Response to S1 recurrent selection and estimation of genetic parameters in effective population sizes of the BS11 maize population

Abstract

Recurrent selection progress is influenced by population size, selection intensity, favorable alleles, and their frequencies. It is necessary to establish optimum number of progenies in maize for population synthesis in recurrent selection programs. Often this has been constrained by limited resources. We studied effective population sizes in maize to estimate response to selection and effect of inbreeding depression, and examine changes in the correlated traits. Four effective population sizes designated 5-Si, 10-Si, 20-Si, and 30-Si programs were developed from the BS11 maize using S rprogeny selection with a common 20% selection intensity. After five cycles of selection the populations per se, populations per se selfed, populations top-crossed to B97 and B73, diallel crosses among CO, C3, and C5 of the populations, Cl x CO crosses and five checks were tested. There was significant and positive response for grain yield in 30-Si, 20-Si. and 10-Si. The highest direct response was 0.21 Mg ha1 in 30-Si, which was double that in 20-Si and 10-S|. Significant unfavorable yield response was obtained from 5-Si due to genetic drift and inbreeding. All agronomic 1 Dept. of Agronomy, Iowa State Univ., Ames, IA 50011. 2 Part of dissertation submitted by the author in partial fulfillment of the requirements for the Ph.D. degree. 3 USDA-ARS, Dept. of Agronomy, Iowa State Univ., Ames, LA, 50011. 4 Corresponding author (krlamkev@iastate.edu).