Genetic and Maternal Variances and Covariances of Kernel Growth Traits in Winter Wheat

Abstract

Early maturity is an essential characteristic of soft red winter (SRW) wheat (Triticum aestivum L. emend. Thell.) cultivars that are grown in a double‐crop system. Historically, breeders have used heading or flowering date as an indicator of maturity. We were interested in assaying variation for postanthesis traits that may affect maturity in a defined reference population of SRW wheat. Forty‐four F5 lines from a single‐cross population, and the 22 reciprocal F1, F2, and F3 kernel generations, were evaluated in several field experiments from 1987 to 1989. Anthesis date, kernel weight at 20 days after anthesis (DAA), kernel growth rate (KGR), final kernel weight, and effective filling period (EFP) were measured. Direct additive and maternal additive components of variance and heritability were estimated. We observed significant variation among the F5 lines for kernel weight at 20 DAA and for KGR, but not for EFP. Significant (P ≤ 0.05) maternal effects for kernel weight at 20 DAA and for KGR were observed in the F1 and F2 generations but were absent in the F3. Heritabilities ranged from 0.16 for EFP to 0.80 for anthesis date in the parental lines. We observed a significant genetic correlation (rG = 0.99, P < 0.01) between kernel weight at 20 DAA and KGR, which leads us to conclude that kernel weight at 20 DAA may be used as an indirect selection criterion for kernel growth rate in developing early‐maturing genotypes.