Abstract
The responses of rhizosphere bacterial communities of Streptomyces (SS14 and IT20 stains) treated-pepper plants following inoculation by Phytophthora capsici (PC) was investigated using Illumina MiSeq sequencing. Distinct modulation of the bacteriome composition was found for PC samples with the highest relative abundance (RA) of Chitinophaga (22 ± 0.03%). The RA of several bacterial operational taxonomic units (OTUs) was affected and caused changes in alpha and beta-diversity measures. In IT20, the RA of Cyanobacteria was enriched compared to SS14 (72%) and control samples (47%). Phylotypes belonging to Devosia, Promicromonospora, Kribbella, Microbacterium, Amylocolatopsis, and Pseudomonas genera in the rhizosphere were positively responding against the pathogen. Our findings show 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.
Highlights
The responses of rhizosphere bacterial communities of Streptomyces (SS14 and IT20 stains) treatedpepper plants following inoculation by Phytophthora capsici (PC) was investigated using Illumina MiSeq sequencing
The disease suppression induced by biocontrol agents is related to interactions between the plant, pathogens, biocontrol agents, the surrounding microbial community, and the e nvironment10. van Elsas et al.[11] showed that an increase in soil bacterial diversity can reduce the relative abundance of pathogens and could be an efficient tactic in controlling plant diseases
Previous studies using biocontrol agents have mainly revealed that the dynamics of soil bacterial populations played a critical role in disease suppression caused by soil-borne fungal[13,14]
Summary
The responses of rhizosphere bacterial communities of Streptomyces (SS14 and IT20 stains) treatedpepper plants following inoculation by Phytophthora capsici (PC) was investigated using Illumina MiSeq sequencing. The soil-borne oomycete pathogen, Phytophthora capsici Leonian, causes the disease of pepper and several important crops[6,7]. Some strategies such as chemical treatment (Ridomil) and biological control have been endorsed to disease management[8,9]. The studies on Phytophthora blight disease suppression affecting pepper were conducted on the characterization and identification of native plant growth-promoting soil bacterial genera such as Bacillus and Pseudomonas and their antagonistic potential. We investigated the hypothesis that P solubilizing or melanin producing strain might boost the soil biodiversity, lead to changes in the abundance of indigenous microbial communities of the rhizosphere and distinctly suppress disease caused by P. capsici
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