Evaluation of bacterial antagonists of Ralstonia solanacearum, causal agent of bacterial wilt of potato

Bacterial wilt of potato caused by Ralstonia solanacearum is one of the most destructive diseases in Kurdistan province, Iran. The objective of the present study was to evaluate antagonistic effects of some rhizobacteria isolated from the rhizosphere of potato plants against R. solanacearum, the agent of potato bacterial wilt. A total of 52 rhizobacteria were isolated and screened for in vitro antagonistic activity against R. solanacearum. Seven isolates with inhibiting effects of the pathogen were identified by phenotypic properties and partial sequencing of 16s rRNA as Pseudomonas fluorescens Pf11, P. fluorescens Pf16, Pseudomonas putida Pp17, Paenibacillus sp. Pb28 and Enterobacter sp. En38, Pseudomonas fluorescens Pp23 and Serratia sp. Se40. Strains Pf11, Pf16, Pp17 and Pb28 significantly inhibited the growth of the pathogen. Strains En38, Pp23 and Se40 showed a moderate or weak inhibition. During greenhouse study, strains were evaluated for their effects in reducing of disease and increasing biomass of potato plants. In according to greenhouse experiment results, isolates Pb28, Pp17 and Pf11 significantly reduced disease by 55.56%, 51.50% and 38.58%, respectively. In addition, plant biomass significantly increased in plants treated with Pb28, Pp17, Pf11 and Pf16, compared to the control. Therefore, this study shows that these four strains have potential to be used as biocontrol agents against R. solanacearum. To confirm their effectiveness as commercial biocontrol agent, it is necessary to evaluate their efficiency in the field conditions in the next studies. (C) 2015 Elsevier Inc. All rights reserved.