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 wor th of the lines that can be developed, is determined by the genes pres ent in the foundation plants. It is, therefore, desirable that the siz e of foundation sample is increased and the foundation plants with bet ter genotypic value are identified early. In the proposed approach, th e 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 ar e evaluated and selfed. The advantages are: (i) the sampling of founda tion plants as HSs rather than S1s nearly quadruples the effective pop ulation size, (ii) HS family evaluation facilitates better identificat ion of the genetic worth of foundation plants than S1 line evaluation since the differences among HS families are due to solely additive gen etic variation whereas those among S1 lines are due to both additive a nd dominance variations, and (iii) the comparison of the performance o f HS families and their S1 lines provides information on the tolerance to inbreeding. The approach should promote the derivation of inbred l ines with upgraded genetic worth.