Drought is a severe abiotic stress that imposes a serious threat to rice productivity. Although previous studies have found that melatonin can promote seed germination, the physiological regulation mechanism of drought tolerance in rice seed germination mediated by exogenous melatonin is still unclear. In order to overcome these challenges, polyethylene glycol 6000 (PEG6000) at concentrations of 20% and 35% was used to simulate osmotic stress. Rice seeds were treated with different concentrations of melatonin (i.e., 0, 20, 100, and 500 μM) to study the effects on germination characteristics, growth and development, superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, malondialdehyde (MDA) content, and soluble protein content. The results showed that the seed soaking treatment using melatonin at a concentration of 100 μM under drought stress effectively promoted the germination rate and improved the biomass of rice seed shoots and roots. Meanwhile, this treatment reduced MDA content to alleviate the oxidative damage of rice seeds caused by drought stress. The two-way ANOVA showed that the effect of single melatonin soaking treatment on rice seed germination was more significant than that of single drought stress and the interaction of drought stress and melatonin (p < 0.05). Using the membership function method, it was shown that the critical gradient of rice seeds under drought stress was 35%, and the critical treatment of interactive treatment was 35% + 100 μM. Through grey correlation analysis, it was found that germination rate (7 d) had the highest grey correlation with melatonin seed soaking treatment to evaluate the mitigation effect of melatonin on drought stress. This study provides a theoretical basis for light and simple cultivation technology for the dry direct seeding of rice.

Rice noodles are one of southern people’s favorite foods in China, so it is important to find the suitable raw rice for rice noodle making. To study the effects of different rice varieties on the quality of fresh wet rice noodles and to explore the relationship between the quality of the rice and the quality of the fresh wet rice noodles, this study to compare the 12 hybrid rice varieties as raw materials analyzed the differences in the cooking quality, texture index, and sensory score of fresh wet rice noodles using the principal component analysis, membership function, and cluster analysis. The results showed that the quality of fresh wet rice noodles prepared from different hybrid rice materials differed significantly. The fresh wet rice noodles made from Liangyou 5836 are of good quality, and they are mainly characterized by a low rate of broken noodles and spit pulp value, high rice noodle hardness, good rice noodle elasticity, strong rice noodle chewiness, and low adhesiveness. Moreover, its sensory evaluation is also better than that of other varieties. The comprehensive evaluation of 12 hybrid rice varieties by subordinate function analysis also showed that Liangyou 5836 was the best. In addition, through principal component analysis and gray analysis, it was found that 14 related indicators of rice quality and fresh wet rice noodle quality were concentrated into four categories, among which gel consistency best reflects the quality of rice and fresh wet rice noodles. Through comprehensive analysis, it was found that an amylose content of about 22% and a gel consistency of less than 40 mm can be used as core indicators to screen varieties suitable for making rice noodles. This study is of great significance for the selection of hybrid rice for both rice quality and fresh wet rice noodle quality.

This study compared the decomposition effects of different microbial agents added to rice straw to screen for efficient and stable microbial agents and achieve effective utilization of rice straw resources. Different microbial agents can accelerate the decomposition of rice straw. The E4/E6 value of rice straw added with the Bacillus subtilis agent was significantly lower than that of rice straw added with other microbial agents on the 30th day. The lignin degradation rates for the Bacillus subtilis agent and Trichoderma viride agent treatments were higher than those of the other treatments from the 5th to 30th days. After adding the Bacillus subtilis agent for 30 days, the degradation rates of hemicellulose and cellulose in rice straw were higher than others, reaching 33.62% and 41.31%, respectively. Through principal component analysis and grey relational analysis, it was determined that the C/N ratio, organic carbon, E4/E6 value, conductivity value, and pH value are important evaluation indicators for the maturity promotion effect. Using the membership function analysis method, it was found that the Bacillus subtilis agent had the best overall performance in straw decomposition. This research provides a new viewpoint for the efficient utilization of straw resources.

Rice straw contains a large amount of lignocellulose which is difficult to be decomposed. The objective of this study was to determine the effect of alkaline pretreatment (sodium hydroxide, NaOH) and microbial agents on the decomposition of rice straw. The experimental detail consisted of NaOH (control and NaOH solution pretreatment) and microbial agent (Bacillus licheniformis agent, Bacillus subtilis agent, Trichoderma viride agent, and no microbial agent) treatments. Compared with no NaOH pretreatment, the pH of NaOH pretreatment increased by 6.30–18.28%, while the electrical conductivity decreased by 49.18%, but the change in total nutrient content was not obvious. Under no NaOH pretreatment, Bacillus subtilis agent improved the temperature of the rice straw decomposition. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in rice straw by 1.39–10.30%. The organic carbon content was reduced by 3.50% and 17.15%. The germination index was greater than 80%. Under NaOH pretreatment, the pile with Bacillus subtilis agent reached the maximum temperature (39.5 °C) on the 12th day. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the content of alkali-hydrolyzable nitrogen and available phosphorus in rice straw by 1.64–11.87%. The humus polymerization, organic carbon, and carbon/nitrogen ratio were reduced by 6.40–44.06%. In addition, gray analysis, principal component analysis, and comprehensive evaluation were used to comprehensively evaluate the effect of straw decomposition. The results showed that Bacillus subtilis agent under NaOH pretreatment and no NaOH pretreatment had the most obvious effect on rice straw composting. This study provides a scientific basis for efficient decomposition of rice straw.

The lodging resistance of rice is a prerequisite for ensuring yield and rice quality. An in-depth analysis of key traits affecting rice lodging resistance is crucial for guiding the cultivation of excellent rice varieties and field production. Given consumer demand for high-quality rice and frequent extreme weather conditions, this study focused on six high-quality conventional rice varieties and compared the main stem internode physical traits, stem and sheath plumpness traits, main stem mechanical properties, yield-related traits, and panicle characteristics of the plants based on field phenotype measurements. Among them, three varieties showed lodging resistance in the field, while the other three varieties all experienced varying degrees of lodging susceptibility. The results showed that lodging-resistant varieties exhibited a more reasonable internode structure, lower plant height, gravity center height, and relative gravity center height, as well as shorter and thicker second internodes (N2). Additionally, they had higher sheath phimosis degree, greater bending stress, internode-breaking moment, and plant-breaking moment, along with a lower lodging index compared to lodging-susceptible varieties. Specifically, lodging-resistant varieties had 0.83–9.61% lower plant height, 4.11–16.10% lower gravity center height, and 0.09–12.68% lower relative gravity center height than those of lodging-susceptible varieties. Their N2 internode length was 8.96–44.69% shorter, while stem and sheath weight ratios were 16.37–268.58% and 8.27–165.01% higher than those of lodging-susceptible varieties, respectively. At the same time, lodging-resistant varieties exhibit the ability to stabilize yield while reducing their own risk of lodging by increasing effective panicles and reducing single panicle weight. In addition, NX42, LD3, and SY17 were ultimately evaluated as low-risk lodging varieties in this study. This study aims to address the lodging problem of high-quality conventional rice and analyze the key mechanisms underlying its lodging resistance. The research provides important theoretical support for genetic improvement of high-quality conventional rice.