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III. Genetics of Qualitative Characters

III. Genetics of Qualitative Characters

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TABLE I

of the I’h(wotylw.: and tlw 1iefrrcwc.c.s 13st:il)lishing the h l o d ~of

1nlicrit;inc.c nncl Assigninq thv S ~ m l m l s



‘4 1,ist of Cerics 13t*imrt(dfor thc Soy1)cwi Ilic.111diiig;i &scription



_.____l_._l_



Symbol

-.



~

.

.

I

_

.

.



A

a

Ah

nh



Bl 4 B ,

h , or h , o r 12,

El

hl



c , c,



c , or c2



cs

CS



D,



dl

Df

df

Dt



at

E

e

F



f

Fe

fe



OT



a,



D,



-~



~



..



1)cscription

....



~.



~



.



Ilctfcrcmx

~



Appww’cI p ~ i l w s ~ x * n ~ ~ ~ ~

Erwt p r i l ~ w c . ~ w x

1,c:nf abscission :it matririty

Dc4aycd nlwission ( T206)a

Bloom on srcd coat ( T 4 )

No bloom

Slrarp prilwsccncc: tip

Blurit pii1)c~sc.cnc.ctip

Cr;ick(d s ( d coat ( T217)

Entirc sccd coat

1hist;incc. to frogoy lcafspot

Snscepti1)ility

Yollow cotyicdons in srecl

Green cotylcdons (T38)

Normal plant

Dwarf plant

Indeterminate stem (T10)

Determinate stem ( T 6 )

Early maturity

Late maturity

Normal stem

Fasciated stem (T173)

Normal iron utilization

Inefficient iron utilization (T203)



. .-



-..



..-



.-~

~- --.



-



~



~---



Kurasn\vn, 1036; Morsr and C:irtt(,r, 1937



l’rolnt, 1950

Woodworth, 10.32, 1933



Ting, 1946

Napii, 19%; hf;itsurira, 1933



a

Athow and Probst, 19S2

Woodworth, 1921; Owm, 1 9 2 7 ~ ; Veatch und

Woodworth, 1930

Stewart, 1927; Wooclworth, 1932, 1933

Woodworth, 1932, 1933

Owen, 1927b

Nagai, 1926; Takngi, 1929; Woodworth, 1932,

1933

Weiss, 1943



‘%



U



TABLE I (Continued)

Symbol



Fl



P

G

g

I

ii

ik



i



K

k

L



I

M

m

Mi,, Mi,, MiR

mi,, mi,, miR

N

n

Na

na



No

fl0



0

0



Description

Brown flecks on black seed coat (T85)

Self black seed coat

Green seed coat (T164)

Yellow seed coat

Light hilum color

Dark hilum color

Dark saddle pattern (T19)

Self dark seed coat (T152)

Dark color on hilum only

Dark saddle pattern (T153)

Dark pod

Light brown pod

Black stripes on brown seed coat (T125)

Self brown seed coat

Resistance to certain races of downy mildew

Susceptibility

Normal hilum abscission

Lack of abscission at hilum (T25)

Broad leaflet

Narrow leaflet, high number of seeds

per pod (T41)

Nodulating plant

Nonnodulating plant (T201)

Brown seed coat (T25)

Reddish-brown seed coat (T27)



Reference

Morse and Cartter, 1937

Terao, 1918; Takahashi and Fukuyama, 1919;

Nagai, 1921; Woodworth, 1921

Nagai, 1921; Nagai and Saito, 1923; Owen, 1928a;

Woodworth, 1932, 1933; Mahmud and Probst,

1953



2E



Nagai and Saito, 1923; Takagi, 1929

Woodworth, 1923

Nagai and Saito, 1923

Geeseman, 1950

Owen, 1928a

Takahashi and Fukuyama, 1919; Nagai, 1926;

Woodworth, 1932, 1933; Takahashi, 1934;

Domingo, 1945 .

Williams and Lynch, 1954

Nagai, 1921



w



s



TABLE I (Continued)



Symbol



Description



0



Oviitc leaflet



o



Oval leafiet, few secds per pod (T122)

Glabrous plant (T43)

Pubescent plant

Normal pubescence

hlinute pubescence ( T31)

Normal plant

Pseudo-mosaic (dwarf plant, crinkled leaves,

sterilc) (T211)

Resistance to Phytophthora rot

Susceptibility

Black seed

Brown seed

Susceptibility to cyst nematodc

Resistance ( T 6 )

Tall, late plant

Short, early plant

Peduncnlate inflorescence ( T208 )

Subsessile inflorescence ( T109)

Nonshattering pods

Shattering pods

Shattering pods

Nonshattering pods

Long, spreading branches

Short, erect branches



PI

PI



p,



P,

Pm

Pm



Hdercnce



E



Domitigo, I015



Nagai and Saito, 1923; Stcwart and Wentz, l9ZG

Stewart and Wcntz, 1926

Probst, 1950



m



B



3

+



8x



I3crnard st ul., 1957



0"2



Nagai, 1921; Woodworth, 1921; Stcwort, 1930;

Williams, 1952



3



CaldwclI et al., 1960



2!



Woodworth, 1923



8



?-



F



r

Van Schaik and Probst, 1958a

Morse and Cartter, 1937

Nagai, 1926; Morse and Carttcr, 1937

Nagai, 1926; Matsuura, 1933



TABLE I (Continued)

Symbol

St



st



T

t



Description



Reference



Normal seed production

Sterility



Owen, 1928b; Woodworth, 1932, 1933



Brown pubescence, black or brown seed coat

Gray pubescence, imperfect Mack or bufl

seed coat



Nagai, 1921; Woodworth, 1921



Normal chlorophyll

Chlorophyll variegation in leaf ( T93)



Woodworth, 1932, 1933



Purple flower

White flower



Tikahashi and Fukuyama, 1919; Woodworth, 1923



Pale piirple flower with W,

Purplish-red flower with W,



Takahashi and Fukuvama, 1919; Matsuura, 1933



Dark purple flower with W ,



Hartwig and Hinson, 1962



X



Yl

Yf



YS

Ys



y,

y4



8

ti



0



Dilute purple flower with W,

Purple flower with W,

Very dilute purple or near white flower

with W,



X



B



M



Five leaflets per leaf (T143)

Three leaflets per leaf



Takahashi and Fukuyama, 1919; Nagai, 1926;

Woodworth, 1932, 1933



Normal green plant

Greenish-yellow, weak plant



Nagai, 1926; Morse and Cartter, 1937



Normal green plant

Green seedling becoming yellow (with g)

(T139)

Normal green plant

Greenish-yellow leaves, weak plant (T102)



Nagai, 1926, Takagi, 1929; Terao and Nakatomi,

1929; Morse and Cartter, 1937

Morse and Cartter, 1937; Woodworth and

Williams, 1938 (as y 5 )



3



w



a

w



TAB1.E I (Continued)



Symbol



F

Q,



Ocscription



Reference



Normd grcrn plant

Ycllow-gwn leavra, low vigor ( 1’1 16 )

Norm.11 green plmt

Pde grccw plant (T136)



hlorsc: m t l C:irtter, 1037; Woodworth and

Williams, 1938 (as y 4 )

Morse and Cartter, 1937; Woodworth and

Williams, 1938



Normal grwn plant

Yellow-green Icaveq in young plant,

becoming grcm (T138)

Normal green pliint

C r e e n i h - y c h v 1eavc.s ( T135)

Norm.11 grwn plmt

Yellow-gt ccn recdling heroming green

(T161)

Normal green pLnt

Lethal yellow plant, Y,, Y , ~ is yellow

green (T219)

Susceptibility to hactcrial pu\tule

Resistance ( recessive)

Normal plant ( dominant )

Dwarf plant, mutation from colchicinc-treatcd

seedling (T210)

Yellow cotyledons in seed ( cytoplasmically

inherited )

Green cotyledons (T-14) (cytoplasmically

inherited)



Morse and Cartter, 1937 (as y H ) ; Williams, 1950



t\3



Bg



+I



Prohst, 1950



9



*

0



m



I’rol)st, I950



3



0



z



Wcbcr



:id



Weiss, 1959



Feaster, 1951; Hartwig and Lehman, 1951



Ei



E



r

Porter and Weiss, 1948



m



Terao, 1918; Owen, 1927a; Veatch and

Woodworth, 1930



E



5 The T numbers designate soybean strains carrying the specified gene( s ) . These strains are maintained by the U. S.

Regional Soybean Laboratory, Urbana, Illinois, and are available to research workers upon request.



N



SOYBEAN GENETICS AND BREEDING



163



much of the qualitative genetic work with soybeans. The genetic basis

for most of the common pigment variants is now well established after

considerable divergence of opinion among earlier investigators. However, many less common pigment types still await genetic investigation,

and the genetic interactions of many of the genes presented in Table I

have not been studied.

1. Flower Color

The flower color of most soybean varieties is either white or purple.

Takahashi and Fukuyama (1919) and Woodworth (1923) established

that this difference is due to a single gene pair with purple ( W 1) dominant to white ( w l ) .A pleiotropic effect of this gene pair on seed color

is described in Section 111, A, 4. In addition the anthocyanin pigment

conditioned by the W 1allele appears in other parts of the plant, notably

in the hypocotyl, frequently in the pulvinules, and during ripening in

the pod wall, petiole, and stem where exposed to strong sunlight. The

degree of this expression varies considerably, but the purple pigment is

always absent in plants of the w1 (white flower) genotype.

Small variations in intensity and in shade of purple are frequently

observed among varieties, and two reports concerning the genetic basis

of these variations have been published. Takahashi and Fukuyama

(1919) reported a ratio of 9 purple to 3 purplish blue to 4 white.

Matsuura (1933) assigned the symbols W zw2 to this effect. Nagai (1926)

similarly reported ratios of 9 purple to 3 purplish red to 4 white. It is

not possible at present to relate these shades of purple to those of any

known soybean varieties and the more recent genetic studies of flower

color have not included such distinctions.

Bicolored flowers occur in a few varieties, such as LAREDO and TANNER. In these flowers the purple color is restricted to an area near the

base of the standard and the remainder of the corolla is white. Hartwig

and Hinson (1962) reported that inheritance of this dilute purple type

involves two loci (W3 w3 and W4 w4) which influence the intensity of

purple. Apparently w3 W4 is the most prevalent genotype, and it produces the typical purple flower color. With 1473 W4 the flowers are dark

purple; with W 3 w4 the flowers are dilute purple; and with w3 w4 the

flowers are white or nearly white. With w1 the flowers are always white,

and the effects of W 3w3and 147, w4 are observable only in W1 genotypes.

Since there is no known source of W2 wz, its relationship to the other

modifying genes could not be tested.



2. Pubescence Color

Pubescence is abundant on the leaf, stem, and pods of most varieties,

and its color gives a distinctive appearance to the plant. Except for



lf34



HERBERT W. JOHNSON AND RICHARD L. BERNARD



occasional intermediate types, the pubescence of soybean varieties

appears either tawny, due to the presence of a brown pigment in most

of the hairs, or gray, due to the absence of the brown pigment from most

of the hairs. The brown pigment is not present in the seedling but usually

becomes apparent by the time the plant has produced several trifoliolate

leaves. Varieties of both color types are commonly grown in the United

States.

The difference in pubescence odor was found by Woodworth (1921)

to be due to a single gene pair with tawny pubescence ( T ) dominant

to gray ( t ) .The important effect of this gene pair on seed color is discussed in Section 111, A, 4.

A few varieties, such as GRANT, carry the T allele but have an intermediate or light tawny pubescence color, and others, such as KINGWA,

have T with a completely gray pubescence color. These types when used

in crosses have given rise to anomalous ratios and difficulties in classification. Probst (1950) reviewed the previous reports of unusual segregation for pubescence color and presented additional data indicating

that pubescence color is conditioned by several gene pairs. Apparently

genes at other loci modify or suppress the effect of T on pubescence

color, but no generally acceptable genetic hypothesis for this has been

published.

3. Pod Color

Three main pod colors are found in soybeans (Nagai, 1926; Williams, 1950), black, brown, and light straw-yellow. The color of the

pubescence on the pod influences its general appearance but the actual

pod wall color is not greatly affected. Takahashi and Fukuyama (1919),

apparently working with brown versus light pod color, reported that

segregation could be explained by a single gene pair with the darker

color dominant. F’1700dworth (1923) reported dark pods dominant to

light and assigned the symbols L 1. Apparently Woodworth‘s “dark

brown” pod was the type here designated black.

Most commercial varieties in the United States have the brown pod

color but quite a few, such as ADAMS, WABASH, DORMAN, and LEE, have

light pods. None of the varieties presently grown is black podded.

4. Seed Color



Soybeans eshihit a great variety of colors and patterns in the seed.

Common seed colors are yellow, green (presumably chlorophyll), black

(intense anthocyanin), and several shades of brown. Various patterns

of black .or brown may occur on yellow or green seed coats.

The differences among most varieties in the black and brown colors



SOYBEAN GENETICS AND BREEDING



165



are explainable in terms of two loci, T t and R T , with modification of

certain gene combinations by 0 o and W1 w1. The differences in the pattern or degree of development of these pigments are controlled by the

allelic series 1, ii, ik,i, with dominance in the order listed. The seed colors

produced by combinations of these genes are presented in Table 11,

based on the results published by Nagai (192l), Woodworth (1921),

Nagai and Saito (1923), Owen (1928a), Stewart (1930), Will'lams

( 1952), and Mahmud and Probst ( 1953).

TABLE I1

The Genetic Basis of the Dark-Colored Pigments in Soybean Seeds

Genotype



TR

TrO

Tro

tRW,

tRw,

tr



I



i



Phenotype



Seed color

Black (with brown pubescence)

Brown (with brown pubescence)

Reddish brown (with brown pubescence)

Imperfect black (with gray pubescence and purple flowers)

Buff (with gray pubescence and white flowers)

Buff (with gray pubescence)

Seed color pattern

Light hilum-dark pigment reduced in intensity, to a gray hilum

(with black genotypes) or completely absent (with

brown or buff genotypes)

Dark hilum-dark color present in hilum only

S a d d l d a r k color present in a saddle-shaped pattern extending from

the hilum over about half of the seed coat

Self-dark color present over entire seed coat



With genotypes I or ii the seed coat still may develop considerable

black or brown pigment. This is called mottling and usually appears in

irregular patterns varying greatly from seed to seed. The color of the

mottling is determined by the same genes that control seed color as

given in the top half of Table 11. Mottling was studied by Woodworth

and Cole (1924) and Owen (1927c), and its development was found

to be much greater under certain environments and to be more common with certain varieties, but the specific environmental and genetic

factors were not ascertained.

Three other genes which affect the black and brown pigment in

seeds have been reported. The gene k (Nagai and Saito, 1923; Takagi,

1929) produces a saddle pattern similar to that of ik.The gene M (Nagai

and Saito, 1923) produces black bands on a brown seed coat. The gene

FZ (Morse and Cartter, 1937) produces brown flecks on a black seed

coat.



166



HERBERT W. JOHSSOS A N I RICHARD L. BERNARD



In all commercial varieties in the United States, except a few blackor brown-seeded hay varieties, the dark pigment is restricted to the

hilum or completely absent, and these varieties have been selected for

low tendency to mottle. Almost all hilum colors listed in Table I1 are

represented in commercial soybean varieties in the United States.

-Among the more common varieties, CHIPPEWA, CLARK, SHELBY, FORD, and

LEE have black hilums ( 2 T R ) ; HILL has a brown hilum (i' T T ) ; OGDEN

and HAWKEYE have imperfect black hilums (ii t R Wl); and ADAMS and

BLACKHAWK have buff hilums of the ii t R w1 genotype while L L N D A ~ ,

also with a buff hilum, is of the i* t T genotype, Among the light-colored

hilum types RICHLASD with a gray hilum is 1 t R WI, EARLYANA with a

V ~ O W

hilum is 1 T I, and XQXMRIX and HAROSOY with yellow hilums

are 1 t 1'.

\Yhen the black and bron-n pigments do not occur in part or all of

the seed coat, its color will be either light yellow or light green depending on the gene pair G g. Terao (1918) first showed that green seed

coat ( G ) was dominant to yellow ( g ) and was monogenic. Most grain

varieties are yellow-seeded, but a few such as OCDEN carry G and have

a light green seed coat. This latter type is considered undesirable for

certain commercial uses of the soybean.

The cowledons of the soybean are green before maturity but turn

yellow in most varieties as the plants mature. However, the cotyledons

of a fen. strains remain green in the ripe seed. The seed coat also remains

green, and the leaves, stems, and pods do not turn yellow on ripening

as the\. do in most soybean varieties. The work of Terao (1918), Woodworth. (1921), and Owen (1997a) showed that two types of green

cotyledons occur, one due to the complementary action of two recessive genes ( d l d 2 ) and one controlled by cytoplasmic factors. The green

cotyledons give some soybean products an undesirable appearance, and

soybeans of this type are not grown as grain varieties in the United

States.



B. PLANTCHARACTERS

1. Pubescence Type

Considerable variation exists among soybeans in the amount, size,

orientation, and distribution of the pubescence, and several types are

distinct enough to permit genetic analysis.

Most varieties in the United States have erect pubescence; but a few

varieties grown in southern United States such as CNS (Grabe, 1957)

and a large number of Asian varieties, especially those from Japan,

have appressed pubescence. In this type the hairs lie nearly flat against

the leaf blade surface except for a few erect ones over the major veins.



SOYBEAN GENETICS AND BREEDING



167



On the rest of the plant the hairs are only slightly less erect than normal.

Appressed pubescence has been reported to be due to a single dominant

gene ( A ) by Karasawa (1936), working with an appressed strain of wild

soybeans, and by Ting (1946), working with an appressed variety of

cultivated soybeans.

A number of varieties grown in Japan are glabrous. Nagai and Saito

(1923), working with an apparent mutation to this type, reported that

inheritance was controlled by a single gene pair (PI pl) with glabrousness dominant. This type of inheritance was also found by Stewart and

Wentz (1926) working with a glabrous Japanese variety. In addition,

Stewart and Wentz reported a recessive mutant ( p z ) which produced

glabrous plants. However, this type might better be described as puberulent or minutely pubescent as it has many short, stubby hairs. The glabrous type has been reported as resistant to a pod borer (Laspeyresia

glycinivorella) (Williams, 1950). Glabrous varieties have never been

grown commercially in this country, and they are very susceptible to

attack by the potato leafhopper (Empoasca fabae).

In another distinctive type, the pubescence is flat and curled and is

deciduous at maturity. Williams (1950) stated that inheritance of this

type (referred to as “appressed) was monogenic, the heterozygote

being intermediate in appearance. This type occurs in a number of

varieties from Japan and Korea. In parts of the United States such varieties suffer severely from feeding by the potato leafhopper.

Ting (1946) found that the inheritance of the shape of the pubescence tip was monogenic with sharp (BZ)dominant to blunt ( b l ) .Grabe

(1957) reported that most United States varieties have a blunt pubescence tip but that a few, such as KINGWA, LAREDO, and MIDWEST, have a

sharp tip.

2. Leaf Shape

A few varieties from Japan have a high proportion of leaves with five

leaflets. The extra leaflets occur at the base of the lateral leaflets. Takahashi and Fukuyama (1919) reported that the fiveleaflet condition is

determined by a single dominant gene (X).

A number of varieties from Asia have a much narrower and longer

leaflet than normal. In crosses, Takahashi and Fukuyama (1919) found

Fz ratios of 1 broad leaflet to 2 intermediate to 1 narrow leaflet, and

Woodworth (1932, 1933) assigned the gene symbols N a nu. A high number of seeds per pod seems to be associated with the narrow leaflet trait,

and frequently many four-seeded pods occur on narrow-leafleted plants.

Takahashi (1934) assumed that the leaf effect and the pod effect were

due to different genes and presented evidence of their close linkage.



168



HERBERT W. JOHNSON AND RICHARD L. BERNARD



However, he did not attempt to prove the existence of two gene pairs,

and high number of seeds per pod and narrow leaflet probably are

pleiotropic effects of the same gene.

A unique type with oval leaflets has been found. The trait was

reported to be a monogenic recessive by Domingo (1945) and the

gene was designated o (not the same as the o controlling reddish

brown seed coat color). Here also the leaf shape character was associated

with the number of seeds per pod, this time with a low number of

seeds per pod. Domingo presented evidence of close linkage between

the leaf and pod traits but did not consider whether the traits were due

to the same gene. Therefore, these leaf and pod effects should be conconsidered to be due to the pleiotropic action of one gene pair unless

future evidence should prove the existence of two separable gene pairs.



3. Stem Type and n4aturity

Varieties which have a determinate, or abruptly terminating, mainstem are common in southern United States ( HILL, HOOD, LEE, and OGDEN,

for example) and in Japan, whereas varieties from Manchuria and

northern United States usually have an indeterminate, or tapering, mainstem. \Voodworth (1932, 1933) reported that this difference in a cross

between the determinate variety PEKING and the indeterminate variety

ILLINI was controlled by a single gene pair, Dt dt, with the indeterminate

type dominant.

Another trait appearing in many varieties grown in southem United

States is that of having a long inflorescence stalk or peduncle, whereas pods

of most northern varieties are sessile or nearly so. Van Schaik and Probst

(1958a) reported that this trait is controlled by a major gene, Se, dominant to subsessile, se. They also concluded that peduncle length was

much affected by modifying genes and by environment.

Nagai (1926) reported that a difference in branching type, long,

spreading branches versus short, erect branches, was due to a single

gene difference with long branches dominant. Matsuura ( 1933) assigned

the gene symbols, S p sp, to this.

An abnormal type of soybean with fasciated stems is occasionally

grown in Japan. Nagai (1936) and Takagi (1929) reported that fasciation is due to a single recessive gene, which was later designated f by

T!’oodworth ( 1932, 1933).

Woodworth (1923) found a population segregating for two fairly

distinct types. A tall, luxuriant, and late-maturing type was reported

to be conditioned by a dominant gene ( S ) and a short, compact, and

early type by the recessive allele ( 8 ) .

Owen (192%) found that maturity tended to be linked with pubes-



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