Rice yield and grain quality are highly sensitive to salinity stress. Salt-tolerant/susceptible rice cultivars respond to salinity differently. To explore the variation in grain yield and quality to moderate/severe salinity stress, five rice cultivars differing in degrees of salt tolerance, including three salt-tolerant rice cultivars (Lianjian 5, Lianjian 6, and Lianjian 7) and two salt-susceptible rice cultivars (Wuyunjing 30 and Lianjing 7) were examined. Grain yield was significantly decreased under salinity stress, while the extent of yield loss was lesser in salt-tolerant rice cultivars due to the relatively higher grain filling ratio and grain weight. The milling quality continued to increase with increasing levels. There were genotypic differences in the responses of appearance quality to mild salinity. The appearance quality was first increased and then decreased with increasing levels of salinity stress in salt-tolerant rice but continued to decrease in salt-susceptible rice. Under severe salinity stress, the protein accumulation was increased and the starch content was decreased; the content of short branched-chain of amylopectin was decreased; the crystallinity and stability of the starch were increased, and the gelatinization temperature was increased. These changes resulted in the deterioration of cooking and eating quality of rice under severe salinity-stressed environments. However, salt-tolerant and salt-susceptible rice cultivars responded differently to moderate salinity stress in cooking and eating quality and in the physicochemical properties of the starch. For salt-tolerant rice cultivars, the chain length of amylopectin was decreased, the degrees of order of the starch structure were decreased, and pasting properties and thermal properties were increased significantly, whereas for salt-susceptible rice cultivars, cooking and eating quality was deteriorated under moderate salinity stress. In conclusion, the selection of salt-tolerant rice cultivars can effectively maintain the rice production at a relatively high level while simultaneously enhancing grain quality in moderate salinity-stressed environments. Our results demonstrate specific salinity responses among the rice genotypes and the planting of salt-tolerant rice under moderate soil salinity is a solution to ensure rice production in China.

An essential feature of modern high‐yielding rice varieties is the production of numerous spikelets, but the physiological mechanism underlying spikelet formation in these varieties remains unclear. In this study, we explored the characteristics of spikelet differentiation and degeneration and the relevant physiological characteristics of rice varieties with different panicle sizes. The regulatory effects of alternate wetting and moderate soil drying (AWMD) on spikelet formation were also measured. We determined that the high spikelet number per panicle and grain yields of large‐panicle rice varieties were primarily due to a higher number of differentiated and surviving secondary spikelets. Furthermore, shoot dry weight, plant nitrogen (N) uptake, plant N concentration, non‐structural carbohydrate (NSC) accumulation in stems, leaf area, and leaf photosynthetic rate from branch differentiation stage (BDS) to spikelet differentiation stage (SDS) were positively correlated with the number of differentiated secondary spikelets per panicle. Plant N concentration, NSC accumulation in stems, and leaf photosynthetic rate at pollen mother cell meiosis (PMC) were negatively correlated with the number of degenerated secondary spikelets. Finally, the number of differentiated secondary spikelets of Huaidao 5 (small panicle size) and Yongyou 2640 (large panicle size) varieties was promoted by 19.2% and 6.6%, and the number of degenerated secondary spikelets was reduced by 14.4% and 6.3%, respectively, under AWMD treatment compared to continuously flooded treatment. Prominent spikelet formation under AWMD resulted from the shoot dry weight, plant N uptake, plant N concentration, NSC accumulation in stems, leaf area, and leaf photosynthetic rate. Collectively, improvements in these key aboveground indices mentioned above during the BDS to SDS and the plant N concentration, NSC accumulation in stems, and leaf photosynthetic rate at the PMC stage would benefit spikelet formation by promoting differentiation and reducing degeneration of secondary spikelets, thereby enhancing yield of large‐panicle rice varieties.

In recent days, there has been a noticeable surge in demand for high-quality rice. However, the influences of salinity on the quality and starch properties of high-quality rice remain unclear. Three high-quality rice cultivars (Nanjing 9108, Nanjing 5055, and Nanjing 46) were studied to investigate the responses of grain quality to salt stress. There were three treatments, including a control zero salt level (0 g·kg⁻¹, CK), and two salt levels of 0.1 g·kg⁻¹ (0.1% salt stress, T1) and 0.2 g·kg⁻¹ (0.2% salt stress, T2). The study involved the assessment of the appearance, milling, cooking, and eating qualities of rice. We also conducted an analysis of pasting properties, an evaluation of starch thermal properties, and an examination of the fine structure of amylopectin. The findings suggest that as the level of salt stress increases, the yield of rice gradually declines, which is primarily due to a significant reduction in the total spikelet number and the ratio of filled grains. Compared with CK treatment, the appearance and milling quality of rice were significantly improved within the T1 treatment. In addition, the protein concentration and amylose concentration were significantly decreased, the gel consistency was significantly increased, and the cooking and eating qualities were improved. In terms of starch properties, the peak viscosity, breakdown value, infrared ratio (1022/995), and short-chain-length amylopectin ratio increased significantly, while the setback value, pasting temperature, gelatinization enthalpy, relative crystallinity, and infrared ratio (1045/1022) decreased significantly. When comparing T2 with CK, the appearance quality and cooking and eating quality had deteriorated, and the milling quality was improved. The changes in the structural and physicochemical properties of starch were opposite to those in the comparison between the T1 treatment and the CK group. Accordingly, we propose that moderate salt stress has the potential to enhance rice quality, even though there may be a slight decrease in yield. This indicates that it is feasible to cultivate high-quality rice in saline–alkali beach areas.