Hayes and Garber - Cucurbit Breeding

222 BREEDING CROP PLANTS
P. Segregating
ratios were in accordance with the above factorial
hypotheses. Wilson (1916) obtained only white tubers
from selfed white-tubered varieties. Similar results have been
obtained by other plant breeders which show that white is a
recessive character. A certain amount of coloring in the young
sprouts or shoots, stems, and sometimes in the leaf petioles was
found associated with the presence of color in the tubers. With
regard to flower color, three white-flowered varieties, selfed,
produced only white flowers; and three out of four colored varieties,
when selfed, produced both colored and white forms.
Color
is, therefore, dominant to its absence. Inheritance of this
character may be explained by assuming the presence of a chromogen
body and modifying factors. Heliotrope flowers are due
to the chromogen body plus a reddening factor; purple flowers
are produced by the addition of a purpling factor; white flowers
may be due to the absence of one or more of these factors.
Fruwirth (1912) found red tubers dominant over white, yellow
flesh over white, and lilac-colored flowers over white. It was
also found that different gradations of color were inherited.
Nilsson (1912-13) found a complicated flower color inheritance.
A variety with violet-blue flowers gave, on selfing, progeny with
red, violet-blue, near-red, purple, dark and light blue, and white
flowers. A variety with light blue flowers, on selfing, yielded
progeny showing simple monohybrid segregation with white
recessive. Evidence that several factors were operating in the
inheritance of tuber flesh color was also obtained. Some of the
varieties with yellow flesh (tubers) bred true when selfed, others
segregated as dihybrids with white recessive.
The inheritance of habit of growth was also studied. Plants
may be upright, bushy, or procumbent. Bushy plants are
heterozygous for habit of growth and many of them exhibit a distinct
tendency to become procumbent. Homozygous forms of
upright and sprawling plants may be isolated easily.
maturity is used as a means of varietal classification. It
Period of
is probably
inherited in the same manner as with other crops.
Sterility of the anthers has been found to be a dominant
character. At first Salaman believed that its inheritance was due
to a single differential factor but later evidence indicated a more
complex manner of transmission.
Plants producing pale heliotrope
flowers were found to be heterozygous for pollen sterility.
MacDougal (1917) crossed the wild potato of Arizona, S.