Evaluation Of Salt Tolerance And Identification Of Quantitative Trait Loci Associated With Salt Tolerance At The Seedling Stage In Rice

The quantitative trait loci (QTLs) for salt tolerance at the seedling stage in rice under salt stress condition (125 mmol/L NaCl) were identified by using a F2:3 population including 177 lines derived from a cross between Nipponbare as female parent and France as male parent which were japonica cultivars. A total of 63 QTLs associated with salt tolerance-related traits were detected.The main results were as follows:1. There was a remarkable discrepancy in salt tolerance score (STS), leaf MDA content (LMC), leaf damage degree (LDD), chlorophyll relative content (SPAD), chlorophyll fluorescence parameters (Fm, Fv/Fm, Y, NPQ, ETR), plant height (PH), leaf K+ concentration (LKC), shoot K+ concentration (SKC), leaf Na+ concentration (LNC) and shoot Na+ concentration (SNC) between Nipponbare and France under salt stress condition. The F3 lines showed transgressive segregation for all traits and showed continuous variation which was suitable for QTL mapping.2. Salt tolerance score (STS) was significantly positively correlated with plant height (PH), relative plant height (RPH), SPAD, leaf K+ concentration (LKC), shoot K+ concentration (SKC) and chlorophyll fluorescence parameters (Fm, Fv/Fm, Y, NPQ, ETR), respectively. STS was significantly negatively correlated with leaf damage degree (LDD), leaf MDA content (LMC), leaf Na+ concentration (LNC) and shoot Na+ concentration (SNC), respectively.3. A genetic linkage map was constructed with 108 SSR markers through the 177 F2 individuals, covering a total length of 1428.3 cM with an average distance of 13.23 cM between adjacent markers in rice genome.4. Using interval mapping, single marker analysis methods, sixty-three QTLs associated with salt tolerance-related traits were detected which were located on all rice chromosomes except 3 and 10. The explanation for phenotypic variations by a single QTL varied from 9% to 19%. Genetic overlapping regions affecting salt resistance detected in the F2 populations were mainly distributed in chromosomes 2, 6 and 8. qETR2b was located on chromosome 2 in the marker interval RM2770-RM145, qETR6b was located on chromosome 6 in the marker interval RM276-RM3330, qLDD8b was located on chromosome 8 in the marker interval RM515～RM7356, explaining 16% , 16%,19% of phenotypic variance respectively. The additive effect of these three QTLs were -0.7, 0.45,-9.43% and the dominant effects were -0.14,-0.66,-13.35%.