Abstract:

Drought is one of the important factors limiting crop production and becoming more and more severe in many regions of the world. Rice (Oryza sativa L.), as a paddy field crop, is particularly sensitive to drought stress. It is estimated that 50% of the world rice production is influenced more or less by drought. Breeding large panicle rice has become one of main targets for super hybrid rice breeding in China, and drought is the direct cause leading to low and instable seed setting rate of them and limits the production potential to full play. Previous research concluded that rice was more sensitive to water stress during meiosis stage. This study was conducted in 2013 cropping season at the Agricultural College of Yangtze University (30°20′N,112°13′E). 21 large panicle rice varieties were selected as materials, and sowing times were arranged according to accumulated temperature and 25 days after sowing, the seedlings were transplanted in to plastic buckets and kept soil water content 40%-50% from the initial of meiosis stage for 10 days as drought treatment. The objective of the study was to screen and identify drought resistant cultivars under the drought stress condition. Seed setting rate and total grains per panicle were investigated and drought resistance index and relative injured rate were calculated and the drought resistance of 21 rice varieties was evaluated by subordinative function value. The results showed that seed setting rate and total grains per panicle of all selection varieties were decreased under drought stress conditions, and the rice varieties with high resistance to drought had lower decreasing extent than the varieties sensitive to drought. Based on the values of subordinate function, 21 large panicle rice varieties were classified into three types, high droughtresistant, resistant and the sensitive. The mean decrease extents in seed setting rate and total grains per panicle of high resistance varieties were 8.69% and 11.48%, and those of sensitive varieties were 5190% and 2815%. R527 and 9311xuan among high resistance varieties showed better performance in the seed setting rate and total grains per panicle under drought stress, and the relative injured rates were 016% and -217%, respectively. R527 and BL006 were selected for further pollination characteristic analysis, the sensitive variety BL006 showed significant decrease in anther length, the pollinated pollens per stigma, the germinated pollens per stigma and the pollen germination rate per stigma and the high resistance variety R527 decreased a little. In this research, the change extent of seed setting rate as not completely consistent with that of total grains per panicle, and these changes were important response to drought stress. Therefore, a joint indicator of seed setting rate and total grains per panicle may be better than only seed setting rate as index for drought resistance screening and identification in large panicle rice, and anther length and pollen germination rate per stigma could be chosen as reference indicators for pollination characteristic analysis, and the difference of drought resistance was closely related with the formation and vitality of male gametes