Fine mapping of qSKC-1, a major quantitative trait locus for shoot K+ concentration, in rice seedlings grown under salt stress

Shoot K+ concentration (SKC) is an important physiological parameter used to evaluate salt tolerance at the seedling stage in rice (Oryza sativa L.). qSKC-1, a major quantitative trait locus for SKC in rice under salt stress, was detected on chromosome 1 using three F2 populations constructed by crossing 'Nipponbare' and its two salt-sensitive mutants (rss2 and rss4) with an indica cultivar 'Zhaiyeqing8' ('ZYQ8'). In this study, the chromosomal location of qSKC-1 was determined precisely by fine mapping. First, the presence of qSKC-1 was confirmed by QTL analysis of a re-constructed 'Nipponbare' × 'ZYQ8' F2 population. Then, F2 plants in which recombination events had occurred near qSKC-1 were identified from the 'Nipponbare' × 'ZYQ8' and rss4 × 'ZYQ8' F2 populations, and their phenotypic values were confirmed by progeny tests. Eventually, by analyzing recombination events in these recombinants, the qSKC-1 locus was mapped precisely to 445 kb between markers RM578 and IM8854. These results will facilitate map-based cloning of the qSKC-1 locus.