Evaluation of Drought Tolerance and Identification of QTL in Single-segment Substitution Lines of Wild Rice at Seedling Stage

【Objective】Drought is one of the main abiotic factors that affect rice productivity. Rice yield can be ensured by screening drought-resistant rice.【Method】Ninety-three single-segment substitution lines (SSSLs) constructed from Oryza. meridionalis and O. glumaepatula and their recipient parents 'Huajingxian 74'(HJX74) were used as the test materials. And 20% PEG-6000 was adopted to simulate drought conditions to perform drought tolerance tests at the seedling stage. Besides, four growth and development traits (relative seedling height, relative seedling dry weight, relative root dry weight and relative root length) were used as evaluation indicators. The membership function method was utilized to sort SSSLs and screen SSSLs with relevant traits significantly different from HJX74. Based on the QTL identification and additive effect analysis, QTL related to drought tolerance traits at the seedling stage was preliminarily identified.【Result】The analysis of correlation between the four growth and development traits and the average membership function value revealed that they were all extremely significantly positively correlated, and could be used as indicators for identifying and evaluating the drought tolerance in the seedling stage of SSSLs. According to the analysis result of the membership function method, the average membership function value of the tested SSSLs ranged from 0.20 to 0.71, and the average membership function value of HJX74 was 0.54. The average membership function value of 29 SSSLs was greater than that of HJX74. Among them, M124 had the largest membership function value, indicating strong drought tolerance of M124. Through single factor analysis of variance, 7 relative seedling height QTLs (qRSH1-1, qRSH1-2, qRSH2-1, qRSH3-1, qRSH3-2, qRSH5-1, and qRSH6-1) were identified from 8 SSSLs (M78-1, M78-2, M124, M107, M151, M103, M130, M115), which were distributed on Chromosomes 1, 2, 3, 5, and 6. Their additive effect was 0.05-0.06, and the phenotypic contribution rate was 6.97%-9.01%. Three relative root dry weight QTLs (qRRDW10-1, qRRDW11-1, and qRRDW11-2) were identified from three SSSLs (M79, M145, M148), which were distributed on chromosomes 10 and 11. The additive effect was 0.12-0.20, and the phenotypic contribution rate was 12.51%-19.95%. A relative seedling dry weight QTL (qRSDW5-1) was identified from 2 drought-tolerant SSSLs (M80, X149), and distributed on chromosome 5, with the additive effect of 0.07 and the phenotypic contribution rate of 10.5%.【Conclusion】A total of 13 SSSLs with drought-tolerant QTLs at the seedling stage are screened, laying a solid foundation for further study on fine mapping and cloning.