Study On Mechanism Of Drought Tolerance And Water Use Efficiency Of Rice Near-isogenic Lines

A total of 18 rice lines with the genetic background of ZS97 and IRAT109 were used to study drought performance and mechanism of drought tolerance in well water and drought treatments. We investigated root characteristics of rice plant under well water and drought treatment using PVC tubes studied. Drought related physiological traits were during the stress period. Agronomic characteristics, grain yield and yield components were evaluated after harvest. Additionally, the eighteen rice lines were used to study the water use efficiency under the well water conditions. The main results are following:1) The lines with the genetic background of ZS97 have the ability of drought tolerance higher than those with the genetic background of IRAT109. But the lines with the genetic background of IRAT109 have the ability of drought avoidance higher than the rice lines with the genetic background of ZS97.2) Based on drought-resistance coefficient and certain agronomic fraits, we chose the rice with the ability of drought resistance higher than their parents.They were N19, N23 and N24 derived from ZS97 and N4 and N11 derived from IRAT109.3) Reasons for the high drought resistance were discussed and identification was done to determine whether their performance characteristics matched with their QTL localization traits. N19 and N23 with higher relative grain fertility and N24 with strong root system, relative spikelets number per plant and relative grain weight all showed higher ability of drought resistance than ZS97 and N23 and N24 matched their performance with certain QTL localization traits. However, the matching of N24 in 2010 was not obvious. Higher drought index comparing to IRAT109 was found in N4 for high number of spikelets per panicle, and N11 for higher relatively grain fertility. These traits, including largest root volume in N11 under control and largest maximum root depth in N15 under stress condition matched with the result of QTL location. Besides, N15 showed lower drought index than IRAT109 because its relative grain fertility was significantly lower than IRAT109.4) We compare the water use efficiency to find what cause the differences among the 18 lines. N6, due to the low water consumption, shows significantly higher water use efficiency than ZS97, and N19 and N20, which have low yield per plant, and N23 and N24 show significantly lower water use efficiency than ZS97. N19 shows low yield per plant because of low grain weight and grain fertility and N20 because of the low number of spikelets per panicle and grain fertility. As consequence of strong root system, N24 has high water consumption, and resulted in low water use efficiency. N12, N15, N36 and N37 shows significantly lower yield water use efficiency than IRAT109. N37 and N15 have low water use efficiency because of their excessive water consumption and low grain fertility, and N12 and N36 was mainly due to low yield per plant. There is no difference of the number of spikelets per plant, spikelets per panicle and grain weight between N12 and IRAT109, except for the grain fertility which appears lower in N12.