Genetic and Physiological Studies of the Rate and Duration of Seed Fill in Soybeans

91 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.Soybean cultivars which had significant genetic differences in the duration of the seed filling period were identified by screening the soybean germplasm collection. Correlations between various measures of the seed filling period, flowering, maturity, seed growth rate, seed dry weight, seed number per unit land area and yield were made. Yield was significantly and positively correlated with long durations of seed filling and seed number. Long durations of seed filling were positively and significantly correlated with large seed and late maturity. The effect of maturity (E) and stem termination (Dt) alleles on the duration of seed filling was evaluated using near isogeneic lines, but the alleles evaluated did not significantly contribute to genetic differences for the rate or duration of individual seed filling. However, stem termination alleles greatly affected the number of days between reproductive growth stages R5 and R7.Crosses were made between parents which differed in the duration of seed filling, maturity, stem termination, seed size, seed growth rate and yield. The F$\sb{2}$ and parental populations were evaluated for the duration of seed filling, seed growth rate and seed size. In general, genetic variation for the duration of the seed filling periods and the seed growth rate was low in the F$\sb{2}$ population. Parental differences in the rate and duration of seed fill were the most important characteristics which influenced variance for these traits in the F$\sb{2}$ populations.Seasonal net leaf CO$\sb{2}$ exchange rate (CER) and N assimilation was evaluated in 2 cultivars with long and 2 with short durations of seed filling. Cultivars with long durations of seed filling maintained measurable CER rates for a longer time after flowering. The N status of the plant did not appear to control genotypic differences in the duration of the seed filling period in these cultivars.U of I OnlyRestricted to the U of I community indefinitely during batch ingest of legacy ETD