Variability in seed dormancy of some improved rice varieties in Sri Lanka

Abstract

prolonged dormancy in rice becomes a problem when seeds of previous season are to be used for immediate sowing. Total absence of dormancy is also a disadvantage as the seed will sprout on the plants in the field. Twenty four rice varieties having different field maturity periods and grain types fSamba, Nadu and Kora/Basmathi type) were tested for their dormancy period. In addition, relationship between husk thickness of seeds and seed dormancy was also assessed. Seed germination test was started from -' iirst day of harvest and it is continued at 7 days interval until each variety illustrates more than 85% of sprouts. Seed viability was also tested at first and fourth week after the harvest to ensure the liveliness. Shortest [11 days] and the longest [55 days) dormancy periods were reported in At 373 and At 303, respectively. At 373 and At 861 with lowest husk thickness of 0.065 mm and 0.075 mm, respectively recorded the lowest dormancy period fless than 20 days from harvest). Among the six scented varieties, r-3 At 898 and At 405 showed the lowest husk thickness and at the same time lowest dormancy period compared to most of the varieties. Varieties which had comparatively higher husk thickness than ' .': tested varieties always did not show a prolonged dormancy. Grain type and maturigu duration did influence on the dormancy period of selected varieties. Although the existence of thin husk shows a tendency in influencing the early breakage of seed dormancy, thick husk in rice grains do not always lengthen the dormancy period of a variety.