at
15mm
50°
C,
petri
mixed,
plates.
and
then
After
each plate was inoculated with an Ilmm disc
fr o m an 8 d a y - o l d c u l t u r e of Ggt on PDA, or f r o m a 15 day-
old
culture
temperature,
fourth,
on
CA.
Following
incubation
at
room
m y c e l i a l g r o w t h was m e a s u r e d on the second,
sixth,
eighth,
PDA-I and PDA-2.
and tenth day after inoculation for
For CA, only one m e a s u r e m e n t was taken
on the 8 th day.
Table
I . Sterol-biosynthesis inhibiting fungicides tested
for activity against Gaeu m anno m vces g ram inis var.
t r i tici.
Chemical
Group
Compound
Name
Formulation
Triazole
Triadimenol
Baytan 3 0 1
Bitertanol
Baycor 1 Q %
Propiconazol
Tilt 3 . 6 E
Etaconazol
CGA 64251
Imazalil
Fungaflor 5.8% or . J anssen
Imazalil 7 5 %
Pharmaceuticals
Prochloraz
Prochloraz 40% E C Boots Hercules
Imidaz ole
Gustafson,
DS1
Inc.
Bayer
Ciba Geigy
O .846EH
Pyrimidine Nuarimol
EL- 2 2 8
Unknown
XE-779 2 5 WP
XE-779
Source
5%
Ciba Geigy
Eli Lilly
Chevron
I
Formulated specifically
as seed treatments,
Data (total a c c u m u l a t e d
factorial
analysis
of
concentration as factors.
each
concentration.
growth)
variances,
were s u b j e c t e d to a
with
Fungicides were
fungicides
compared
and
within
16
Fungicidal/Fungistatic Activity Tests
To
determine
if
the
highest
dosages
experimental materials were fungicidal,
fungi s t a t i c ,
the orig i n a l
rather
of
the
than merely
four discs from p lates s h o w i n g
very little or no mycelial growth were removed and used to
inoculate
fungi aide-free
PDA
or
CA plates
(Fig.
I).
These
plates were incubated at room temperature and the extent of
mycelial
growth was determined
e x p e r i m e n t u s i n g CA,
on the seventh day.
In the
two of the discs w e r e re plated onto
PDA and the other two onto CA.
Virulence Tests
The
ultimate
purpose
of
these
tests
was
to determine
w h e t h e r there was any carry over effect of the f u n g i c i d e s
on the virulence
growing
of Ggt.
Inoculum
on fungicide-free
t r e a t m e n t s that a l l o w e d
vitro p o i s o n food tests
transfer
to
m edium
consisting of mycelium
was
obtained
some mycelial
(Fig.
fungicide-free
f u n g i c i d a l / f u n g i s t a t i c a c t i v i t y (Fig.
case,
to
the
g r o w t h in the in-
1C) or fro m
medium
either from
in
the s u b s e q u e n t
the
ID).
study
of
In the first
an 1 I mm disc of mycelium from each, treatment was used
inoculate
source
fungicide-free
of i n o c u l u m
In the second case,
for
PDA
plates;
these
the v i r u l e n c e
plates
test (Fig.
those plates with some mycelial
c o n s t i t u t e d the source of inoculum.
were
IE).
growth
Fr o m these plates,
a
2 0 mm disc was removed and used to inoculate wheat seedlings
17
Fungicides
Fungitoxicity/
Fungicidal Tests
I
Virulence Tests
Fig. I.
Flow sheet showing sequence of tests to determine the effect
of sterol-biosynthesis fungicides on virulence of Gaeumannomyces
graminis var. tritici on wheat seedlings.
CV..
Pondera
Leach
(Fig.. IF)..
T a p ered
Co., C a n b y 1
Conetainer
plastic
OR)
16.5
conetainers
cm
long
(Ray
x 3.0
cm
diameter were filled with a sterile mixture of Bozeman silt
loam soi l , sand,
of inoculum
and peat moss (1:1:1 by volume).
was placed horizontally
The disc
in the conetainer I cm
be l o w 3 w h e a t seeds, w h i c h wer e then c o v ered w i t h 2 cm of
soil
mix..
Ten c o n e t a i n e r s per t r e a t m e n t w e r e used.
conetainers were fertilized with
solution.
6
After
weeks,
the
removed and the roots washed
assessed
After
1/2 s t r e n g t h
seedlings
free
of soil..
were
The
Hoaglands
car e f u l l y
They were
then
for infection using a scale from I to 5 (Table 2).
each
plant
was
assessed
disease index per treatment
E[(# of plants)
for
(BI) was
d i s ease
severity,
a
calculated as follows:
(Infection score)]/Total
# of plants
Dry weight of the shoot of each plant was also determined..
Field Trials
Inoculum Preparation
Two hundred
and fifty grams of oat kernels plus 2 0 0 ml
of w a t e r w e r e a u t o c l a v e d in 9 5 0 c c M a s o n jars for I hr.
next day,
small
one petri plate culture of Ggt was chopped into
p i e c e s and m i x e d Wi t h the oats..
then i n c u b a t e d
a ir
dried
The
f or
at ro o m
one
The
c u l t u r e s were
t e m p e r a t u r e for 3 weeks,
week..
contamination of the oats,
To
test
and then
colonization
and
at least 20 kernels were surface
s t e r i l i z e d w i t h 0.5% NaOCl and then plated onto PDA.
Ggt
colonized oats were stored at room temperature in card board
boxes until used.
B e f o r e their u s e , the oat k e r n e l s w e r e
fragmented for 5 seconds in a Waring
envelopes
with
the
to be used
soil
for
as i n o c u l u m
greenhouse
blendor and packed in
in the field,
experiments.
The
or m i x e d
original
i s o l a t e w a s o b t a i n e d f r o m Dr. D. E. M a t h r e from nat u r a l l y
infected wheat
Table
2.
plants in the field. .
Scale used to assess infection bv Gaeumannomvces
eraminis var. tritici on wheat nlants.
Infection
score
Symptoms
I
No symptoms; leaves green
2
Discoloration of the roots o n l y ; leaves green
3
D i s c o l o r a t i o n o b s e r v e d in the root and c r o w n
tissues; leaves green
4
Discoloration
roots heavily
chlorotic
5
C o m p l e t e d i s c o l o r a t i o n of the c r o w n tissue;
he a v y r o t t i n g of the roots;
p l a n t s nearly
dead.
of the entire c r o w n tissue;
di s c o l o r e d ;
leaves somewhat
20
Seed Treatments
Five fungicides in different doses were tested as seed
treatments
(Table
3)»
The
products
were
mixed
with
water
and applied as a slurry using 50 ml/kg of seed.
Table 3•
Sterol-bio synthesis inhibiting fungicides tested
as s e e d t r e a t m e n t s a g a i n s t G.
u m_a n n_o m_y_c_e_s
graminis var. tritici.
Doses
g a.i ./kg of seed
Triadimenol
0.16,
0.31,
0.47
Propiconazol
0.01,
0.02,
0.04
XE-779
0.11,
0.22
Prochl oraz
O
OJ
Imazalil
O
in
O
O
Zf
Fungi aide
O
Planting
Three field experiments were planted May 3-6,
the
A.
H.
consisted
received
Post
Research
of 4 rows,
6g
of
seed
Farm,
west
3 m long
and
40cm
p l a nted
with
a
inoculum was applied with the seed,
no
inoculum
Treatments
received
of
5 g of
I 985
Bozeman.
apart.
cone
Plots,
Each
seeder.
at
row
Ggt
and the treatments with
autoclaved
oats
per
row.
with less than Sg of inoculum were made up to a
total of Sg with autoclaved
oats.
21
Evaluation of Fungicides
Based
on the r e s u l t s
of the p o i s o n food tests,
five
fungicides were selected for testing as seed treatments for
p o t e n t i a l control of take-all.
tested are g i v e n in Table 3 .
also
tested.
randomized
the
main
This
and
was
design
fungicides
replications.
Inoculum
inoculum
3m
per
V a r i o u s i n o c u l u m rates wer e
experiment
block split-plot
plots,
The f u n g i c i d e s and doses
rates
row.
A
established
with
as
inoculum
subplots
used w e r e
check
with
I, 2,
no
in
rates
with
and
a
as
four
Sg
inoculum
of
but
autoclaved oats was included.
Six weeks after planting,
five plants from each of the
border r o w s w e r e pulled, the r o o t s w a s h e d free of soil, and
lesion
severity
Disease
index
previously.
weight
assessed
per
plot
Number
of the shoot
seed attachment)
using
was
of
the
scale given in Table 2.
calculated
tillers
(NT)
(all p o r t i o n s
of each plant (DW)
per
as
plant
and
dry
of the plant above
the
were also determined.
All plots w e r e s c o r e d for above ground
times during the season,
1-5
scale
severely
was
used
stunted
8 and
where
plants
12 weeks
I =
and
healthy
very
described
low
after
s y m p t o m s two
planting.
plants,
and
A
5
=
population of plants
remaining in the plot.
At harvest
number
time
of t i l l e r s
(August
per
one
19)»
meter
the number
from
of plants and
an inner
row
we r e
22
recorded,
and
g r a i n yield
was
evaluated
from
the
other
inner row that w as e n d - t r i m m e d to 2.6 m.
Analyses
effects
of
of v a r i a n c e
inoculum
differences
Variance),
were
the
were
rates
and
indicated
comparisons
within each inoculum
rate.
performed
to e x a m i n e
fungicides.
by
the
among
If
ANOVA
the
statistical
(Analysis
fungicides
were
of
made
A regression analysis was made
to c o r r e l a t e D I w i t h n u m b e r of t i l l e r s and dry w e i g h t
the
of
plants.
Since
the l e s i o n
severity
was
scored
with
discrete
v a l u e s (I, 2, 3, 4, and 5), no n- no r m ali ty of data and no nhomogenicity
data
of variances
on l e s i o n
(C a t i g o r i c a l
(Statistical
severity
Data
was
suspected.
were
analyzed
Modeling)
Analysis
System)
For
us i n g
procedure
program.
this reason,
This
the
of
CATMOD
the
procedure
SAS
was
designed to handle count data in the same manner that ANOVA
programs
handle
converted
measurement
to n u m b e r
data.
empty
c ells,
scores
of p lants in each r e s p o n s e
and a n a l y z e d using these counts.
of
The raw
row
scores
wer e
category,
Due to the large n u m b e r
were
collapsed
into
two
c a t e g o r i e s (I, 2, 3) and (4, 5) for data analysis.
Effect of Soil Fumigation
An experiment
of
soil
was established
fumigation
on
the
to determine
activity
of
the effect
t r i a d i m e nol
and
23
propiconazol
split-plot
against
take-all.
a randomized
covered with
block
or n o n f u m i g a t e d
F u m i g a t e d plots w e r e treated w i t h
b r o m i d e at the rate
of 46.4g/m^.
Plots w e r e left
p l a s t i c for 4 8hr and then a l l o w e d to aerate
for a n o t h e r 4 8 h r s before
treatment
was
design with either fumigated
soil as the m a i n plot.
methyl
It
combinations
planting.
of
Sub plots
triadimenol
(0.16
wer e
and
seed
0.31
g
a.i/kg of s e e d ) , or p r o p i c o n a z o l (0.01 and 0.0 2g a.i/kg of
seed)
and i n o c u l u m
rates of 0,
and 4g of i n o c u l u m
2,
per
3.0m row.
Six weeks after planting,
border r o w s wer e pulled,
lesion
severity
Disease
assessed
index
previously.
per
Number
five plants from each of the
roots
using
plot
was
washed
the
free
of soil,
and
scale given in Table 2.
calculated
as
described
of tillers per plant and dry weight of
the shoot of each plant were also determined.
All plots w e r e scored for above g round s y m p t o m s two
times
1-5
during the season,
scale
severely
was
used
stunted
8 and
where
plants
and
12 weeks
after planting.
I = healthy
very
low
plants,
population
and
of
A
5 =
plants
remaining in the plot.
At harvest
number
time
of t i l lers
recorded,
and
(August
per
19),
the number
one m e t e r
g r a i n yi e l d
was
from
an inner
evaluated
in n e r row that w as end- t r i m m e d to 2.6 m.
of plants and
from
row
the
wer e
other
24
Analyses
of v a r i a n c e
were
performed
to e x a m i n e
the
e f f e c t s of f u m i g a t i o n , i n o c u l u m rate, and fungicides.
If
s t a t i s t i c a l d i f f e r e n c e s w e r e i n d i c a t e d by the AN OV A , the
comparisons
among
fungicides
and
w i t h i n each f u m i g a t i o n level.
inoculum
rate
were
made
A r e g r e s s i o n a n a l y s i s w as
m a d e to c o r r e l a t e g r a i n y i e l d w i t h all of the p a r a m e t e r s
measured.
Lesion
procedure
converted
severity
of
the
data w a s
SAS
to n u m b e r
analyzed
program.
empty
cells,
raw
the C A T M O D
scores
of p lants in each r e s p o n s e
and a n a l y z e d u sing these counts.
of
The
us i n g
row
scores
were
category,
Due to the large n u m b e r
were
collapsed
into
two
c a t e g o r i e s (I, 2, 3) and (4, 5) for data analysis.
Effect of Inoculum Placement
In the above
two tests,
the Ggt inoculum was added to
the f u r r o w w i t h the seed, and thus was in close p r o x i m i t y
to
the
t r e ated
seed.
To
determine
if
triadimenol
and
p r o p i c o n a z o l w e r e a c t i v e w h e n the i n o c u l u m w a s r a n d o m l y
distributed
in
the
upper
10
cm
of
soil,
inoculum
was
b r o a d c a s t over the soil s u r f a c e and then r o t o t i l l e d into
the soil to a depth of 10 cm.
Treatments
triadimenol
at 0.31
for
this
experiment
g a. i/kg of seed,
consisted
propiconazol
of
at 0.0 2g
25
a.i/kg
of
seed,
and
a non-treated
check.
Inoculum
was
a p p l i e d e ither to the row w i t h the seed at r a t e s of 0, 2,
or 4 g / 3 m row
or b r o a d c a s t
on the
soil
s u r face
and then
rototilled in to a depth of 10 cm, using rates of 90 or 180
kg/ha.
This
test
was
established
w i t h four r e p l i c a t i o n s ,
plots,
and
planting,
pulled,
fungicides
w i t h i n o c u l u m rates as
as
five p l a n t s f r o m
roots
washed
as a s p l i t - p l o t
free
subplots.
Six
each
border
of
of the
soil,
and
weeks
after
rows
were
seve r i t y
D i s e a s e index
per plot was calculated as described previously.
tillers per plant and dry weight
the m a i n
lesion
a s s e s s e d u s i n g the scale g i v e n in Table 2.
design
of the shoot
Number of
of each plot
were also determined.
Al I pl o t s w e r e scored for above g r ound s y m p t o m s two
times during
1-5
scale
severely
the season,
was
used
stunted
remaining
in
rototilled
and
based
on
inner
rows.
where
plants
the
8 and
ma d e
very
P e r cent
no-inoculum
counts
I = healthy
and
plot.
converted
of
t he
in one
SAS
to n u m b e r
low
of
meter
planting.
plants,
population
treatments
Data of lesion severity
procedure
12 weeks after
white
was
from
and
of
heads
also
each
A
5 =
plants
in
the
determined
of
the two
was analyzed using the CATMOD
program.
The
raw
scores
of p l ants in each r e s p o n s e
and a n a l y z e d u s i n g these counts.
were
category,
Due to the large n u m b e r
26
of
empty
c ells,
row
scores
were
collapsed
into
two
c a t e g o r i e s (I, 2, 3) and (4, 5) for data analysis.
G reenhouse Tests
Inoculum Location
To
determine
whether
relation to a triadimenol
of the fungicide,
as
to
of
inoculum
16.5
A growth
cm
cone tainers.
growth
medium
of
fen
at
rates
peat
moss,
cm
was used
tapered
plastic
i n o c u l u m w as m i x e d w i t h the
of 0.1,
w as
1.0,
and
5.0%
by weight.
the seed,
(B) 1 cm
5 replications,
using
or 0.6 4 g a. i./kg seed
of s p r i n g w h e a t
(Fig.
c o n d u c t e d as a split plot design
fungicide
as m a i n
rate and position as sub plots.
seeds
width
fine
or (C) t h r o u g h o u t the e ntire m e d i u m
The e x p e r i m e n t
0.3 1,
3•0
w a s p l a c e d (A) I cm below
above the seed,
with
x
Ggt oat kernel
medium
The i n o c u l u m
long
in
set up with inoculum location
and Bozeman silt loam soil (1:1:1 by volume)
fill
2).
location
treated seed affects the activity
tests were
a variable.
sand,
the
cv.
doses
plots,
of
0,
0.16,
and i n o c u l u m
Each conetainer received 4
Pondera.
This
experiment
was
conducted, two times.
The
Hoaglands
conetainers
solution.
were
Plants
irrigated
were
with
harvested
1/2
strength
after
5 weeks
for the first exp e r i m e n t , and 6 weeks for the second.
was washed from the roots and infection assessed
Soil
using the
27
Fig. 2.
Location of Ggt inoculum with respect to Pondera wheat seed
used to test activity of triadimenol.
28
scale
d e s c r i b e d in Table 2.
Dry
weight
of the shoots of
each of 6 week old plants was also recorded.
Raw
scores
of
infection
severity
of
both
experiments
w e r e a n a l y z e d us i n g the C A T M O D p r o c e d u r e
of SAS program.
Raw
p lants
scores
response
were
converted
category,
to
number
of
in
and analyzed using these counts.
a large n u m b e r of em p t y cells,
each
Due to
raw scores w e r e col l a p s e d
int o two c a t e g o r i e s (I, 2, 3) and (4, 5) for data analysis.
Infection
severity
DI and a n a l y z e d
of
the
second
trial
as a s p l i t - p l o t
s e p a r a t e the factors,
was
analysis
fungicides,
transformed
to
of v a r i a n c e
to
i n o c u l u m presence,
and
location of inoculum.
Soil
Since
was
soil
pH can affect
of i n t e r e s t
triadimenol
pH.
seed
To this end,
to
know
5.5, 6.4,
and 7.0.
good g r o w t h
whether
treatment
would
3 soils were
in the G a l l a t i n Valley,
the severity
the
also
of take-all,
effectiveness
be affected
collected from
Montana,
To p r o vide
final
a sphagnum
peat
by soil
cereal fields
a medium
that w o u l d
allow
coneta i n e r s ,
these
soils were mixed, with sand and peat in a ratio of
5.5,
a
w h i c h had natural pHs of
of p l a n t s in the t a p e r e d
sand: I pe a t by volume.
of
it
I. soil:I
For the soil wit h an initial pH of
of
pH 3•9
pH of 5.0 for the mixture.
w as
used
resulting
in
a
The pH 6.4 soil was mixed
29
with
another
sphagnum
final pH of 6.0.
peat
of pH 4.8
that r e s u l t e d
The pH 7.0 soil was mixed with
of pH 7.5 that r e s u l t e d in a final pH of 7.2.
each mixture was autoclaved for I hr.
autoclaved
mixtures
were
then
in a
a fen peat
A p o r t i o n of
Autoclaved and non-
infested
with
oat
kernel
i n o c u l u m p r e p a r e d as d e s c r i b e d previously, at the rate of
I g/ IOOg mixture.
Treated
and nontreated Pondera
in tapered plastic conetainers
filled
with
experiment
the
proper
consisted
replications
soil-inoculum
of 24
Conetainers
controlled
release
were
fertilized
fertilizer
free
and
weight
at
(Osmocote
the p l a n t s w e r e harvested,
dry
soils
' The
with 5
(autoclaved
and fungicide-doses as
w e e k s later,
of soil
mixture.
treatments
plot design with
and nonautoclaved) as the main plot,
subplots.
seed was planted
16.5cm long x 3.0cm diameter
of a total
in a split
wheat
of shoots
seeding
with
14-14-14).
Six
the roots w a s h e d
of
each
plant
and
i n f e c t i o n s e v e r i t y u s i n g the scale g i v e n in in Table 2 were
recorded.
described
Raw
the
Disease
per
plot
was
calculated
as
previously.
scores
CATMOD
converted
index
of
infection
procedure
to n u m b e r
and analyzed
e m p t y cells,
of
SAS
severity
program.
were
analyzed using
Raw
scores
of p lants in each r e s p o n s e
using these
counts.
wer e
category,
Due to a large number
of
raw s c o r e s w e r e c o l l a p s e d in t w o c a t e g o r i e s
30
'Mt
2 , 3)
analysis
and
was
(4,
5)
made
to
for
data
correlate
dry weight.
Number
a split-plot
analysis.
analysis.
A
regression
infection score
with
shoot
of plants per container was analyzed in
Host Species and Cultivars
To
and/or
determine
cultivars
performance,
cultivars
Manitou,
Lewis
influence
on
Ggt
were
tested.
of
different
infection
I d u r u m wheat,
and
and 3 barley
( d u r u m ) , Fortuna,
b arley seed w a s t r e a t e d w i t h
Seeds
tapered
were
plastic
planted
triadimenol
and fen peat
weight.
moss
T he
randomized
conetainers
(1:1:1
filled
seed
old
by v o l u m e )
experiment
design with
inoculum-no
week
Pondera,
plus
with
set
up
I%
as
4 replications.
dressing
plants
was
for
were
at 0.31 g
in 16.5 cm long x 3.0 cm
m i x t u r e p r e p a r e d w i t h B o z e m a n silt l o a m soil,
Six
species
triadimenol
4 s p r i n g wheat,
Ward
host
and N e w a n a s p r i n g wheat, and Hector, Betzes, and
a i / k g seed.
wide
the
each
a
A
inoculum
by
completely
was
and
growth
fine sand,
check
cultivar
harvested
a
of
no
included.
assessed
for
infection and dry weight as described previously.
Raw
the
scores
CATMOD
of infection
procedure
c o n v e r t e d to n u m b e r
and
of
SAS
severity
were
program.
analyzed
Raw
s cores
of p lants in each r e s p o n s e
analyzed using these
counts.
Due
to a large
using
were
category,
number
of
31
e m p t y cells,
( 1 , 2,
analysis
3)
and
was
dry weight.
raw
scores w e r e c o l l a p s e d in t wo cat e g o r i e s
(4,
made
5)
to
Number
in a split-plot
for
data
correlate
of
plants
analysis.
analysis.
infection
per
A
score
container
regression
with
were
shoot
analyzed
32
RESULTS
Poison JFood Tests
All
tested,
PDA.
of
the
1000,
fungicides
100,
However,
and
10
at lower
at
yM,
the
h igher
inhibited
concentrations
mycelial
growth
on
concentrations the fungicides acted
differentially, with some compounds being more effective in
reducing mycelial
the
fungicides
triadimenol
least
were
yM,
7 0 35 or
than others
X'E - 7 7 9 ,
all
inhibitory
r e d u c t i o n at 1.0
0.01
growth
prochloraz,
equally
b ut
yM.
it
still
At 1.0 yM,
etaconazol,
effective;
bitertanol
effected
a nd
was the
a 4 6 35 g r o w t h
At the l o w e s t c o n c e n t r a t i o n tested,
prochloraz and imazalil
more
(Table 4).
while
the
still inhibited
remaining
compounds
growth
were
by
only
minimally inhibitory or not at all.
After
containing
the
transfer
fungicide
of
at
mycelial
10
yM
to
discs
fr o m
media
f u n g i c i d e - free
PDA
m y c e l i a l g r o w t h resumed,
i. e. , all of the t r e a t m e n t s w e r e
fungistatic
the highest
(1000
yM),
in action.
h o w e v e r , .only
resumption
of growth;
(nuarimol,
imazilil,
growth
(triadimenol,
(Table 5).
At
the
concentration
bitertanol
others
prochloraz)
propiconazol,
allowed
allowed
either
tested
normal
no growth
or a restricted abnormal
etaconazol,
and
XE-779)
33
TABLE
4.
Effect
of v a r i o u s
inhibiting fungicides
on potato
dextrose
sterol-biosynthesis
on in v i t r o m y c e l i a l
agar.
i
I -G
I -P
I 3
I O
I G
I hO
Mycelial
(mm) 1
Fungicide concentration
Fungicide
I OOO
100
10
I .0
Nuarimol
O
Imaz al il
O
Prochloraz
O
Triadimenol
O
Bitertanol
3-0
Propiconazol 0
Etacohaz ol
0
XE-779
0
0 .6
I .6
0.4
0
3 •I
1.9
0
I .0
1.9
1.9
2.1
I .I
3 .I
2.6
I .2
I .5
4.6
5.3
2.0
2.7
17.4
5.5
2.4
I .7
^ After
1.9
10 days; g r o w t h
(]1M)
0.1
0.01.
29.6
I 0.2
2.9
8.9
36 .9
8.4
9.6
19.5
31.1
9.2
11.1
35.0
39.5
28.1
32.4
38.1
of check = 37.9 mm; LSD (P= 0.05) =
34
Table
5.
Propensity
inhibiting
fungistatic
tritici.
of v a r i o u s s t e r o l - b i o s y n t h e s i s
c o m p o u n d s to be f u n g i c i d a l
or
to D a e u m a n n o m y c e s £ r a m i n i s var.
Pattern of Growth^
Fungicide
Fungicides
1000
Nuarimol
Imaz al il
Prochloraz
Triadimenol
Bitertanol
P r opiconazol
Etaconaz ol
-
+
++
+
+
+
XE-779
Concentration
(JiM) 2
100
10
++
++
+
+
++
++
++
++
++
++
++
++
++
++
++
++
I
G r o w t h on f u n g i c i d e - f r e e PDA.
- =
no g r o w t h ;
abnormal restricted growth; ++ = normal growth.
+ =
^ C o n c e n t r a t i o n of f u n g i c i d e to w h i c h the m y c e l i u m was
previously exposed but later transferred to fungicide-free
PDA.
Table 6 shows
that exposure
to the fungicides did not
have any i n f l u e n c e on the v i r u l e n c e
of v a r i a n c e
were
equally
indicated
effective
that
in
of Ggt. . The a n a l y s i s
c u l t u r e s from
causing
all t r e a t m e n t s
infection
in
comparison
w i t h the check i n o c u l u m w h i c h had not been e x p o s e d to any
fungicide.
35
Table 6 .
Effect of previous mycelium exposure to various
s t e r o l - b i o s y n t h e s i s i n h i b i t i n g f u n g i c i d e s on
v i r u l e n c e of G a e u m a n n o m_y_c e s .gram in is var.
tritici to Pondera spring wheat.
Disease Index^
Fungicide
Fungicide
Concentration
(JiM)^
1000
100
I 0
I .0
0 . 1
NT3
NT
NT
4.7
3-8
4.0
5.0
4.9
4.8
4.6
4.8
4 . I
3.0
3.7
3-3
4 . I
4 . I
4.0
4.3
4 . I
3.8
4.5
3.9
4.7
4.6
4.8
3.8
4.6
3.4
3.3
4.3
4.0
4.8
4.3
3.8
Nuarimol
Imaz al il
Pro chi oraz
Triadimenol
Bitertanol
Propiconazol
Etaconazol
4.8
4 . I
4.6
4.3
4.6
XE-779
-
0.01
4.5
3.4
4 . 1
—
5.0
—
3-7
4.0
s I (.if of plants) ( I n f e c t i o n score)] / Total if o r plants; On
a sc a l e f r o m I to 5 w h e r e an i n f e c t i o n score of I= no
i n f e c t i o n ; 5 = pi ant n early dead.
D i s e a s e score for the
check w a s 4.2.
2
C o n c e n t r a t i o n of f u n g i c i d e to w h i c h the m y c e l i u m w as
previously exposed but later transferred to fungicide-free
PDA and then used as inoculum.
T= not tested
The mycelium
of Ggt did not produce pigmentation on CA
and growth was slower than on PDA.
The mycelium grew 37 mm
on PDA in 8 days and 26mm on CA.
When the fungicides were
t ested
using
generally
growth
occurred
of
the
base
medium,
their
e f f ects
more severe than when tested on PDA.
f u n g i cides,
several
CA as
but
the
at
some
1000
and
growth
fungicides
100
w as
(Table
M
with
observed
7 ).
were
No mycelial
any
at 10
Bitertanol
of
the
M with
was
again
36
the
l e a s t .toxic
pro chi or a z ,
of
the
eight
propiconazol,
fungicides.
e taconaz ol,
Nuarimol,
XE- 7 7 9
and
at c o n c e n t r a t i o n s d o w n to 1 . 0
strongly inhibitory
wer e
M but
less so at l o w e r c o n c e n t r a t i o n s .
Contrary to 'the test on
PDA,
only slightly inhibitory
imazalil
and p r ochldraz
at 0 . 1
and 0 . 0 I %M.
Table
7.
were
Effect of various sterol-biosynthesis inhibiting
f u n g i c i d e s o n in v i t r o m y c e l i a l g r o w t h of
G a e u m anno m yces gram inis var. tritici on Czapek’s
agar.
Mycelial Growth (mm) ^
Fungicide Concentration
Fungicide
1000
Nuarimol
Imaz al il
Prochl or az
Bitertanol
Propiconaz ol
Etaconazol
XE- 7 7 9
1 At the
= 1.0
0
0
0
0
0
0
0
8 th d a y ;
100
I0
0
0
0
0
0
0
0
0
0.5
0
4.0
0.5
0.5
0.5
growth
of
(yM)
I .0
0 .I
0.01
2 .2
9.7
0.6
10.2
4.0
3.7
2.2
12.5
16.2
8.2
13.7
12.2
14.5
18.7
15.0
15.5
19.0
15.7
check = 2 6 .0 mm;
LSD
16.2
14.7
25.2
(P = 0.05)
Field Trials
Evaluation of Fungicides
The
factors,
of
statistical
analyses
indicated
inoculum rate and fungicides,
inoculum
rate
x
par a m e ter s evaluated
fungicides
in this
were
that
the
main
and the interaction
significant
experiment
except
for
for
all
number
37
°tillers
of 6 w e e k old plants.
effect on n u m b e r
Only f u n g i c i d e s had an
of t i l lers per plant,
but not levels
of
inoculum.
W h e n the f u n g i c i d e - d o s e s
inoculum
rate
(Table
8 ),
expected,
close
to one
for
ino c u l u m .
rose
the
all
c o m p a r e d w i t h i n each
disease
index
treatments
with
was,
as
no added
W i t h Ig of i n o c u l u m per row, the DI of the check
to
2.5.
fungicides
The best
were
Even
at
this
low
level
differed in their ability
control
was provided
of
to protect
infection,
the plants.
by XE-77 9 at O' . 2 2 g a.i./kg
and by t r i a d i m e n o l at 0 .31 and 0.47 g a.i./kg.
The DI for
other compounds and rates did not differ.significantly from
that of the u n t r e a t e d
d o u b l e d to 2 g/row,
best
control
highest rates.
was
check.
W h e n the i n o c u l u m rate was
DI of the check i n c r e a s e d to 3.4.
achieved
with
triadimenol
at
The lowest rate of triadimenol,
the
The
two
the highest
rate of X E - 7 7 9 and i m a z a l i l , and both rates of p r o c h l o r a z
provided intermediate,
but significant,
control.
i no cul u m / r o w , the DI of the c h e c k was 3 .5 .
highest
rates
as compared
of
triadimenol
to the nontreated
lowered
check
At 5 g of
Only the
significantly
(Table 8 ).
two
the DI
38
Table
8.
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
s p r i n g w h e a t o n . s e v e r i t y of take - a l l disease
after 6 weeks in the field.
Disease I ndex^.
Inoculum Rate
Dose
g a.i./kg
Fungicide
Triadimenol
Propiconazol
XE-779
Prochl draz
Imaz alii
0.16
0.31
0.47
0.01
0.02
0.04
0.11
0.22
0.20
0.40
0.05
0.10
Untreated
(g/3m)
0
' I
2
5
I .O2
I .5
I .0
1.4
1.3
I.0
1.9
I .3
I .3
I .2
I .I
I.2
1.3
2 .I
I .9
I .6
2 .0
2 .1
. 2.7
2 .5
I .5
2.6
2.5
2.3
2.5
2.5
2.3
I.8
I .9
3.5
3.2
3.2
3-3
2.7
2.6
2.8
3.0
2 .4
3.4
3.2
2.7
2.3
3.8
3.8
3.8
3.8
3.8
3.5
3-4
3.3
3.4
3.5
1D I =
e I (# of plant s') x ( I n f e c t i o n score) ] /Total .# of
plants ; on a s c a l e f r o m I to 5 w h e r e an i n f e c t i o n
score
of I= no visible symptoms and 5 = almost dead plants ■
2LSD
(P=O.05) = 0 . 6
The a n a l y s i s
of shoot dry
weight indicated
separation of treatment
groups was
With
the average
no added inoculum,
untreated
ch e c k w as 614
fluctuated
widely,
of the check.
distinguished
with
not as clear as for D I.
mg/plant.
weights
that the
both
dry weight (DW) of the
The other
treatments
above and
At the inoculum rate of Ig/row,
below
that
the analysis
11 groups of treatments and the check had the
39
At 2 g of inoculum per row,
second highest D W .
there were
still 10 g roups but now Ggt i n f e c t i o n a f f e c t e d DW and the
check
had
analysis
the
second
of D I , the
triadimenol
inoculum
treatments
two
at 0.31 and
ra t e ,
there
but all
lowest
weight.
highest
DWs
wer e
0.47g a.i./kg seed.
were
I2
three doses of triadimenol
groups
Triadimenol
Propiconazol
Dose
g a.i./kg
0.16
0.31
0.47
0.01
0.02
0.04
0.11
0.22
0.2
0.4
0.05
0 .I
Check
1 LSD
of
stood out as
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
s p r i n g w h e a t on shoot dry w e i g h t of 6 we e k old
p lants in the field a r t i f i c i a l l y i n f e s t e d w i t h
G a e u m annom vces g ram inis var. tritici.
Fungicide
Imaz al il
with
(Table 9 ).
Inoculum Rate
Prochl oraz
the
At the highest
Shoot Dry Weight
XE-779
to
obtained
recognizable
the best treatment with the highest DWs
Table 9.
Similar
(P = 0.05)=6.0
(mg)
(g/3m)
0'
'I
2
6 191
477
662
578
583
729
637
765
578
621
560
613
614
6 36
557
565
569
66 I
433
703
619
525
615
587
573
666
569
741
629
374
584
448
46 I
543
6 26
540"
520
521
435
5
553
663
662
356
315
273
295
324
397
501
412
418
. 26 1
40
Regression analysis
slope
b = - 0.0 0 3
R2 =O.31.
and
a
of D I vs.
shoot dry weight gave a
coefficient
This r e g r e s s i o n a n a l y s i s
crop stage,
infection
by Ggt
does
of
determination
of
c o n f i r m s that at this
not yet
have
a strong
e ffect on the p h y s i o l o g y of the w h e a t plants as in d i c a t e d
by their dry weight.
Analysis
showed
that
of
number
there
treatments.
of t i l l e r s
were
However,
per 6 - w e e k
differences
when
among
fungicide
c o m p a r e d w i t h i n each i n o c u l u m rate,
old plant
fungicide
treatments
were
no d i f f e r e n c e s a m o n g
t r e a t m e n t s w e r e found at any of the i n o c u l u m rates (Table
10).
Although
different
the
the
amount
rates of inoculum
plants,
it
c l e arly
of
d i s ease
did affect
did
not
produced
shoot dry
significantly
by
the
weight of
influence
tillering.
Regression analyses of disease index vs number
of
per
tillers
coefficient
of
plant
gave
determination
I 0 % of the v a r i a t i o n in n u m b e r
disease
index.
a
slope
R2 =O.!
b = -0.46
but
the
indicated that just
of t i l lers w a s r e l a t e d to
41
Table
10.
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
s p r i n g w h e a t on n u m b e r of tillers per plant of 6
week old plants grown in the field artificially
infested
w i t h £ a e u m_a n n o m y o e s ^ r a m i n i s var.
tritici.
Number
of tillers per plant
Inoculum Rate
Dose
g a.i./kg
Fungicide
Triadimenol
Propiconazol
XE-779
Prochl oraz
Imazalil
0.10
0.31
0.47
0.01
0.02
0.04
0.11
0.22
0.20
0.40
0.05
0.10
Check
0
I
2
2.7 1
2 .8
3.4
3.0
3.1
3-3
3.1
3.6
2.9
3.0
3.2
3-5
2.6
3.1
3.0
2.7
3.0
3-7
2.9
3.5
3 .I
3.0
3.4
3.5
3.9
3.2
3.0
3.5
3.4
2.5
3.4
3 .1
2.8
3.0
3.1
3.0
3-3
3.5
2.5
clearly
showed
(g/3m)
5
3.0
3.4
3.3
2.5
2.4
2 .1
.2.2
2.7
. 2.7
3.0
3.0
3 •I
2 .1
(P = 0 .05)=0. 8
1LSD
Foliar
symptoms
t r i a d i m e n o l in r e d u c i n g the e f f e c t s
8 th week,
the
superiority
of take-all.
At 2g/ row,
clear
and only
evidence
of d i s e a s e d
plants,
there was
triadimenol
p r e v e n t e d s y m p t o m s f r o m d e v e l o p i n g at this time.
of 5 g / r o w , most
disease.
At the
no foliar symptoms were observed at the inoculum
rate of Ig/row w i t h any treatment.
rate
of
However,
plots
p lants
showed
in
At the
s evere e f f e c t s of the
triadimenol
plots
showed
42
greatly
reduced symptoms,
lowest dose (Table 11).
increased
Four weeks later,
considerably,
symptoms
of
with only slight symptoms at the
and
disease.
no
disease severity
treatment
However,
prevented
triadimenol
all
did
s i g n i f i c a n t l y reduce s y m p t o m s e v e r i t y as c o m p a r e d to the
untreated
check (Table 11).
The DIs for the 0.31 and 0.4?g
a.i./kg seed doses w e r e 2 . 5
the
and 2 . 2
as c o m p a r e d to 4 . 7
for
check.
Late in the season,
number
of
plants
and
take-all had a marked influence on
number
of
t i l l e r s / m.
The
average
n u m b e r of live p l a n t s / m for the u n t r e a t e d ch e c k w as 61, 41,
3 2 , and
rates
13
plants
(Table 12).
7 3 f 58,
for. the 0 , 1 , 2 , and
respectively
inoculum
The average number of tillers/m was 105,
19 at the 0 , I, 2 , and
and
5 g/row
(Table
1 3 ).
5 g of i n o c u l u m
Although
some
of
rates,
the fungicides
had a protective effect by diminishing the number of plants
and
tillers
lost
to
take-all
increased from 0 to 5 g/row,
most
adverse effect on plant number.
Table
12
for
the
caused
since
remaining
compensate
Disease
only
inoculum
treatment.
reduction
produced
by
reduction in number
Ig
of
more
inoculum/row
of plants and a
30%
However,
in
for the r e d u c t i o n in plant n u m b e r
induced
was
This phenomenon is seen in
a slight
plants
the
of the fungicides had an
non-inoculated
fungicides
the
when
tillering
t i l lers
to
(Table 1 2 ).
produced
a
33%
reduction in number
43
Table
11.
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
spring wheat on severity of take-all after 8 and
12 weeks in the field.
Foliar Disease Index I
8 weeks
12 weeks
Ino c . Rate
Fungicide
Dose
g a. i. /kg
Triadimenol
0.16
0.31
0.47
Propiconazol 0 . 0 1
0.02
0.04
XE- 7 7 9
0.11
0.22
Prochloraz
0.20
0.40
Imazalil
0.05
0.10
Untreated
0
I
2
I .O2. I .1
I .7
1.0
I .I I .I
I.0
I .I I . 0
I .0
I .4 2.4
I .I I .5
2.4
I .I I .9 2 . 2
I.0
I.2
2.4
I .2
I .4 2 . 0
I.0
I.8
1.3
I .0
I .4 .1 .9
I.2
2.4
1.7
I .3 2 .I 2 . 6
1.0
2.2
I.2
(g/3 m)
5
0
1.8
I .4
I .I
4.1
4 .0
4 .I
3.9
3.9
3.6
3.2
3.7
3.6
3.9
I .0
I .0
I.0
I .0
I .0
I .2
I.0
I .0
I.0
I .0
1.7
I.2
I .2
I .
2.2
I .0
I .5
2.7
3.0
3.0
2.0
2.0
2.7
2.2
2.5
3.0
2.7
2
5
2.0
I .2
I -7
3.5
3.2
3-2
3.0
3.0
2.5
2.7
3-2
3-2
3.2
3.2
2.5
2.2
4.7
4.5
4.7
4.5
4.7
4.5
3.7
4.2
3.7
4.7
4
On a scale fro m I to 5 w h e r e t = no v i s i b l e s y m p t o m s and
5 = s e v e r e l y s t u n t e d p l ants and very low p o p u l a t i o n of
plants remaining in the plot.
2LSD (P=0.05)=0.6
44
Table
12.
Effect
of
sterol-biosynthesis
inhibiting
f u n g i c i d e s a p p l i e d as
s e e d t r e a t m e n t s to
Pondera spring wheat on number of live plants/m
in
plots
artificially
infested
with
Gaeumannomvoes eraminis var. tritioi.
Number
of pi ants/m
. Inoculum Rate
Fungicide
Dose
g a.i./kg
Triadimenol
0.16
0.31
0.47
Propiconazol
0.01
0.02
0.0 4
Prochloraz
0.11
0.22
0.20
Imaz alii
0.40
0.05
XE-779
0.10
Check
1LSD (P=0.05)=9.6
0
49.5 1
46.2
51 . 7
44.5
42.0
35.0
44.7
40.0
47.5
41 . 7
I
(g/3m)
2
43.5
46.2
52.5
29.0
.45.7
43-2
46.5
19.2
32.2
17.0
26.2
25.5
41.0
25.5
32.2
28.2
32.5
38.0
27.2
35.5
25.0
25.0
18.7
31.7
38.2
28.2
22.2
60.7
40.7
5
31.0
33-2
43.5
8.5
9.2
7 .2
I0 . 7
12.5
17.5
25.5
14.5
14.7
13.0
45
of
tillers
in
the
plots,
however,
those
of
the
untreated
check.
both traits were
check
(Table
12
In
the
triadimenol
significantly superior
and
13).
By
doubling
to
the
i n o c u l u m f r o m I to 2 g , the n u m b e r of p l ants and n u m b e r of
tillers
was
reduced
by
and
52%
compared to tjie uninoculated
respe c t i v e l y ,
55%,
At 5 g of inoculum,
control.
the reduction was very drastic and the untreated
a 7 9%
r e d u c t i o n in n u m b e r of p lants and an
number of tillers.
a slight
was
increase
compared
statistically
r e d u c t i o n in
82%
to
different
the
check,
only
triadimenol
in i n c r e a s i n g the n u m b e r
(Table
adversely
14).
exhibited
reflected
The
affected
phytotoxic
by
of
check.
Similar to the other parameters evaluated,
also
check had
Although prochloraz and Imazalil showed
plants as compared to the untreated
was
as
the
amount
e f fect
of
grain yield
of
the
inoculum
fungicides
by the r e d u c t i o n in n u m b e r of p l a n t s / m was not
in grain yield.
One and 2g of inoculum
grain yield reduction of 33
and 6 3 % ,
two highest rates of triadimenol
to the u n t r e a t e d - u n i n o c u l a t e d
fungicides
provided
this
respectively,
allowed yields
check.
protection.
None
of
caused a
but
the
comparable
the
other
W h e n the i n o c u l u m
p r e s s u r e w a s very high ( 5 g ) , t r i a d i m e n o l w a s not able to
p r e v e n t yi e l d r e d u c t i o n c ompletely.
doses of t r i a d i m e n o l ,
Even at the highest
there w a s a 4 1% yield r e d u c t i o n in
46
c o m p a r i s o n w i t h the check w i t h no in o c u l u m ; however,
yields were 184% of those for the untreated check.
inoculum
rate,
all
highest
dose
At this
the other fungicides resulted in yields
l o w e r t h a n that of the check e x cept prochloraz,
its
the
had
a 1 2 0 % increase
over
w h i c h at
the unt r e a t e d
check.
Table 1 3 .
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
s p r i n g w h e a t on n u m b e r of t i l l e r s / m
in plots
artificially infested with
u m^i) n_p m_y_c_e_s
g r a m inis var. tritici.
Number '
of tillers/m Inoculum Rate
Fungicide
Triadimenol
Propiconazol
XE-779
Prochl oraz
Imaz al il
Dose
g a.i./kg
'0.16
0.31
0.47
0.01
0.02
0.04
0.11
0.22
0.20
0.40
0.05
0.10
Check
1LSD
(P=0.05)=24.0
0
I091
102
I 05
100
96
86
I 03
96
I 04
95
89
84
105
(g/3 m)
I
2
5
79
100
113
67
I 06
55
75
69
73
78
67
60
73
85
92
95
36
48
5.9
49
71
73
57
54
47
58
54
68
77
22
I 8
10
16
22
24
50
32
34
I 9
-
47
Table
14.
Effect
of
sterol-biosynthesis
inhibiting
fungicides applied as seed treatments to Pondera
s p r i n g w h e a t on gr a i n yield of p l a n t s g r o w n in
field plots
artificially
infested
with
G u a m annom yces gram inis var. tritioi.
Grain Yield
Inoculum Rate
Dose
g a, i. /kg
Fu n g i cide
Triadimenol
Propiconaz ol
XE-779
Prochloraz
Imaz al il
194.0
231 . 2
241 .7
134.5
179.5
144.5
215.5
201 . 3
171.0
165.7
168.8
177.7
176.7
(g/2 . 6
2
I
3 0 2 .O 1
274.2
298.5
292.5
272.0
261 .5
.289.0
302.8
305.0
288.8
280.3
253.5
.264.8
O .16
0.31
0.47
0.01
0.02
0.04
0.11
0.22
0.20
0.40
0.05
0.10
Untreated
1LSD
0
(g)
m)
5
188.5
289.5
234.5
116.0
111.8
127.7
140.7
130.7
166.0
138.0
I 48.7
132.7
96.7
90.5
91 . 0
157.0
15.0
37.2
47.5
. 27.2
34.2
53.0
121 . 7
51.7'
39.2
55.2
(P=O.05)=52.6
Effect of Soil F u m igation.
Results
6
week
old
variance
factors,
as
of
statistical
p lants
in
were
the
fumigation,
significant
CATMOD
same
of lesion severity
using
procedure.
the
analysis
Only
on
of
the
main
i n o c u l u m rate, and fungic i d e s ,
were
(Table 15).
not significant.
the
analysis
Interactions among factors were
Al I 3 inoculum levels were different from
48
each other with
an LSD of 0.2.
The average DI for the non-
ino c u l a t e d check was 1 .5 , for 2 g of i n o c u l u m / r o w
2.9,
and
for
fungicides
at
0.16
from
4
g
were
plants
g a.i./kg
the non-treated
of p l a n t s fro m
inoculum/row
compared,
0.31
and
of
was
3.4.
treated
with
triadimenol
significantly
propiconazol
pr opico naz ol
0.02
The average DI
0 . 0 1 g a.i./kg it
g a.i./kg
it
was
When
different
t r e a t e d seed at 0 . 1 6
triadimenol
check it was
it
check with an LSD = O .3.
w a s 2 .2 , for
treated
were
it w a s
was
2 .8 , and of
g a.i./kg
2.9,
the
for
no n-
3 .0 .
For the DI for l e s i o n s e v e r i t y of 6 w e e k old plants,
there
was
performance
no
evident
interaction
of the fungicides,
of
fumigation
and
and the r e s p o n s e was very
similar to that in the first experiment,
where
plants from
seed t r e a t e d w i t h e ither dose of t r i a d e m e n o l
had a l o w e r
lesion severity
had
than the
untreated
check.
Fumigated
plots
a higher DI than the corresponding non-fumigated plots
(Table 16).
49
Table 15.
A n a l y s e s of v a r i a n c e of seven p a r a m e t e r s that
m e a s u r e i n f e c t i o n by G a e u m a n n o m vces g r a m i n is
var. _t r j._t i_cj. on P o n d e r a s p r i n g w h e a t in
artificially infested field plots.
Fumigation^
Infection Parameters
M.S.
P-val^
Inoculum^
M.S.
Fungicides3
P-val
M.S.
P-val
0.019
38.0
0.000
3.8
0.000
7.5E-2
0.907
21.6
0.000
1.7
0.023
53.6Ek-I .
0.950
13.BEk-S
0.000
Aerial Disease Index 5 64.5
0.001
64.8
0.000 .
#Plants/m
52.1Eh-2
0.002
12.4Ek-3
0.000
13.9Ek-2
0.000
#Tillers/m
1.5.3&-3
0.084
59.3&-3
0.000
34;6Ek2
0.000
Grain Yield
33.4E*
0.014
29.0Ek4
0.000 . 36.9E+2
0.203
Disease Index^
#Tillers/plant1
23
6
5
*
Dry Wt/plant2*
11.3
l8.8Ek-4
2.6
0.000
0.000
1 Fumigated and non-fumigated soil
2 0 , 2 , and 4 g of infested oat kernels/3 m row
3 Seed treatments with triadimenol 0.16, 0.32; propioonazol 0.01 and 0.02 g
a.i./kg seed; and check with no fungicide
^ After 6 weeks
5 After 12 weeks
6 At 0.05 level of significance
Table
16.
E f f e c t of s o i l f u m i g a t i o n on t a k e - a l l d i s e a s e i n d e x and
performance of sterol-biosynthesis inhibiting fungicides applied
as seed treatments to Pondera spring wheat.
Disease Index
6 weeks'*
non-fiinricrated
8 weeks?
fiimipahed
nnn-fiimigated
InocuLun Level (g/gm)
EUngLcide
Dose
g a.i./kg 03
2
0
4
2
12 weeks^
fumigated
non-fimigated ' Dimigated
Inoculun Level (g/gm)
4
0
2
4
0
2
4
Inoculun Level (g/gm)
0
2
4
0
2
4
1.1 2.0 2.7
1.6 2.1 2.5
1.4 2.7 3-2
1.3 2.8 2.9
1.0
1.0
1.2 1.9
1.2 1.6
1.6 2.7 3.9
1.4 2.6 3.1
1.0 2.5 3.5
1.2 2.2 2.7
2.5 4.2 5.0
2.2 4.2 4.7
Propioonazol
0.01
0.02
1.3 3.2 2.9
1.3 2.7 3.5
2.1 3-5 4.5
1.7 3.8 3.9
1.0 2.5 4.0
1.0 2.1 3.6
2.2 3.9 5.0
1.3 4.0 4.7
1.2 3.5 4.5
1.0 3.2 4.0
3.7 4.5 5.0
2.5 5.0 5.0
1.3 3.1 3.3
2.1
1.1
1.8 3-1
1.4 4.5 5.0
1.2
Untreated
3.6 4.5
on
0.16
O.gl
^ Obtained from symptoms of roots and stems; L3) (P=0D5)=0.7
2 Obtained from foliage symptoms; eigit weeks LSD(P=0D5)=0.6; twelve weeks I^D (P=ODb)=O.?
3 Grams of infested oat kernels/g m row
I
CO
Triadimenol
4.2
2.5 5.0 5.0
51
When
was
the
effect
evaluated
inoculum
at
rate,
different
8 th
the
and
(Table
of the v a r i o u s
fungicide
15)..
fumigated
1 2 th
and
week,
l e vels
Disease
fumigation,
were
index
significantly
increased
when
the
soil
w as
16)..
With reduced competition. Ggt was more aggressive and
triadimenol
did
prior
f a c t o r s on foliar DI
not
have
to i n f e s t a t i o n w i t h Ggt (Table
the
opportunity
plants as it did in the non-fumigated
to protect
plots..
the
Early in the
season (6 th and 8 th weeks) both doses of triadimenol showed
a DI reduction even in the fumigated plots, but by the 12th
week,
the inoculum pressure overcame the protective effects
of the triadimenol..
The
effect
reflected
in
experiment,
of
reduced
grain
yield
(Table
17)..
on
DI
As
in
was
the
also
first
grain yield was drastically reduced in infested
non-f umigated plots..
yield
competition
reduction
of
Two and 4g of inoculum
45
8 5 %,
and
caused a grain
respectively,
but
triadimenol at 0.32g a.i./kg seed allowed only
a 25 and
57%
reduction,
however,
the
respectively..
In fumigated plots,
disease effect was so overwhelming
untreated
9 3 %,
c h e c k in the i n f e s t e d
respectively,
triadimenol
protection.
at
2g
that
grain yield of the
plots w as r e d u c e d 97 and
and
4g
at 0 . 3 2 g a.i./kg w a s
not
of
able
inoculum;
and
to s u s t a i n any
F u m i g a t i o n by i t s e l f had a m a r k e d
effect on
52
yield
than
and the fumigated
the
untreated
non-fumigated
plot.
check had 60%
A phytotoxic
less yield
response
to
f u m i g a t i o n w a s also o b s e r v e d as f o liar s y m p t o m s after 12
weeks
(Table
Table 17 .
16).
Effect of soil fumigation with methyl bromide on
grain yield in field plots artificially infested
with G a e u m annom yces g ram inis and performance of
sterol-biosynthesis inhibiting fungicides
a p p l i e d as seed t r e a t m e n t s to P o n d e r a spring
wheat.
Grain Yield
(g/2.6 m)
Non-fumigated
Fumigated
Inoculum Level
Fungicides
Dose
g a. i. /kg
0
2
4
0
2
51 .0
101.8
119.0
141 .5
28.0
27.2
2.7
12.5
92.7
96.5
12.7
28.0
46.5
127.5
14.2
4.2
7.5
4.2
130.0
34.5
96.7
2.5
6.7
Triadimenol
0.16
0.32
2 4 1 .71 1 2 6 . 0
238.3
176.5
Propiconaz ol
0.01
0.02
3 53.2'
304.5
Untreated
1 LSD
236 . 2
(g/3m)
.
4
(P=O.05)= 69.3
When grain yield was regressed against BI,
number
of
t i l l e r s / m,
significantly
coefficient
only
correlated
of determination
DI
with
at
the
yield
12th
week
was
( r = 0.9 5 ),
R2 = 0.89 indicated
the variation in yield was explained by BI.
dry weight,
that 89%
The
of
53
Effect of Inoculum Placement
The a n a l y s i s
showed
a
of v a r i a n c e
significant
distribution
of
difference
inoculum
(0,
18 Okg/ha), and to fungicides
but
not
to
the
of DI of 6 w e e k old plants
2,
interaction.
significant.
on lesion
The
two
and
to
4g/row
level
and
90
and
and
(triadimenol and propiconazol)
When
analyzed using the CATMOD procedure,
was
related
lesion
severity
only level
fungicides
was
of inoculum
had a similar
effect
severity.
The level
of infection in plots in which
the inoculum
w a s r-ototilled int o the soil w a s not as high as w h e n the
i n o c u l u m w a s p l aced in close p r o x i m i t y to the seed (Table
18).
In the u n t r e a t e d
plots,
on l y 4g of i no c ul u m / 3 m row
had a s i g n i f i c a n t l y h igher DI (3.2) tha n that of the noni no c u l a ted check.
represents
only
damage
produced
furrow
was
A l t h o u g h 4 g of i n o c u l u m per 3 m of row
33kg
by
of
this
almost
t wo
broadcast-rototilled
inoculum/ha,
amount
times
inoculum
fungicides propiconazol
the
infection
of i n o c u l u m
higher
rate
than
of
in
the
and
the .seed
highest
I 80kg/ha.
The
and t r i a d i m e n o l did not have any
s i g n i f i c a n t effect on D I, and it w a s not d i f f e r e n t from the
DI
of untreated plots.
54
E f f e c t of i n o c u l u m l e v e l and p l a c e m e n t on
s e v e r i t y of take - a l l of 6 w e e k old P o n dera
spring wheat in the field.
untreated
I.I
I .4
1.9
3.2
I .23
4
2.5
90.
1.5.
I .7
1.4
2.0
I 80
CM
2.3
O
2
CM
Broadcast .
■ O2
Propiconazol
0 .0 2g a. i ./kg
UJ
In the
furrow
Triadimenol
0 .32g a.i./kg
O
Inoculum
Inoculum
Placement
Rate
Index^
ro
Disease
O
Table 18.
I On a sc a l e f r o m I to 5 w h e r e I = no v i s i b l e s y m p t o m s and 5
= s e v e r e l y s t u n t e d p l a n t s and very low p o p u l a t i o n of
plants remaining in the plot.
n
0 = non-infested oat kernels placed in the furrow together
with the seed.
2, 4,= g of infested oat kernels placed in
the f u r r o w t o g e t h e r w i t h t h e seed.
90, 180 = k g / h a
infested oat kernels broadcast on the soil and rototilled
in to a d epth of 10cm.
^LSD(P=O .0 5)=0.7
The n u m b e r
of t i l l e r s of 6 w e e k old p l a n t s w as not
influenced
by
t he
application
fungicides.
Nevertheless,
dry
of
inoculum
or
by
the
weight of 6 week old plants
w a s r e d u c e d w h e n the i n o c u l u m was placed in c o n t a c t w i t h
the seed (Table 19),
the inoculum
was
in concordance with a higher DI.
broadcast
and
rototilled
into
the
When
plot,
there was ho significant effect of infection on dry weight.
55
Table 19.
E ffect of i n o c u l u m level and p l a c e m e n t on dry
w e i g h t of 6 w e e k old P o n dera s p r i n g w h e a t in the
field.
Dry Weight
Inocul urn Inoculum
Triadimenol
Placement
Rate
0.32g a.i./kg
In the
furrow
(mg)
Propiconazol
0.02g a. i. /kg
untreated
O1
581.82
526.5
460.2
2
427.3
515.7
286.3
4
393 •I
325.3
310.1
90
478.5
469.9
489.3
I 80
554.5
444 .7
514.9
Broadcast
^0 = non-infested oat kernels placed in the furrow together
with the seed.
2, 4 ,= g of infested oat kernels placed in
t h e f u r r o w t o g e t h e r w i t h the seed.
90, 1 8 0 = k g / h a
infested oat kernels broadcasted in the soil.
2LSD
(P=0.05)=211.4
By
the 8th week,
the effect
visually reflected
in
The
I (no
aerial
DI
was
the
of root infection was not
a erial
portion
symptoms)
or
of
very
the
plants.
close
to
I,
except for the 4g of inoculum/row
of untreated
(D1=3.1) and
propiconozal
month
the
of
the
(DI=3.6)
infection
broadcast
inoculum
of infection;
thus,
plots.
were
One
more
treatments
evident
later,
(Table
did not produce
triadimenol
did not show
effects
20).
The
a high level
a significant
protective effect as it did when the inoculum was placed in
the row.
This
same
e ffect
was
observed
in
grain
yield
56
(Table
2 1).
Aerial
DI
of
I2 w e e k
old
plants
yield were strongly correlated (R2 = O.83),
in
the
evaluation
fumigation
of
as they also were
fungicides
a nd
effect
None
the
ot h e r
experiments.
of
and grain
of
so i l
measured
variables were correlated with yield.
Table
20.
E f f e c t of i n o c u l u m l e v e l a n d p l a c e m e n t on
s e v e r i t y of t a k e - a l l of 12 w e e k old P o n d e r a
spring wheat in the field.
Disease Index^
Inocul urn
Placement
In the
furrow
rate
Triadimenol
2
2.0
4
.1.0
I .0
3.5
4.0
3.7
90
1.2
'I .7
I .5
I 80
I .7
2.0
2.0
CO
fc-
I .5 3
Untreated
OJ
O2
Propiconazol
O
Broadcast
Inoc.
4
On a scale f r o m I to 5 w h e r e I = no v i s i b l e s y m p t o m s and
= s e v e r e l y s t u n t e d p l a n t s and very low p o p u l a t i o n of
plants remaining in the plot.
5
2 0= non-infe s ted oat kernels place in the furrow together
w i t h the seed.
2,4 = g of i n f e s t e d oat k e r n e l s toge t h e r
w i t h the seed.
90 ,1 80 = k g / h a of i n f e s t e d oat k e r nels
broadcasted in the soil;
3 LSD(P=0.05)=0.5
57
Table 21
Interaction of seed treatment and inoculum rate
and p l a c e m e n t of Ggt on gr a i n y i e l d of Pondera
spring w heat.
Grain Yield
Inocul urn Inocul urn Triadimenol
Placement
Rate
0.3 2g a. i. /kg
In the
furrow
Broadcast
(g / 2 .6m) 1
Propiconazol
0.02g a.i./kg
untreated
O1
2 8 5 .42
278.9
257.4
2
180.4
132.9
101 .6
4
158.9
57.1
99.0
90
250.1
247.3
236 .1
I 80
26 I .2
211.2
196.7
<1
0 = non-infested oat kernels placed in the furrow together
with the seed.
2, 4,= g of infested oat kernels placed in
t he f u r r o w t o g e t h e r w i t h t he seed.
90, 180= k g / h a
infested oat kernels broadcasted in the soil.
2 LSD
(P = 0 .05)=52.0
The percentage
ra t e
was
17.4
and
of white heads for the 90kg/ha inoculum
for
the
I 80kg/ha
was
27.8
(Table
22).
Contrary to the other response variables evaluated for this
experiment,
p er
plot.
reduction
kg/ha,
propiconazol reduced
Triademenol,
with
3 .5 ? and
respectively.
the number
however,
13.5?
of white heads
allowed
whiteheads
at
a
90
greater
and
I 80
58
Table 22.
Effect of a m o u n t of b r o a d c a s t & ^ e urn anno m^_c_es
K ram inis inoculum on percentage of white heads
of P o n d e r a s p r i n g w h e a t as a f f e c t e d by seed
treatment.
Percentage of white heads
Inoculum
Dose
g a.i./kg
Fungi aide
(kg/ha)
0
90
I 80
13.5
Triadimenol
0.32
——
3.5
Propiconazol
O .02
——
9.5
2.3
17.4
Untreated
.
18.5
28.7
Greenhouse Tests
Inoculum Location
The analysis of variance
to
determine
treatment
factors
however,
the
e ffect
efficacy
and
showed
more restrictive,
of
infection
experiments.
presented
An
The
in Table 23.
the experiments
location
differences
CATMODE
on
seed
for
procedure
all
was,
so it was the analysis used in
for
severity
a v e rage
inoculum
significant
interactions.
the presentation of results
Means
of
of data from
DI
number
were
from
of infected
very
both
similar
plants.
in
both
experiments
is
59
Table 23•
Effect of triadimenol seed treatment on severity
of take-all of seedlings of Pondera spring wheat
in t h e g r e e n h o u s e as a f f e c t e d by i n o c u l u m
position.
Disease Index^
Triadimenol
Ino c . Rate2
1
2
%
Inoculum3
Location
0
0.16
0
0.1
0 .I
0.1
I .0
I .0
I .0
5.0
5.0
5.0
Above
Below"
Around
Above
Below
Around
Above
Below
Around .
I .0
I .5
I .6
3.3
3.9
4.4
4.7
4.8
5.0
5.0
I .0
I .4
I .0
2.9
3.4
I .5
4.2
4.7.
3:1
4.7
(g/a. I ./kgj
0.32
0.64
. I .0
I .2
I .0
I .7
3-7
I .0
4.5
4.2
I .8
4.5
I .0
I .4
I .0
I .5
3.4
I .I
3.8
4.2
I .0
4.7
[(# of plants) ( I n f e c t i o n s c o r e ) ] / T o t a l # of plants; on
a scale f r o m I to 5 w h e r e an i n f e c t i o n score of I= no
in f e c t i o n ; 5 = plant n e a r l y dead.
V a l u e s are the average
of two experiments.
Percentage
(w/w).
3 With
of
respect
When
infested
to the
compared
triadimenol
oat
kernels
with
each
were different
untreated
a.i./kg
Ra t e s
of
of
check
was
triadimenol,
inoculum
Differences
among
mixture
seed (see Fig. 2).
other,
from
For
also
ra t e s
three
of
doses
of
check but no
The average DI for
0.16,
the D I* s w e r e
were
all
3.8.
the
the untreated
differences were observed among doses.
the
in g r o w t h
0.32,
3.0,
2.6,
statistically
inoculum
and
were
0.64 g
and
2.4.
different.
observed,
60
except
f or
inoculated
1.6,
was 2.7»
1.0.
3.3,
different
of
check.
check w a s
were
0.1/8
For 0.1,
and 4.0.
for below
The
compared
1.0,
and
5.0%
Locations
of i n o c u l u m
throughout
1.9,
x inoculum
the container,
x inoculum
position,
rate
and
however,
was
at
inoculum,
there
is
i n o c u l u m location.
for
interaction
was
very
the
3.8.
rate
x
significant
From Table 23,
highest
between
in
rates
fungicide
of
and
W h e n the i n o c u l u m w a s above the seed
and all through the growth medium,
treatments
also
The interaction of
it
least
were
inoculum
but not in the second.
that
the D I tS
above the seed
the DI was
the first experiment
obvious
non-
and when inoculum was
inoculum location were not significant.
is
the
i noculum,
and the average DI for
the seed was
fungicide
fungicide
with
The a v e rage DI for the n o n - i n o c ula ted
among them
distributed
inoculum
similar
to
the DI for the fungicide
the
untreated
the inoculum was located below the seed,
reduction in infection for all doses
i n o c u l u m rates of 1.0 and 5.0%.
check.
When
there was a marked
of triadimenol at
the
Soil M
Infection severity
soil
pH (Table
24).
on s e e d l i n g s
Although
there
w i t h i n c r e a s e d do s e s of t r i a d i m e n o l
was not affe c t e d
was
reduction
by
on DI
in a u t o c l a v e d soils,
the reduction was very
slight,
n o n - a u t o c l a v e d soils,
a p r o t e c t i v e effect of t r i a d e m e n o l
was observed regardless
and infection was
high.
In
of the r e a c t i o n of the soil.
At
0.1 6 g of a.i./kg of t r i a d i m e n o l , the DI was above 3.0. This
means that infection advanced
lower
stem.
Wi t h
higher
to or was established in the
doses,
however,
infection
w as
limited to the.roots. I
Table 24.
Effect of soil pH and triadimenol seed treatment
on s e v e r i t y
of t a k e - a l l
of
artificially
inoculated Pondera spring wheat seedlings in the
greenhouse.
Disease Index^
Autoclaved
soils
Non-autoclaved
soils
Soil pH
Soil pH
Fungicide
Untreated
Triadime nol
Triadimenol
Triadime nol
Dose
g a. i/kg
5.0
6.0
7.2
5.0
6.0
7.2
0 .16
O'.32
0.48
5.0
4.9
4.2
4.5
5.0
4.9
4.8
4.1
4.9
4.8
4.4
4.2
3.6
3-4
2.7
2.4
4.0
3-1
2.5
2.5 '
3.9
3.3
2.9
2.8
I e [ (# plants) x (Infection s core.) ]/Total # of plants; on a
s c a l e fr o m I to 5 w h e r e an i n f e c t i o n score of 1 = no v i s i b l e
symptoms and 5=almost dead plants.
62
Host Species and Cultivans
The effect
of triadimenol
seed
treatment
on the DI of
the d i f f e r e n t s p e c i e s - c u l t i v a r s is p r e s e n t e d in Table 25..
There
had
w as a great v a r i a t i o n in DI..
the l o w e s t
barleys
had
Triadimenol
level
lower
of i n f e c t i o n
infection
significantly
reduced
The
barley
(D 1 = 2.7)..
than
cv. L e w i s
In general,
spring
infection
level
wheats..
for
all
species-cultivars..
Table 25..
Effect of t r i a d i m e n o l seed t r e a t m e n t of wh e a t
and barley cul tivars on severity of. take-all.
Disease Index^
Cultivar
Ward (DW)2
Fortuna (SW)
Pondera (SW)
Manitou (SW)
Newana (SW)
Hector (B)
Betzes (B)
Lewis (B)
Untreated
Triadimenol
3-5
5..O
5.0
4.0
4.2
3.5
39
2.7
0 .32g a..i/kg
2.7
3 -.4
3.9
3..0
3-5
2.5
2.6
2.0
6[(# plants) x (Infection score)]/Total # of plants; on a
scale f r o m I to 5 w h e r e an i n f e c t i o n score of 1 = no v i s ible
symptoms and 5 = al most dead plants.
^DW=Durum wheat; SW=Spring wheat; B=Barley.
DISCUSSION
The
results
of
this
study
indi c a t e
that
all
of the
f u n g i c i d e s tested w e r e e f f e c t i v e i n h i b i t o r s of g r o w t h of
Ggt.
Prochloraz
and imazalil
achieved more that 50 percent
g r o w t h i n h i b i t i o n w i t h a c o n c e n t r a t i o n as low as 0.0 T u M.
Sensitivity
exhibited
of
by
inhibitors.
complete
Ggt
is
other
very
fungi
to
inhibition
of growth
equivalent
al. , 19 8 4;
and
Siegel
of
imazalil
A s Jser^iJL l.u.s
Bitertanol
Ggt.
the
C - I4
sensitivity
dimethylation
of Penicillium
to about 0.1 uM
Ragsdale,
were
n i du_i a ns
1 978).
needed
(Siege l
to
and
italicum
(Kerkenaar
However,
inhibit
are
et
l arger
growth
of
1 97 8 ).
Ragsdale,
w as the least i n h i b i t o r y of all f u n g i c i d e s to
It p e r m i t t e d
fungicides
were
Sancholle
et
h a r z i a num
.was
etacon a z o l ,
growth
the
to
The reported m i n imum concentrations that cause
0.01 - 0.05 ug/ml,
amounts
similar
g r o w t h at 1000 uM w h i l e
completely
al.,
(1 9 8 4 ) r e p o r t e d
sensitive
but 5 . 0
inhibitory
u g / ml
to
of
low
all
at
that
the other
this
level.
TrjL^hoderma
concentrations
propiconazol
only
of
gave 7 2 %
inhibition.
S e v e r a l p o s s i b l e m e c h a n i s m s of r e s i s t a n c e have been
described
(1 9 8 0 ) have
(Siegel,
reported
1981),
an
but only
Wa a r d
energy-dependent
and
afflux
Nistelrooy
mechanism
for rapid excretion of nuarimol and imazalil in Aspergillus
64
nI d uI a n s .
Fungal
resistance
inhibitors appears mutagenic,
all
members
that
in
of
the
the
cas e
sterol-biosynthesis
and resistance is general for
(S i e g e l , I 9 8 1).
group
of
to the
bitertanol,
the
This
suggests
relatively
low
sensitivity of Ggt is not a resistance mechanism. .
All
of
imaz a l i l ,
the
and
fungicides
p rochloraz,
tested,
were
except
fungistatic
nuarimol,
in
action.
Propiconazol has been reported as fungistatic to Sclerotium
r o_l f_s_i_i ( S a n e h o l l e ,
amnivorum
(Whitson
a 1 , 1984)
et
and
a nd £ h^jn.a.t.o.t r j.£h u m
1 9 8 6 ).
Hine,
Since
functional
s t e r o l s are g e n e r a l l y believed, to serve as c o m p o n e n t s of
membranes,
it m ay be e x p e c t e d that changes in the sterol
c o m p o s i t i o n of p l a s m a m e m b r a n e s r e s u l t s in a l t e r a t i o n of
cell p e r m e a b i l i t y (Han c o c k and W e e t e , 1985; Saneholle, et
al., I 984).
These
the physical and
lead
to
growth.
after
changes would
chemical
properties of the
restricted
abnormal
The exposed
mycelium,
it is t r a n s f e r r e d
be reflected in changes in
or
complete
however,
cell wall
inhibition
can resume
to f u n g i c i d e - f r e e
that
of
growth
medium.
This
mechanism of inhibition seems not to affect pathogenicity.
Although
of Ggt,
all of the fungicides were
only
triadimenol
w as
able
d i s e a s e d e v e l o p m e n t in the field.
imazalil
and
significant,
prochloraz
protection
to
greatly
influence
The f u n g i c i d e s X E - 7 7 9 ,
provided
of young
toxic to mycelium
intermediate,
plants
at
moderate
but
doses
65
of
inoculum,
but
under
.high
t r i a d i m e n o l was effective.
stems
was
already
severe
inoculum
pressure
I n f e c t i o n of ro o t s and l o w e r
after
six weeks
of plant
but infection did not yet have an effect on the
of the p l a n t s at this t i m e
and
plant
foliar
dry weight.
symptoms
only
growth,
physiology
as i n d i c a t e d by tiller n u m b e r
As i n f e c t i o n
developed,
progressed
however,
and the d i s e a s e h ad a m a r k e d
i n f l u e n c e on n u m b e r of plant tillers, and s u b s e q u e n t l y on
grain
yield.
I n o c u l u m rate g r e a t l y i n f l u e n c e d i n f e c t i o n severity
w i t h l o s s e s in g r a i n yield as high as 80 percent.
these
circumstances,
high l e v e l s
From
only
of i n f e c t i o n
this study,
triadimenol
and
was
able
thus r e d u c e d
Under
to prevent
yield
losses.
it w a s not p o s s i b l e to d e t e r m i n e why the
other fungicides failed to influence disease severity since
they
were
howev e r ,
not
toxic
in
v i._tr o .
N ot
all
fungicides
used,
w e r e f o r m u l a t e d as seed t r e a t m e n t s and some m a y
have
protection.
fungicides
moved
into
the
plant
to
provide
systemic
In a l i m i t e d test to detect m o v e m e n t
within the plant,
>in a sufficient
amount
only
triadimenol
to restrict
mycelial
of the
was detected
growth
of Ggt
( u n p u b l i s h e d data).
Conditions
favorable.
Not
for
the
only
development
was
of
infection
take-all
were very
established
at
the
66
lowest rate of inoculum used (1g/3m row), the damage to the
plants
the
allowed substantial
soil
greatly
increased
disease
and
losses
Although
the
soil
not
losses in yield.
in
where
the
yield
this
k n o w n as a s u p p r e s s i v e
damaging
were
even
experiment
soil
Fumigation of
effect
more
was
the
dramatic.
conducted was
to take-all
been continuously cultivated with wheat,
of
and
had
not
destruction of the
natural microflora by fumigation allowed Ggt to rapidly and
aggressively
colonize
devastating
fungicide
was
not
initial
effects.
was
disease
the
roots
minimum
with
very
protection.
performance
pathogen,
more
capable
the
plants
The
of
of
became established,
that
but
this
and
causing
fungicide
detectable,
triadimenol
delayed
w i t h only slig h t l y less
occurred in the non-treated
g r o w i n g season,
It
triadimenol
by Ggt
was
yield
infection
but when the fungicide was translocated,
Infection
the
in a noncompetitive
infecting
once
minimumal,
protection may indicate
for some time,
poor
or if the
to
translocated.
the
was the result of t h e .inability to delay
infection,
environment,
severe
exerted only
clear whether
soil
i nfect
Under this a g g r e s s i v e attack,
triadimenol
in fumigated
and
damage
Ggt
than
check.
can occur
at
any
ti m e
during
the
but early i n f e c t i o n s wo u l d have a longer
time to become established and cause serious destruction of
the root
and crown portion of the plant.
Early
monitoring
67
of s y m p t o m s i n d i c a t e d that i n f e c t i o n of
occurred
in
young
plants,
but
with
the root s y s t e m
no
consequences
on
P h y s i o l o g y of the plant as o b s e r v e d in plant dry weight and
number
ro o t s
of
tillers.
promotes
In m i l d
growth
(Sko u , 1 975) w h i c h may
of
infections,
additional
destruction
adventitious
of
roots
c o m p e n s a t e for the loss of roots.
This may e x p l a i n why there w as l i t t l e or no d a m a g e to young
plants.
Green
house
results
indicated
that
triadimenol
protects very efficiently the lower stem of the plant above
the seed but not the roots.
below
W h e n the i n o c u l u m w as placed
the see d , infection did not advance past the point of
seed a t t a c h m e n t to the l o w e r stem of t r i a d i m e n o l treated
plants.
P lants
damage.
Although
Fellows
in
this
Ggt
(I 93 8 ) states
condition
can infect
did
not
any part
that invasion
of
crown
suffer
great
of the plant,
tissue
occurs
mainly through systemic infection from the roots.
This
property
of
tissue fro m invasion,
the
protection
stages,
of
and the
triadimenol
of
protecting
crown
the fact that the critical point in
wheat
capa c i t y
p lants
is
of w h e a t
at
and
the
early
barley
growth
to produce
adventitious roots as long as crown tissues are not damaged
to compensate
for
infected
roots,
make
triadimenol
a very
promising alternative for the control of take-all on spring
wheat.
69
LITERATURE CITED
Bal l i n g e r , D . J., and K o l l m o r g e n , J. F.
19 8 6 . Glasshouse
and field e v a l u a t i o n of be n o m y I and t r i a d i m e f on
a p p l i e d at s e e d i n g to control take - a l l in wheat.
Plant Pathology 35:61-66.
Bateman, G. L.
1 980.
Prospects for fungicidal control
take-all of wheat.
Ann. Appl. Biol. 96:275-282.
of
Bateman,
G. L. 1981.
E f f e c t s of soil a p p l i c a t i o n of
benomyl against take-all (G a e u m ann o m vces g r a m i n i s ) and
f o o t r o t d i s e a s e s of wheat.
J. of Plant D i s e a s e and
Protection 88:24 9-255.
Bateman,
G. L.
1982.
F o r m u l a t i o n s of s o i l - a p p l i e d
f u n g i c i d e s for c o n t r o l l i n g t a k e - a l l (G a e u mannoraises
g r a m inis var. tritici) in experiments with pot-grown
wheat.
J . of Plant D i s e a s e s and P r o t e c t i o n 89:480.486 .
Bateman,
G. L.
1984.
E f f e c t s of
s u r f a c t a n t s on the
performances of soil-applied fungicides against takeall ( G a e u m a-nn o m_yces g r a m i n i s var. tritici) in wheat.
J. of Plant Diseases and Protection 91:345-353.
Bateman,
G. L.
1984.
S o i l - a p p l i e d f u n g i c i d e s for
controlling take-all in field experiments with winter
wheat.
Ann. A p p l . Biol. I 04:459-4 65.
B a t e m a n , G. L.
1 9 85.
The e f f e c t s of d i s t r i b u t i o n of two
s o i l - i n c o r p o r a t e d f u n g i c i d e s on control of take-all
(G a e u m a n no m.yc e s .graminis var. tritici) in wheat,
J.
of Plant Disease and Protection 92:194-203.
B a t e m a n , G. L , and Nicholls, P. H.
1 982.
E x p e r i m e n t s on
soil d r e n c h i n g w i t h f u n g i c i d e s a g a inst take-all in
wheat..
Ann. Appl. Biol. 1 00:1 97-303.
B o c k u s , W . W . 1 9 82.
T r i a d i m e n o l seed t r e a t m e n t r e d uces
fall i n f e c t i o n s of w i n t e r w h e a t by G a e u m a n n o m y c es
g r a m inis var. tritici.
Phytopathology 72:972
(Abst.)
Bockus,
W. W .
1 9 8 3E f f e c t s of f a l l i n f e c t i o n by
Ga e u m annom vces gram inis var. 'tritici and triadimenol
seed t r e a t m e n t on s e v e r i t y of take-all in w i n t e r
wheat.
Phytopathology 73:540-543.
70
Brown,
M . E., a n d H o r n b y ,
D.
1971.
B e h a v i o u r of
0£hiojbolus s r a m i n i s on slides buried in soil in the
p r e s e n c e or a b s ence of w h e a t seedlings.
Trans. Br.
My col. So c. 56:95-1 03.
B u c h e nauer, H.
1977.
Mode of a c t i o n of t r i a d i m e f o n in
Ustila^o
a v e n a e.
Pesticide
Biochemistry
a nd
P h y s i o l o g y 7:309-320.
Christ e n s e n ,
N. W., Taylor, R. G., Jackson, T. L., and
Mit c h e l l , B. L.
1981.
Chlo r i d e e f f e c t s on w a t e r
p o t e n t i a l s and yi e l d of w i n t e r w h e a t i n f e c t e d w i t h
take-all root rot.
Agron. J. 7 3:1053-1058.
Clarkson,
D . T., D r e w ,
M . C., F e r g u s o n ,
I. B., and
Sanderson,
J . 1 975.
The effect of the take-all
fungus, Gaeum annom vces g ram inis f on the transport of
ions by wheat plants.
Physiol. Plant Pathol.
6:75 t 84
Cook,
de
R. J., Huber, D., Pow el son, R. L. , and B r u e h l , G. W.
1968.
Occurrence of take-all in wheat in the Pacific
Northwest.
PI. Dis. Reptr. 52:716-718.
W a a r d , M . A.,' a n d v a n N i s t e r o o y , G . M .
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