Inbreeding Effects in Two Subpopulations of a Maize Variety

Abstract

Maize breeding program of Kasetsart University has emphasized its effort in developing corn varieties through population improvement. Recurrent selections such as S1 selection, full-sib and half-sib family selection (5) are often used in increasing favorable genes in the improved population. The breeding procedure involves the extraction of families, progeny testing, and recombining by intermating among the selected families. Expected gain from selection depends partly on number of lines recombined to form a new population (1). More improvement is expected when less number of lines involved in the recombination. However, the population derived from less number of lines may results in inbreeding depression. Sign, et al. (6) studied inbreeding effects resulted from 6 different ievels of inbreeding depression in Jarvis Golden Prolific and Indian Chief varieties. They found that the inbreeding depression increased as the inbreesing levels increased in grain yield, plant height , ear height, days to silk, and number of ears. Other investigators such as Cornelious and Dudley (2) and Stringfield (7) found similar results. Therefore, the proper number of selected families involved in forming the improved variety is of interest among maize breeders in other to anoid inbreeding depression, Information on this is quite limited at present.