Salt stress in the rice field is one of the most common abiotic stresses, reducing crop productivity, especially at reproductive stage, which is very sensitive to salt stress. The aim of this investigation was to study mRNA-related Na+ uptake/translocation and Na+ enrichment in the cellular level, leading to physiological changes, growth characteristics, and yield attributes in FL530 [salt-tolerant genotype; carrying SKC1 (in relation to high-affinity potassium transporters controlling Na+ and K+ translocation) and qSt1b (linking to salt injury score) QTLs] and KDML105 (salt-sensitive cultivar; lacking both QTLs) parental lines and 221–48 (carrying SKC1 and qSt1b QTLs) derived from BILs (backcross introgression lines) at 50% flowering of rice, under 150-mM NaCl until harvesting process. The upregulation of OsHKT1;5 (mediating Na+ exclusion into xylem parenchyma cells) and OsNHX1 (Na+/H+ exchanger to secrete Na+ into vacuole) and downregulation of OsHKT2;1 and OsHKT2;2 (mediating Na+ restriction in the roots, leaf sheath and older leaves) in cvs. FL530 and 221–48 (+ SKC1; + qSt1b) under salt stress were observed. It restricted Na+ level in flag leaf, thereby preventing salt toxicity, as indicated by maintenance of photon yield of PSII (ΦPSII), net photosynthetic rate (Pn), transpiration rate (E) and overall growth performances. In contrast, Na+ enrichment in flag leaf of cv. KDML105 (−SKC1;−qSt1b) caused the reduction in ΦPSII by 30.5% over the control, leading to the reduction in Pn by 62.3%, in seed sterility by 88.2%, and yield loss by 85.1%. Moreover, the negative relationships between Na+ enrichment in flag leaf, physiological changes, and yield traits in rice crop grown under salt stress were demonstrated. Based on this investigation, rice genotype 221–48 was found to possess salt-tolerant traits at reproductive stage and thus could prove to be a potential candidate for future breeding programs.

中文翻译：

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盐胁迫下水稻回交基因渗入系Na+稳态相关基因的表达水平及耐盐能力

稻田中的盐胁迫是最常见的非生物胁迫之一，会降低作物生产力，尤其是在对盐胁迫非常敏感的生殖阶段。本研究的目的是在细胞水平上研究 mRNA 相关的 Na+ 摄取/易位和 Na+ 富集，从而导致 FL530 [耐盐基因型；携带 SKC1（与控制 Na+ 和 K+ 易位的高亲和力钾转运蛋白有关）和 qSt1b（与盐损伤评分相关）QTL] 和 KDML105（盐敏感品种；缺乏两个 QTL）亲本系和 221-48（携带 SKC1 和qSt1b QTL）源自 BIL（回交基因渗入系），水稻开花 50%，在 150 mM NaCl 下直至收获过程。OsHKT1 的上调；5（介导 Na+ 排除进入木质部薄壁组织细胞）和 OsNHX1（Na+/H+ 交换器将 Na+ 分泌到液泡中）以及下调 OsHKT2;1 和 OsHKT2;2（介导根、叶鞘和老叶中的 Na+ 限制）。观察到盐胁迫下的 FL530 和 221-48 (+ SKC1; + qSt1b)。它限制了旗叶中的 Na+ 水平，从而防止了盐毒，如维持 PSII 的光子产量 (ΦPSII)、净光合速率 (Pn)、蒸腾速率 (E) 和整体生长性能所表明的。相比之下， cv. 旗叶中的 Na+ 富集。KDML105 (-SKC1;-qSt1b) 导致 ΦPSII 比对照减少 30.5%，导致 Pn 减少 62.3%，种子不育减少 88.2%，产量损失 85.1%。此外，旗叶中Na+富集与生理变化、并证明了在盐胁迫下生长的水稻作物的产量性状。基于这项调查，发现水稻基因型 221-48 在生殖阶段具有耐盐性状，因此可以证明是未来育种计划的潜在候选者。