Difference in flower production and pod set performance among soybean cultivars with different stem-termination types and maturity groups

To elucidate the difference in flowering and pod set between soybean cultivars, five determinate type and three indeterminate type cultivars with different maturities were grown under vinyl-house conditions during the year 1998. The later the maturity of the cultivar, the larger the number of nodes and length of main stem. The numbers were also higher for indeterminate cultivars than determinate cultivars. The seed yield range was 128-294 g among cultivars, and was higher in the late maturing cultivars than in the early maturing cultivars. The number of flowers per day was maximum during 5-10 days after the onset of flowering. Afterward, it decreased over time in the indeterminate type, whereas it peaked again 20-30 days after the onset of flowering in the determinate type. The later the maturity of the cultivars, the larger the number of flowering organs, and the higher the percent contribution of flowers on the basal order racemes than that on the secondary and higher order racemes. The percent pod set ranged 23-42% among cultivars and was lower in the late maturing cultivars. Clearly, the later the maturity of the cultivar, the larger the number of flowers, pods and yield in spite of the decrease in percent pod set. Indeterminate cultivars showed a larger number of nodes and percent contribution of the primary racemes on the number of flowers than that of the secondary and higher order racemes. In determinate cultivars, the later the maturity of the cultivar, the larger the number of flowers, which results in a decrease in percent pod set, so seed yield depends on the number of pods on the higher order racemes.