QTL Analysis Of Alkaline Tolerance At Seedling Stage In Rice

Rice is not only the most important food crops in the word. but also has the staple food for more than half the population in China. So to improve the yield of rice to ensure food security is of great significance. However high concentrations of salt in the soil severely inhibit the growth of rice. It is a major abiotic stress that limits rice production worldwide. Rice is a kin d of salt-sensitive crops, its salt and alkali resistance of significant differences between, and inhaibition of rice growing in alkaline saline soil is even more serous. Therefore, understanding the genetic mechanism controlling rice alkali tolerance, especially the rice alkali-resistant QTL analysis, it is of great significance to improve the alkali tolerance of rice varieties, reduce the alkaline damage and improve the utilization of saline-alkali land.The F2:3 population derived from the cross “Caidao× WD20342” were used in the study. Alkali stress were carried out at the seedling stage, and alkali tolerance traits were analyzed by QTL.Then screening 2 sub-populations through the initial location results to conduct accurate location to the seedling height control and the main QTL effect of Na+ concentration on the ground respectively, as well as forecasting the candidate gene.In order to mining alkali resistance of major QTL and find it in more precise location on a chromosome.These results should have an important significance for positional clone and molecular breeding in alkaline resistance related genes in rice. The results were as follows:(1) Two parents in alkali tolerance performance at the seedling are WD20342 stronger than Caidao under alkali stress. SVC、SH、SFW、SDW、RDW、SAT、SNC、SKC、SNK、RNC and RNK were significant or very significant differences between the two parents in F2:3 population. Same individual appear partial separation distribution, the other characters are in line with the normal distribution, which meet the genetic typical characteristics of quantitative trait.(2) SVC、SH、SFW、SDW、RFW and RDW decreased obviously under alkali stress compared with those of traits under normal conditions, it indicate that high concentrations of sa lt in the soil severely inhibit the growth of F2:3 population.(3) There was highly significant positive correlation with RNC and RKC, but SNC was highly significant negatively correlated with SKC in F2:3 population, indicate that the processes of Na+ and K+ uptake in rice were considered to occur in parallel and competition occurred when Na+ and K+ in the roots were transported to the shoots.(4) F2:3 population were used as experimental materials, constructed with 151 SSR markers those were selected from 1000 SSR markers, a total length of 2469.14 cM, the average distance between the makers for genetic mapping of 16.78 c M.(5) A total of 29 QTLs were identified at the seedling stage. q SNC3 and q SH7 were two major QTLs that explained 21.24% and 20.09% of the observed phenotypic variation respectively.(6) Based of the results in the previous study, the closely linked SSR makers were used for detect target gene(q SNC3、q SH7), and some other polymorphic markers for background selection. Subsequently, two near isogenic lines of Caidao, named q SNC3-NIL and qSH7-NIL for fine mapping of major QTLs, q SNC3 and q SH7.(7) Fine mapping was done to narrow down the interval by adding more SSR makers for the target interval of q SNC3 and q SH7. Then, q SNC3 was narrowed to the physical distance of 81.37 kb and flanked between RM1221 and RM4404, q SH7 was narrowed to the physical distance of 180.67 kb(genetic distance of 0.9c M) and flanked between RM336 and RM5495.(8) q SH7 has forecasted 23 coding genes in total, it can be proposed that the LOC_Os07g3659, LOC_Os07g36544, LOC_Os07g36500, LOC_Os07g36520, LOC_Os07g36530 have candidate genes of q SH7. q SNC3 has forecasted 17 coding genes in total, it can be proposed that the LOC_Os03g62500 and LOC_Os03g62620 have candidate genes of qSNC3.