Identification Characteristics On Drought Tolerance And Adaptability On Water Stress In O. Sativa L.

There are two parts in the research. One part is making a systematic study on the relationship between different traits and drought tolerance (Luo,2005) . The drought identification method and facilities, which based on soil moisture gradient, was used to this study. One hundred and forty eight cultivated rice varieties and 76 introgression lines in background of Zhong 413 were grown in greenhouse for drought screening. Analysis was made on drought related physiologic traits and agronomic characteristics. The correlation and regression between yield and yield components, and the relationships between the physiologic traits and drought tolerance were analyzed. The changes of physiologic traits under drought stress were also analyzed. The other part is exploration on the ecological adaptability of different varieties under different water treatments. Six varieties were planted in PVC pipes under 7 different water treatments to study the difference of water ecological amplitude of upland/paddy rice. The root and relationships between the root and drought resistance were also studies in the experiment. The main results are as follows:1. The results showed that signification differences were existed in yields of different varieties between well-irrigated and drought condition. The yield decreased markedlyunder drought condition . The reasons for the yield decreasing were seed-settingpercentage and 100-grain weight decreased.2. The relative fertility of 148 cultivated rice varieties were normal distribution, and the relative fertility of most varieties is equal to 1. There is no significant differences between well-irrigated and drought condition of 80% of 148 cultivated rice varieties. 75% introgression lines showed better drought resistance than the recurrent parental line Zhong 413. There is only 19 ILs showed more drought sensitive than Zhong 413.3. The multiple regression equations were built up to estimate the contribution to grain yield (Y) from four important component factors, i.e. fertility percentage (X₁), panicle number per plant (X₂), spikelet number per panicle (X₃), and 100-grain weight (X₄), respectively. The equation was Y=-19.564+ 11.304X₁+ 2.026X₂+0.046X₃+2.722X₄ under irrigated condition, and Y=-12.590+12.510X₁+1.413X₂+0.034X₃+1.270X₄ under the drought stressed environment.4. The obervations of leaf water potential and canopy temperature can reflect different levels of drought resistance. The relationships between leaf water potential and yield reduction rate is r=-0. 316^*, and the relationships between canopy temperature and yield reduction rate is r=0. 324^*, the relationships between chlorophyll content and yield reduction rate is r=0. 076. So chlorophyll content is unsuitable as a reliable physiologic trait alone for the screening of drought tolerance.The upland rice showed high leaf water potential and low canopy temperature, and dried spikelet under drought condition. The paddy rice showed leaf rolling, lower leaf dessication, and growth delay.5. The ecological amplitude of a selected introgression line in background of Zhong 413 is wider than other varieties, and no difference in yield under 7 water treatments. The ecological amplitude of Teqing/Zihui100 is the narrowest among 6 varieties. The Hanyou 3 performed well in recovered growth after restored irrigation.6. There is significant relationship between the root and drought resistance. The ratio of deep root in proportion to total root can partly reflect drought resistance.