An inheritance and cytological study of the rabbit-eared rogue or Tare of garden peas, Pisum sativum
L.
by William L Marchant
A THESIS Submitted to the Graduate Division in partial fulfillment of the requirements for the degree
of Master of Science in Agronomy at Montana State College
Montana State University
© Copyright by William L Marchant (1949)
Abstract:
The "rabbit-eared" rogue or Tare of garden peas Pisum sativum L. is a recurring mutation which
appears in certain varieties. Four varieties with different rates of Tare expectancy were studied. These
were Laxton's Superb, with a Tare expectancy of one Tare in 200 plants: Thomas Laxton, with one
Tare in 250 plants; Teton, with one Tare in 670,000 plants and Perfection which throws no Tares. A
pure-line Tare strain originally taken from Thomas Laxton was also studied.
Plantings were made in the greenhouse at Montana State College during the winter of 1948-49. Crosses
were made with the varieties using the Tare as male parent. Young flowers in the bud stage were taken
from the plants for cytological study.
Seed obtained from the crosses was planted in comparison with the parent in randomised plots and
measurements were made of the plant stipules and internodes.
The Ferric-acetocarmine squash technique was used to stain the chromosomes of the tapetal tissue of
the anthers. Irregular mitotic divisions were noted and consisted of chromosome bridges, laggards and
fragments. The percentage of irregular mitotic cell divisions was as follows: Laxton's Superb 26.2, Tare
20.0, Thomas Laxton 19.1, Teton 7.7 and Perfection 7.37.
A definite correlation between the amount of Tares produced in a variety and the percentage of mitotic
irregularities in a variety was noted.
The stipule ratio, length over width, increased in all the varieties, except in Perfection, and even Tare
and plants showed an increase as the plants matured. There was a greater correlation between the
stipule ratios of the plants and the Tare parents than between the F1 and the Type parents.
There was a correlated increase in the internode length of all the varieties and the plants. The
correlation, however, was stronger between the Tare and the than between the Type and the plant
internodes. AN INHERITANCE AND CITOLOGICAL STUDY
OF THE rtRABBIT-EAREDwROGUS OR TARS
OF GARDEN PEAS, Pisnm sativ u m L.
by
WILLIAM L. MARCHANT
A THESIS
Subm itted to th e G raduate D iv is io n in p a r t i a l
f u l f i l l m e n t o f th e re q u ire m e n ts f o r th e d eg ree
of
M aster o f S cien ce in Agronomy
at
Montana S ta te C o lleg e
A pproved:
( ^
~Y
_
Head o f M ajor D epartm ent
(
s
'
/
Chairm an, Examining Cominitte e
c
Bozeman, Montana
2
ACKNOWLEDGEMENT
The a u th o r w ishes to acknowledge th e g u id a n ce , encouragem ent and
a s s is ta n c e g iv e n him hy D r. E riia rd t R. Hehn i n th e c o n d u c tin g o f t h i s
s tu d y .
Acknowledgement i s a ls o made to D r. W alter H. P ie r c e o f th e
A ss o c ia te d Seed G row ers, In c . who s u p p lie d th e seed u sed and who was
in s tru m e n ta l in I n t e r e s t i n g th e a u th o r i n th e problem s re g a rd in g th e
T are o f garden p e a s .
89333
3
'JtABLS
or
OOJbITKNfS
LISTING OF TABLES, GRAPHS AND FIGURES
Page
................................................. 4
6
ABSTRACT....................................................
INTRODUCTION ............................................
. . . . . . . . . . . .
REVIEW OT LITERATURE........................................ . . • ....................
MATERIALS AND METHODS...........................................
8
. .1 0
l4
EXPERIMENTAL RESULTS.........................................................................................21
DISCUSSION ............................................ ...................................... .... • . . . .33
SUMMARY................................................
LITERATURE CITED ..................................................................................
37
.3 8
4
LIST CF TABLES
T able I
T able IZ
Table I I I
Page
O b se rv a tio n s o f mi to t i c d iv is io n s o f th e a n th e r
t a p e t a l c e l l s o f L ax to n 's S uperb, Thomas Laxton T a re ,
Thomas L axton, Teton and P e r f e c tio n ............................... , . 27
S tip u le r a t i o and in te rn o d e le n g th a v e ra g e s o f F. and
p a r e n t p la n ts ...................... . . . . . . . . . . . . . .
28
C a lc u la te d c o r r e l a t i o n s o f p a r e n t and F^ p o p u la tio n s
f o r s t i p u l e r a t i o and In te rn o d e le n g th . ...........................
29
LIST CF GBAI HS
Graph I
Average p e rc e n ta g e s o f m ito tic I r r e g u l a r i t i e s o c c u rln g
In th e m ito tic c e l l d iv is io n o f th e a n th e r ta p e t a l c e l l s
In Thomas L ex to n , T a re , l e x t o n 's Superb, Te to n and
P e r f e c tio n . . . . . . . . . . . . . . . . . . . . . .
30
Graph I I
Average s t i p u l e r a t i o s p l o t t e d to show th e c o r r e l a t i o n
between th e
and i t s p a r e n ts ............................................ .... 31
Graph I I I
Average in te rn o d e le n g th s p l o t t e d to show th e c o r r e la tio n
betw een th e F^ and i t s p a r e n t s .......................... ....
32
LIST CF FIGURES
F ig u re I .
A. P la n ts o f th e Thomas Laxton v a r i e t y . B. P la n ts o f
th e Teton v a r i e t y . C. P la n ts o f th e Thomas L sxton
T are. The p ic tu r e s show th e b ro a d , b lu n t s t i p u l e s
o f Thomas Lexton and Teton i n c o n tr a s t to th e narrow
p o in te d s t i p u l e s o f th e Tare p l a n t s . . . . . . . . . . I J
F ig u re 2 .
A. P la n ts o f th e P e r f e c tio n v a r i e t y . B. P la n ts o f the
L a x to n 's Superb v a r i e t y . 0 . P la n ts o f Thomas Laxton
T are. The p i c t u r e s show th e b ro a d , b lu n t s t i p u l e s and
s h o r t in te rn o d e s o f P e r f e c tio n and L axton1a Superb
compared to the narrow , p o in te d s t i p u l e s and lo n g
in te rn o d e s o f the Tare p l a n t s . . ............................................ 18
5
LIST C7 HOTESS c o n t’d
F ig u re 3*
F ig u re 4 .
Page
A - Thomae Laxton X T a r e ( I e f t) and Thomae Laxton
( r i g h t ) showing narrow s t i p u l e s o f F^ p la n t
i n coiitr- s t to broad s t i p u l e s o f Thomas L a rto n . , . 19
B - Photograph o f Teton ( l e f t ) and Teton X Tare
showing narrow s t i a le o f F^................................................ 19
A - PUoto g rap h o f P e r f e c tio n ( l e f t ) and F 1 ( r i g h t )
showing broad s t i p u l e and s h o r t in te rn o d e s o f
P e r f e c tio n compared to narrow s t i p u l e and lo n g
in te rn o d e s o f T are......................
. . . .
.
. . .
B - P hotograph showing s h o r t b ro a d -le a v e d L ax to n 19
Superb p la n ts compared to t a l l narrow e tip u le d
F1 p l a n t s .................. ............................................................ .... .
F ig u re 5»
A - Photom icrograph o f m ito s is a t anaphase showing a
chromosome g rid g e and frag m e n t............................................ 22
B - Photom icrograph o f m ito s is a t anaphase showing a
chromosome b r i d g e ......................................................................22
F ig u re 6 .
M ito tic c e l l d i v is io n a t anaphase
A - Sormal s e p a r a tio n o f chromosomes.
B - C - D - I r r e g u l a r d iv is io n w ith chromosome b rid g e
formed a c r o s s th e e q u a to r ia l p l a t e .
C - Shows two chromosomes, in a d d itio n to th e b rid g e ,
la g g in g behind th e m a jo rity o f chromosomes.......................
Drawings made w ith th e a id o f a camera Iu c I d a .
20
20
23
6
ABSTRACT
The *r a b b it- e a r e d " rogue o r Tare o f g ard en p e as Plemn sativum L.
I s a r e c u r r in g m u te tlo n which a p p e a rs In c e r t a i n v a r i e t i e s .
w ith d i f f e r e n t r a t e s o f T are expectan cy were s tu d ie d .
These were l a x t o n 's
Superb, w ith a T are e x p ectan cy o f one T are i n 200 p l a n t s ;
w ith one Tare i n 250 p l a n t s ;
Four v a r i e t i e s
Thomas L axton,
T e to n , w ith one Tare i n 6 /0 ,0 0 0 p la n ts and
P e r f e c tio n which throw s no T a re s .
A p u r e - lin e T are s t r a i n o r i g i n a l l y
ta k en from Thomas Laxton was a ls o s tu d ie d .
P la n tin g s were made in th e greenhouse a t Montana S ta te C o lleg e
d u rin g th e w in te r o f 19*18-49.
u s in g th e T are a s male p a r e n t.
C ro sses were made w ith th e v a r i e t i e s
Young flo w e rs In th e bud s ta g e were
ta k e n from th e p la n ts f o r oyt o lo g ic a l stu d y .
Seed o b ta in e d from th e c ro s s e s was p la n te d in com parison w ith th e
p a r e n t i n random ized p l o t s and m easurem ents were made o f th e p la n t
s t i p u l e s and in te r n o d e s .
The F e r r l c - a c e tocarm ine squash te c h n iq u e was used to s t a i n the
chromosomes o f th e ta p e t a l t i s s u e o f th e a n th e r s .
I r r e g u l a r m ito tic
d iv is io n s were no ted and c o n s is te d o f chromosome b r id g e s , la g g a rd s and
fra g m e n ts.
fo llo w s :
7 .7
The p e rc e n ta g e o f i r r e g u l a r m ito tic c e l l d iv is io n s was as
L a x to n 's Superb 2 6 .2 , Tare 2 0 .0 , Thomas Laxton 1 9 .I , Teton
aad P e r f e c tio n 7»37*
A d e f i n i t e c o r r e l a t i o n between th e amount o f T ares produced in a
v a r i e t y and th e p e rc e n ta g e o f m ito tic i r r e g u l a r i t i e s in a v a r i e t y was n o te d .
The s t i p u l e r a t i o , le n g th o v e r w id th , in c re a s e d i n a l l th e v a r i e t i e s ,
e x c e p t i n P e r f e c t i o n , and even Tare and
p la n ts showed an in c re a s e a s
7
th e p l a n t s m atured.
r a t i o s o f th e
There was a g r e a t e r c o r r e l a t i o n betw een th e s t i p u l e
p la n ts a n d th e T are p a r e n ts th an between th e
and th e
Type p a r e n ts .
There was a c o r r e la te d in c re a s e i n th e in te rn o d e le n g th o f a l l th e
v a r i e t i e s and th e P^ p l a n t s .
betw een th e T are and th e
ln te rn o d e s
The c o r r e l a t i o n , how ever, was s tr o n g e r
th an betw een th e Type and th e F^ p la n t
J
8
AU INHlHI TAHCE AND CTTCLOGICAl STUDY
OF THE #BABBIT-EAEXD*RCGUS OR TAHl
0? GARDEN PEAS P ls u a sativum L.
hy
W illiam I . M arehant
INTRODUCTION
The " R a b b it-e a re d " Rogue o r T are o f g arden peas i s a n o f f - ty p e p la n t
which o c c u rs i n many v a r i e t i e s o f g ard en peas Piaum sativ u m La
These
p la n ts a r e d is tin g u is h e d from th e ty p e p la n ts o f th e v a r i e t i e s i n which
th e y o r ig in a te d by b e in g d a rk e r in c o lo r , h a v in g more narrow s t i p u l e s ,
m a tu rin g s l i g h t l y e a r l i e r and by b e in g a s t a l l o r s l i g h t l y t a l l e r th an
th e Type p l a n t s . There i s l i t t l e , i f a n y , d if f e r e n c e betw een th e number
o f nodes o f th e T are and th e Type.
Any d if f e r e n c e betw een th e two in
p l a n t h e ig h t i s due to ln te m o d e le n g th .
Because T ares a r e c o n sid e re d u n d e s ir a b le by com m ercial c an n e rs and
3
f r e e z e r s o f p e a s , th e se e d -p ro d u c e rs must ta k e m easures to in s u r e th e re
b e in g a s few T are p la n ts a s p o s s ib le p r e s e n t i n t h e i r seed c ro p s .
At
p r e s e n t two p r a c tic e s a re u sed by com panies p ro d u cin g q u a l i t y pea seed
to c u t down th e number o f Taree p r e s e n t i n t h e i r s to c k s .
In th e f i r s t method th e T ares a re removed from p ro d u c tio n f i e l d s
by crews o f men h a n d p u llin g th e u n d e s ir a b le p l a n t s .
T h is i s , o f c o u rs e ,
an e x tre m ely ex p en siv e p ro c e d u re .
In the second method e a r ly g e n e ra tio n l i n e s o f new m a te r ia l a re d is ­
c ard ed i f an abnorm ally h ig h p e rc e n ta g e o f Tare i s p r e s e n t.
Some su cc e ss
h a s been o b ta in e d in p ro d u cin g r e l a t i v e l y T a re -fre e v a r i e t i e s by o u tc r o s s in g to v a r i e t i e s which do n o t throw T a re s .
9
T hle s tu d y was I n i t i a t e d In th e hope t h a t means c o u ld he found to
e n ab le p l a n t b re e d e rs to c y to l o g i c a l l y s c re e n b re e d in g m a te r ia l and
e lim in a te l i n e s which m ight be p o t e n t i a l Tare p ro d u c e rs.
The v a r i e t i e s chosen f o r t h i s work had wide ran g e o f Tare ex­
p e c ta n c y , o r m u ta tio n r a t e , v a ry in g from one T are e x p ec te d I n two
hundred p la n ts to a v a r i e t y which throw s no T a re s.
«
' '
'-T=., " -4
Because o f th e g e n e r a lly co n fu sed s i t u a t i o n re g a rd in g th e naming
o f p ea v a r i e t i e s , i t i s v e ry d i f f i c u l t to t r a c e th e p a re n ta g e to th e
o r i g i n a l s o u rc e .
There does n o t a p p ea r to be a common so u rc e f o r
v a r i e t i e s p ro d u c in g Tares#
10
REVISW CF LITERATURE
The n arro w , p o in te d s tlp u le d m u ta tio n o r " ra b b it- e a r e d * rogue In
g arden p e a s , Pleum e a tlvum L ., h as been s tu d ie d g e n e ti c a lly t y many
w o rk ers.
In 1915 B ateeon and P e lle w (I)
re p o rte d t h a t i n c ro s s e s w ith
th e p a r e n t o r b ro a d , o b tu s e ly s tlp u le d ty p e , th e rogue c h a r a c te r i s
d o m inant, and t h a t in th e Fg and su cc e ed in g g e n e ra tio n s o n ly rogues
a p p e a r.
They(P) l a t e r n o te d l n t e r n e d ia te form s which on s e l f -
f e r t i l i s a t i o n gave v a ry in g p ro p o r tio n s o f ro g u e s, in te rm e d ia te s and
Types i n t h e i r p ro g e n ie s .
The in te r m e d ia te s , showing a h ig h p e rc e n ta g e
o f rogues among t h e i r o f f s p r i n g , d is p la y e d a p ro g r e s s iv e in c re a s e in th e
p e rc e n ta g e o f rogues to n o n-rogues among t h e i r progeny when com paring
p la n ts d e riv e d from th e lo w er nodes w ith o f f s p r i n g from th e u p p e r nodes
o f th e same In te rm e d ia te p l a n t .
T h is change in r a t i o betw een th e two
c la s s e s o f p la n ts was accounted f o r by a c o rre sp o n d in g In c re a s e among
th e male gam etes o f th o se b e a rin g th e f a c t o r f o r ro g u e s.
B r o th e r to n ( J ) , In 1923, re p o rte d s e g re g a tio n i n th e F 2 g e n e ra tio n
o f c ro s s e s betw een Gradus rogue and ty p i c a l p la n ts o f Mumny, a nonrogue p ro d u c in g p ea v e r i e t y .
However t h i s s e g re g a tio n o f rogue and Type
p la n ts i n th e Fg and F j g e n e ra tio n s d id n o t fo llo w any known M endellan
ra tio .
The ro g u es g r e a tly outnum bered th e n o n -ro g u es.
The F^ g e n e ra tio n
p la n ts resem bled th o se d e s c rib e d by B ateso n and P ellew a s in te rm e d ia te s .
In o r d e r to o b ta in a more e x a c t com parison o f th e ro g u es and Types,
and th e F 1 and F2 g e n e ra tio n s o f h y b rid s betw een th e two,
B ro th e rto n
I/ Numbers in parentheses refer to literature cited on page
11
m easured th e le n g th and w id th o f th e s t i p u l e s from th e f o u r th to th e n in th
node o f th e v a rio u s p la n ts he was w orking w ith .
le n g th o f s t i p u l e was th en c a lc u la te d .
The r a t i o o f w id th to
He s t a t e s , "The F 1 h y b rid s up to
th e sev e n th node a r e l i k e th e ty p e , o r In te rm e d ia te betw een th e type
rogue$ above th e sev e n th node th e p la n ts become r a p id ly more ro g a e llk e * .
He f u r t h e r s t a t e s , "The In flu e n c e o f th e ty p e p a r e n t, In c ro e s e s b e tween th e Types and rogue I s a p p a re n t o n ly In th e F i p l a n t and a t o n ly
th e low er nodes*.
B ro th e rto n advanced th e h y p o th e s is t h a t rogues a r i s e de novo from th e
p a r e n t ty p e tqr m u ta tio n o f a s in g le f a c t o r , x to X, and t h a t th e h e te r ­
ozygous Xx co m b in atio n I s v e ry u n s ta b le .
The f a c t o r x In th e p rea^n ce o f
X r e a d ily m u ta tin g to £ d u rin g som atic developm ent so t h - t a t gam etogenesls
th e F1 h y b rid o f Type w ith rogue I s homozygous f o r the rogue f a c t o r XX.
He c a l l s th e a lle lo m o rp h o f X In Mummy x* and s t a t e s t h a t I t d i f f e r s
from x o f th e ro g u e -p ro d u c in g v a r ie ty In b e in g more a te b i o , r a r e l y . I f
e v e r , m u ta tin g to X when i n th e homozygous x 'x 1 c o n d itio n .
In th e h e te r ­
ozygous Xx1 co m b in atio n (F^ and su cc e ed in g g e n e ra tio n s o f rogue X Mummy),
how ever, th e c o m b in a tio n , w h ile b e in g more s ta b le th an th e SLx germ plasm
o f rogue x Type, n e v e r th e le s s I s f a i r l y u n s ta b le , and x* m u tates f r e q u e n tly
to X.
The f r e q u e n t change o f x o r x* to X d u rin g th e developm ent o f th e
p la n t I s c a l l e d "mass som atic m utation" and th e u n eq u al p r o p o r tio n o f th e
two k in d s o f gam etes form ed, x o r x*;X , r e s u l t s In m asking th e tru e Mend e lia n I n h e r ita n c e .
Miss P e lle w (S ) s t a t e s , "F 1 ro g u e s, e$ ty p e X ro g u e , end r e c i p r o c a l ,
c ro s s e d back w ith Type, g iv e rogues and a n o c c a s io n a l Type and In te rm e d ia te
12
p la n t.
The e x c e p tio n a l p la n ts have come from
th e r e c ip r o c a l c r o s s .
The
x I y p e , and n o t from
rogue a p p e a rs to d i f f e r o n ly In d e g re e from
th o s e In te rm e d ia te p la n ts which a r i s e sp o n tan e o u sly In t h e v a r ie ty S a rly
S l a n t , and w hich g iv e a m ix tu re o f T ypes, In te rm e d ia te s and ro g u e s.
A
h ig h e r p ro p o r tio n o f Types and In te rm e d ia te s come from th e fem ale gametes
th a n from t h e m ale, and from th e low er nodes than from th e u p p e r* .
B unten, (4) In 193°* r e p o rte d the d ip lo id chromosome number o f Oradus
p e a s , w hether Type o r ro g u e , to be l 4 .
Matauura (6 ) and Wings (1 2 ).
T h is co n firm s th e o b s e rv a tio n s o f
Miss Bunten s t a t e s , * I f B r o th e r to n 's h y p o th e sis
c o n c e rn in g mass som atic m u ta tio n i s to be a p p lie d h e r e , i t must be b ased , a s
B ro th e rto n assum es, on some change o th e r th a n chromosome number*.
The occurence o f som atic m u tatio n s h as been r e p o r te d l y Emerson (5)
i n c o rn .
He s tu d ie d a v a r ie g a te d v a r i e t y o f maize t h a t had a w h ite p e ric a p
w ith numerous re d s p o ts o f v a ry in g s i z e .
G e n e tic a lly th e s e p la n ts were
homozygous f o r th e r e c e s s iv e gene f o r w h ite .
He c o n sid e re d t h i s gene to be
u n s ta b l e , m u ta tin g sp o n tan e o u sly in to th e dom inant a l l e l e f o r re d .
Conse-
q u e n tly each re d s p o t on the k e rn e l was made up o f c e l l s which came from
one c e l l In which such a m u ta tio n had o c c u red .
Som atic m u ta tio n s o c cu r f r e q u e n tly in th e buds o f some p l a n t s .
a r e known a s bud s p o r t s , o r bud m u ta tio n s.
These
The Haval o range i s an example
o f a f r u i t i n g body produced on a sh o o t d eveloped from a bud m u tatio n ( 9 ) .
In many in s ta n c e s men w orking w ith peas have n o ted s id e s h o o ts , from a Type
p l a n t , which were ro g u e lik e and which produced seed which in tu r n bred
T are p la n ts w h ile the main p a r t o f th e p l a n t produced seed b re e d in g tru e
to Type
13
The la c k o f e e g re g e tlo n In a c ro s s between Tare and
p la n ts
In th e T2 g e n e r a tio n may be a t t r i b u t e d to d i f f e r e n t i a l p o l l i n a t i o n .
The p o lle n g r a in s c a r r y in g th e Tare garnet may be a b le to e f f e c t f e r t ­
i l i z a t i o n ahead o f th e p o lle n g r a in s c a r r y in g th e !type gam ete.
Because
th e Tare c h a r a c te r i s d o m inant, th e r e c e s s iv e Type c h a r a c te r s would,
th e r e f o r e , n e v e r a p p e a r.
Many c a s e s o f v a r ia b le p o lle n v ig o r , such as i s p o s tu la te d above,
have been r e p o r te d .
f ic ie n c y In m aize.
S ta d le r (11) has r e p o r te d a chromosome segment de­
The p o lle n g r a in s c a r r y in g the d e f ic ie n c ie s were
s m a lle r th an norm al a n d , e x c e p t In r a r e c a s e s , f a i l e d to produce a p o lle n
tu b e , c o n se q u e n tly b e in g u n a b le to f e r t i l i z e an o v u le .
M untzlng ( 7) w orking
w ith o rc h a rd g r a s s , found th a t p o lle n g r a in s c a r ry in g th e h a p lo id and d ip ­
l o i d chromosome numbers were h ig h ly f e r t i l e , w h ile th o se w ith In te rm e d ia te
chromosome numbers were v e ry low in f e r t i l i t y .
14
MATERIALS AM) METHODS
J j
The v a r i e t i e s used in t h i s stu d y were L ax to n 1s Superb H 4 3 6 llt (T lg .2 B );
P e r f e c tio n H46876, (F ig .2 A ); Teton H47912, (F ig . IB );
Thomas Laxton
H451201, (F lg .lA ) and Thomas Laxton T are H4gl04$, ( F ig .lC ) .
The Thomas
Laxton T are l i n e o r ig in a te d a s a s in g le p l a n t s e le c tio n i n Thomas Laxton
H451201 and was grown f o r th re e seaso n s (1946-1948) a s an in d iv id u a l l i n e .
I t i s a tr u e T are and showed no s e g re g a tio n d u rin g th e th r e e seaso n s
grown.
A ccording to u n p u b lish e d d a ta re c o rd e d by A a so c ia ted Seed G row ers, I n c . .
w orkers and g iv e n to th e a u th o r by Dr. W. H. P ie r c e , th e fo llo w in g r a t e s o f
T are e x p ectan cy have been d e term in e d f o r th e v a r i e t i e s u n d e r c o n s id e ra tio n :
L a x to n 's Superb
Thomas Laxton
T eton
P e r f e c tio n
H4367I
HU51201
H47912
H46876 Ho
I T are i n 200 p la n ts
I T are i n 250 p la n ts
I T are i n 670,000 p la n ts
T ares
A pproxim ately 2$ seed s o f each o f th e v a r i e t i e s and Tare were p la n te d
on November 2 7 , 1948 I n th e greenhouse a t Montana S te te C o lle g e .
were spaced one in c h a p a r t in rows 20 in c h e s a p a r t .
The seed s
The s o i l was fum igated
w ith a form aldehyde s o lu tio n two weeks p re v io u s to th e p la n tin g to reduce
th e d anger from s o il- b o r n e p l a n t p a th o g e n s.
The v a r i e t i e s Thomas L axton, L ax to n ' s Superb and T are began blossom ing
on December 28, 1948, Teton on th e 30 th and P e r f e c tio n on Jan u a ry 7 » 1949.
C ro sses were made w ith the v a r i e t i e s , u s in g th e Tare a s th e male p a r e n t.
A second p la n tin g o f th e v a r i e t i e s and T are was made on F eb ru ary 2 ,
1949 in o rd e r t h a t buds co u ld be secu red f o r c y to lo g i c a l stu d y .
I / R e fe rs to A ss o c ia te d Seed G row ers, In c . l i n e number
15
The F1 seed from th e T are c ro s s e s and p a re n ts was p la n te d on Feb­
ru a ry 25th f o r com parison.
The seed s were p la n te d In group# as fo llo w s:
F1 Thomas L axton X T a re , Thomas L ax to n , and T are;
and T are;
F1 Teton X T a re , T eto n ,
F1 L ax to n ’ s Superb X T a re , L a x to n 's Superb, an d T are;
P e r f e c tio n X T a re , P e r f e c tio n , and T are.
F1
Four seeds o f each F1 and
v a r i e t y w ere p la n te d fo u r In ch es a p a r t In rows e ig h t in c h e s a p a r t .
The
v a r i e t i e s were random ized w ith in groups and th e groups w ith in r e p l i c a t i o n s .
Two r e p l i c a t i o n s were p la n te d .
F ig u re s 3 ®ad U show F1 p l a n t s .
S tip u le le n g th and w id th was measured In c e n tim e te rs a t th e f i r s t
th rough th e s i x t h node above th e s o i l s u rfa c e .T h e second ln te m o d e e th ro u g h
th e f i f t h above th e s o i l s u rfa c e were a ls o m easured.
The fTeenhouse te m p e ratu re was m ain ta in ed a t %3^F.
T h is i s a l i t t l e
h ig h e r th an Is c o n sid e re d d e s ir a b le f o r Plsum , b u t t h i s te m p e ra tu re re ­
duced th e tim e r e q u ir e d f o r flo w e rin g and made i t p o s s ib le to grow two
c ro p s d u rin g th e w in te r months o f ig^S-U g.
The r e l a t i v e hu m id ity was h e ld a s c lo s e to 60 p e rc e n t a s was p o s s ib le ,
and th e day le n g th was k e p t a t l 6 h o u rs by u s in g a r t i f i c i a l l i g h t .
I t was found th a t th e blossom bud c e l l s underw ent th e maximum number
o f m ito tic d iv is io n s when they were ap p ro x im a te ly I . 5 to 3 mm. in le n g th .
C o n sid e ra b le d i f f i c u l t y was e n co u n te re d in o b ta in in g p o lle n m other
c e l l s In d i v i s i o n and co n eeg u en tly m e io tlc o b s e rv a tio n s a r e n o t in c lu d e d
in th is re p o rt.
In o rd e r to stu d y chromosome b e h a v io r th e buds were p lu ck ed and
Im m ediately Immersed i n C a rn e y 's s o lu tio n (6 :3 :1 ) and h e ld a t room temp­
e r a tu r e f o r a minimum o f th re e days o r u n t i l e lid e s were p re p a re d .
The
16
F e r r ic - a c e to -c a rm in e squash method o f a l i d e p r e p a r a tio n was u sed a s fo llo w s:
1.
2.
3.
4.
5.
6.
The hud was removed from the C am oy s o lu tio n and th e a n th e r s
d is s e c te d from the bud.
The a n th e r s were immersed i n 10# HCl f o r a p p ro x im a te ly oneh a l f m inute on an o v e r-tu rn e d b e a k e r.
The HCl was th e n b lo tte d away and 2 to 4 dro p s o f a c e to -c a rm in e
s t a i n (& gm. carm ine p e r 100 c c . a c e t i c a c id ) were u sed to c o v er
th e a n th e r s .
One drop o f G e r r lc - a c e ta te was added and a t l r r e d in to th e s t a i n
w ith a d is s e c t i n g n e e d le . The a n th e re were l e f t to s t a i n f o r
o n e -h a If h o u r.
A f te r s t a i n i n g th e a n th e r s were mounted in A ceto -carm in e on a
s l i d e , c o v e re d , squashed by p r e s s in g th e c o v er s l i p w ith the
h a n d le o f a d i s s e c t i n g n e e d le then h e a te d f o r a few seconds
o v e r an a lc o h o l las%).
The c o v er s l i p s were s e a le d w ith a tem porary s e a l su g g este d by
Sm ith (10) and h e ld in p la c e w ith a c lo th e s - p i n . The s e a l
u s u a ll y d r ie d w ith in a h a lf - h o u r , b u t th e c lo th e s - p i n was l e f t
in p la c e o v e r n ig h t.
Chromosome draw ings were made f r e e hand and a ls o w ith th e a id o fa
cam era-Iu c I d a .
P htom lcrographe were ta k en w ith a 35mm. cam era.
17
c
f ig u r e I .
A. P la n ts o f th e Thomas Laxton v a r i e t y . B. P la n ts o f th e Teton
v a r i e t y . C. P la n ts o f th e Thomas Lexton T a re . The p ic tu r e s show
th e b ro a d , b lu n t s t i p u l e s o f Thomas Laxton and Teton in c o n tr a s t
to th e narrow p o in te d s t i p u l e s o f th e Tare p l a n t s .
18
F ig u re 2 .
A. P la n te o f th e P e r f e c tio n v a r i e t y . B. P la n ts o f th e L ax to n 'e
Superh v a rie ty * C. P la n te o f Thomae Laxton T a re . The p ic tu r e s
•how th e b ro a d , b lu n t s t i p u l e s and s h o r t I n t e m o d es o f Per­
f e c tio n and L a x to n 'e Superb compared to th e n arro w , p o in te d
s t i p u l e s and lo n g ln te rn o d e e o f th e Tare p l a n t s .
19
B
f ig u r e 3 . A - Thomae Laxton X T a r e ( I e f t) and Thomae Laxton ( r i g h t )
showing narrow s t i p u l e s o f ? i p la n t In c o n t r a s t to broad
s t i p u l e s o f Thomas L axton.
B - P hotograph o f Teton ( l e f t ) and Teton X Tare ( r i g h t )
showing narrow s t i p u l e o f T^e
20
F ig u re 4 .
A .- P hotograph o f P e r f e c tio n ( l e f t ) and F1 ( r i g h t ) showing
broad s t i p u l e and s h o r t in te rn o d e s o f P e r f e c tio n compared
to narrow s t i p u l e and lo n g in te rn o d e s o f T are.
B .- Photograph showing s h o r t b ro a d -le a v e d L a x to n ts Superb
p la n ts compared to t a l l narrow s tip u le d F% p l a n t s .
21
EXPERIMENTAL RESULTS
M ito tic o b s e rv a tio n s were made o f th e ta p e t a l t i s s u e o f th e a n th e r s
o f Thomas L ax to n , Thornes Lexton T a re , L a x to n 's S u p erb , Teton and P e r f e c tio n .
I r r e g u l a r i t i e s o f th r e e ty p e s , b r id g e s , la g g a rd s and frag m en ts,w ere
o b se rv e d .
The number o f th e s e a b e r r a tio n s p re s e n t In each c e l l were
n o te d and a r e re c o rd e d In T able I .
A b rid g e was c o n sid e re d to be p r e s e n t In a c e l l when a t anaphase th e re
wes n o ted a d e f i n i t e s t r e t c h i n g a c r o s s th e e q u a to r ia l p l a t e o f one o r more
chromosomes,
f ig u r e s 5 and 6 I l l u s t r a t e th e type o f c o n f ig u r a tio n s con­
s id e r e d a s b rid g e s .
A la g g a rd was c o n sid e re d to be p r e s e n t In a c e l l when a t anaphase th e re
was n o te d a chromosome w hich d e f i n i t e l y lag g ed behind th e m a jo rity o f chrom­
osomes in s e p a r a tin g and moving to th e p o le s o f th e d a u g h te r c e l l s .
These
chromosomes looked a s though th ey may have been p a r t o f a b rid g e which had
b ro k en , f o r i n most c a s e s th e re was a p a i r p r e s e n t, one moving to each o f
th e p o le s , and i n f ig u r e 60 two chromosome la g g a rd s a re shown.
A fragm ent was c o n sid e re d to be p r e s e n t when a t anaphase o r te le p h a s e
th e r e was n o te d a chromosome o r p ie c e o f a chromosome w hich had f a i l e d to
move to th e d a u g h te r c e l l and rem ained u n a tta c h e d n e a r th e e q u i t o r l a l p l a t e .
There were o n ly th re e c a s e s o f t h i s type o f a b b e ra tio n n o te d .
F ig u re 5A
i l l u s t r a t e s one o f th e s e frag m e n ts.
In th e v a r i e t i e s L a x to n 's S uperb, Thomas Laxton and Teton the p e r ­
c e n ta g e o f la g g a rd s was h ig h e r th an th e p e rc e n ta g e o f b r id g e s .
In Thomas
Laxton Tare and P e r f e c tio n the p e rc e n ta g e o f b rid g e s was h ig h e r th an th e
p e rc e n ta g e o f la g g a r d s .
22
A
B
F ig u re $. A - Photom icrograph o f m lto e le a t anaphase showing a chrom­
osome b rid g e and frag m en t.
B - Photom icrograph o f m ito s is a t anaphase showing a chrom­
osome b rid g e .
23
F ig u re 6.
M ito tic c e l l d iv is io n a t anaphase.
A - Normal s e p a r a tio n o f chromosomes.
B - C - D - I r r e g u l a r d iv is io n w ith chromosome b rid g e
formed a c ro s s th e e q u a to r ia l p l a t e .
C - Shows two chromosomes, in a d d itio n to the b rid g e ,
la g g in g behind th e m a jo rity o f chromosomes.
Drawings made w ith th e a id o f a camera lu c id a
24
The p e rc e n ta g e o f I r r e g u l a r m ito tic d iv is io n * i s g iv e n in th e r i g h t
hand column o f T able I .
Theee f ig u r e s were computed by d iv id in g the number
o f c e l l s u n d e rg o in g i r r e g u l a r m ito tic d iv is io n s by th e number o f c e l l s
o b serv ed u n d e rg o in g m ito s is .
T his f ig u r e does n o t tak e in to acco u n t th a t
i n some o f th e c e l l s o b serv ed th e re was more th an one b rid g e o r la g g a rd .
The p e rc e n ta g e o f i r r e g u l a r i t i e s o b serv ed v ery c lo s e ly co rre sp o n d s to
th e m u ta tio n r a t e , o r ta r e expectancy f i g u r e s , n o ted in th e s e c tio n on
M a te ria ls and M ethods, (L ax to n 1s Superb I T are in 200 p l a n t s , Thomas Laxton
I T are i n 250 p l a n t s , Teton I Tare in 670,000 p la n ts and P e r f e c tio n no T a r e s ) .
The m ito tic i r r e g u l a r i t i e s o b serv ed a re shown in Graph I .
M easurements o f s t i p u l e w id th and le n g th were made and from th e se
f ig u r e s th e s t i p u l e r a t i o (L ength o v e r w id th ) was com puted.
a c o m p ila tio n o f th e s t i p u l e r a t i o s .
Table I I i s
C o r r e la tio n c o e f i c i e n t s were c a l­
c u la te d f o r th e s t i p u l e r a t i o s a t th e v a rio u s nodes and a r e l i s t e d in
T ab le I I I .
Because o f th e sm all numbers u sed in th e se c a lc u la tio n s th e s i g n i f ­
ic a n c e o f th e " r" v a lu e s i s d o u b tfu l.
They d o , how ever, in d ic a te th e tr e n d .
In o rd e r to o b ta in a measurement o f th e c o r r e l a t i o n betw een th e s t i p u l e
r a t i o s o f T are and Type, F i and T are and ? i and Type c o r r e l a t i o n c o e f ic ie n ts
were c a lc u la te d g ro u p in g a l l th e p la n ts in to th e fo llo w in g c a te g o r ie s T a re ,
Type, and F^.
The r e s u l t i n g “ r" v a lu e s a re :
Type end Tare c o r r e l a t i o n c o e f l c i e n t O.276 I f
F 1 and Tare
"
"
0.745**
F 1 and Type
"
"
0.490*
I / * .0 5 L evel o f s ig n if ic a n c e
**.01 L evel o f s ig n if ic a n c e
25
These f ig u r e s in d ic a te t h a t th e re i s no s i g n i f i c a n t c o r r e l a t i o n between
Type and Tare p la n t s t i p u l e r a t i o s end t h a t a lth o u g h th e re i s some c o r r e l a t i o n
betw een the
an4 Type p la n t s t i u le r a t i o s th e re i s a much s tro n g e r c o r­
r e l a t i o n betw een th e s t i p u l e r a t i o s o f th e
and Tare p l a n t s .
T h is i s to
be e x p ec te d a s B ateson and F e lle w ( 1 ,2 ) , P e lle w ( 8 ) and B ro th e rto n ( 3 ) de­
term in ed t h a t th e ta r e c h a r a c te r i s dom inant.
There d id n o t a p p ea r to be
any s t r i k i n g t r a n s i t i o n from Type-resem blance to T are-resem b lan ce a s th e
p l a n t s m atured ac o bserved by B ro th e rto n ( 3 ) .
With th e e x c e p tio n o f P e r­
f e c tio n th e re was a d e f i n i t e in c re a s e i n th e s t i p u l e r a t i o o f a l l the
p la n ts a s th e y m atured.
T h is i s c o n tr a d ic to r y to B ro th e rto n ’a Type p la n ts
which m ain ta in ed a c o n s ta n t s t i p u l e r a t i o th ro u g h o u t t h e i r grow th.
The seco n d , t h i r d , f o u r th and f i f t h in te rn o d e s o f a l l th e p la n ts u n d er
c o n s id e r a tio n were m easured and th e r e s u l t s a r e g iv en in T able I I and in
Graph I I I .
C o r r e la tio n c o e f i c i e n t s were c a lc u la te d f o r th e in te m o d e le n g th s and
a r e in c lu d e d in T able I I I .
C o n sid e rin g th e sm all number o f p la n ts sampled
th e r e i s a good c o r r e l a t i o n betw een a l l o f th e in te rn o d e le n g th s o f p la n ts
com pared, w ith the e x c e p tio n o f the Teton g ro u p .
These h ig h c o r r e l a t i o n
c o e f i c i e n t s I n d ic a te t h a t th e in te rc e d e le n g th s in c re a s e d p r o p o r tio n a lly
f o r a l l th e p la n ts a s th ey m atured.
The lu te m o d e le n g th f ig u r e s were grouped in th e same manner as f o r
th e s t i p u l e r a t i o s and th e fo llo w in g c o r r e l a t i o n c o e f i c i e n t s were determ ined*
Type and Tare
F1 and T are
F 1 and Type
c o rre la tio n c o e fic ie n t
“
"
"
"
. 659**
.879**
.5910*
26
H ighly s i g n i f i c a n t c o r r e l a t i o n s e x i s t between th e Type and. T a re ,
and between th e
and Tare p l a n t s .
The c o r r e l a t i o n betw een
and
Type i s s i g n i f i c a n t , b u t i s n o t a s s tro n g a s t h a t between th e o th e r
p la n ts .
27
T able I
V a rie ty
L a x to n 's
Superb
O b se rv a tio n s o f M ito tic D iv is io n s o f th e A nther T a p e ta l C e lls
o f L a x to n 1S Superb, Thornes Laxton T a re , Thomas L axton, Teton
and P e r f e c tio n .
No.
C e lls
Observed
28
2
28
3
28
9 ....
P la n t
No.
B rid g es
P e r P la n t
No.
7i
5 17.8
8 2 8 .6
9
32.1
2
11-29
5
6
11-30
I
24
3
13
11
10
4
Av.
Thomas
Laxton
2
3
9
10
il
13
1J6
15
9
26
16
6
0
35.8
I ir
39.3
3 3 .4
4
0
2
I
7
0
3
12.5
0
0
1
4
9 .1
0
0
I
13.3
10
0
2
2 6 .9
5
4
0
0
2 3 .5
0
11.1
15.8
2
3
b
7
S
9
4
31
15
13
I
14
0
0
I
I
0
9
Av r
P e rf e c tio n
25.0
0
I
7 .7
I
9-1
I 10.0
Ir 2 5 .0
15.8
Ay.
Teton
10
26.2
Av.
Thomas
Laxton
T are
Laggards Fragm ents
P e r P la n t P e r P la n t
% No.
Np.
%
0
0
7 25.0
I
2
3
4
5.
6
0
0
6.7
7.7
4 o .o
2 5 .0
1#
58.8
0
13.3
5 5 .5
1 5 .4
0
0
2
0
7 .1 5
Irre g u la r
C e lls
No.
%
5
17.7
25.0
7
10
I
4 ,l6
0
0
0
0
0
0
0
0
0
1 .5 4
9
0
0
0
0
0
0
0
0
0
0
0
0
5
0
1
2
2
2
I
0
6.5
13.3
7-7
20.8
0
7.70
18.2
3
30.0
2
50 .0
2 0 .0
5
2 9 .4
0
0
3
2 0 .0
7
2 2 .2
2 6 .9
2
0
2 3 .r ~
0
3 5 .7
26.2
2.38
0
19.1
0
1
2
0
0
0
0
0
0
0
0
0
0
2
0
0
3.23
13.3
15.4
0
0
0
2 .6
0
0
;
7 .2
7-7
9
0
1
2
15.4
2
8 .0
1
2
0
8.0
0
13
25
5
0
0
0
1
3 8 .5
4 .0
2
0
22
0
0
I
8 .0
4 .5
0
0
0
0
25
I
0
0
2
0
8 .0
9
4 .0
0
0
28
3
0
0
0
0
0
0
0
10.7
g-g.... .
J j 8I -
2
7.15
7.70
4.55
7,1 5
7.37
28
T able I I . S tip u le R atio and In ta rn o d e Length A verages o f
No.
RSP P I .
Thomaa1 I • 4
U
Laxton I I
Av.
4
Tare
I
II
?
At .
T .L .x
Tare
I
II
2
I
At .
Teton
T are
T e t.x
Tare
I
II
Av.
;
II
Av.
I
II
AXg.'.
L ax t.
I
Suoerb I I
Av.
T are
I
SI
Av.
L .S .x
I
Tare
II
Av.
P e rfI
e c tlo n I I
Av.
T are
I
II
Av.
P e r f .x I
Tare
II
Av.
4
4
4
3
4
4
3
3
3
4
2
STinJLE RATIO AV£RAGKS»______
Node
I
3
4
6
2
5
1 .7 3 ' 1.68» 1 .6 3 ' 1 .5 8 ' 1 .7 5 ' 1 .8 3 '
1.60 1.78 1.47 1.67 1 .7 0 1.78
1.67 1 . 73 1.55 11.63 1.73 1.81
1 .9 5 2.28 1 .8 5 1.9 5 1.78 2.2 2
1 .7 7 2 .0 6 2 .0 0 1.93 2 .0 0 2.20
iJg b 2.17 1.93 1 .9 4 1.8 9 2.21
—
2 .2 0 2 .0 5 2 .0 5 2 .0 5 2 .1 5
1.53 1.70 1.73 1.8 0 1 .8 0 2.00
1.87 1.88 1.89 1.9 3 1.98 2.00
1.80
i t 75
1 .5 5
1.65
... l.-73_ 2.20
1.50 1.70
1.62 1.95
1.50 1,98
1.37 1.63
1 .4 4 1.77
1.43
1.62
1,55
1 .5 3
1 .5 4
1 .9 3
1.77
1 .8 5
1 .7 0
1.65
l .(>8
1.43 i.4 o
1.63 T T T
1.30 1.53 1.53
1 .4 0 ' 1 .9 0 1.86
1.70 1.92 2 .0 0
1.55 1.91 1.98
i.4 o 1.80 1.80
1.30
1.6 3
2 .6 0
1.82
1 .9 5
1.83
1.8 9
l.J O
1 .6 5
1.68
1.60
1 .7 5
1 .8 0
1.7 8
2 .1 8
2 .1 0
2 .1 4
1.93
1.9 3
1.93
and P a re n t P la n ts .
INTSRJtGDE LENGTH*
Node
3
4
2
5
• 28« 5 5 ' 61« 81«
15 25 47 70
22 4o 54 76
27 51 9* 88
28 54 60 78
28 53 7b 83
20 27 47 34
29 38 57 80
25 33 53 60
32
2T
29
29
28
29
1.75
1.88
1.82
2.28
52 63
43 56 66
40 69 76
21 53 9 65? 65 87
36 62 92
21 -35 54 T p
30 56 68 s4
26 46 T l 72
2.16
2.2 2
2.10
2.35
2.2 5
1.70
1.70
1.70
2.13
21
21
21
2.60
1.4 3
1 .7 0
1.5 6
2 .0 7
2 .1 5
2 .3 0
1 .8 0
2 .0 5
2.0 5
29
28
... 34
1.5 0
1.58
2 .0 0
2.16 _ .
2.11 2 .1 5
26
26 32 46
39 44 51
33 39 49
52 7 9 . 88
56 61 98
54 70 93
5? 67 112
0
1 .4 0
4
3
4
4
0
2
1.80
•w
1.80
1.80
1.8 0
2 .0 5
2 .0 5
34
1,73
1.52
1.70
1.59
1.35
1.80
1.72
1.80
I .76
2 .0 8
1.9 5
1.75
1 .3 7 ____
1.5b
H l 16 33
12 19 37
12 18 35
28 4? 61
32 60 65
1.58
2.02
1 .4 5
1.5 7
1.51
2 .0 8
2 .1 8
2 .1 3
mmmm
ammm
1.61 1.67
1.80
1.75
1 .6 5
1 .7 0
1 .9 5
1.98
e*«-
mmmrn
1 .7 5
1.75
1.65
1.65
2.00
1.70 1.7 0
1 .7 0 . 1.70
* Measurements In c e n tim e te r!
1 .7 0
1 .7 0
2.20
2.3 0
2.25
2 .0 5
2 .0 5
52
67 112
21
36
29
85
102
63
94
23 39 52
-____ D - D 2- 5?
72
72
30
54
29
T ab le I I I . C a lc u la te d C o r r e la tio n o f P<=r e n t and F
S tlo u le R atio and In te rn o d e L ength.
P a n u la tio n s C o rre la te d
P o p u la tio n s f o r
C o r r e la tio n C o e f ic ie n ts
S tio u le R atio
. 957* U
Thomas Laxton X Tare
F l X T are
F^ X Thomas Laxton
.191
.7 0 9
.4 5 5
.97%*
.963*
Teton X T are
F, X Tare
F1 X Teton
.630
.9 5 0
.6 6 7
.861
.932
.903
Ladtton Superb X T are
F1 X Tare
F1 X Laxton Superb
.263
.9%7**
.27%
S r
P e r f e c tio n X Tare
F1 X Tare
F1 X P e r f e c tio n
I / + S ig n if ic a n t to the
+ • S ig n if ic a n t to the
- .5 2 6
* • 4o6
.5 3 2
05 p o in t
Ol p i t n t
.985*
.723
. 993**
• 7997
30
TOTAL I R R E e u v t a
CELL DIVISIONS
L A G G A R D5
TETOfI
sworea
Graph I .
lam rut
Average p e rc e n ta g e s o f m ito tic i r r e g u l a r i t i e s
o c c u rin g in the m ito tic c e l l d iv is io n s o f th e
a n th e r ta p e t a l c e l l s in Thomas L ax to n , T are,
L a x to n 's Superb, Teton and P e r f e c tio n .
ISBiBiSSfiiISC
IiiiBfiiiBiS
31
Graph I I .
LA#'** & Sw»f**
T**e
A JfT
T amaas L aavms
Average s t i p u l e r a t i o s p lo tte d to show the
c o r r e l a t i o n betw een th e
and p a r e n ts .
32
THOMAS LAXTON
TARE
TL XT
TFTOM
TARF
T E T XT
LAXTOMS SVPERA
TARE
y
L .S X T
/
P E f K F F CTlOM
TARE
PERf. X T
2 m.
3»
y
IMTCRMODE
Graph I I I
Average in te rn o d e le n g th s p l o tte d to show th e
c o r r e l a t i o n betw een the
and p a r e n ts .
33
DISCUSSION
There a p p e a rs to be a d e f i n i t e c o r r e l a t i o n between t h e Tare ex p ectan cy
and the p e rc e n ta g e o f m ito tic c e l l i r r e g u l a r i t i e s o b se rv e d .
L axton1s Superb
had 26.6 p e r c e n t m ito tic i r r e g u l a r i t i e s and a Tare ex p ectan cy o f one Tare
in
200
p la n ts .
As i l l u s t r a t e d in Graph I th i s i s th e h ig h e s t p e rc e n ta g e
o f i r r e g u l a r i t i e s observed and a ls o th e h ig h e s t m u ta tio n r a t e .
Thomas
Laxton was second i n m u ta tio n r a te w ith one Tare ex p ected in 25O p la n ts
and a m ito tic i r r e g u l a r i t y o f 19.1 p e r c e n t.
Teton h as a Tare ex p ectan cy
o f one p l a n t in SyOlOOO and a m ito tic i r r e g u l a r i t y o f 7 .7 p e r c e n t.
P e r­
f e c tio n throw s no T ares and had an observ ed m ito tic i r r e g u l a r i t y o f 7.37
p e r c e n t.
The f a c t t h a t P e r f e c tio n showed a m ito tic i r r e g u l a r i t y o f 7*37 p e r
c e n t and throw s no T ares seems to in d ic a te t h a t a l l m ito tic i r r e g u l a r i t i e s
do n o t le a d to T a re s.
A ll b rid g e s and la g g a rd s o b v io u sly do n o t le a d to I r r e g u l a r chromo­
some d i s t r i b u t i o n in th e d a u g h te r c e l l s .
The p re sen c e o f th e se b rid g e s
and la g g a r d s , how ever, would le a d to th e assum ption t h a t sh o u ld the chrom­
osomes b reak a p a r t a t any p o in t o th e r th a n a t th e o r i g i n a l te rm in a ls o f
th e chromosomes t h a t d u p lic a tio n o f a segm ent o f one chromosome would tak e
p la c e in one d a u g h te r c e l l and the o th e r d au g h ter c e l l would have a de­
l e t i o n o f th e same s e c tio n o f th e chromosome.
I t i s q u ite p a s s ib le th a t
th e d a u g h te r c e l l s c o u ld c a r r y on d iv is io n w ith t h i s d u p lic a tio n and
d e l e t i o n , one c e l l le a d in g to th e c r e a tio n o f ta r e c h a r a c t e r i s t i c s in a
manner d e s c rib e d by B ro th e rto n as "Mass Som atic M u ta tio n s".
I t i s a p e c u li a r f a c t t h a t when a T are i s c ro s se d w ith a normal
3U
p l a n t th e re l a no s e g re g a tio n o f th e norm al type ta k in g p la c e In th e Fg
n o r Ie th e r e an e x p re s s io n o f s t e r i l i t y e x h ib ite d in any o f the progeny.
A p o s s ib le e x p la n a tio n o f the above phenomenon may be made by
p o s tu l a t i n g t h a t th e p o lle n g r a in s c a r r y in g th e i r r e g u l a r i t y (p ro b ab ly
th e d u p lic a tio n ) a re c a p a b le o f p ro d u c in g a germ tube more v ig o ro u s than
th e o th e r type p o lle n g r a in s ( th e ones c a r r y in g the d e le tio n ) and con­
s e q u e n tly they alw ays f e r t i l i z e th e o v u le .
In a c a s e o f t h i s s o r t th e p o lle n g r a in s c a r ry in g th e T are e h a e a o te r
would alw ays a f f e c t th e f e r t i l i z a t i o n and s in c e t h i s c h a r a c te r I s dom inant
th e r e c e s s iv e c h a r a c te r would n ev er ap e a r .
In o th e r w ords, th e re would
be no s e g r e g a tio n o f Tare and Type c h a r a c t e r s , which i s e x a c tly what
happens i n c ro s s e s o f Tare w ith Type p l a n t s .
The a u th o r h a s no p ro o f t h a t p o lle n g r a in s c a r r y in g th e Tare c h a r a c te r
a r e more v ig o ro u s th an th o se o f th e Type c h a r a c te r , b u t t h i s i s a p o s s ib le
e x p la n a tio n o f the cau se o f la c k o f s e g r e g a tio n .
B r o th e r to n 1S c o n je c tu re t h a t th e T are i s caused by a p o in t m u tatio n
I s open to d e b a te .
The f a c t th a t th e T are p la n ts a re so d r a s t i c a l l y
d i f f e r e n t from the Type p la n ts would I n d ic a te t h a t n o t a m inute p o in t i s
In v o lv ed in t h i s m u ta tio n , b u t r a t h e r t h a t a segment o f a chromosome
c a r r y in g s e v e r a l g e n e s , i s r e s p o n s ib le .
O rd in a rily segm ental In te rc h a n g e I s n o t to be e x p ec te d in mltori. s .
The chromosomes do n o t e x h ib it the a t t r a c t i o n between homologous p air s which
o c c u rs i n m e io e le , b u t h e re Incom plete s e p a r a tio n o f a p a r t o f th e d a u ^ ite r
chromosomes ap e a r s to take p la c e .
T here must have been some fo rc e which
cau sed p a r t o f th e chromosomes to ad h ere and le a d to th e b rid g e s p re v io u s ly
35
d e s c rib e d .
The h e te ro c h ro m a tin m a te r ia l composing th e pea chromosomes must be
weak, a c c o u n tin g f o r th e i n s t a b i l i t y o f pea p la n ts in g e n e r a l.
I f t h i s h e te ro c h ro m a tin m a te ria l com posing th e backbone o f th e chromo­
some i s a s weak as i t a p p ea rs to b e , th e end o f one chromosome a tta c h e d to
a n o th e r chromosome c o u ld be broken o f f by th e fo rc e o f th e chromosomes
moving to th e p o le s o f th e d iv id in g c e l l .
T his a c tio n would le a d to th e
d u p lic a tio n o r d e le t io n o f a segment o f th e chromosome a s su g g e ste d .
In c r o s s e s o f Type p la n ts w ith th e T are th e T ere c h a r a c te r was found
to be dom inant.
T his e u b s tla n te s th e f in d in g s o f B ateson and P ellew ( I )
and B ro th e rto n ( 3 ) .
The s t i p u l e r a t i o o f th e
p la n ts o f c ro s s e s o f Tare
tim es Thomas L axton, L axton' s Superb, T eton and P e r f e c tio n was d e f i n i t e l y
o f Tare ty p e .
B ro th e rto h r e p o rte d a t r a n s i t i o n from T y p e -lik e s t i p u l e to T a r e - lik e
s t i p u l e as th e
p la n t m atured.
There was n o te d a d e f i n i t e in c re a s e i n th e s t i p u l e r a t i o o f a l l the
p la n ts ,
Type, T are and
in t h i s s tu d y .
e x ce p t th o se o f th e P e r f e c tio n v a r i e t y , c o n sid e re d
T h is i s somewhat c o n tr a d ic to r y to B ro th e rto n 1S fin d in g s a s
h i s Type p l a n t s m ain ta in ed a f a i r l y u n ifo rm s t i p u l e r a t i o th ro u g h o u t t h e i r
grow th.
A d e f i n i t e p o s i t i v e c o r r e l a t i o n e x is t e d between the in te rn o d e le n g th s
o f a l l th e p la n ts m easured.
A lthough the c o r r e l a t i o n c o e f i c i e n t s l i s t e d in
T ab le I I I a r e n o t a l l s i g n i f i c a n t , th e In te rn o d e le n g th s o f a l l the p l a n t s ,
e x c e p t P e r f e c tio n , in c re a s e d q u ite c o n s i s t e n t l y from node to node.
The c o r r e l a t i o n c o e f i c i e n t s c a lc u la te d f o r the in te rn o d e le n g th o f Type
36
and T a re ,
and T a r e , end F l and T y p e were s i g n i f i c a n t .
There was a h ig h e r
c o r r e l a t i o n between F^ and T are th a n between F1 and T y p e p l a n t s .
T h is Ie
to be e x p ec te d a s th e T are c h a r a c te r s a r e c o n sid e re d to be dom inant o v er
th e Type c h a r a c te r s .
37
SUMMARY
i.
Four v a r i e t i e s o f garden p eas Pisum sativ u m L. w ith th e fo llo w in g r a t e
o f T are e x p ec ta n cy were s tu d ie d :
L e x to n 's Superb
Thomas Laxton
Teton
P e r f e c tio n
2.
I Tare i n 200 p la n ts
I Tare i n 2$0 p la n ts
I T are i n ByOl OOO p la n ts
No T ares
Chromosome i r r e g u l a r i t i e s c o n s is tin g o f b r id g e s , la g g a rd s and f r a g ­
ments were n o te d in the m ito tic c e l l d i v i s i o n s , and th e fo llo w in g
p e rc e n ta g e s o f i r r e g u l a r c e l l d iv is io n s were re c o rd ed :
L axton1s Superb
Thomas Laxton
P e r f e c tio n
2 6 .2
1 9 .I
7*37
T are
Teton
2 0 .0
7*7
There a p p e a rs to be a c o r r e l a t i o n betw een the number o f m u tatio n s in
a v a r i e t y w ith number o f i r r e g u l a r i t i e s in m ito s is .
3.
The s t i p u l e r a t i o , le n g th o v er w id th , in c re a s e d in a l l the v a r i e t i e s
and the Tare and
p l a n t * , e x ce p t P e r f e c tio n , a s they m atured.
There
was a g r e a t e r c o r r e l a t i o n betw een th e s t i p u l e r a t i o s o f the F^ p la n ts
and th e Tare p a r e n t th a n o f the
4.
p la n ts and th e Type p a r e n t.
The in te rn o d e le n g th o f a l l th e p la n ts in c re a s e d in a p ro p o r tio n a l
amount a s they m atured.
There was a g r e a t e r c o r r e l a t i o n between th e
in te rn o d e le n g th s o f th e F j and Tare p a r e n t than betw een th e F 1 and
Type p a r e n t.
3S
LITERATURE! CITED
I*
BATFSOH, W. and PELL IWf C. Cn th e g e n e tic s o f 11ro g u es" among c u lin a r y
p e as Plstun sativ u m . J o u r . G e n e tic s 5 : 13- 36 . 1915.
2.
.
__________________ ___. The g e n e tic s o f "ro g u es" among c u lin a r y
peas Pisuni sativ u m . P ro c . Roy. Soc. (London) (B) 9 1 t1 8 6 -I 95 . 1920.
3.
BROTH RTONf S .E ., J r . F u r th e r s tu d ie s o f the in h e r ita n c e o f rogue ty p es
in garden peas Plsum sativ u m L. J o u r , A gr. Res. 2 4 : 815- 952 , I 923.
4.
BUHTENf ISABEL. A p re lim in a ry r e p o r t on th e chromosome complement o f
" r a b b it- e a r e d rogues" in c u lin a r y p e as P is u a sativ u m L. Amer. J o u r.
B ot. 17:1 3 9 -1 ^2 . 1930.
5.
EMERSON , R.A.
The I n h e r ita n c e o f a r e c u r r in g so m atic v a r ia tio n in
v a r ie g a te d e a rs o f m aize. Amer. N e tu r. 4 8 :8 7 -1 1 5 . i g i 4 .
6.
MATSUURAs
H. A b ib lio g r a p h ic a l monograph o f p la n t g e n e tic s .
1929 Sd2, re v . and e n l . f f S f p p . S apporo, Jap o n . 1933»
7.
MUNTZINGf A. The e f f e c t s o f chromosomal v a r ia tio n in d a o t y l l s .
H e r id ita s 23 : 113- 235. 1937.
8.
PELLEHf C. F u r th e r d a ta on th e g e n e tic s o f "ro g u es" among c u lin a ry
p e as Pisum s a tivum . 5 I n t e r n a t . K ongress V ererbung. B e r lin
V erh an d lu n g er. 2. 192%.
9.
SHAMELf A .D ., SCCTTf L.B. and POMEROY , S.C . A stud^f o f bud v a r i a t i o n
in th e n a v a l o ran g e. U .S.D .A . B u i. 6 2 3 :1 -1 4 6 . 1918.
The a c e to -c a rm in e sm ear te c h n iq u e .
1900-
10.
SMITH, LUTHER.
J a n . 1947.
S ta in Tech. 2 2 ,
11.
STABLER, L .J . Cn th e g e n e tic n a tu re o f Induced m u ta tio n s i n p l a n t s .
I I . A h a p lo -v ia b le d e fic ie n c y i n m aize. Mo. R es. B u i. 2 0 4 :1 -2 9 . 1933*
12.
WINGEf 0 . C o n trib u tio n s to th e knowledge o f chromosome numbers in
p l a n t s . C e llu le 35*306-324. 1925.
MONTANA STA t p ijim /C B erw ,
3 1762 10014829 3
V'VV
NS 78
MSSi
cop. 2
~
--- ----- --- 89338
Ndir
N !3 3 i-
6-Op. Z.