Agronomic and physiological traits facilitating better yield performance of japonica/indica hybrids in saline fields

Abstract It is of great interest to utilize saline fields to promote rice production in China. Previous studies reported greater yield productivity of japonica/indica hybrids (JIH) over indica hybrids (IH) under nonsaline fields. It has still not been established how salinity stress intervenes with rice yield and whether JIH would exhibit superior grain yield than IH under saline field conditions. This study investigated three JIH and three IH cultivars grown at the two sites that differed significantly in soil salinity, namely, nonsaline (Wulie, abbreviated as WL) and saline (Tiaozini, abbreviated as TZN) fields, in Yancheng, Jiangsu, China. The panicles per m2, spikelets per panicle, filled-kernel percentage, and kernel weight of JIH and IH were reduced, and a 36.0 %–43.5 % loss in grain yield was observed with salinity stress at TZN compared with WL. For JIH and IH, the shoot biomass and leaf area index (LAI) at jointing, heading, and maturity were all reduced at TZN compared to those at WL; similar results were also detected for root biomass, root length and volume, and root bleeding rate after heading. Compared with IH, JIH produced a 24.8 % higher grain yield under saline field conditions at TZN across two years. Four agronomic and physiological traits were summarized for superior grain yield of JIH compared to that of IH with salinity stress under field conditions. First, JIH had an enlarged sink size potential of a greater number of spikelets per panicle. Second, a synergistically increased biomass accumulation and harvest index of JIH, supported by higher biomass accumulation and LAI at the main growth stages and improved NSC remobilization after heading. Third, JIH had an improved stay-green characteristic, indicated by a higher leaf area per plant, SPAD values, and leaf photosynthetic rate after heading. Fourth, JIH exhibited a better root morpho-physiology than that of IH after heading, showing a larger and deeper root structure and higher root bleeding rate. These results indicated that the limited shoot and root growth were responsible for the yield penalty of rice under saline field conditions. JIH's improved agronomic and physiological traits facilitated superior yield performance over IH with salinity stress under field conditions.