Plant breeding interpretations of the effects of bulk breeding on four populations of beans (Phaseolus vulgaris L.)

Summary The effect of bulk breeding on yield and its components was studied in two high-yielding and two low-yielding bean crosses until the F₆ generation. It was found that bulk breeding on the whole did not alter the mean values in the high-yielding crosses, but that there was a steady increase in the mean values of the low-yielding crosses with generation. As well as mean values the use of variance as a determinant of cross potential was also studied. It was found for characters markedly influenced in their expression by the environment, of which grain yield is the prime example, that progeny variance did not differ significantly from parental variance. It was concluded that interplant competition was the factor of the environment responsible for this effect.