Abstract

                                Seed dormancy in rice (Oryza sativa L.) is important to avoid losses due to germination rains during harvesting. Four indica type rice cultivars (Basmati 370, Type 3, P2 and PR106), as well as F3 seeds obtained from a cross of Basmati Type3 with seed dormancy and non-dormant and non-basmati P2, were used to investigate the genetic control of seed dormancy at different temperatures and days after harvesting (DAH). The seeds of non-basmati rice cultivars germinated immediately after harvesting, while seeds of the traditional Basmati cultivars, Basmati 370 and Type 3 remained dormant. Seed dormancy in Basmati cultivars was hull_x0002_imposed, and could not be overcome by the usual heat treatment of seeds at 45 C for 72. Both the Basmati cultivars continued to have a dormant seeds up to 50 DAH. The F3 seeds from 160 F2 plants from a cross of Basmati Type 3 with non-Basmati P2 were investigated for genetics of seed dormancy. The F3 seeds of F2 plants segregated for dormant: non-dormant seeds at 50 DAH at room temperature in 13:3 ratio, suggesting that two genes one dominant and another recessive controlled seed dormancy in Basmati cultivars. For heat-treated seeds at 50 DAH, a 1:3 ratio of dormant: non-dormant F2 plant/F3 seeds was observed and this response ratio was maintained up to 100 DAH without heat treatment, indicating the long term effectiveness of the recessive gene controlling the seed dormancy. The dormancy conditioned by the dominant gene was overcome by heat treatment whereas the part controlled by the recessive gene continued to be effective.

Key words : Oryza sativa, basmati rice, germination, heat treatment, seed dormancy