Development Of Drought Tolerance Introgression Lines Of Common Wild Rice (O.rufipogon Griff.) From Dongxiang In Jiangxi Province And QTL Mapping Of Drought Tolerance

The study on mechanism of rice drought tolerance has become one of hotspots in the field of rice science because of serious shortage of water resource worldwide. Common wild rice (Oryza rufipogon Griff.), the ancestor species of cultivated rice (Oryza sativa L.), has far more diverse in genetic background than cultivated rice, which possesses favor genes that can not be detected in cultivated rice. In this study, a set of 159 substitution lines (BC4F5 and BC₄F₆) carrying variant introgressed segments from Chinese common wild rice (Oryza rufipogon Griff.), collected from Dongxiang county, Jiangxi Province, in the background of Indica cultivar (O.sativa L.), Guichao 2 was used to identify QTLs of drought tolerance. The main results were as follows:1. Drought tolerance of rice seedlings with two and half leaves was identified by means of 30% PEG solution. A total of 12 QTLs related to drought tolerance were detected, of which four QTLs detected on chromosome 2, 6 and 12 appeared positive additive effects. The special attention was required for the QTLqSDT12-2 near the SSR marker RM17 on chromosome 12. Not only it was detected several times but also expressed stably for 8 days when seedlings were subjected to water stress with PEG. Dynamic QTL mapping indicated that different QTL expressed in different periods.2. There were 7 QTLs related to root basal thickness detected, of which four QTL, qBRT6. qBRTll, qMBRTl and qMBRTll, appeared positive additive effect that means alleles from wild rice can increase root basal thickness of introgression lines.3. Eighteen lines with different reactions to PEG treatment were grown in basins for confirming their drought tolerance, and correlation analysis among various traits was performed at their seedling stage. The results told that drought tolerance evaluated by PEG method did not agree with conclusion from basin treatments. In addition, both results from PEG treatments and basin cultivation did not correlated with root basal thickness from plants cultivated in field.4. Comparison of drought tolerance of these introgression lines under upland and lowland conditions indicated that not only seedset ratio and 1000-grain weight but also number of filled grains per panicle decreased obviously, whereas number of total kernel per panicle was generally changeless. The three QTLs, qPH1-1, qPH1-2 and qPH1-3 were detected under both upland and lowland condition, but it was not the case for other QTLs. Correlation analysis of drought tolerance in seedling and mature stage indicated that in the first two days the results of PEG treatment were more consisent with that obtained from field evaulation, whereas the results of basin cultivation have less correlation with other traits except its significant negative correlation with root basal thickness.