Study On The Genetic Basis Of Drought Resistance At Reproductive Stage In Rice

Drought especially late season drought is one of the main abiotic constraints in rice production, and the genetic basis of drought resistance in rice is very complex due to different mechanisms mixed together which resulted in slow progress on drought resistance breeding in rice. In this study, a genetic linkage map was constructed for mapping QTLs for drought escaping (via early heading), drought avoidance (mainly via root traits) and tolerance using a RIL population of 180 lines from a cross between an indica lowland rice and upland japonica rice. Genetic analysis of drought resistance at reproductive stage in field with different types of soil was also conducted to find the possible mechanism of late season drought resistance in rice under field conditions. The main results were as follows:1. The comparison of drought resistance between two parents revealed that drought tolerance was the main drought resistance mechanism of the parent Zhenshan 97, whereas for the upland and japonica parent, IRAT109, the ability of drought avoidance (root traits and water keeping ability) was higher than Zhenshan 97, and drought resistance can also be achieved by water distribution in IRAT109.2. A genetic linkage map was constructed based on the data of 245 loci assayed on the 180 individuals by Mapmaker analysis. The map covered a total of 1530cM with an average interval of 6.2cM between adjacent loci.3. Nine QTLs for heading date were detected under four environments with different day-length and temperature. Their relations with yield and the QTL by environment interactions analysis revealed that it is possible to breed rice varieties with early maturing, high yield and unsensitive to environments, which is very important to drought escaping in rice.4. Similar drought stress was applied at same stage (booting to anthesis) on each rice plant grown in PVC pipes on the basis of staggering seeding date in the year 2003 and 2004. Correlation analysis revealed that relative yield (RY, corresponding to drought susceptibility index) had no significant correlation with flowering time, biomass and most of the root traits investigated in two years, suggesting that drought escaping was...