Abstract: To screen high-yield rice varieties or hybrids with good tolerance to low temperature at flowering stage, the ecological adaptability of 12 late-maturing, high-yield rice hybird and varieties(line) with similar growth duration had been evaluated at flowering stage by 3 times of sowing under natural conditions. Under low temperature stress at flowering stage, relative damage degree values of major agronomic traits were as following order. grains per panicle, yield per plant, seed-setting rate, spikelets per panicle, plant height, panicle length, 1000 seed weight;and relative cold damage percent (RDP) of yield per plant was very significantly positive correlated with RDP of grains per panicle, RDP of seed-setting rate, score for color of flag leaf, score for delayed time of heading period. Cold tolerance differs distinctly in rice genotypes at flowering stage. The morphological indexes, e. g. RDP of grain-setting rate and grains per panicle, color of flag leaf, delayed time of heading period, bract panicle rate had been used to evaluate tolerance to low temperature at flowering stage.95LR102, a line derived from the cross of an indica variety and a japonica variety, has strong tolerance to chilling injury. Some hybrids, e. g, V644, V46, which have been popularly planting as late rice in Hunan, have better adaptability.

Key words: Rice, Flowering stage, Chilling injury, Ecological adaptability