Hayes and Garber - Cucurbit Breeding

96 BREEDING CROP PLANTS
susceptibility in F 3 ,
while resistant F 2 plants were of two kinds:
(1) those which produced only resistant progeny and (2) those
which segregated, both resistant and susceptible plants being
obtained.
Size Characters. Nilsson-Ehle (1908) made numerous studies
of inheritance of size characters. In a cross between two
saliva varieties which differ in height, transgressive segregation
occurred in F 2 . Forms were selected and the studies continued
FIG. 22. Culms of resistant and susceptible varieties of oats. From left to
right: Victory, susceptible to stem rust; a susceptible F% plant of Victory X
White Russian; a resistant Fz plant of Victory X White Russian; resistant White
Russian.
through F 4 and F b .
Segregation was of a complex nature.
Transgressive segregation also occurred in crosses involving leaf
breadth, kernel size, and number of florets to the spikelet. The
results were explained on the multiple factor hypothesis, but the
actual factors involved could not easily be determined. Maturity
may be considered under this heading, for it behaves in a similar
manner. From crossing early and later maturing oats', Caporn
(1918) obtained intermediate maturity in FI and segregation
in F*. The author suggests that three factors will quite satis-