Dynamics of soil bacterial communities modulated by two Streptomyces strains responding to disease suppression caused by Phytophthora capsici

Streptomyces isolates were screened and selected for in vitro ability to antagonize Phytophthora capsici the causal agent of blight and damping-off of pepper. SS14 and IT20 strains mitigated blight disease severity better than Ridomil®. In a second step, the responses of rhizosphere microbial communities of two Streptomyces treated-plants was investigated following pathogen inoculation. The distinct modulation of the bacteriome composition was found for P.capsici samples (PC). A higher relative abundance of Chitinophaga was observed only in PC. The relative abundance of several bacterial OTUs was affected and caused changes in alpha and beta-diversity measures between two Streptomyces treatments. In IT20, the abundance of Cyanobacteria was enriched compared to SS14 at the phylum level. Phylotypes belonging to Devosia, Gallionella, Arenimonas, Promicromonospora, and Amylocolatopsis genera were correlated with an increase in plant biomass and disease suppression. Our findings expose that the phosphate solubilizing strain IT20 has higher microbial community responders than the melanin-producing strain SS14. Also, positive interactions were identified by comparing bacterial community profiles between treatments that might allow designing synthetic bio-inoculants to solve agronomic problems in an eco-friendly way.