Hayes and Garber - Cucurbit Breeding

260 BREEDING CROP PLANTS
recommended for self-fertilized crops or more specifically
for crops which yield ample seed on selfing. When such a plan
is adopted for naturally cross-fertilized crops it becomes necessary
to insure selfing by artificial means. By reducing ordinary varieties
to pure lines, a much more exhaustive study of the material at hand
may be made, and on the basis of this study desirable combinations
affected by hybridization or pure lines of commerical value
may be isolated. The method which is adopted after the isolation
of homozygous lines through self-fertilization will depend
on the degree in which vigor is lost as a result of selfing. That
homozygous lines may be isolated in squashes is a demonstrated
fact, the result of three years' study as carried on by John Bushnell,
of the Minnesota Station. Some lines which are comparatively
uniform appear vigorous while others are less vigorous. Types
for markedly different characters which are relatively uniform
have been isolated.