Genotype and harvesting time influence development of hard seeds and its physico-chemical constituents in green gram (Vigna radiata (L.) Wilczek)

Hardseededness, a major seed quality constraint in legumes, is a widespread trait across the green gram genotypes and released cultivars in India and beyond. Its occurrence is controlled by genetic as well as environmental factors includingharvesting stage in most legumes. However, the effects of these factors and the associated alterations in the physico-chemical constituents on hard seed development in green gram is still unclear. A study conducted in 2019-20 on 6 hard seed (HS) and 6 non-hard seed (NHS) green gram genotypes under southwest monsoon conditionsin New Delhi, India. It showed that the days to anthesis were fewer for NHS type but varied across genotypes and increased progressively with growing degree days. Seeds harvested from 10 randomly tagged plants at 14, 21, 28 and 35 daysafter anthesis (DAA) showed that proportion of hardseed was significantly influenced by harvesting time, genotype, and their physico-chemical constituents. Percent hard seed was 16.75 when harvested at 14 DAA in HS type, which gradually increased to 21.38, 31.73 and 38.06 respectively at 21, 28 and 35 DAA (P < 0.05). Delayed harvesting increased both acid soluble and insoluble lignin, xylose, arabinose, and total phenol contents and hardness breaking force both in HS and NHS types (P < 0.05). A sharp increase in hard seeds after 21 DAA suggests that to get lower percent hard seeds in predominantly HS genotypes, harvesting should be done by 21 DAA under southwest monsoon season (Rainy season) in northern India.