Construction Of Introgression Lines Of Rice With Drought Resistance And Gene Expression Profile Analysis Of Parents Under Drought Stress

Rice(Oryza sativa L.) is one of the most important food crops in China. Drought has a significant impact for the distribution and yield of rice. Rice has developed physical morphology and biochemical and metabolic mechanisms to respond or adapt to drought stress. In this study, forward genetic approach was used for constructing introgression lines with drought resistance using Kongyu131, a widely planted japonica rice variety in Northeastern China, as recipient parent. Several rice germplasms with relatively high resistance to drought stress were selected as donor parents. The introgression lines with improved drought resistance will be used for identification and cloning of drought resistance QTLs and generation of new breeding materials. Meanwhile, genome-wide expression profiling by using RNA-Seq was performed for the parental varieties with significant difference in drought resistance, which provides useful information to select candidate genes for genetic engineering of drought resistance by reverse genetic approach.The main research results are as follows:1. Through phenotypic identification of the drought-resistant donor parents used for constructing introgression lines, we found that upland rice Zhonghan5 showed strongest drought resistance among 8 different donor parents, and evaluation standard of drought resistance was determined accordingly, which provided the basis for subsequent screening on drought resistance of introgression lines.2. Construction of introgression lines with drought resistance was initiated by using rice Kongyu131 as a recipient parent and a few drought-resistant varieties as donor parents. After two generations of backcrossing and one generation of selfing, 20, 34 and14 lines(populations) at BC2F2 generation were generated for the donor parents Sugeng 2,Balila, and Zhonghan 5, respectively.3. Genome-wide expression profiling was conducted for three varieties with sharp difference in drought resistance: Zhonghan5 with strong drought resistance, Balila with moderate drought resistance, and rice Kongyu131 with weak drought resistance under mild and severe drought stress conditions. Results showed that gene expression pattern inZhonghan5 was largely different compared to that in Balila and Kongyu131 under both mild and severe drought stress, and these differential expressed genes might be related to the molecular basis of the strong drought resistance of Zhonghan5. Among the three varieties, most of drought- responsive genes are the same, but many of them showed significant difference in the expression level in response to the drought stress. Through Gene Ontology analysis, we found that, under severe drought stress, genes related to lipid and glyceraldehyde-3-phosphate dehydrogenase metabolism had specific expression and obvious enrichment in Zhonghan5. Overlapping analysis of the drought-responsive genes among the varieties provided large amount of information for drought-resistant candidate gene cloning and related molecular mechanisms analysis in further studies.