Salinity Effects on Agro‐Physiological Characteristics and Yield Formation of Rice Differing in Salinity Tolerance in Saline Lands

Saline fields hold great promise for boosting rice production in China. Salinity‐tolerant/susceptible rice cultivars respond differently to salinity, yet limited research has focused on how salinity modulates their agro‐physiological traits and grain yield of rice under saline field conditions. This research aimed to explore how salinity affects rice yield formation and identify key agro‐physiological characteristics underlying differential tolerance responses. Field experiments were conducted with salinity‐tolerant rice (Yannongjing 3426 and Nanjingyan 1) and salinity‐susceptible rice (Wuyunjing 30 and Huajing 5) under low salinity (LS) and high salinity (HS) over 2 years. Rice grain yield was reduced by 34.2%–54.9% at HS across 2 years, compared with LS. The increased salinity stress led to lower shoot biomass and stem non‐structural carbohydrate (NSC) content, accompanied by higher harvest index and NSC reserve remobilization. Meanwhile, the increased salinity stress brought higher leaf (sodium) Na + concentration and Na + /(potassium) K + ratio, accompanied by reductions in post‐heading leaf SPAD value and photosynthetic rate, and total accumulation of nitrogen (N), phosphorus (P), and K. Salinity‐tolerant rice yielded 10.1% (LS) and 27.1% (HS) more than salinity‐susceptible rice. Salinity‐tolerant rice at HS maintained lower leaf Na + concentration and Na + /K + ratio, but higher shoot biomass and harvest index, post‐heading leaf SPAD value and photosynthetic rate, stem NSC content and remobilization, K + concentration in leaf, and total N, P, and K accumulation than salt‐susceptible rice. The present study indicated that salinity stress reduced rice grain yield by 34.2%–54.9%. The superior yield of salinity‐tolerant rice over salinity‐susceptible rice under HS was attributed to larger sink size and higher sink‐filling efficiency, driven by the favourable agro‐physiological traits.