Evaluation of genetic variability using full-sib families within and between the BS10 and BS11 synthetic maize (Zea mays L.) populations for the original and tenth cycle of selection
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Genetic variances may change when selection is applied to a population. Populations should be monitored for genetic variance changes that may affect future selection progress. The BS10 and BS11 maize (Zea mays L.) populations have undergone 13 cycles of reciprocal full-sib recurrent selection. The objectives of this study, therefore, were to determine the genetic variation among full-sib families, evaluate the frequency distributions, and report correlations among all traits for the original (C0) and tenth (C10) cycles of selection for the populations per se and the population cross. One hundred full-sib families for each population were evaluated in four environments using a replications-within-sets incomplete block design. Data were collected for machine-harvestable grain yield (Mg ha-1) adjusted to 155 g kg-1 grain moisture, percent root and stalk lodging, percent dropped ears, plant and ear height scores (a relative scale of one to five, where one is low and five is high), anthesis date (number of days from planting to 50% of the plants with at least 50% anther extrusion), and silking date (number of days from planting to 50% of the plants with emerged silks). All traits were measured in four environments, except anthesis and silking date which were recorded only in two environments. Mean squares were equated with expected values and genetic variances were estimated. Grain yield genetic variances indicated a decrease, although not significant, for the BS10 population. The interpopulation grain yield genetic variance increased, but not significantly. Genetic variances for most other agronomic traits were decreased when comparing the C0 with C10 inter- and intrapopulations. Changes in genetic variance were accompanied by complementary changes in genotype by environment interaction variance. Frequency distributions indicated the inter- and intrapopulation means for all traits have moved in a desirable direction after 10 cycles of reciprocal full-sib recurrent selection. The genetic and phenotypic correlations did not reveal any trends. Although, the interpopulation genetic variance has decreased for most agronomic traits, except grain yield, agronomic progress should continue in the BS10 and BS11 reciprocal full-sib recurrent selection program.