Genotypic Variation for Duration of Seedfill in Soybean1

Abstract

The length of the seed filling period is related to yield in soybean [Glycine max (L.) Merr.] and may be useful as a selection criterion in cultivar development programs. Genotypes from the World Soybean Germplasm Collection were grown in the field at Lexington, Ky. to estimate the genotypic variation in seed filling period that is available and to compare methods of estimating the seed filling period. Nine (1980), 14 (1981), and 59 (1982) genotypes were grown in four‐row plots 6 m long with 0.76 m between rows with two replications using conventional cultural practices. The length of the seed filling period was estimated from whole plant growth stages (R4 to R7 and R5 to R7) and from the effective filling period (EFP) determined from individual seed measurements. Significant genotype differences were found each year for all estimates of the filling period; however, genotypes with filling periods significantly longer than the longest filling period of a check cultivar were identified only in 1982. There was a significant genotype ✕ year interaction for 13 genotypes in the test for 2 years. The interaction seemed to result from the differential effects of moisture stress on the seed filling periods of the unadapted genotypes. There was a consistent relationship between the growth stage estimates of seed filling period and EFP over all genotypes and across 2 years; however, late maturing check cultivars (MG IV and V) showed longer filling periods, based on growth stage estimates, than MG III check cultivars; but there were no significant differences in EFP. The genotypes with long filling periods could be useful in developing higher yielding soybean cultivars, even though significant genotype ✕ year interactions frequently occur.