Genetic Changes Associated with Different Methods of Recurrent Selection in Five Maize Populations: I. Directly Selected Traits

Abstract

Several methods of recurrent selection have been developed in maize (Zea mays L.), but information is lacking on which is most effective. A confounding factor is that progress may be hindered by inbreeding depression associated with random changes of allelic frequencies due to the constraints of small effective population sizes. The objectives of this study were to (i) compare the effectiveness of four selection methods in five maize populations (CGSynA, CGSynB, CGG, CGN, and CGW) improved for performance indices involving grain yield, grain moisture, and plant lodging, (ii) separate effects of selection from those due to random drift, and (iii) estimate additive and dominance gene effects contributing to response to selection. Four selection procedures were compared: modified ear‐to‐row (ME) in CGSynA, CGSynB, CGG, and CGN; half‐sib family (I‐IS) in all five populations; seffed progeny (S) in all five populations; and reciprocal recurrent selection (RRS) in CGSynA and CGW. In general, performance indices increased with concomitant increases in yield and decreases in moisture and lodging. Generally, S was the most effective selection procedure and HS was second best. Response to selection was attributed to changing the frequencies of alleles with mostly (i) dominance effects. in ME selection, (ii) additive effects in S and, (iii) either dominance or additive effects in HS and RRS. Estimates of genetic drift effects were predominantly of the opposite sign from the direction of response to selection. The S procedure resulted in the greatest genetic drift in three of the five populations, whereas HS suffered minimal genetic drift effects. This study indicated that there is no selection method that is best under all circumstances.