Pantoea jilinensis D25 enhances tomato salt tolerance via altering antioxidant responses and soil microbial community structure.

As a major challenge to global food security, soil salinity is an important abiotic stress factor that seriously affects the crop growth and yield. In this study, the mechanism of salt resistance of Pantoea jilinensis D25 and its improving effect on salt tolerance of tomato were explored with salt resistance-related genes identified in strain D25 by genomic sequencing. The results showed that in comparison with the treatment of NaCl, strain D25 significantly increased the fresh weight, shoot length, root length, and chlorophyll content of tomato under salt stress by 46.7%, 20%, 42.4%, and 44.2%, respectively, with increased absorptions of various macronutrients and micronutrients and decreased accumulation of Na+. The activities of defense enzymes (peroxidase, catalase, superoxide dismutase, phenylalanine ammonia-lyase, and polyphenol oxidase) were enhanced, while the content of malondialdehyde was decreased. The results of quantitative real-time PCR analysis showed that the expressions of genes (SlSOS1, SlNHX1, SlHKT1.1, SlSOD1, SlAPX2, SlAOS, SlPin II, Solyc08g066270.1, Solyc03g083420.2 and SlGA20ox1) related to ion transporters, antioxidant machinery, key defense, serine/threonine protein kinase synthesis, and gibberellin (GA) signal protein were up-regulated and were the highest in the treatment of both NaCl and strain D25. The activities of enzymes (dehydrogenase, urease, invertase, and catalase activities) related to soil fertility were enhanced. The results of 16S rRNA sequencing showed that soil microbial diversity and the abundance of probiotics (e.g., Acidibacter, Limnobacter, and Romboutsia) were significantly increased. Our study provided strong experimental evidence to support the agricultural application of strain D25 in the promotion of growth in crops.