The consumption of high-quality rice is increasing. Low temperatures during grain filling may affect the starch synthesis of high-quality rice and thus affect the quality of the rice itself. In this study, two high-quality conventional rice cultivars and two high-quality hybrid rice cultivars were selected and sown at a low temperature and normal temperature in the field. The low temperature during grain filling increased the amylose content, final viscosity, setback, short amylopectin chain ratio, and degree of amylopectin branching in four high-quality rice cultivars; meanwhile, the amylopectin content, gelatinization temperature, proportion of medium-long chain amylopectin, and the short-range order of starch decreased. Compared with the normal temperature, the alterations in the physicochemical and structural qualities of high-quality conventional rice cultivars YZX and NX42 were less significant at lower temperatures. The starch quality of high-quality conventional rice was more stable than hybrid high-quality 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.

Rice depends on its root system to perceive drought, a major environmental constraint that leads to severe yield losses worldwide. To dissect the underlying molecular basis, we conducted a comparative analysis of drought-sensitive (WAB) and drought-tolerant (IR65) rice genotypes that exhibited divergent drought tolerance at the seedling stage. After exposure to 15% PEG6000 (−0.4 MPa) for two days, the shoot and root architectural traits of IR65 were better than those of WAB seedlings. Measurements of physio-biochemical parameters (SOD, CAT, POD, APX, H₂O₂, and proline) suggest that IR65 seedling roots exhibit greater ROS scavenging and osmotic adjustment capacity than WAB, aligning with tolerance to PEG-induced water deficiency. Transcriptomic assessments of roots identified 802 commonly differentially expressed genes (DEGs) during the drought time course (12, 24, and 48 h) in WAB and IR65. They were clustered into eight groups based on their expression profiles and mainly enriched in phytohormone signaling, protein phosphorylation, and transcription factors. Using weighted gene co-expression network analysis (WGCNA), nine significant modules were identified based on n = 382 of the DEGs. A total of 12 DEGs up-regulated in IR65 were distributed in five modules, and five of them were selected for rapid functional validation through in vivo yeast expression. The results showed that transgenic yeasts were tolerant to simulated drought conditions (135 mM PEG3350), indicating that these genes would be potential targets for rice improvement in drought tolerance in the future.