Differences in flowering habit between determinate and indeterminate types of soybean

Abstract

The differences of flowering habit, yield and yield components between determinate (cultivar Tatisuzunari) and indeterminate (cultivar Touzan 69) soybean were examined in relation to raceme order. Although flowering habit, i.e., successive flowering from basal to apical nodes was the same in both types, the succession of flowering on low order racemes on the main stem increased more rapidly (1.4 nodes per day) in Tatisuzunari than in Touzan 69 (0.8 nodes per day). In Tatisuzunari flowering on a higher order raceme began after flowering of the first order raceme had finished, but in Touzan 69 flowering on the first order raceme continued upto higher nodes accompanied with flowering on higher order racemes thus producing a higher number of flowers. In Tatisuzunari, the flower shedding rate was higher, the higher was the raceme order, but in Touzan 69 the shedding rate was highest in the first and second order racemes. The pod setting ratio on all racemes was higher in Tatisuzunari than in Touzan 69. In Tatisuzunari, the 100 seed weight was similar on every raceme, although that on the second order racemes with compound leaves was slightly higher. In Touzan 69, it decreased with the increase of raceme order. The second order raceme with compound leaves played a pivotal role for the determination of total number of nodes, number of flowers, pod setting ratio, number of pods per plant and 100 seed weight in Tatisuzunari. However, in Touzan 69, racemes contributing to yield were limited to the first and second racemes. In Touzan 69, leaf length decreased drastically from basal to apical nodes, favoring the even distribution of light in the canopy, whereas, in Tatisuzunari, the leaf length increased from lower to higher nodes.