A halotolerant growth promoting rhizobacteria triggers induced systemic resistance in plants and defends against fungal infection.

A halotolerant rhizobacteria, Klebsiella species (referred to MBE02), was identified that had a growth stimulation effect on peanut. To gain mechanistic insights into how molecular components were reprogrammed during the interaction of MBE02 and peanut roots, we performed deep RNA-sequencing. In total, 1260 genes were differentially expressed: 979 genes were up-regulated, whereas 281 were down-regulated by MBE02 treatment as compared to uninoculated controls. A large component of the differentially regulated genes were related to phytohormone signalling. This included activation of a significant proportion of genes involved in jasmonic acid, ethylene and pathogen-defense signalling, which indicated a role of MBE02 in modulating plant immunity. In vivo and in vitro pathogenesis assays demonstrated that MBE02 treatment indeed provide fitness benefits to peanut against Aspergillus infection under controlled as well as field environment. Further, MBE02 directly reduced the growth of a wide range of fungal pathogens including Aspergillus. We also identified possible molecular components involved in rhizobacteria-mediated plant protection. Our results show the potential of MBE02 as a biocontrol agent in preventing infection against several fungal phytopathogens.