Practical merit of delayed selection after single and recurrent mutagenic treatments—II. Optimum generation for selection

Criteria for predicting optimum selection procedure in mutation breeding of self-pollinating crops were discussed and formulated. Based on the mathematical formulae and some numerical computations, the efficiency of delayed selections was examined and the following derived as a general conclusion.

Delayed selection in M₃~M₅ generations is of great practical merit when plants mutated at multiple loci are to be obtained. This method is considered promising even for the detection of single-locus mutants when difficulty in discrimination of the objective mutants is large, and/or when permissible population size per generation is small, probably below 10,000, as a rough estimate. It is, in general, thought that fifteen or more M₂ plants should be derived per M₁ spike or panicle. Small progeny size per M₁ spike such as one, two or three as proposed by Yoshida et al. seems of limited utility.