Soybean Germplasm Evaluation for Length of the Seed Filling Period 1

Abstract

Increasing the length of the seed filling period has been suggested as a means of increasing yield in several crop species. The objectives of our study were to measure the seed filling period of soybean [Glycine max (L.) Merr.] plant introductions of Maturity Groups III to V, and to determine whether available data on beginning bloom and maturity of soybean plant introductions could be used to identify potentially useful strains for extending the seed filling period. Strains from the soybean germplasm collection of Maturity Groups III to V were planted in the field in 1978 and 1979. Strains varied for reproductive period (days from beginning bloom to no normal green pods), seed filling period (days from beginning seed fill to physiological maturity) and filling period estimate (days from beginning seed fill to maturity). The range of the seed filling period among strains was 18 to 54 days with a mean of 40 days. Strains were found that had longer seed filling periods than most current cultivars. Strains with longer seed filling periods maintained seed growth at the end of seed filling for a longer time than strains with a shorter seed filling period. The reproductive period, seed filling period, and filling period estimate were highly correlated across years, which indicated genetic control of the characters. The characters were highly correlated with each other which indicated that any of the three methods could be used to evaluate the length of the seed filling period. We suggest that soybean strains from the germplasm collection could initially be selected for length of the seed filling period by using available data for the time between flowering and 95% mature pods. Selected strains could be more precisely evaluated by measuring the seed filling period as conducted in this study.