Hayes and Garber - Cucurbit Breeding

150 BREEDING CROP PLANTS
The Lyon bean has a whitish stiff pubescence on its young shoots,
leaf and calyx. The hairs on the pods form a fine down and
average 0.5 mm. in length. The FI was covered with irritating
hairs. The hairs on the pods were about 1.5 mm. long. These
contain a gummy substance in the hollow points and readily
pierce the human skin, causing an irritation lasting several
minutes. In F 2 about nine-sixteenths of the plants bore stinging
pods (long stiff hairs which pierce the skin). Some were more
developed than in FI. Two factors are necessary for the production
of stinging pods. One of these factors, B, is contained by
the Lyon bean while C is contained by the Velvet bean. Color
of pubescence showed segregation in F 2 , giving 13 whitish to
3 black pubescent plants. The dehiscence of pods behaved as
a dominant. Most of the pods on the FI plants burst open when
mature. In the F z generation segregation occurred. Long
pods crossed with short pods gave approximately a 3:1 ratio in
the second generation although minor factors for pod length were
discovered. In the inheritance of seed color it has been suggested
that three factors are concerned, each of which produces some
mottling even when heterozygous and in the absence of the two
other factors. Purple color appears in the Florida velvet bean
on the under surface of the first pair of simple leaves, on the
stems as a mark on the leaf axil, on the wings and standard and on
the stems and petioles on the side exposed to the sun; while the
Lyon lacks the purple color.
Purple color proved dominant in
F.i and a 3 :1 ratio was obtained in F 2 .
only a single factor being
involved. The characters, time of flowering, size of flower
clusters, and size of plant gave unmistakable evidence of segregation
in the second generation. Each of the crosses Florida
x Lyon, Lyon x Florida, and Florida x Yokohama produced about
50 per cent, pollen sterility in the FI generation. Aborted ovules
were found on plants showing pollen sterility. Belling satisfactorily
explained the results by postulating two factors, K present
in Florida, and L present in Lyon and Yokohama. The
presence of either K or L, but not both, gave rise to normal
pollen and ovules. Combinations of KL or kl in the gametes
resulted in pollen or ovule sterility.
Mutations. Coe (1918) has attributed the origin of early
maturing velvet beans to mutations. C. Chapman and R. W.
Miller, both of Georgia, and H. L. Blount of Alabama, separately
discovered early maturing mutants growing in fields planted to