Induced Systemic Resistance in the Bacillus spp.—Capsicum chinense Jacq.—PepGMV Interaction, Elicited by Defense-Related Gene Expression

Abstract

Induced systemic resistance (ISR) is a mechanism involved in the plant defense response against pathogens. Certain members of the <i>Bacillus</i> genus are able to promote the ISR by maintaining a healthy photosynthetic apparatus, which prepares the plant for future stress situations. The goal of the present study was to analyze the effect of the inoculation of <i>Bacillus</i> on the expression of genes involved in plant responses to pathogens, as a part of the ISR, during the interaction of <i>Capsicum chinense</i> infected with PepGMV. The effects of the inoculation of the <i>Bacillus</i> strains in pepper plants infected with PepGMV were evaluated by observing the accumulation of viral DNA and the visible symptoms of pepper plants during a time-course experiment in greenhouse and in in vitro experiments. The relative expression of the defense genes <i>CcNPR1</i>, <i>CcPR10</i>, and <i>CcCOI1</i> were also evaluated. The results showed that the plants inoculated with <i>Bacillus subtilis</i> K47, <i>Bacillus cereus</i> K46, and <i>Bacillus</i> sp. M9 had a reduction in the PepGMV viral titer, and the symptoms in these plants were less severe compared to the plants infected with PepGMV and non-inoculated with <i>Bacillus</i>. Additionally, an increase in the transcript levels of <i>CcNPR1</i>, <i>CcPR10</i>, and <i>CcCOI1</i> was observed in plants inoculated with <i>Bacillus</i> strains. Our results suggest that the inoculation of <i>Bacillus</i> strains interferes with the viral replication, through the increase in the transcription of pathogenesis-related genes, which is reflected in a lowered plant symptomatology and an improved yield in the greenhouse, regardless of PepGMV infection status.