Mitigation of bacterial spot disease of pepper (Capsicum annuum L.) using diseased plant-recruited microorganisms to modulate the rhizosphere microbiota

Plants and their rhizosphere microbial communities actively interact with each other to create optimal growth and defense conditions. It is known that when a plant becomes diseased, the plant secretes various metabolites or signaling substances that can attract protective beneficial or helpful microorganisms from the surrounding soil as a response. This is the basis of the 'cry for help' hypothesis, which proposes that stressed roots emit distress signals that recruit beneficial microbes able to mitigate the stress. Here we hypothesized that the bacterial diseased pepper plants might harbour some rhizosphere microorganisms which could be distinctively different from the healthy pepper plants. In this study, we investigated the structural shifts in the pepper ( Capsicum annuum L.) rhizosphere microbiota following infection by the spot disease pathogen Xanthomonas euvesicatoria . Through microbial community analyses, we identified specific bacterial taxa such as Rhodanobacter and Arachidicoccus that appeared to influence or contribute to community differentiation. To validate the protective roles of these recruited microbes, we applied the selected strains as targeted inoculants together with known plant growth-promoting bacteria (PGPB). Microbial treatments, particularly the single-strain Rhodanobacter treatment (T2) and a four-strain consortium (T4), significantly reduced the proportion of diseased leaves by 72%. Furthermore, microbiome analysis of the treated rhizosphere showed a partial recovery of Mucilaginibacter , an indicator of plant health that had been depleted under disease conditions. This study suggests that the pepper plant actively recruits beneficial rhizosphere microbes in response to X. euvesicatoria infection to support its immunity. Utilizing the plant-recruited microorganisms provides a sustainable and targeted biocontrol approach that both inhibits pathogen proliferation and reestablishes ecological balance in the rhizosphere. This microbiome-informed approach presents an environment-friendly alternative to conventional chemical pesticides in managing pepper bacterial spot disease.