Effect of harvesting time and seed storage on seed coat colour and seed quality of mungbean varieties

Changes in seed coat colour of mungbean seeds is a major problem during storage. Effects of harvest and storage time on changes of seed coat colour were investigated in 1996-1997 at Chai Nat Field Crops Research Center. Near-isogenic lines carrying black pods vs tan pod of Kamphangsaen 1 (KPS 1) were studied for interaction between harvest and storage time. The results revealed that change in change in seed colour increased with increasing harvest and storage time. For black pod lines, seeds harvested in 5 weeks after physiological maturity (PM) the seed coat colour changed markedly (up to 43 percent) followed by seeds harvested at 4 weeks after PM. Seeds harvested at PM and 1 week after PM showed the lowest seed coat colour changes at each storage time. At each harvest time, seed coat colour change significantly increased with increasing storage time from 3 to 9 months. At each storage time, percent germination was highest in seeds harvested at PM and 1 week after PM, and lowest in seeds harvested at 5 weeks after PM. At each harvest time, percent germination decreasing with increasing storage time from 0 month up to 12 months. The effect of harvest and storage time on seed coat colour change of tan pods was generally similar to that of the black pods. At each storage time, changes in seed coat colour increased with delaying harvest time. Changes of seed coat colour was highest with seeds harvested at 5 weeks after PM (up to 23 percent) and lowest with seeds harvested at 1 week after PM. Change of seed coat colour significantly increased with increasing storage time from 3 months to 12 months for seeds harvested at 2, 3 and 5 weeks after PM. For seeds harvested at PM, 1 and 4 weeks after PM, changes of seed coat colour increased with increasing storage time from 3 to 9 months, whereas there as no significant difference in seed coat colour between 9 and 12 month storage. At each storage time, germination was highest in seeds harvested at PM and 1 and 2 weeks after PM, whereas the others showed no significant differnces.