Selection for yield in early generations of self-fertilizing crops

Summary

If a breeder is to apply selection to a cross-population of a self-fertilizing crop and wishes to maximize his chances of finding a productive genotype, he will have to introduce yield tests in the F₃ lines. Should he not do so because of his intention to work on many populations simultaneously, his tests would be considerably less accurate and the finding of a favourable combination more or less a matter of mere chance.

Bulk breeding will result in genetic drift or numbers of plants too large to manage, or in a combination of both.

Application of the Single Seed Descent for quantitative characteristics causes such a genetic drift, that the method is not to be recommended.

Multiple crosses (double-crosses) to improve quantitative characteristics require populations of a size, that cannot be realized and/or selected. This type of crosses is more suited for cases in which qualitative characteristics form the breeding goals and when it is impossible to obtain the favourable combination using only two varieties.

Genic recessive male sterility may be a means to raise large progenies. In the F₃ it confuses the issue of yield of fruits or seeds, which is highly vulnerable in any case. In the F₂ its significance for finding the proper recombinant is very low.