DURATION AND RATE OF GRAIN FILLING IN SELECTED WINTER-WHEAT POPULATIONS .1. INHERITANCE

Grain yield of wheat (Triticum aestivum L.) is determined in part by kernel weight, which is a function of the rate and duration of grain fill (GF). The lack of information regarding the inheritance of GF rate and duration prompted this study to determine the relative magnitude of genetic components and combining ability estimates for the GF parameters. Parents and F-1 generations resulting from a 4 x 4 diallel mating scheme were grown in space-planted experiments in 1987 and 1988. The plots were sampled at 2- to 3-d intervals after anthesis to obtain GF data. Significant genotypic variation for GF rate, duration, and kernel weight was observed in both seasons. Genotype x year interaction was not significant for any of the GF traits. General combining ability (GCA) effects for GF rate, duration, and kernel weight were larger than specific combining ability (SCA) effects, with 2GCA/(2GCA + SCA) values of 0.981, 0.978, and 0.958, respectively. Both combining ability analyses and estimates of the genetic components from the diallel indicated that a primary part of genetic variability for the GF traits was associated with additive gene action. However, dominance effects also appeared to be involved in the inheritance of GF duration and kernel weight. Narrow-sense heritability estimates ranged from 0.79 for kernel weight to 0.89 for GF rate. Results suggested that early-generation selection for both duration and rate of GF and kernel weight should be effective in changing these characters within the material studied.