Physiological characterisation and fine mapping of a salt-tolerant mutant in rice (Oryza sativa)

Salt-tolerant mutants are valuable resources for basic and applied research on plant salt tolerance. Here, we report the isolation and characterisation of a salt-tolerant rice (Oryza sativa L.) mutant. This mutant was identified from an ethyl methanesulfonate-induced Nipponbare mutant library, designated as rice salt tolerant 1 (rst1). The rst1 mutant was tolerant to salt stress and showed significantly higher shoot biomass and chlorophyll content, but lower lipid peroxidation and electrolyte leakage under NaCl stress. The improved salt tolerance of this mutant may be due mainly to its enhanced ability to restrict Na+ accumulation in shoots under salt stress conditions. Genetic analysis indicated that the salt tolerance of the rst1 mutant was controlled by a single recessive gene. Quantitative trait locus (QTL) mapping for salt tolerance was performed using an F-2 population of rst1 x Peiai 64. Two QTLs were detected, in which the locus on chromosome 6 was determined to be the candidate locus of the rst1 gene. The rst1 locus was subsequently shown to reside within a 270.4-kb region defined by the markers IM29432 and IM29702. This result will be useful for map-based cloning of the rst1 gene and for marker-assisted breeding for salt tolerance in rice.