Evaluation of the saline tolerance of gamma-ray-induced mutant lines of rice (Oryza sativa L.) under field conditions

Abstract Rice is highly sensitive crop to salt stress, especially at reproductive stage, and obtaining salt-tolerant genotypes is key for the rice production in salt-affected soils. In this study, ten mutant lines (obtained through gamma ray and pre-selected for their tolerance to salinity) accompanying by three Iranian traditional rice varieties (TRVs) were evaluated for biochemical and morpho-physiological parameters related to salt tolerance under saline field condition. The experiment was conducted as a randomized complete block design with three replications during two growing seasons. The salt tolerant mutant lines exhibited higher proline accumulation, K+ concentration, and activities of antioxidant enzymes, and lower Na+ concentration, Na+/K+ ratio, malondyaldehide (MDA) content that led to higher grain yield and quality under saline field condition, as compared with TRVs. Higher yield in these tolerant mutants was associated with more number panicle per hill, number filled grain per panicle, and 1000-grain weights. Results of correlation as well as principle component analysis also indicated that grain yield had high correlated with proline content, Fv/Fm index, stomata conductivity, SOD activity, MDA content, concentration of sodium (Na+) and Na+/K+ ratio at the reproductive stage under saline field condition, indicating that indirect selection according to these physiological criteria would be more effective approach for screening salt tolerance. According to these results, mutant lines 13 − 3, 32 − 18 and 22 − 1 indicated superiority in the grain yield and agronomical traits such as early- maturity and dwarfism, and also desirable grain quality that are promising mutant lines for cultivation in salt-affected coastal areas.