Identification of QTLs associated with salt or alkaline tolerance at the seedling stage in rice under salt or alkaline stress

Abstract

The QTL analysis of dead leaf rate (DLR) and dead seedling rate (DSR) during the seedling stage under salt or alkaline stress were conducted, in order to provide the scientific basis for the fine mapping and cloning of QTLs associated with salt or alkaline tolerance, and for the salt or alkaline tolerance of SSR marker assisted rice breeding. The recombinant inbred line (RIL) population F8 including 200 lines derived from the cross “Yiai 1 × Lishuinuo” were used in the study. The DLR and DSR of RIL and its parents were evaluated under 1.5 % NaCl of salt stress and pH8.7 to pH8.9 of alkaline stress, respectively. The results showed that DLR was a quantitative trait controlled by multiple genes, and DSR was a quantitative trait controlled by a few major genes and many other minor genes together under salt stress; DLR and DSR under alkaline stress were quantitative trait controlled by multiple genes. The genetic linkage map with 155 SSR markers which overlay the whole rice genome of 1541.5 cM and with the average distance of 9.95 cM between each two markers was constructed. Seven additive QTLs and three pairs of AA epistatic QTLs associated with DLR and DSR under salt or alkaline stress were identified, Of them, qDSRs8 - 1 with LOD of 6.54 and observed phenotypic variance of 15.96 % under salt stress, and qDLRa5 - 3 with LOD of 3.51 and observed phenotypic variance of 8.32 % under alkaline stress were new detected QTLs, which can be used in the breeding program in rice to get salt or alkaline tolerance rice cultivars in the future. The results also showed that excellent gene resource could be detected from any one rice germplasm; mechanisms for salt tolerance and alkaline tolerance in rice was different; additive QTLs were closely related with the resistance to salt injured in rice but epistatic effects of AA were closely related with the resistance to alkaline injured in rice.