Genetic Variability for Yield after Four Cycles of Reciprocal Recurrent Selections in Maize1

Abstract

The primary objective of my study was to determine the relative change in genetic variation after four cycles of reciprocal recurrent selection for yield in maize (Zea mays L.). Estimates of additive genetic variance (σ2A) and variance due to dominance deviations (σ2D) were obtained for the original (C0) Stiff Stalk Synthetic and Corn Borer Synthetic #1 populations; for the syn. 3 generation of the reconstituted populations (C4) after four cycles of reciprocal recurrent selection for yield; and for the syn. 3 generation of the hybrid populations formed by crossing the original synthetic varieties (CO ✕ CO) and the CA reconstituted populations (C4 ✕ C4). cross‐classification mating design (Design II) was imposed on each population to form half‐sib and full.sib progenies. Twenty sets were produced, each containing 16 full‐sib progenies formed from crossing four randomly selected S0 males and Sl females, for each population, and grown at three locations.There was no difference in the estimates of σ2A for the CO and C4 Corn Borer Synthetic No. 1 populations. The estimates for Stiff Stalk Synthetic showed a decrease from the CO to the C4 , which approached the 10% probability level. There was a significant reduction in the estimates of σ2A from the CO ✕ CO to the C4 ✕ C4 hybrid populations. All the estimates of σ2A exceeded twice their standard errors. None of the changes in the estimates of σ2DD was significant between the populationsFour cycles of reciprocal recurrent selection showed an increase in yield of the Stiff Stalk Synthetic and hybrid populations and a decrease in Corn Borer Synthetic No. I populations. It appeared that only modest gains have been made for yield with a reduction in genetic variation.