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Potato is ranked as one of the most important food crops. Bacterial wilt caused by Ralstonia solanacearum and blackleg and soft rot caused by different species from genera Pectobacterium and Dickeya are considered two of the most important diseases of the potato. Biological control is the optimal strategy for controlling pathogens in crops generally, including bacteria. The present study aimed to evaluate the antagonistic effects of two Bacillus amyloliquefaciens strains, SS-12.6 and SS-38.4, against bacterial pathogens isolated from the potato in Serbia, such as R. solanacearum, Pectobacterium carotovorum, Pectobacterium brasiliense, and Dickeya dianthicola. The diameter of the inhibition zones formed by ethyl-acetate extracts of SS-12.6 and SS-38.4 strains show much higher values than the inhibition zones of supernatants, which implies the main power of these antagonists’ potential lies in lipopeptides. The effectiveness of the treatment (19.7–44.5%), based on the difference in weight of potato tubers on the fifth and 15th day after treatment (DAT), showed that the antagonistic strains were almost equally effective in the suppression of P. carotovorum, P. brasiliense, and D. dianthicola strains. Strains SS-12.6 and SS-38.4 exhibited the efficacy in the suppression of R. solanacearum wilt from 28.64 to 60.22%. The analysis of the area under the disease progress (AUDPC) confirmed differences among pathogen control treatments and biocontrol treatments with B. amyloliquefaciens strains in all trials. This study shows that the two B. amyloliquefaciens strains, SS-12.6 and SS-38.4, can potentially be used as biocontrol agents against potato pathogens.

Plant pathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) was recently described as a pathogen of winter oilseed rape in Serbia. A metabarcoding approach was used to study bacterial community composition changes in the phyllosphere and rhizosphere of different winter oilseed rape types (lines, cultivars, and hybrids) naturally infected with Xcc. This study also aimed to examine the potential of indigenous Bacillus and Pseudomonas isolates to suppress Xcc. Infection with Xcc leads to depletion of bacterial diversity in the plants' phyllosphere and explicitly decreasing the abundance of genera such as Exiguobacterium, Massilia, and Pantoea with potentially beneficial properties. Strains identified as Bacillus velezensis X5-2, Bacillus megaterium X6-3, and Pseudomonas orientalis X2-1P obtained from oilseed rape phyllosphere were found to be effective against Xcc in vitro and in vivo when applied as a whole-culture and as a cell-free supernatant. The greenhouse in vivo tests on winter oilseed rape plants with three selected biocontrol strains lead to a disease reduction of 82.37% and 72.47% in preventive and curative treatments, respectively. Genetic screening showed potential for the biosynthesis of surfactin, kurstakin, bacillomycin D, and iturin in B. velezensis X5-2, as well as surfactin and kurstakin in B. megaterium X6-3. Gene phcA encoding phenazine-1-carboxylic acid was detected in P. orientalis X2-1P. The chemical composition of ethyl acetate and benzene extracts of three biocontrol strains obtained by GC–MS and HPLC-ESI-qTOF/MS analyses indicates numerous volatile organic compounds (alkenes, benzenes, carboxylic acids, indoles, pyrazines, etc.), lipopeptides, and/or antibiotics, for many of which antimicrobial potential is proven. We assume that this wide range of metabolites is responsible for the exhibited biocontrol activity against Xcc. These results recommend all three biocontrol strains for further studies for use as agents for biocontrol of

Two strains of Bacillus sp., SS-12.6 and SS-13.1, showed very strong antibacterial and antifungal activity against phytopathogens. The PCR analysis showed that both strains have the genes for biosynthesis of iturin, bacillomycin and surfactin. Kinetics of production of antimicrobial substances in these strains showed that synthesis started at the beginning of exponential phase of growth. Maximum of activity was slowly reached at the beginning of stationary growth phase and was maintained until the end of observed period. Ethyl acetate extracts of cell-free supernatants of both strains were particularly active against several postharvest fungal pathogens, in vitro and in vivo, in the experiment with apple fruits. Mass spectrometry analysis of ethyl acetate extract of the supernatant of strain SS-12.6 confirmed the presence of antimicrobial lipopeptide surfactin. (c) 2013 Elsevier Inc. All rights reserved.