Hybrid rice typically surpasses conventional rice in terms of biomass, yield, and stress resistance, whereas developing and utilizing saline–alkali-tolerant hybrid rice is crucial to obtain crop harvests from salt-affected soils. In the present study, conventional rice varieties (paternal parents), i.e., Hua-Zhan and 9311, and four hybrid varieties, i.e., Xiang-Liang-You-Hua-Zhan, Jing-Liang-You-Hua-Zhan, Guang-8-You-Hua-Zhan, and Y-Liang-You-1-Hao, denoted as V1, V2, V3, V4, V5, and V6, respectively, received an application of two salt levels, i.e., 0% and 0.3% saltwater irrigation, during 2022–2023. The results reveal that the V1 (parental parent) had the highest salt tolerance index, which was significantly greater than that of its hybrid rice varieties, i.e., V3, V4, and V5. Moreover, the salt tolerance index of V2 (paternal parent) was also greater than that of its hybrid rice (V6). The lower salt tolerance index of the hybrid varieties might be owing to the lower relative loss number of effective panicles, total number of grains per panicle, seed setting rate, and thousand-grain weight. Moreover, our study revealed that the appearance of different rice varieties was enhanced at a salt concentration of 0.3%. Among all the rice cultivars, the largest reductions in chalkiness and chalky grain rate were observed in hybrid rice V3, i.e., 81.13% and 63.49%, as well as V6, i.e., 84.03% and 87.53%, respectively. The protein and sodium contents and sodium-potassium ratio of all the rice cultivars increased significantly under salt stress; however, no significant effect on cooking or sensory quality were noticed in all rice varieties under saline conditions. Overall, salt stress negatively affected the grain yield and quality, but hybrid rice is more salt-tolerant than conventional rice, harnessing heterosis to improve the yield of saline-tolerant rice.

Soil salinization is one of the most important abiotic stresses which can seriously affect the growth and development of rice, leading to the decrease in or even loss of a rice harvest. Increasing the rice yield of saline soil is a key issue for agricultural production. The utilization of heterosis could significantly increase crop biomass and yield, which might be an effective way to meet the demand for rice cultivation in saline soil. In this study, to elucidate the regulatory mechanisms of rice hybrids and their parents that respond to salt stress, we investigated the phenotypic characteristics, physiological and biochemical indexes, and expression level of salt-related genes at the seedling stage. In this study, two sets of materials, encapsulating the most significant differences between the rice hybrids and their parents, were screened using the salt damage index and a hybrid superiority analysis. Compared with their parents, the rice hybrids Guang-Ba-You-Hua-Zhan (BB1) and Y-Liang-You-900 (GD1) exhibited much better salt tolerance, including an increased fresh weight and higher survival rate, a better scavenging ability towards reactive oxygen species (ROS), better ionic homeostasis with lower content of Na⁺ in their Na⁺/K⁺ ratio, and a higher expression of salt-stress-responsive genes. These results indicated that rice hybrids developed complex regulatory mechanisms involving multiple pathways and genes to adapt to salt stress and provided a physiological basis for the utilization of heterosis for improving the yield of rice under salt stress.