Soybean Flower Abortion: Genetics and Impact of Selection on Seed Yield

Although soybean [Glycine max (L.) Merr.] plants shed many flowers prior to pod development, the effect of this loss on realized seed yield has not been measured. Objectives of this work were to: (i) measure genotypic variation in raceme flower abortion (FA) and related traits, (ii) determine heritability of these traits, and (iii) study the impact of selection for differing levels of FA on seed yield. Field studies were conducted from 1982 through 1986 with 10 soybean genotypes differing in raceme length, number of flowers per raceme (FPR), and level of raceme FA, and with progeny from 13 crosses among them. The FA ranged from a low of 27% for ‘Amsoy’ to a high of 78% for ‘Chusei.’ Yearly variation in FA was detected only for two genotypes, but four genotypes showed annual variation in flowers raceme⁻¹. Exceptions to the normal association of high FA with high number of flowers raceme⁻¹ and distal flower positions on the raceme were observed in these genotypes and their progeny. Mean heritability estimate measured in F₂ for 13 crosses was 47% for FA compared to 64% for FPR. Two populations were developed from the cross IX93-100 ✕ Amsoy by selecting families on the basis of level of FA for all flowers on two racemes per plant in the F₃ generation. When seed yield of the F₃ derived lines in the F₆ generation was measured, the yield of the higher yielding parent (Amsoy) was exceeded by 66% of the families selected for low FA. Of the population selected for high FA, 35% exceeded the yield of Amsoy and 17% yielded significantly less. Plant growth traits like maturation date, pod type, weight seed⁻¹, and FPR were also altered by this procedure. Selection on the basis of the fate of flowers higher than the fourth position on the raceme in long raceme segregates is suggested as a procedural improvement for future research. Cooperative investigations of the South Dakota Agric. Exp. Stn. and USDA-ARS, Brookings, SD 57007. Journal Series no. 2422. This paper reports results of research only. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products or vendors that may also be suitable.