Isolation and identification of endophytic bacteria from potato tissues and their effects as biological control agents against bacterial wilt

Abstract

Ralstonia solanacearum, as a causative agent of potato wilt disease, is one of the deadliest diseases worldwide, and also in the Kurdistan province, Iran. Given the importance of the disease, the aim of the present study was to isolate endophytic bacteria from potato plant tissues such as the tuber, root, stem, and leaf, to investigate their antagonistic effects on R. solanacearum. In this regard, 236 endophytic bacteria were isolated and screened in vitro. As a result, 31 isolates were found as potential antagonists against potato wilt pathogen. For phenotypic and genotypic characterization, biochemical and pathogenicity tests as well as 16S rRNA gene sequence analyses were performed. 11 isolates as representatives of different taxa were selected for further investigations. These were identified as: Bacillus pumilus Bp91, B. pumilus Bp1, B. pumilus Bp49, B. licheniformis Bl17, Paenibacillus peoriae Pa86, Pseudomonas brassicacearum Psb101, P. brassicacearum Ps169, P. putida Ps52, Chryseobacterium indologenes Ch54, C. lathyri Chl98, and Microbacterium phyllosphaerae Mi41. Notably, the maximum inhibitory effects were observed by Pseudomonas brassicacearum Psb101, P. brassicacearum Ps169, Paenibacillus peoriae Pa86, Pseudomonas putida Ps52, and Bacillus licheniformis Bl17, by forming 17.6, 17.4, 17.3, 15.5, 15.2 mm diameter inhibition zones against R. solanacearum on nutrient agar medium, respectively. Based on the results of the greenhouse test, all 11 selected isolates simultaneously reduced the disease by 27–55% and also significantly increased plant growth.Among these, the five strains Pseudomonas brassicacearum Psb101, P. brassicacearum Ps169, P. putida Ps52, Paenibacillus peoriae Pa86, and Bacillus licheniformis Bl17 were introduced hereby as the most effective antagonists and growth enhancers under both laboratory and greenhouse conditions.