Biological Control of Fusarium Dry Rot of Potato Using Some Probiotic Bacteria

In this study, the antagonistic activity of 1,000 bacterial isolates from different areas of Iran and two isolates of Pseudomonas fluorescens: CHA0 and UTPf5 were individually assayed against two isolates of Fusarium solani and two isolates of F. oxysporum that cause potato dry rot in Mashhad, Iran. Using in vitro dual culture plate technique, most of the tested isolates significantly reduced mycelia growth of Fusarium spp. on PDA after 7 days of incubation at 25oC, compared to the untreated control. Thirty bacteria isolates with the most inhibition and P. fluorescens CHA0 were selected for experiments on potato tubers. All isolates were tested on tuber of potato cultivar Agria under in vivo conditions. There was no significant difference between rot diameter by P. fluorescens CHA0 and the infected control, but other isolates reduced dry rot development after 21 days of incubation at 25-27oC, as compared to the untreated control. However, three isolates, namely, VUPf40, VUPf44, and VUPf506 that belong to the P. fluorescens species were the most effective. Talc-based formulation of these three effective bacteria and P. fluorescens CHA0 were assessed for their in situ efficacy against potato dry rot development, caused by F. solani FPO67, on treated tubers compared to the control. The formulation of these bacteria significantly decreased dry rot development, but only P. fluorescens VUPf506, with 79.8% reduction of fungi development, and 18.57% prevalence, was the most effective in reduction of potato dry rot in natural conditions. Based on these results, P. fluorescens VUPf506 can be considered as a promising alternative to chemical fungicides.