Synergistic Alleviation of Saline-Alkali Stress and Enhancement of Selenium Nutrition in Rice by ACC (1-Aminocyclopropane-1-Carboxylate) Deaminase-Producing and Biogenically Synthesized Nano-Selenium.

Soil salinization and selenium (Se) deficiency threaten global food security. This study developed a composite bioinoculant combining ACC deaminase-producing and biogenically synthesized nano-selenium (SeNPs) to alleviate saline-alkali stress and enhance Se nutrition in rice ( L.). A strain of with high ACC deaminase activity was isolated and used to biosynthesize SeNPs with stable physicochemical properties. Pot experiments showed that application of the composite inoculant (S3: + 40 mmol/L SeNPs) significantly improved seedling biomass (fresh weight +53.8%, dry weight +60.6%), plant height (+31.6%), and root activity under saline-alkali conditions. S3 treatment also enhanced panicle weight, seed-setting rate, and grain Se content (234.13 μg/kg), meeting national Se-enriched rice standards. Moreover, it increased rhizosphere soil N, P, and K availability and improved microbial α-diversity. This is the first comprehensive demonstration that a synergistic bioformulation of ACC deaminase PGPR and biogenic SeNPs effectively mitigates saline-alkali stress, enhances soil fertility, and enables safe Se biofortification in rice.