In vitro assessment of the antagonistic potential of Bacillus spp. and Pseudomonas spp. against Xanthomonas campestris pv. campestris isolated from winter oilseed rape in Serbia

Abstract

Background: Yield and quality of oilseed rape and other Brassicacceae vegetables are affected with plant pathogenic bacterium Xanthomonas campestris pv. campestris (Xcc), both worldwide and in Serbia. Considering the losses that can arise as a consequence of the infection with this pathogen, there is an increasing need for finding the effective and environmentally safe method for its suppression. Objectives: With the aim to find a promising biological control agent for managing Xcc infection on winter oilseed rape in Serbia, this research was based on evaluation of the in vitro antagonistic potential of the Bacillus- and Pseudomonas-like isolates obtained from the phyllosphere and rhizosphere of the diseased and healthy winter oilseed rape plants. Methods: Well diffusion technique was used to evaluate the potential inhibitory activity of the whole cultures and cell-free supernatants of the 36 Bacillus- and Pseudomonas-like isolates, against the collection of Serbian winter oilseed rape Xcc isolates. DNA of the isolates which were able to inhibit Xcc growth was amplified with the primers based on the sequences of tuf and gyrB genes for Bacillus- and Pseudomonas-like isolates, respectively and sequenced. Results: Nine Bacillus spp. isolates whose whole cultures showed antagonistic potential were identified as B. thuringiensis/B. cereus (5); B. valezensis (1); B. mobilis (1); B. megaterium (1) and B. halotolerans (1), while six Pseudomonas spp. isolates were identified as P. orientalis (4) and P. fluorescens (2). Only five isolates within three species (B. valezensis, B. megaterium and P. orientalis) had both, the activity of the whole culture and supernatant.