Effective population size, genetic variability, and gains from recurrent selection in the BS11 maize population

Abstract

Establishing an adequate effective population size is important in maize (Zea mays L) recurrent selection programs. The objectives of the study were to detemriine the magnitude of additive genetic variance after 5 cycles of selection among four Srprogeny selection programs with effective population sizes of 5,10,20, and 30 but with a common selection intensity of 20%, to predict the gains of S2, Si, full-sib, and modified-ear-to-row recurrent selection methods with varying effective population sizes, and to compare the predicted gains with the realized gains obtained in a related study. Using the BS11 cycle 0 (CO), 5 cycles of Si-progeny selection were conducted by intermating 5,10,20, or 30 lines to form a population for the next cycle of selection. The cycle 5 populations of the 5,10,20, and 30 Si-programs were referred to as C5-5, C5-10, C5-20, and C5-30, respectively. One hundred-thirty BS11 C5 Si lines from each of the selected populations and 100 BS11C0 Si lines were topcrossed to BS11 CO. The half-sib progenies were evaluated at five environments in a replication within sets randomized incomplete block design. Using the variance estimates of the BS11C0, the predicted gain cyde' was calculated based on trait perse selection and selection using an index Results showed that the additive genetic variance for grain yield ranked C5-5 > C5-20 > CO > C5-30 > C5-10 but differences among populations were not significant. Results of the predictions indicated that the trend was similar for the trait perse selection and index selection. Although the predicted gain cycle' for a trait in a recurrent selection method increased with increasing effective population size, differences among the predicted values were agronomically insignificant. The comparison between the predicted gains and the realized gains obtained in a related study revealed that intemnating greater number of individuals would not result in a significant response over a few cycles of selection. Based on the results of the study, 1 conclude that there is no distinct advantage of using larger effective population size to maintain genetic variability and to realize gain in a short-term maize recun^nt selection program.