Hayes and Garber - Cucurbit Breeding

242 BREEDING CROP PLANTS
shell beans may be thrashed is of economic importance. In this
group, color, size, and shape of seeds are usually included in
varietal descriptions. Both productivity and disease resistance
may differ strikingly in different varieties of beans.
Inheritance. Seed-coat color has been shown by Shaw and
Norton (1918) to involve several factor differences. The work
was carried on with twenty-one varieties including more than
40,000 plants. Crosses between mottled and self-colored varieties
yielded mottled beans in FI and showed 3 : 1 ratios in F 2 .
Mottled X white varieties gave mottled in FI, and in F% the ratio
of 9 mottled to 3 self-colored to 4 white usually resulted. It was
demonstrated that pigment patterns and pigment colors were
controlled by distinct factors. All plants with white or eyed
beans bore white flowers while plants with mottled or self-colored
beans usually bore pink flowers.
The inheritance of stature in beans, as in peas, is in some crosses
dependent on a single factor difference while in other crosses
several factor differences are involved. Emerson (1916) has
explained the result of crossing a tall pole (indeterminate growth)
bean and a short bush (determinate growth) bean or a short
The
pole bean and a tall bush bean, by a three-factor hypothesis.
following values to be added to an initial value of three internodes
were assigned to the factors : Factor A either homozygous
or heterozygous added 10 internodes approximately, while factors
B and C each added two internodes when homozygous and
one when heterozygous. Results were explained factorially
as follows:
Parent 1 AABBCC = 17 internodes or AAbbcc = 13 internodes
Parent 2 aabbcc = 3 internodes or aaBBCC = 7 internodes
Fi AaBbCc = 15 internodes or AaBbCc = 15 internodes
Many new forms would naturally be produced in F 2 .
Tschermak (1916) has brought together and summarized the
FIG. 60. Flower structure of bean.
1 . Small branch showing a, developing pod ; b, c, flowers in different stages of
development.
2. Front view of fully opened flower a, calyx; b, wing; c, standard; d, keel.
3. Enlarged keel.
4. Keel with outer part broken away to show b, style; c, anther; d, undeveloped
pod; e, ovary.
5. 6. Longitudinal and cross section of pod.
7. Enlarged stigma showing a, stigma hairs.
8. Anther.
Size: 1, n; 2, about 2n; 3 to 8, greatly enlarged.