Pantoea jilinensis D25 promotes tomato growth and induces resistance to tomato gray mold (causative agent Botrytis cinerea)

Pantoea jilinensis D25, a strain isolated from tomato rhizosphere soil, was used to treat tomato gray mold. To elucidate the mechanisms behind strain D25's antifungal and growth-promoting effects, we assessed its performance both in vitro and in vivo. The results showed that strain D25 exhibited the ability to solubilize phosphorus and potassium and fix nitrogen. Moreover, the application of strain D25 significantly enhanced various growth parameters of tomato plants, including plant height, root length, fresh and dry weights, and total chlorophyll content. Specifically, plant height increased by 22.83 %, root length by 33.76 %, fresh weight by 77.75 %, dry weight by 52.36 %, and total chlorophyll content by 26.76 %. Upon application of strain D25, the activities of biocontrol-related soil enzymes were enhanced. Furthermore, strain D25 successfully colonized both tomato roots and soil. Notably, it exhibited substantial efficacy in preventing tomato plants from Botrytis cinerea, as evidenced by a 77.95 % reduction in the lesion area on tomato leaves after 5 days of inoculation. Root and soil colonization by P. jilinensis D25 likely explains the observed plant growth-promoting effects, which were evident in vitro and in vivo. The reduction in disease symptoms appears to be primarily driven by the induction of defense-related gene expression. Through enzyme activity assays and quantitative real-time fluorescence PCR (qRT-PCR), strain D25 was found to promote the activities of defense-related enzymes while decreasing malondialdehyde levels. In addition, strain D25 exhibited a preventive effect against tomato gray mold by enhancing the expression of systemically acquired resistance-related genes, including SIPR-a, SIPR3, SlPAL5, SlEIN2, SlMYC-2, and SlPDF1.2. Notably, the expression of SlEIN2 was significantly up-regulated, indicating activation of the ethylene signaling pathway. Therefore, strain D25 could be used as a biocontrol agent and has great potential to control tomato gray mold.