Studies on the Vigour of Soybean Seeds : I. Varietal Differences in Seed Vigour

The association of flowering, growth period, reproductive growth period, seed size, the occurrence of defective seed and seed coat colour with varietal differences in seed vigour were investigated using 38 late maturing cultivars originating from Indonesia, America and Japan under the climatic condition of Fukuoka City. The results show that varietal differences in seed vigour were clearly demonstrated by standard germination after 6 days of accelerated ageing at 40℃, 100 % RH (ranged from 2.7 to 98.7 %) although their seed viability ranged narrowly (from 76.0 to 100 %). The genotypical traits, except flowering and growth period, in question were associated with varietal differences in seed vigour as a single factor, respectively. It was also revealed that the climatic condition of middle autumn (daily mean temperature was 15℃ and total rainfall was 5.5 mm from 1 to 10 November 1983) facilitated the highest vigour of resulting seeds. Field weathering by high temperature and rainfall in early autumn, and a possible occurrence of cold injury in late autumn lowered the seed vigour. Excluding seed coat colour, a stepwise regression analysis resulted in predominant contribution of seed size, showing negative correlation on varietal differences in seed vigour in terms of standard germination. In terms of electrical conductivity, however, the varietal differences in seed vigour were particularly controlled by reproductive growth period and the occurrence of defective seed. As far as other factors were almost at the same level, the genotypes with black seed coat colour were more vigorous than those with light seed coat colour