IMPROVING THE SAMPLING AND IDENTIFICATION OF FOUNDATION PLANTS FOR INBRED LINE DEVELOPMENT BY INTEGRATING SELFING WITH HALF-SIB FAMILY EVALUATION

Inbreeding is carried out to develop inbred lines in maize (Zea mays L.) and other cross-pollinated crops. The sampling of foundation plants in a source population for inbreeding is critical, as the genetic worth of the lines that can be developed, is determined by the genes present in the foundation plants. It is, therefore, desirable that the size of foundation sample is increased and the foundation plants with better genotypic value are identified early. In the proposed approach, the foundation plants in a source population are phenotypically selected, and sampled as half sibs (HSs) rather than selfs (S1s), HS families are evaluated and selfed to develop S1 lines, and S1 lines or bulks are evaluated and selfed. The advantages are: (i) the sampling of foundation plants as HSs rather than S1s nearly quadruples the effective population size, (ii) HS family evaluation facilitates better identification of the genetic worth of foundation plants than S1 line evaluation since the differences among HS families are due to solely additive genetic variation whereas those among S1 lines are due to both additive and dominance variations, and (iii) the comparison of the performance of HS families and their S1 lines provides information on the tolerance to inbreeding. The approach should promote the derivation of inbred lines with upgraded genetic worth.