Simultaneous inoculation with beneficial and pathogenic microorganisms modifies peanut plant responses triggered by each microorganism

Abstract

Plant signaling pathways activated by single microbial species may be modified by the presence of other microbial groups. Here, link between phenotypic changes of peanut plants co- inoculated with Bradyrhizobium sp. SEMIA6144, Bacillus sp. CHEP5 and Sclerotium rolfsii, and molecules involved in peanut responses to each microorganism was evaluated. Phenolic compounds content, peroxidase activity and AhSymRK gene expression were evaluated in plants co-inoculated and inoculated with each microorganism. Peroxidase activity, associated with peanut response to the pathogen, was induced earlier in plants co-inoculated than in those inoculated only with S. rolfsii, in coincidence with their more tolerant phenotype to this pathogen. The increase in phenolic compounds content induced by the biocontrol agent Bacillus sp. CHEP5 was affected by the co-inoculation with Bradyrhizobium sp. SEMIA6144. However, the bacterial protection against S. rolfsii remains unaltered. In co-inoculated plants, AhSymRK gene expression level was similar to plants inoculated only with the microsymbiont, in concordance with their symbiotic phenotypes. We demonstrated that responses triggered in peanut plants by single microbial species populations are modified in presence of others, highlighting the relevance to improve our understanding about plant responses to soil microbial communities.