The selection of parents for synthetic varieties of outbreeding diploid crops.

As a criterion for the selection from a population of individuals with a high potential as parents of synthetic varieties, the general varietal ability of an individual is defined as the mean expression of all possible synthetics of a given size(s) having this plant as a common parent. Using known expressions for the prediction of the performance of advanced generations of diploid synthetic varieties, general varietal ability is expressed in terms of the F 1 and I 1 progenies of the plants under test, and is found to be a simple function of the polycross (g.c.a.) and inbred progeny means, where the contribution of the inbred progeny varies according to n and s. The implications and use of such a progeny test in the breeding of out-pollinating crops is discussed.