Salinity is a serious limiting factor for the growth of rhizobia. Some rhizobia are tolerant to salt stress and promote plant growth, but the mechanisms underlying these effects are poorly characterized. The growth responses and osmoprotectants in four Bradyrhizobium strains were examined under salt stress in this study. Two-dimensional electrophoresis (2-DE) and mass spectrometry were conducted to investigate protein profiles in rhizobia exposed to salt stress. Subsequently, salt tolerance in stylo (Stylosanthes guianensis) inoculated with rhizobia was further detected in hydroponics. Results showed that the Bradyrhizobium strain RJS9-2 exhibited higher salt tolerance than the other three Bradyrhizobium strains. RJS9-2 was able to grow at 0.35 M NaCl treatment, while the other three Bradyrhizobium strains did not grow at 0.1 M NaCl treatment. Salt stress induced IAA production, and accumulation of proline, betaine, ectoine, and trehalose was observed in RJS9-2 but not in PN13-1. Proteomics analysis identified 14 proteins regulated by salt stress in RJS9-2 that were mainly related to the ABC transporter, stress response, and protein metabolism. Furthermore, under saline conditions, the nodule number, plant dry weight, and N concentration in stylo plants inoculated with RJS9-2 were higher than those in plants inoculated with PN13-1. These results suggest that the tolerance of RJS9-2 to salt stress may be achieved by the coordination of indole-3-acetic acid (IAA) production, osmoprotectant accumulation, and protein expression, thus promoting stylo growth.

As consumer awareness regarding health and nutrition continues to increase, there is a growing demand for fresh, nutritious fruits such as green grapes. However, the short storage life and susceptibility of these fruits to spoilage lead to significant commercial losses. Currently, the plastic wrap method is commonly used to keep green grapes fresh, but this packaging effect is limited and not environmentally friendly. Therefore, there is an urgent need to explore sustainable and effective preservation methods. In this study, a high-pressure microfluidization technique was employed to prepare an essential oil nanoemulsion with a ratio of Tween 80 to clove essential oil of 1:1, and a biopolymer-based film solution was prepared using dual-modified tapioca starch and chitosan loaded with clove essential oil nanoemulsion. The dual-modified tapioca starch/chitosan/SiO₂/1.25 wt % clove essential oil (DM/Ceo-1.25) solution coating was successfully applied for the packaging and preservation of fresh green grapes. Compared with the CK and polyethylene wrap (PE) groups, the DM/Ceo-1.25 coating significantly improved the quality of the green grapes, increasing the storage period of the green grapes from 4 to 8 days at room temperature. On the 10th day of storage, the coated grapes retained significantly better quality, with a hardness of 4.01 N, a titratable acidity of 1.625%, an anthocyanin content of 1.013 mg/kg, and a polyphenol content of 21.32 μg/mL. These results indicate that the DM/Ceo-1.25 solution coating developed in this study can be used as a new active material for fruit preservation and provides ideas for the development of safer and more sustainable food packaging.