LAUSR

Abstract Soil salinity is a major environmental stress causing significant loss of crop productivity. Barley (Hordeum vulgare L.) is one of the few field crops that can grow in salt-affected fields and varietal differences in productivity under salinity conditions were known. To clarify the trait most responsible for grain production under salt stress, barley cultivars that were salt tolerant (OUE812) or salt sensitive (OUC613) were grown from seedling to harvest stage in vermiculite containing various concentrations of NaCl. Dry weight of aboveground parts and grain weight decreased significantly with increasing NaCl concentration. The dry weight of the aboveground parts and grain weight decreased more significantly in OUC613 than in OUE812 for plants treated with 150 mM and 200 mM NaCl. A marked reduction in ripening percentage caused significantly decreased grain production in OUC613 as compared with OUE812. In plants treated with 200 mM NaCl, the photosynthetic rate decreased three weeks after starting the NaCl treatment, but a significant difference between cultivars in photosynthetic rate did not appear until seven weeks of NaCl treatment. OUE812 kept a higher photosynthetic rate during ripening than did OUC613 and dry matter production during the period from ripening to harvest was significantly larger in OUE812 than in OUC613. Keeping a higher photosynthetic rate might have contributed to higher grain production in OUE812. Higher ripening percentage and higher rate of photosynthesis during ripening might be target traits in breeding to improve the tolerance of barley to long-term salt stress.