Identification of quantitative trait loci associated with salt tolerance at seedling stage from Oryza rufipogon
Lei Tian^{1, 2}, Lubin Tan², Fengxia Liu², Hongwei Cai², Chuanqing Sun²*

¹College of Agriculture, Ningxia University, Yinchuan 750021, China.
²State Key Laboratory of Plant Physiology and Biochemistry; National Centre for Evaluation of Agricultural Wild Plant (Rice); Laboratory of Crop Heterosis and Utilization of Ministry of Education; Beijing Key Laboratory of Crop Genetic Improvement and Genome of Ministry of Agriculture; Department of Plant Genetics and Breeding, China Agricultural University, Beijing 100193, China.
*Corresponding author. Tel: +86-010-6273 1811; Fax: +86-010-6273 1811. E-mail address: suncq@cau.edu.cn

Abstract
Soil salinity is one of the major abiotic stresses affecting plant growth and crop production. In the present study, salt tolerance at rice seedling stage was evaluated using 87 introgression lines (ILs), which were derived from a cross between an elite indica cultivar Teqing and an accession of common wild rice (Oryza rufipogon Griff.). Substantial variation was observed for four traits including salt tolerance score (STS), relative root dry weight (RRW), relative shoot dry weight (RSW) and relative total dry weight (RTW). STS was significantly positive correlated with all other three traits. A total of 15 putative quantitative trait loci (QTLs) associated with these four traits were detected using single-point analysis, which were located on chromosome 1, 2, 3, 6, 7, 9 and 10 with 8%–26% explaining the phenotypic variance. The O. rufipogon-derived alleles at 13 QTLs (86.7%) could improve the salt tolerance in the Teqing background. Four QTL clusters affecting RRW, RSW and RTW were found on chromosome 6, 7, 9 and 10, respectively. Among these four QTL clusters, a major cluster including three QTLs (qRRW10, qRSW10 and qRTW10) was found near the maker RM271 on the long arm of chromosome 10, and the O. rufipogon-derived alleles at these three loci increased RRW, RSW and RTW with additive effects of 22.7%, 17.3% and 18.5%, respectively, while the phenotypic variance explained by these three individual QTLs for the three traits varied from 19% to 26%. In addition, several salt tolerant ILs were selected and could be used for identifying and utilizing favorable salt tolerant genes from common wild rice and used in the salt tolerant rice breeding program.

Keywords: common wild rice (O. rufipogon Griff.); introgression lines; salt tolerance; seedling stage; quantitative trait locus.