Abstract: 【Objective】Salinization and alkalinization of soil are becoming worse and worse during these years, and the concentrations of Na⁺, K⁺ and Na⁺/K⁺ ratio could be taken as the criterial indicators of saline-alkali tolerance in plant. Therefore, the QTL analysis of Na⁺, K⁺ concentration and Na⁺/K⁺ ratio in shoots and roots of rice at the seedling stage under salt or alkaline stress were conducted in the present study in order to provide a scientific basis for the rice genetic mechanism of salt and alkaline tolerance and molecular marker assisted breeding. 【Method】 The recombinant inbred line (RIL) population derived from a cross Dongnong 425 (high yield and quality) as the female parent and Changbai 10 (salt tolerance) as the male parent. A genetic linkage map was constructed with 102 SSR markers, covering 1 915.05 cM of rice genome at an average interval of 18.77 cM. The concentrations of Na⁺, K⁺ and Na⁺/K⁺ ratio in shoots and roots were phenotyped under 140 mmol·L^-1 NaCl of salt stress and 0.15% Na₂CO₃ of alkali stress at seedling stage. The correlation analysis by using SPSS v19.0 program and QTL analysis by using QTL IciMapping v3.3 program of the complete interval mapping method were conducted.【Result】The Na⁺ and K⁺ concentrations in shoots were higher than in roots under salt and alkaline stress in both the parents and RILs. All traits almost presented gaussian distribution, conforming typical genetic model of quantitative traits and the requirements of the QTL mapping. The results of correlation analysis showed that the concentrations of Na⁺ and K⁺ had a significant positive correlation in shoots and roots under salt and alkali stress, whereas there was no significant correlation between salt and alkali stress. A total of fifteen QTLs were detected under salt and alkaline stress, QTLs are located on different chromosomes between salt and alkali stress. Five QTLs were detected under salt stress, including one QTL associated with the concentration of K⁺ in shoots, which was located on chromosome 8 in the marker interval RM1308-RM281, explained 6.83% of phenotypic variance. Three QTLs associated with the concentration of Na⁺ in roots, which were located on chromosome 3 and 8, of which, qSRNC3-1 explained the maximum (16.41%) of phenotypic variance. One QTL associated with the concentration of K⁺ in roots, explained 3.52% of phenotypic variance. No QTL were found to be associated with the concentration of Na⁺, Na⁺/K⁺ ratio in shoots, and Na⁺/K⁺ ratio in roots. A total of ten QTLs were detected under alkali stress, including one QTL associated with the concentration of Na⁺ in shoots, which was located on chromosome 2 in the marker interval RM1347-RM48, explained 14.41% of phenotypic variance; One QTL associated with the concentration of K⁺ in shoots was located on chromosome 2 in the marker interval RM1255-RM213. Three QTLs associated with the Na⁺/K⁺ ratio in shoots, which were located on chromosomes 2, 7 and 10, respectively, of which, qASNK2 explained 7.57% of phenotypic variance. One QTL associated with the concentration of Na⁺ in roots, which was located on chromosome 3 in the marker interval RM293-RM232, explained 13.71% of phenotypic variance. Two QTLs associated with the concentration of K⁺ in roots, which were located on chromosome 1 in the marker interval RM5-RM9 and chromosome 2 in the marker interval RM12865-RM12941, respectively. Two QTLs associated with Na⁺/K⁺ ratio in roots, which were located on chromosome 3 and 4, of which, qARNK3 explained 10.48% of phenotypic variance. By comparing the mapping results, most of the detected QTLs were in the same or adjacent chromosomal regions of previously reported QTLs for tolerance to salt and alkali stress. In addition, two QTLs, namely qASKC2 and qARKC2, were not reported in previous studies, implying the possibility to be new QTL for tolerance to alkali.【Conclusion】The uptake and transport of the Na⁺ and K⁺ were considered to be parallel and independent under salt and alkali stress. The uptake of Na⁺ and K⁺ in roots and the transport in shoots had different genetic mechanism. The concentrations of Na⁺ and K⁺ between salt and alkali stress were independently inherited.

Key words: japonica rice, salt stress, alkaline stress, Na⁺ and K⁺ concentrations, SSR markers, QTL