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All Graduate Theses and Dissertations
Graduate Studies
1962
A Genetic Investigation of a Yellow Plant Color
Characteristic in Winter Wheat
John Oscar Evans
Utah State University
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Evans, John Oscar, "A Genetic Investigation of a Yellow Plant Color Characteristic in Winter Wheat" (1962). All Graduate Theses and
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A GENETIC INVESTIGATION OF A YELLOW PLANT
COLOR CHARACTERISTIC IN WINTER WHEAT
by
John Oscar Evans
A thesis submitted in partial fulfillment
of the requirements for the degree
of
MASTER OF SCIENCE
in
Crop Breeding
Approved:
Major PJ;.OfesJ>or
lJ!!iin A"f Graduate Studies
UTAH STATE UNIVERSITY
Logan, Utah
1962
r
'-"·
ACKNOWLEDGMENTS
I am deeply i ndeb t ed t o my ma j or professor , Dr . Wade Dewey , no t
only f or supply i ng the ma t e r ial and hi s sugges tions on thi s thes i s , bu t
a l so fo r hi s t rue f riends hi p and unders t a nding s ince I have known him .
To my commi ttee , Dr. DeVere McA llis t er , and Dr . Or son Ca nnon, I
wi s h t o express my s i nce r e apprecia ti on fo r the i r s ugge s ti ons thr oughout
the cour se of the i nvestiga tion .
To my wife, Beverly, I owe much cr edit, for her encour agement a nd
ass i s t ance he l pe d i mmeas ur ably i n compl e t ing this thes i s .
J ohn Osca r Eva ns
TABLE OF CONTENTS
Page
INTRODUCTI ON
REVIEW OF LITERATURE
3
MATERIALS AND METHODS
6
Description of Parents
Po ss ibili ty of Non- Genetic Fac tor s Conditioning the
Character
Crosses Used
Plant ing and Cl assification Procedures
EXPERIMENTAL RESULTS
I nherit ance of Awns
Inheritanc e of Chaff Color
Inheri tanc e of Ye l low Pl ant Co lor
Crosses involving the yel low pa rent a l line
(217 - 6- 3- 2)
Crosses involving green carrier l i ne s
Crosses involv ing non- car rier lines
Backcrosses
6
8
9
9
12
12
12
14
16
21
29
30
DISC USS I ON
31
SUMMARY AND CONCLUSIONS
37
LITERATURE CITE D
39
LIST OF TABLES
Table
Page
1.
Cross numbers and parental lines used in this study
2.
Fz inheritance of awn type
13
3.
F2 inheritance of chaff color
13
4.
Test for independence between awn type and chaff color
15
5.
F2 inheritance of yellow plant color in cross 549
18
6.
F] inheritance of yellow plant color in cross 549
19
7.
F2 inheri t ance of yellow plant color in cross 546
20
8.
F2 inheritance of yell01" plant color in cross 544
21
9.
F3 inheritance of yellow plant col or in cross 556
25
10.
F3 inheritance of yell01• plant color in cross 516
26
11.
Digenic F3 inheritance of yellow plant color i n cross 506
28
12.
Monogenic
F3 inheritance of yellow plant color in
9
cross 506
28
13 .
F2 inheritance of yellow plant color in cross 504
29
14 .
Suggested genotypes and phenotypes of the parental
selections
32
F2 genotypes , phenotypes and their breeding behavior in
F3 in crosses 516, 5a 6 and 556
35
F2 inheritance of yellow plant color i n crosses 506, 516
556
35
F1 genotypes , phenotypes and F2 segrega tion with respect
to the yellow plant characteristic
36
15 .
16.
17 .
LIST OF FIGURES
Fi gur e
Page
1.
A yel l ow r ow of selection 217-6-3- 2 s hown in comparison
wit h rows of normal green selec tions
2.
A seve r e yellow plant (left) as compared with a normal
green pl ant
17
3.
A typic a l ye ll ow F1 popul at ion of crosses 550 and 610
22
4.
Three seve re ye llow pl ants (each l abel led with a red
t ag) which were typi cal of the ye llow F2 plants of
cer t a i n crosses
24
INTRODUCTION
The objective in wheat hybr idization primarily is to obtain new
varieties which are of a greater agronomic value than existing varie tie s.
Frequently, however , crosses whic h obviously will not produce superior
commercial types are made and studied in order to obtain genetic infor-
mation which may be useful to the breeder.
This latter phase of breeding,
i.e ., the accumulation of genetic informa ti on , provide s the basis for
this study.
The characteristic involve d man i fests itself as a premature yellowing of the leaves.
It was first observed in the progeny of a cross
between two normal green plants.
Apparently the yellowing is caused by a chlorophyll bre akdown or
deficiency.
It is characterized by the appearance of a yellow color in
the leaf blade and sheath .
With the loss of chlorophyll the plant i s
gradual ly weakened and may die prematurely.
The yellowing is not
restricted to sma ll are as of the leaf but rather appears to be quite
uniform over the entire leaf blade.
At the time the character was first observed it was suspected that
the plants were s uffering from an insufficient amount of nitrogen, s ince
in many instances the appearance of the character quite closely resembles
the symptoms of nitrogen deficiency.
Certain cereal viruses which induce
premature yellowing also came under suspicion.
That the yellowing was
genetic rather than a deficiency or pathogenic response became obvious
when the plants were grown under controlled conditions.
2
Since the condition ser i ously limit s the agronomic val ue of the
plants which ex hibit it, and genetic factors which condition the yel l owi ng
are apparently c arried by several normal appea ring wheat selections pres -
ently being used in the wheat breeding work a t Logan, it is important to
determine the number of factors involved and the nature of their inheri tance.
REVIEW OF LITERATURE
As far as the au thor could determine, on ly two studies have been
reported in the l iterature wh i ch reasona bly relate to thi s study .
Kostyuchenko (1936) studied the degree of viability among F
of several crosses .
cross to another .
1
seedlings
He observed distinct levels of yellowing from one
The Fz ratios of non- viab l e to viable approached a
9: 7 pattern , indicating two complimentary factors invo l ved in the phenomenon .
He also found that cer t ain crosses produced F1 progenie s that were
entire l y inviable, leading him to suggest that mor e than two fac tors
must exist t o explain the differe nce among the F1 's.
The second study was reported by Jens en (1957) a t Cornell.
He
obse rved a chlorophyll deficient select i on which had normal green leaves
when young but which t urne d prematurely yellow .
In crossing the ye llow
selec tion wit h the normal green var iety Yorkwin, he observed the yellow
condition to be par tia lly dominant to normal green.
The dif fere nce
between yellow and green appeared to be monogenic.
Several other s t udies have been reported which deal with chlorophy ll
mutants in wheat but whi ch bear less dire ct l y on this investigation.
Nea tby (1933) discovered a mutan t seedling in an F5 line of common whe a t
while studying the inheritance of reac tion t o stem rust.
The seedl ing
exhibited yellow leaves and never acquir ed the deep green color of the
normal plant s.
He was able to maintain the pl an t, and after s tudying the
progeny of several crosses involving the yel low pl ant with normal plants
concluded that the inheritance of the yellow color was contro ll ed by a
4
single pair of factors.
Neatby refers to the low frequency of chlorophyll
mutations in wheat by stating, "the one about to be described is the only
chlorophyll deficient seedling ever to be found in common wheat."
A yellow-striped wheat was reported by Poa and Li (1946).
They
found this to be strictly a case of maternal inheritance, the pollen
parent having no obvious effect on the characteristic.
However, all
attempts t o is ola t e a pure breeding variegated line were unsuccessful.
Smith and Harrington (1929) observed the presence of pur e white
seedlings in the F2 population of the cross Vernal ernrner x Marquis spring
wheat.
They found the segregation patterns both in field and greenhouse
trials to closely approximate a 63:1 ratio.
This indicate s the presence
of three genetic factors governing the appearance of albinos.
They
concl uded th at one line probably carries two recessive genes for albinism
which are complimentary to a third gene for a lbini sm carrie d by the
o ther, and that the interaction of the three complimentary genes when
present in a homozygous state inhibit chlorophyll development .
Herbert and Middleton (1955) observed lethal F1 's in a cross between
two normal appear ing varieties.
When they crossed Atlas 66 with Quanah,
the resulting F1 plants appeared normal until they were approximate l y
eight to twelve inches high.
The plants gradually yellowed and weakened
and the hybrids faile d to reach the heading stage.
Whether or not the
factor for lethality carried by Atlas 66 is the same as that respons ible
for contributing to the yellow color in this study remains open to
question.
All reports on chlorophyll aberrations in whea t have establis hed
the exceedingly low frequency with which they occur .
Barley, on the
other hand, exhibits a considerably higher rate of chlorophyll mutations.
5
Since chlorophy ll changes are easily detected it is not likely that they
are not recognized in wheat.
The difference in frequency of these aber -
rations between barley and wheat has attracted the interest of many plant
breeders a nd geneticists .
Stadler's (1929) general view regarding the
stability of chlorophyl l development in the polyp l oi d wheats serve s as
a basis for assigning genotypes to the parent lines i n this study.
He
concludes that the low frequency of chlorophyll deficiencies in hexaploid
wheat is due to gene reduplication .
MATERIALS AND METHODS
Desc ripti on of Parents
Seven parental lines were selecte d to be used in thi s study.
Selection 217-6- 3- 2 was the only line t o express the yellow color
directly.
It exhibits the distinct golden- yellow color of the leaf
blade and sheath and apparently breeds tru e for it (Figure 1).
was a selection f r om a (Ridit x Re lief) x (Orfed x Elgin) cross.
217 -6- 3- 2
It is
an awned , white-chaffed selection apparently normal in all respects excep t
chlorophyll development.
Norin 10/Brevor 11 sel. 1, Atlas 66, 112 a -1 05 -6-4 and 193a -465-l-2
were selected as parents since they appeare d green but had be.en observed
previously to be carriers of factors for the expression of the yel low
co l or.
112 a -1 05 - 6- 4 is a selection from a cross involving Ridit x (Kanred
x Sev i er).
It is a fully awned, bronze chaffed wheat which in many
respects shows promise of being valuable breeding material .
193a- 465-l-2 is an awned, bronze chaffed segregate selected from a
cross betwe e n se l ec tion 112 a -1 2-6
(a sister selection to 112a-105-6-4)
and the variety Rex.
Atl as 66, a soft red winter variety, shows a very light yellow
mottling of the leaves in the later s tages of it s vegetative growt h .
Two a dd itional parental lines were used which were consi dere d to be
non- carriers of yellow factors as they produced yellow progeny only when
crossed with the yellow parent.
Any of several hundred common varieties
7
Figure 1 .
A yellow row of selection 217 - 6- 3- 2 shown in
comparison with rows of normal green se l ections
8
could have been used here.
Hussar and CI 12932 were arbitrarily chosen
as the non-carriers for this study.
Possibility of Non-Genetic Factors
Conditioning the Character
The pattern and regularity with which the yellowing occurred made
it appear genetical ly controlled.
However, yellowing is frequently
caused by other factors such as , drought, old age, nutrient deficiency
or diseas e .
Plants were grown in several locations and under conditions where
nutrients were added to the soil.
The progeny of certain crosses were
consistently yellow while the parent lines and progeny of other crosses
growing in the same location at the same stage of maturity were normal
green.
The reoccurrence of the yellowing only in certain crosses from one
year to the next eliminated the possibility of a soil-borne or insect
transmitted virus.
The experiments were also conducted in the greenhouse
whereby a closer control on the environmental factors could be maintained.
Observations made in the greenhouse agreed with those made in the field.
Through the use of reciprocal crosses where the seed chain was broken it
became apparent that it was not the result of a seed transmitted virus.
All attempts to transmit a virus from the affected plants to the normal
ones proved unsuccessful.
Since no pathogenic organism or environmental factor could be
associated with the condition, it seemed reasonable to assume that the
characteristic was conditioned by genetic factors .
9
Crosses Used
Cro sses tvere made in 1957 involving each of the parental lines in
combination with each other .
Cro ss numbers, parental lines and their
phenotypes are shown in Table 1.
Table 1.
Cross numbers and parental lines used in this study
Cross number
Parents
504
506
516
193a-465 - l-2 x Atlas 66
193a-465-l-2 x Norin 10/Brevor 11
112 a -1 05 -6-4 x Atlas 66
green x green
544
546
549
217 -6-3- 2 x CI 12932
217-6-3-2 x Hussar
217 - 6-3 -2 x Norin 10/Brevor 11
yellow x green
yellow x green
yellow x green
550
552
553
217 - 6- 3-2 x 112a -105-6-4
112a- 105-6-4 x Hu ssar
Hussar x Norin 10 /Brevor 11
green x green
green x g reen
554
555
556
Hussar x CI 12932
112a-105 -6- 4 x CI 12932
112 a-105-6-4 x Norin 10 /Brevor 11
green x green
557
610
612
CI 12932 x Norin 10 /Brevor 11
217-6 - 3- 2 x 193a- 465-l-2
112a-105 - 6- 4 x 193a-465 - l-2
g reen x green
Phenotype of parents
green x green
green x green
yellow x green
green x green
green x green
yellow x green
green x green
Planting and Classification Procedures
First generation plants were grown both under greenhouse and field
conditions.
Each plant was spaced approx imately one foot apart to per -
mit the production of a large amount of seed.
the plants were not under heavy competition fo
This also insured that
moisture or nutrien t s.
The F1 plants were carefully observed at frequent intervals
10
throughout their grm<ing period and were classified according to the
degree of yellowing expressed.
plant so as to identify the
Sma ll paper t ags were affixed to each
y~lluw
plantl::i a t har vest time .
The tagging
both in this and in later generations was comple ted sufficiently early
so as not t o include plants that were ye llowing due to natural ma tur a tion.
When the F1 plants were mature, each plant was individually harvested and
threshed.
The F2 families were planted in the fa ll of 1959.
A V- be lt seeder
was used t o space the pl ant s approximately four inches apart.
Spacing
the pl ants help e d t o facilitate c l ass ification and a ided in the surviva l
of the l ess vigorous ye ll ow pl a nt s .
Each
Fz
fami l y in a cro ss was planted
and classif i ed sepa rate l y in order to check the consistency of segrega tion
pat t erns within a cross and to e liminate plants which might have been
"se i fs .. rather tha n true F1' s.
Plants wi thin eac h family wer e examined severa l times during the
grow ing season.
Each plant expressing any ye llow c olor was identified
wi t h a t ag s i gnify ing the degree of yel lowing .
The majority of c rosses
were mede reciprocal l y to test the possibility of maternal inher itance
or of a seed transm itted viru s .
the
Fz
Since there was c lose agreement be tween
segregating patterns of both the direct and the reciprocal of each
cross, they were combined.
In the fall of 1960 each cro ss was pl ante d in F3.
r ows were sown with s eeds from sing le Fz pl ant s.
r ows were us ed t o verify the
Fz
Here, f ive foot
The data from the F3
pl ant cl a s s i f ic a tion .
In some crosses segregation was taking place for the awne d versus
awnless condition and/or for bronze chaff versus white chaff.
Although
a genetic s tud y of the se char acter isitcs was not a direct opje c tive of
11
this inves ti ga tion, cl ass ificat i ons for awn t ype a nd chaff color were
made.
The Fz plan t s were class i f i ed acco rding to the behavior of F3
rows.
The inve s ti ga tion was des i gne d to s tudy the first backc ross gener a tion in addition t o the F1 , Fz and F3 .
Howeve r, complicating fac tors
preve nted the obta ining of sufficient backc ro ss mater i a l to be considere d
r e lia bl e .
The backcross parents we r e planted in the fall of 1960.
ina tion and winter s urvival was good .
Germ-
The next summer when the crosses
were to be made it was observed that the flowering period of the F1 p l an t s
expressing the yellow co l or di ffe r e d from tha t of the normal parental
lines by seve n to ten day s .
Consequently, only a few pollinations could
be made .
Heavy spring thaws in the spring of 1962 provided the second compl i ca ting fac tor.
A large portion of the backcross nur sery wa• destroyed
by eros i on or by a heavy depos it of s ilt on the young pl a nt s .
The bac k-
cross mater i a l which survived i s repor t e d .
The da t a wer e analyze d by ch i- s quare ca l culat i ons for goodness -orf it t o hypothesized ratios.
EXPERIMENTAL RESULTS
Part of the crosses studied were segregat ing for awn type and chaff
color in addition to yellow plant color.
Although not a major part of
the study, data on segregation patterns of the characteristics were
recorded.
Inheritance of Awns
Atlas 66 was the only awnless parental line used in this investigation .
For the purpose of this s tudy, plants with awn-t ips were con-
sidered awnless.
When the awnless parent was crossed with 112a-105-6-4
(cross 516) and 193a-465-l-2 (cross 504) the r 1 plants were awnless.
This indicates the awn le ss condition is dominant over awned.
cases Fz segregation proved to be monogenic (Table 2).
In both
Small chi- square
values and high probabilities indicate that the segregat ion fits the 3:1
hypothesis quite closely.
Consistency from cross to cross was also
evidenced by the sma ll interaction chi - square.
Inheritance of Chaff Color
Two selections used in the study possess a dark bronze chaff color.
When crossed with the white chaffed wheats, the resulting F1 exhibited
bronze chaff.
Bronze , therefore, appear s to be dominant over whi te .
The segregation in r 2 fo llowed a 3:1 pattern.
Fz data summarizing the
awn inheritance of five crosses are presented in Table 3.
agreement is evident between observed and expected ratios.
A rather close
13
Table 2 .
F2 inheritance of awn type
Awnless
Obs . llxp.
Cross
516
Total
plants
d.f.
p
27
25.25
101
. 169
.50 - . 70
254 251.25
81
83.75
335
.1202
.50 - .70
.2821
. 50 - . 70
.0122
.90 - .95
.2699
.50 - . 70
Total x 2
Pooled x 2
x2
75.7 5
74
504
Awned
Obs.
llxp.
328 327. 00
108
109.00
486
Interaction x2
Calcula t e d on the basis of 3:1 r atio.
Ta ble 3.
F2 inheritance of chaff co l or
Cross
504
506
516
556
619
Bronze chaff
Obs.
Exp.
248
362
81
71
265
25 1. 25
360.75
75.75
77 .25
257.2 5
White chaff
Obs. Exp.
87
119
20
32
78
83.75
120.25
25.25
25.75
85.75
Total
Plan t s
d . f.
x2
p
335
481
101
103
343
1
1
1
1
1
.1681
. 0172
1. 455 3
2.0225
.9338
.50-. 70
. 90 - .95
.20-.30
. 10-.20
• 30- . 50
5
4.5969
. 30- .50
.0882
.70-.90
4.5087
. 30-.50
Total x 2
Poole d x 2
1027
1022.25
336
340 . 75
Inte r ac t ion x 2
Ca lcul a t e d on the basis of 3:1 rat i o.
1363
4
14
The two crosses segregating for awn and awnlessness were a lso segrega ting for chaff color.
To test for independence between the two
characters a simultaneous classiflcaLion for awns and chaff color was
made.
If the two characters were inherited independent of each other,
an approximate 9:3:3:1 ratio would be expected in F2 .
The close com-
parison of observed and expected values in Table 4 supports the hypothesis
that the genes conditioning awn type and chaff color are independent.
The mode of inheritance of these t wo characters was found to be the same
as that reported by more intensive investigations completed by Harrington
(1922) , Dhesi (1950) and Swenson (1960).
Inheritance of Yellm; Plant Color
One complication in studying the ye l low char acteristic is the
numbe r of gradations or degrees of yellowing expressed.
The degree of
yellowing for an F1 is quite consistent for a given cross but varies
considerably from cross to cross.
In certain crosses the expression of
the character in some F2 segregates was much more pronounced than tha t
expressed in the F1 .
The effects of environment undoubtedly have some influence on the
expression of the character; however, the F1 classification conducted in
three years agreed with only minor exceptions.
It was observed that the
F2 and F3 classifications, when rep ea ted in different years, could be
reliably duplicated .
The yellow plants were classified into three groups:
yellow, (2) moderate yellow, and (3) severe yellow.
(1) mild
The mild yellows
were plants which displayed the yellow co l or only in the leaf blade.
These plants were almost as vigorous as normal green plants.
Seed se t
Table 4 .
Test for independence between awn type and chaff color
Cross
Awnless J2lants
Bronze chaff
White chaff
Obs.
Obs. ExJ2.
EXJ2 .
504
175
188.43
67
62.81
71
62 . 81
22
516
54
56.81
21
18.93
19
18.93
7
Awned J2lants
Bronze chaff White chaff
Obs. ExJ2.
Obs. ExJ2.
Total
plants
d. f.
x2
p
20.93
335
3
2. 3592
. 30 - . 50
6.31
101
3
. 4408
. 90 - . 95
6
2.8000
.80 - .90
3
2.4993
. 30 - .25
3
. 3007
. 95 - .97
Total x 2
Pooled
229
245.25
88
81.75
Interaction x2
Calcula ed on the basis of 9:3:3:1 ratio.
90
81.75
29
27.25
436
16
appeared in most respects to be normal, wi th a slight amount of shriveling
in some instances.
Plant s classified as moderate yellow we re considerably less vigorous
and in most cases smaller than the green plan t s.
These plants exhib ited
the yellow color in the l eaf sheath as well as in the bl a de.
The moderate
yellows consistently produced seed which was shrive led .
The severe yellow seedlings expressed the greatest intensity of
yellow color (Figure 2).
plants s t ar t ed to head.
In most instances they died before the normal
Seldom did they survive more than a few weeks.
Since the severe yellow F1 ' s failed to produce seed, Fz segregat ion could
no t be s tudied in these crosses.
For purposes of ana l ysis , t he three
classifications of yellow in the F2 we r e groupe d into one yellow category.
The r es ult s of the yellow color investiga tion will be presented in
fou r ma j or groups:
(1) crosses involving the yellow parental line
(217-6-3-2) , (2) crosses involving green carr i er line s, (3) cr osses
involving non- carrier lines a nd (4) backcrosses.
Crosses i nvolving the ye ll ow parenta l
line (217-6 - 3- 2)
Cross 549 is a cros s between 217-6- 3- 2 and Nor in 10/Brevor 11.
r es ulting F1 of this cros s expressed a mild yellow color.
di ff iculty in distinguishing these F1 ' s from the normal green F1' s .
F
2
The
There was no
In
the segrega tion for ye llow versus green plant s follows a 3:1 pa ttern
(Table 5).
The close correspondence of observe d and expe cted va lues s up-
ports the hypothes i ze d r a tio and indicates that the parents probably
differ by one factor pair.
If the parental lines dif fer by only one fac tor pair, the
17
Figur e 2 .
A severe yellow plant (left) as compared wiLt .h a
normal green plan t
18
Ta bl e 5.
F2 inherit ance of yel low pl ant co lor in cross 549
Yellow Ela nts Green Elants To tal d. f.
Obs.
Exp. Obs.
Exp . plants
Family
x2
p
153
152. 25
50
50.75
203
. 01 48
153
162.00
63
54 .00
216
2.0000
.10 - .20
3
159
168 .75
66
56.25
225
2.2533
.10 - .20
4
158
156. 00
50
52.00
208
. 1025
. 50 - .70
Total x 2
4
Poo l e d x 2
623
639.00 229
213.00
Interaction x2
852
3
4. 3706
0
0
90 -
0
95
30 - . 50
1.6024
.50 - .70
2 . 7682
.30 - .50
Ca lcul a t ed on the basis of 3:1 r atio .
he tero zygous
Fz's
would be expected to segre gate in a 3:1 ratio when
planted in F 3 rows .
Plant counts wit hin an F3 row were made on 20
segregating rows selected at random.
Segrega tion within the rows was
t ak ing place for green, mild ye llow and yellow plants with the predominant
cla ss be ing the mild ye llow plants.
The intermediate c l ass was considered
t o be made up of plants carrying the genetic factors in a heterozygous
condition.
The ye llows were grouped and a na lyzed as shown in Table 6.
Close approximation of the ob served and expected values provides additional evidence for the 3:1 hypothes is.
In cross 546 the yellow plant was cro ssed with Hu ssar.
ing F1 ' s were mild yellow.
brid pattern (Table 7 ) .
The result-
Segregation in F2 appeared to follow a dihy -
The low chi - squar e values indica te segregation
for yellow versus green in this cross a pproximates a hypothe s ized 9:7
ratio.
Thi s indicates that the gene tic makeup of 217 - 6 - 3- 2 with regard
19
Table 6.
F3 inheritance of yellow plant color in cross 549
Row no.
1
2
3
4
5
6
7
8
9
10
ll
12
13
14
15
16
17
18
19
20
Yellow
Obs . Exp .
Green
Obs. Exp.
Total
plants
d. f.
1
1
14
24
31
16
35
15.75
23 . 25
32 .25
16.50
36.75
7
7
12
6
14
5.25
7.75
10.75
5.50
12.25
21
31
43
22
49
36
35
32
41
30
32.25
36 . 00
32.25
40.50
31.50
7
13
13
12
10.75
12.00
10.75
13.50
10.50
43
48
43
54
42
31
39
16
28
16
33.00
40.50
18 .00
30.00
17.25
13
15
8
12
7
ll. 00
13.50
6.00
10.00
5.75
44
54
40
23
19
21
21.00
25.50
21.75
27.75
24 . 75
9
7.00
8 .50
7.25
9.25
8.25
28
34
29
37
33
21
28
24
ll
13
8
9
9
Pooled x 2
537
556.50
205
185.50
Interaction x2
Calculated on the basis of 3:1 ratio.
p
. 7774
.0966
.1937
. 0605
.3333
. 30
.70
.so
.80
.so
-.so
-.80
-.70
-. 90
-.70
1.7441
.lllO
.0077
.0245
.2856
.20
.so
.95
.80
.50
-. 30
-. 70
-. 97
-.90
- .70
.4848
. 2221
.8888
.5333
. 3622
. 30
.so
. 30
. 30
.50
-. 50
-.70
-.50
-.50
-.70
1
1
1
.7618
3.1761
. 1033
. 0089
.0908
.30
.30
. so
.95
.80
-.50
-. 50
- .70
-. 97
-.90
20
10.2665
. 95 -.97
2. 7 330
. 05 -.10
7.5335
.95 -. 97
1
1
1
1
1
1
1
1
24
Total x 2
x2
1
742
19
20
Table 7 .
F2 inheritance of yellow plant color in cross 546
Yellow Elants
Obs.
Exp.
Family
Green Elants
Obs.
Exp .
Total d . f.
plants
x2
p
ll4
107.44
77
83.56
191
.9155
. 30 · .50
2
99
108.00
93
84.00
192
1 . 7142
.10 · .20
3
104
103.50
80
80.50
184
.0055
. 95 ·.97
4
92
100.6 9
87
78.31
179
1. 7142
.10 -.20
4. 3494
. 30 -.50
.6142
.50 - .70
3. 7 352
.30 -.50
Total x 2
Pooled x 2
4
409
419.62
337
326 . 38
746
Interaction x2
3
Calculated on the basis of 9:7 r atio.
to the yellow color characteristic proba bly differs from Hu ssar by two
factor pairs.
Cross 544 is a cross between 217-6-3- 2 and CI 12932 .
duced was mild yellow and F
2
The F1 pro -
segregation again approximated nine yellow
to seven green plants (Table 8).
Thus, Cl 12932 also appears to differ
from the yellow se lection by two factor pairs.
The similarities in behavior of Hussar and Cl 12932 when crossed
with 217-6-3-2 indicate that they possibly have like genotypes for yellow
versus green color.
Additional evidence tha t they are genotypically alike
for this character is seen
554).
~<hen
they are crossed with each other (cro ss
The F1 produced as a result of this cross is normal green.
Cross 550 is a cross between 217 - 6-3-2 and 112a-105-6-4.
non- viable F1 was produced
~<hich
A small
died soon after emergence (Figure 3) .
Greenhouse and field attempts to maintain the seedlings failed.
The
21
Table 8.
F2 inheritance of yellow plant color in cross 544
Family
Yellow elants
Exp.
Obs.
Green elants
Obs.
Exp.
Total
d. f.
plants
x2
p
115
118.69
96
92.31
211
.2622
.50 -.70
2
95
105.75
93
82.25
188
1. 4977
. 10 -.20
3
102
102 . 37
80
79.63
182
. 00 30
.95 -. 97
4
96
109 . 12
98
84.88
194
3. 5774
.05 -.1 0
5. 3403
. 30 -.50
2.6256
.10 -. 20
2.7 147
.30 -.50
Total x 2
Pooled x 2
4
408
435.94
367
339.06
775
Interaction x2
3
Calc ulat ed on the bas is of 9:7 ratio.
r es ults were identic a l when the rec iproc a l of cross 550 was made.
When 217-6-3-2 was cro ssed ••ith 193a - 465-l- 2 (cr oss 610) the r es ults
were the same as those observed wi th cross 550.
The F1 perishes while in
the seed ling s tage.
Crosses 550 and 610 indicate that 112 a-1 05 - 6-4 and 193a-465 -l-2 do
not behave in the same manner as other green parental lines when crosse d
wi th the ye ll ow parent .
The severe yellow F1 suggests that ll2 a -105-6-4
and 193a-465-l- 2 contribute a f actor for yellowing which is not identic a l
with tho se carried by 217-6- 3- 2.
Crosses involving green c ar rier lines
Selections 112a-105-6-4 and 193a-465-l-2 behaved s imilarly in crosses
with 217-6-3-2 and were suspected of carrying identical genotypes for
yellow plant co lor.
To te s t the s i milarities of their genotypes these
22
Figure J,
A t yp ical ye llow F1 popu lation of crosses 550 and 610
23
selections were crossed with each other (cross 612).
The F1 produced
was normal green and no segregation for yellow types appeared in F2 .
Cross 552 is a cross between 112a- 105 - 6- 4 and Hussar .
The F1 1 s
were normal green and only green plants we re produced in F2 .
When 112a-105-6-4 was crossed wi th CI 12932 (cross 555) the F1 again
was normal green.
No segregation took place in the F2 .
Crosses 552 and 555 provide additional evidence that CI 12932 and
Hussar are genotypically similar with regard to factors control ling
yellow co l or.
The normal green F1 , which results when they are crossed
with the known carrier 112a- 105- 6-4 indicates that they probably do not
carry factors for yellowing.
Cross 556 involves 112a-1 05 - 6 - 4 and Norin 10/Brevor 11 .
exhib ited a moderate yellow color.
The F
1
The pl ants were considerably stunt ed
and the seed produced was quite shrive l ed .
Segregation for yellow and green occurred in F2 .
The degrees of
yellowing were not a s evident as in the crosses involving 217-6-3- 2 .
The ye llow plan t s we re all considerably stun ted.
The F2 data show that
the segregating pa tterns were not consistent with the hypothesized 9:7
ratio.
Of the 218 F2 plants, 82 were yel low and 132 were green .
While
examining the ye ll ow F pl ants it was noted that many of them had withered
2
a lmo st immediately after emergence (Figure 4) .
ye llow plants formed seed .
Only 49 percent of the
Since the predominant phenotype observed in
Fz failed to follow the phenotype of the F1, it i s s uggested that a por tion of the ye llow Fz plants either failed to emerge or died prior to
counting, thus accounting for the lower number of yellows than wou ld
normal l y be expected.
This s uggestion is supported by observations made
24
Figure 4.
Three severe yellow plants (each labelled with a red
tag) which were typical of the yellow Fz plants of
certain crosses
25
in F3.
Forty- two F3 rows of cross 556 were planted with seed from the
yellow F plants.
2
plant.
Nineteen of these rows failed to produce a single
The remaining 23 rows segrega t ed for yellow versus gr een in
approximate ly a 9:7 pattern (Table 9).
This suggests that Nor in 10/Brevor
ll carries a pair of factors for yellowing which is not identical with
the far tor contributed by 112 a - 105 - 6- 4.
Tabl e 9.
F3 inheritance of yellow p l an t color in cross 556
Ye11mo Elant
Exp.
Obs .
Row no.
Green E1ant
Obs.
Exp.
Total d. f.
plants
1
2
3
4
5
13
12
10
11
7
12.38
12. 38
11.25
11.82
6.75
9
10
10
10
5
9.62
9.62
8.75
9.18
5.25
22
22
20
21
12
6
7
8
9
10
10
15
9
19
16
10.69
12.38
11. 82
21.38
16.87
9
7
12
19
14
8.31
9 . 63
9.18
16.62
13 . 13
19
22
21
38
30
Total x
2
Pooled x 2
1
1
1
1
1
10
120
127.69
107
99.31
227
Interaction x2
9
x2
p
.0709
.0266
. 3173
.1300
. 0211
. 70
. 70
. 50
.50
.80
-. 90
-. 90
-.70
- .70
-. 90
.1017
. 70
.20
.10
.30
.70
-. 80
-. 30
- .20
l. 26 72
l. 5389
.6057
.1023
- .so
-. 80
4.1817
.90 - .95
1.0585
.30
3.1232
.95 - .97
-.so
Calculated on the basis of 9;7 ratio.
Cross 516 involves ll2 a - 105-6-4 and Atlas 66.
color was expressed by the F1 .
A moderate yellow
In F2 140 plants were classified.
Sixty- two of the plants exhibited either modera t e or severe yellow while
78 appeared green.
As in cross 556, a smaller number of yellow plants
than expected were obs erved in r 2 .
Here again , it is suspected tha t some
26
of the severe yellow plants were not being included in the F2 ratio
because of their failure to survive long enough to be counted.
The
yellow classes observed were identical with those found in cross 556.
Each plant expressing the color was distinctly stunted.
Fifty-three
percent of the yellm• plants failed to mature to a point of setting
seed.
Seed from the 29 yellow F2 plants was planted in F3 .
rows failed to produce any plants.
observed.
classified.
Five F3
No true breeding yellow rows were
Ten of the 24 segregating rows were selected at random to be
The yellow and green plants in each row were counted.
The
close comparison of observed and expected ratios fit the expected 9:7
r a tio (Ta bl e 10).
The digeni c ratios indic a te tha t these two parental
lines differ by two factor pairs.
Table 10.
F3 inheritance of yellow plant color in cross 516
Row no.
Yellow Elant
Obs.
Exp.
Green El an t
Obs.
Exp.
1
2
3
4
5
13
17
19
18
24
10.12
18 .00
16.32
16 .88
25.32
2l
7.88
14.00
12.68
13.12
19.6 8
6
7
8
9
10
18
19.69
ll. 81
24.75
12.38
13.50
17
10
14
9
12
15.31
9.19
19.25
9.62
10.50
11
30
13
12
5
15
10
12
Total
plants
d. f.
x2
18
32
29
30
45
l
l
1
1
1
1.8721
.1269
1. 0064
.1699
.1573
.10
.so
. 30
.so
. so
-.20
- .70
-.s o
-.70
- .70
35
21
44
22
24
. 3315
.1268
2. 5431
.0709
. 3808
.so
.50
. 10
.80
.so
- .70
-. 70
-.20
-. 90
-.70
6.7857
.60 -.80
.5290
.40 - .60
6.2567
.50 - .70
Total x 2
Pooled x 2
10
175
168 . 75
125
131.25
Interaction x2
Calculated on the basis of 9:7 ratio.
300
9
p
27
The similarities between this cross and cross 556 suggests that
Atlas 66 and Norin 10 / Brevor ll are genotypically alike at the yellow
color loci.
To te st the similarities of their genotypes, each was crossed
with l93a-465 -l -2 and the segrega tion patterns a nd behavior studied.
Cross 506 involves l93a-465-l-2 and Norin 10/Brevor 11.
The F1
produced as a result of crossing these normal green lines was moderate
yellow.
In the F , segregation occurred for yellow and green pl ants.
2
A
total of 308 yellow plants were observed in the F2 population, of which
130 (42 percent) failed to he ad.
In F3 each of the 328 green F2 plants gave rise to a row of green
plants.
Of the 178 F3 rows planted from seed of yellow F
2
plants, 27
were devoid of plants, 8 bred true for yellow and 143 segregated.
segregating patterns were observed within the F3 rm.s.
Two
The low chi-square
va lues in Table 11 indicate that this is a satisfactory fit for the
hypothesiz ed 9:7 ratio and the values in Table 12 support a 3:1 segregation pattern.
Both of these F3 ratios wou ld be expected if the parents
differ by two factor pairs.
The information obtained from the a bove cross presents additional
evidence that the genetic makeup of l93a-465-1 - 2 and 112a-105-6-4 with
respect to yellow color are the same since Norin 10/Brevor ll x ll2a-105 6-4 (cross 556) showed the same
se~regation
pattern as Norin 10/Brevor
11 x l93a-456 - l-2 (cross 506).
Cross 504 i s a cross between l93a-465 -l-2 and Atlas 66.
plants were a moderate yellow.
The F1
Crosses presented previously have indicated
that ll2a - 105-6-4 and 193a-465-l-2 a r e geno typically alike for the color
trait.
If this assumption is valid, the pattern of F2 segregation should
coincide with that of cross 516 (ll2a-105 - 6-4 x Atlas 66) .
28
Table 11.
Di genic F3 inheritance of yellow pl an t color in cross 506
Yellow Elant
Obs.
Exp.
Row no.
Obs.
Exp.
To t al
plant s
d . f.
x2
p
11
11
23
19
10
28
1
1
1
1
.1560
1. 5476
.0556
.22 67
.50 -.70
.10 -. 20
.80 - .90
.so - . 70
.99 -1.00
.50 -.70
.80 - .90
.30 - .5 0
Green Elant
1
2
3
4
12
8
6
17
12.94
10 . 69
5.63
15.75
11
10.06
8. 31
4. 37
12.25
5
6
7
8
18
24
12
8
18.00
22.50
12.37
10.12
14
16
10
10
14.00
17.50
9.63
7.88
32
40
22
18
.0000
.2285
.025 2
1.0143
9
10
14
14.62
14.62
8.44
19 . 12
12
13
11.38
11. 38
6.56
14.88
26
26
15
34
.0599
.410 1
.0849
.0925
11
9
20
12
4
13
6
14
To tal x 2
12
Pooled x2
161
164.82
132
128.18
293
Int e r ac tion x2
11
.80
.50
.70
. 70
-. 90
- . 70
-. 90
- . 90
3. 9013
.90 -. 95
.2023
.50 -.70
3.6990
.95 -.97
Calcul a ted on the bas is of 9:7 ratio.
Tab l e 12.
Monogenic F3 inheritance of yellow plant color in cross 506
Row no.
13
14
15
Yellow El ant
Obs.
Exp .
12
9
24
12 . 00
8 . 25
25 .50
Green El ant
Obs.
Exp.
4
2
10
4.00
2.75
8.50
Total
plants
16
11
34
Total x 2
Pool e d x 2
d . f.
3
45
45.75
16
15.25
Interaction x 2
Calculated on the basis of a 3: 1 ratio.
61
2
x2
p
.0000
. 2726
. 35 29
. 99-1.00
.50 - . 70
.50 - .70
. 6255
.70 -.90
.0490
.70 - .90
. 5765
.70 - .80
29
The total number of plants produced in F
2
was 513.
The general
appearance of the F2 population was similar to that of cross 516.
The
green plants appeared normal in every respect while the yellow plants
were all considerably stunted.
F2 data presented in Table 13 show a
close approximation of the hypothesized 9:7 ratio.
Table 13.
Cross
504
F2 inheritance of yellow plant color in cross 504
Yellow plant
Obs .
Exp.
289
288.57
Green plant
Obs.
Exp.
224
Total
plants
224 . 43
p
d. f.
513
.0014
.95 - .99
Calculated on the basis of 9:7 ratio.
There is an obvious inconsistency between this cross and cross 516.
The Fz ratio in cross 516 fit a 7:9 ratio better than a 9:7.
This fact
does not necessarily discredit the supposit i on that the same two factor
pairs are opera ting in both cases.
In studying the F2 da t a of cross 504
it is evident that a larger proportion of the yellow plants were present
to be classified.
Fifty-six percent of the yellow plants failed to head
in cross 504 as compared with 42 percent in cross 516.
Cross 553 is a cross between Hussar and Norin 10/Brevor 11 .
The
F1 was green and segregation did not take place in the F2 population.
Cross 557 involved CI 12932 and Norin 10/Brevor 11.
The progeny of
this cross were all classified as green.
Crosses i nvolving non- carrier lines
Cross 554 is a cross between Hussar and CI 12932.
were normal green .
No segregation took place in F2 .
The F1 plants
CI 12932 and Hussar
30
were the on l y two parent al lines that consistently produced only green
progeny when crossed with each of the other green parents.
Backcrosses
A l arge r amo unt of backcross data would be ex tremely helpful in
de t ermining the ac tual genetic constitut i on of each parental line .
The
difficu l ties encountered in performing the backc rosses made it impossible
to observe the segr ega ting pa tterns of most of the backcrosses involving
F1 plants which exhibited the yellow color.
Since the normal green F1 plants r eached ma turity approximately a t
the same time as the pa rental l ines , a fai r ly l arge amount of this type
of backc r oss ma terial was obtained.
In eac h case wher e the F was gree n,
1
the backcross t o e ither par ent faile d t o produce any yellow plants.
DISCUSSION
The results of this investigation indic ate that the inheritance of
this particular yellow plant color characteristic in wheat is conditioned
by more than a single pair of genes.
The mono and d i genic ratios plus
the nonviable F1 ' s of certain crosses suggest the action of at least
three factor pairs.
Since the hexaploid nature of vulgare wheat is a
matter of common know l edge, it seems reasonable to suspect that a pair
of factors influencing the yellow characteristic might be carried in
each of the thre e genomes.
Two groups of green carrier types were observed among the parental
lines used in this study.
When crosses were made between the two groups
(crosses 556, 516, 506 and 504) the F1 plants were moderate yellow and
segregation in F
2
followed a dihybrid pattern, indicating that each
group carries a single but different factor pair, neither of which i s
capable of expressing the yellow color by itself.
When cross 612 was
made within one group the F was normal green and no F2 segregation took
1
pl a ce.
A cross wi thin the other group was not made.
When either of the two carrier groups was crossed with non-carrier
lines (crosses 552, 553, 555 and 557), the F1 was normal green.
The fact
that the F1 's and F2 ' s of the carrier x non-c arrier cross we re green ,
supports the assumption that only one factor is not capable of causing
the character to come to expression.
One parental line (217 - 6- 3-2) exhibited the character directly and
when crossed with the non-carrier group resulted in a mild yellow F1 and
dihybrid segregation in F2 .
This suggests tha t 217 - 6-3 - 2 carries two
32
factor pairs for the yellow color and that at least two yellow factors
must be present in order for the character to be expressed.
Crosses
involving 217-6-3-2 and one group of carriers showed monofactorial segregation, indicating that they possess one yellow factor in common.
Crosses between 217-6-3-2 and lines within the other carrier group
resulted in a non-viable F .
1
This provides evidence that the factor
pair carried by this group of carriers is not identical with the two
pairs of factors carried by 217-6-3-2 and thus strongly indicates the
existence of a third yellow color factor.
These r esults suggest the following hypothesis.
The ye ll ow color
appears to be partially dominant to normal green and requires two of the
three yellow color factors to be at least heterozygous for expression of
the character.
In keeping with these assumptions the genotypes presented
in Table 14 are suggested for the various parent lines.
Table 14.
Phenotype
Suggested genotypes and phenotypes of the parental selections
Normal green
(non-carrier)
Yellow
Normal green
(carrier)
- - - - -1--------- -------- - - - - - - - - - ·--- - Genotype
Y1Y1 Y2Y2 Y3Y3
YlYl Y2Y2 y3y3
Y1Yl Y2Y2 Y3Y3 Y1Y1 Y2Y2 Y3Y3
Parental
selections
Hussar
CI 129 32
217-6-3-2
Norin 10/
Brevor 11
llZa-105-6-4
Atlas 66
193a-465-l-2
The symbol y has been chosen to represent the factors condit ioning
the yellow character.
Small y represents the gene responsible for yellow
color and large Y the gene responsible for the normal green color .
The
33
subscripts 1, 2 and 3 are used to identify each of the three loci involved;
therefore, the three pairs of factors operating can be designated Y1y 1 ,
Y2yz and Y3Y3·
Hussar and CI 12932 are normal wheats carrying only the genes for
green color.
Their genotypes might then be expected to be Y1Y1 Y2Y2 Y3Y 3 .
Selection 217 - 6-3- 2, which expresses the yellow color directly, is suspected of carrying two yellow factors and could be designated YlYl Y2Y 2
Y3Y3 .
This genotype is supported by the observed dihybrid segregation
in crosses 544 a nd 546 which involve 217 - 6- 3-2 and non-carriers.
Norin 10/Brevor 11, which is representative of one of the carrier
groups , is thought to possess one yellow factor in common with 217 -6-3- 2
since they yield monogenic ratios when crossed.
be assigned the geno typ e YlYl YzYz y 3y 3 ,
This carrier group could
The non- viable F1 's of crosses
550 and 610 indica t e that a third yellow factor is introdu ced when selec tions from the second carrier group is crossed with 217-6-3-2.
The ten-
tative geno t ype of thi s group of carriers would be Y1Y 1 Y2Y2 y 3y 3 .
It
is s uspec t ed that the non-viable F1 's carry a yellow factor at each of
the three loci and that this combination results in their premature death.
Provided the plants could be cultured and maintained to the point of
maturing seed, a trigenic ratio would be expected in the F2 generation
of crosses 550 and 610.
Obs ervations made during the F1 , F2 and F 3 genera tions of these
crosses all support the suggested genotypes with only minor exceptions.
Crosses which deviated from the expected ratios (506, 516 and 556) all
showed a deficiency of Fz plants expressing the yellow color.
It is
signifi cant that in all three crosses this deficit approximated threesixteenths.
A possible explanation can be seen by examining the genotypes
34
and FJ breeding behavior of the three crosses in Tab l e 15 .
Since it was
reasonably subs t antiated by observations i n F3 (Tables 9, 10, 11 and 12)
that a portion of the F2 plants did not emerge or did not survive long
enough to be counted , it is suspec ted tha t the three-sixteenths which
we r e going out in these crosses were of the genotypes YlYl Y2Y 2 y 3y 3 and
YlYl YzYz y 3y 3 .
It can be noted tha t both geno types possess the homo-
zygous YJYJ factor in combination wi th at least one y 1 gene.
Based on
the degree of yellowing observed in crosses involving y y , this fac t or
3 3
is suspected of be ing more severe in its e ffect than ei ther YlYl or YzYz ·
See dlings which ca rry y 3y 3 i n combination with a t least one other color
fac t or are suspected of e ither failing t o emer ge or dying very ear l y.
Since the pr opo rtion f a ilin g t o emerge i s r easonably consistent, the Fz
data were t es t ed for goodness -of - f it to a 6:7 r a tio.
Tabl e 16 s hows a
c l ose approx imation of the observed and expec t e d values in crosses 506
and 516; however , cross 556 conforms to the 6:7 ratio rather poorly.
A summary of the crosses, the F1 pheno ty pe and suggested geno types ,
and Fz segr egat ion patterns i s presented in Table 17.
In keeping wi th the proposed geno t ypes and three gene hypothesis,
it wou ld be suspec t ed that a third carrier group (Y 1Y1 y 2 y2 Y3Y3 ) should
exist.
This group could be ident ified by the digenic ratios with each
of the two carrier groups r eporte d here and a monogenic r at i o wi th
21 7-6-3 - 2 .
35
Table 15 .
Fz genotypes, phenotypes and their br eeding behavior in F3 in
crosses 516, 506 and 556
Fz genotypes
Frequency
Fz phenotype
Green
ylyl y3y3
ylyl Y3Y3
2
Green
Y1Y1 Y3Y3
1
Green
Y1Y1 Y3Y3
Green
YlYl Y3Y3
Green
Yell ow
4
Y1Y1 Y3Y3
Yellow
Y1Y1 Y3y3
Yellm<
2
Y1Y1 Y3Y3
Yellow
Y1Y1 Y3Y3
Table 16 .
Ass umed behav ior
in FJ
F3
ratio
)
)
)
)
)
)
)- )
)
)
)
)
)
Breed true for
)
)-)
)
Segregate for
yellow and green
6
Fa il to emerge or
3
)
) -)
)
7
green
s urv i ve
F2 inheritance of yel l ow plant color in crosses 506, 516 and 556
Yellow El ant
Ob s .
Exp .
Green Elant
Obs.
Exp.
Total
plant s
506
473
465.72
536
543.34
1009
. 2ll2
.60 - .80
516
61
64.61
79
75.39
140
. 3745
.50 - . 70
556
82
98 . 76
132
ll5 . 22
214
5.2853
. 01 - .05
Cross
Calculated on the basis o f 6:7 ratio.
d. f.
x2
p
Table 17 .
F1 genotypes , phenotypes and F2 segr egation with respect to the yellow plant characteristic
Cross
Parent s
549
217 - 6- 3- 2 x Norin 10 /Brevor 11
Y1Y1 Y2y2 Y3Y3
mild yellow
3:1
546
217 - 6- 3- 2 x Hussar
Yl yl y2Y2 y3y3
mild yellow
9:7
544
217 - 6- 3- 2 x CI 12932
YlY1 Y2Y2 Y3Y3
mild yellow
9:7
554
Hussar x CI 129 32
Y1Y1 Y2Y2 Y3Y3
green
550
217 - 6-3 - 2 x ll2a - l05-6-4
Ylyl Y2Y2 Y3Y3
severe yellow
unknown
610
217 - 6- 3- 2 x l93a- 465 -l- 2
Ylyl Y2Y2 Y3Y3
severe yellow
unknown
612
ll2a - l05 - 6- 4 x l93a - 465-l - 2
ylyl Y2Y2 Y3Y3
green
552
ll2a- l05-6 - 4 x Hussar
Y1Y1 Y2Y Y3y 3
2
green
555
ll2a - l05 - 6- 4 x CI 12932
Y1Y1 Y2Y2 Y3Y3
green
556
ll2a -l 05-6 - 4 x Norin 10 /Brevor
Ylyl Y2Y2 Y3Y3
moderate yellow
516
ll2a - l05-6-4 x Atlas 66
YlYl Y2Y2 Y3y 3
moderate yellow
506
l93a - 465-l-2 x Norin 10/Brevor
Y1Yl Y2Y2 Y3Y3
modera t e yellow
504
193a - 465 - l-2 x Atlas 66
Ylyl y2y2 Y3Y3
moderate yellow
553
Hussar x Norin 10/Brevor 11
Ylyt y2y2 y3y3
green
557
CI 12932 x Norin 10/Br evor ll
Y1yt Y2Y2 Y3Y3
green
F1 genotype
aplants classified as gr een in F1 did not show segr egation in F2·
bFz ratio as adjus t ed by F3 segregation patterns .
F1 phenotypea
F2 ratio yellow green
9:7
SUMMARY AND CONCLUSIONS
The inheritance of a yellow plant color character in winter wheat
was investigated .
and F3.
The expression of the character was studied in F1 , F
2
Crosses were made directly and in reciprocal to examine the
possibility of cytoplasmic or maternal inheritance.
Based on the results
of the inves tigation , the following conclusions may be drawn .
1.
Since the yellow color was not randomly produced throughout the
field but confined to certain crosses and in definite patterns from
generat i on t o genera tion, the genet ic origin of the character appears to
be well esta bli shed .
2.
The mono and digenic ratios in addition t o a non- viable F1 in
certain crosses indicate that three pairs of gene tic factors are operating to condition the character.
3.
The character exhibits partial dominance over normal green.
4.
Its expression requires two of the three loci to carry factors
for yellowing at least i n heterozygous condition.
5.
Two grou ps of carrier types exis t.
yellow F1 and a monogenic
Fz
One group produces a mild
ratio when . crosse d with the yellow selection
while the second group produces a non- viable F1 in combination with thi s
selection.
Crosses between the t wo groups result in a dihybrid F ratio,
2
whereas crosses within a group produce normal green plants.
6.
One selec tion, apparently true breeding for the character, is
genotypically different from either carrier group .
7.
Var i ous intensities of yellowing are expressed pointing to the
somewhat additive nature of the genes responsible for the character.
38
The presence of a yellow gene at each of the three loci, promotes a
severe yellowing which re su lts in premature death of the affected plants.
8.
Green plants, when allowed to se lf-pollinate, do not segregate
for yellow in later generations.
9.
No pathogenic organism or nutritional disorder appears to be
directly assoc iated with the character.
Due to wide differences in the parental material it i s impossible to
directly compare the result s of this s tudy with any reported in the
literature .
Additional inve s tigations might be conducted to verify the
observations made here and to examine the problems not fully explained in
this study.
In future studies bac kcross material involving each parent
and its F1 would be helpful in supplementing F , F2 and F3 observations.
1
Although different i a l ma t ur ity of the parenta l l i nes prevented the
utiliz a tion of backcross data in this investigation, it is probable that
the use of staggered planting date s and space planting to promote l a te
tillering would alleviate this difficulty .
It is noted that the variety Ridit is in the ancestral line of one
of the carrier groups and the yellow selection.
Future studies might
explore the genetic relationship that exists between Ridit and these
line s with respect to the yellow plant character .
LITERATURE CITED
Dhesi, N. S. 1950. Inheritance of resistance to races of covered smut,
awns , and chaff color in a wheat cross . (M . S. Thesis Dept. of
Agronomy) Utah State University, Logan, Utah .
Harrington, J. B. 1922. The mode of inheritance of certain characters
in wheat . Sci. Agr. 2:319-324.
Hebert, T. T. and G. K. Middleton.
Agron. Jour. 47:196.
1955 .
Lethality in a wheat cross .
Jensen, N. F. 1957. The inheritance and influence of a dominant
chlorophyll deficient character in wheat. Agron. Jour. 49:529-531.
Kostyuchenko, I. A. 1936. The premature perishing of the hybrids in
wheat crosses. Bul. Appl. Bot. Leningrad . Series A (19):127-37.
(Original article not reviewed; refer to Plant Breed . Abs. 8:27.
abs. no. 99 1937).
Neatby, K. W. 1933.
159- 162.
A chlorophyll mutation i n whea t .
Jour . Hered. 24:
Pao, W. K and H. W. Li. 1946. Maternal inheritance of variegation in
common whea t. Jour. Amer. Soc . Agron. 38:90-94.
Smith, W. K. and J. B. Harrington.
20:19 - 22.
1929.
Whe a t a lbinos.
Jour. Hered .
Stadler, L. J . 1929. Chromosome number and the mutation rate
and Triticum. Proc. Nat. Acad. Sci. 15:876-881.
in~
Swenson, R. J. 1960 . A dia llelic study of six chaff variations in wheat.
(M. S. Thesis. Dept. of Agronomy) Utah State University, Logan, Utah .