Characterization and Mapping of a Salt-Sensitive Mutant in Rice ( Oryza sativa L.) Characterization and Mapping of a Salt-Sensitive Mutant in Rice ( Oryza sativa L.).

A salt-sensitive mutant designated rice salt sensitive 2 ( rss2) was isolated from the M2 generation of the rice cultivar Nipponbare mutagenized with ethyl methanesulfonate (EMS). This mutant exhibited a greater decrease in salt tolerance with a significant increase in Na+ content in its shoots. Genetic analysis indicated that the increase in Na+ in rss2 was controlled by a single recessive gene. Further genome-wide analysis of the linkage map constructed from the F2 population of rss2/Zhaiyeqing 8 (ZYQ8) showed that two quantitative trait loci (QTLs) on chromosomes 1 and 6 were responsible for the Na+ concentration in shoots, which explained 14.5% and 53.3%, respectively, of the phenotypic variance. The locus on chromosome 1, but not that on chromosome 6, was also detected in the F2 population of Nipponbare/ZYQ8, suggesting that the QTL on chromosome 6 was responsible for the salt sensitivity in rss2. By analyzing the recombination events in 220 mutant individuals of an enlarged mapping population of rss2/ZYQ8, the rss2 locus was precisely mapped to an interval of 605.3 kb between insertion/deletion (InDel) markers IM21962 and IM22567. This finding will facilitate the cloning of the rss2 locus and provide insight into the physiological mechanisms of salt sensitivity in rice. [ABSTRACT FROM AUTHOR]