Characterisation of potential microbial antagonists against brown rot disease

Abstract

It is already known that plant microbiota can not only be neutral or negatively affect the host, but also promote its growth and even protect it from various stresses, including pathogens. After noticing the benefits of microorganisms, the development of biological products that could replace mineral fertilisers and chemical plant protection products began. Nowadays, there are various studies about local beneficial microorganisms for crops and orchards, but the availability of biological products against specific pathogens is still scarce. One of the examples is brown rot disease, whose causative agent is the extremely aggressive pathogen Monilinia fructigena, which affects both pome and stone fruit orchards. To fill this gap, the microorganisms of the local plum orchard were investigated. The aim of the study was to identify the isolated plum orchard microorganisms and to describe their properties at the genetic potential level and antagonistic abilities to inhibit M. fructigena pathogen. Microorganisms were isolated from the local plum orchard rhizosphere, plum buds and fruits. Pure cultures were tested against M. fructigena. In total, 12 isolates showed antagonistic activity ranging from 56% to 90%. Whole genome-sequencing data revealed three distinct genera of bacterial organisms (Bacillus pumilus, B. velezensis, Lysinibacillus agricola, Pseudomonas chlororaphis, P. fluorescens, and P. graminis) and one genus of yeast-like fungi (Aureobasidium pullulans). KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, antibiotic resistance, pathogenicity, and secondary metabolites were predicted as related to antagonism and growth promotion. In conclusion, all 12 isolates are potential biological control strains with important application value for future development of biocontrol products in the Baltic region. The results of the study and additional experiments with fruits and field trials will help to further investigate the mechanism of all these microbial isolates in the biological control of plant diseases and promote their application.