M. Vatankhah - Department of Plant Protection, Vali-e-Asr University of Rafsanjan, Rafsanjan, Islamic Republic of Iran.
R. Saberi Riseh - Department of Plant Protection, Vali-e-Asr University of Rafsanjan, Rafsanjan, Islamic Republic of Iran.
M. Moradzadeh Eskandari - Department of Plant Protection Research, Agricultural and Natural Resources Center of Khorasan-Razavi, Mashhad, Islamic Republic of Iran.
E. Sedaghati - Department of Plant Protection, Vali-e-Asr University of Rafsanjan, Rafsanjan, Islamic Republic of Iran.
H. Alaie - Department of Plant Protection, Vali-e-Asr University of Rafsanjan, Rafsanjan, Islamic Republic of Iran.
H. Afzali - Department of Plant Protection Research, Agricultural and Natural Resources Center of Khorasan-Razavi, Mashhad, Islamic Republic of Iran.

In this study, the antagonistic activity of ۱,۰۰۰ bacterial isolates from different areas of Iran and two isolates of Pseudomonas fluorescens: CHA۰ and UTPf۵ 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 ۷ days of incubation at ۲۵oC, compared to the untreated control. Thirty bacteria isolates with the most inhibition and P. fluorescens CHA۰ 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 CHA۰ and the infected control, but other isolates reduced dry rot development after ۲۱ days of incubation at ۲۵-۲۷oC, as compared to the untreated control. However, three isolates, namely, VUPf۴۰, VUPf۴۴, and VUPf۵۰۶ that belong to the P. fluorescens species were the most effective. Talc-based formulation of these three effective bacteria and P. fluorescens CHA۰ were assessed for their in situ efficacy against potato dry rot development, caused by F. solani FPO۶۷, on treated tubers compared to the control. The formulation of these bacteria significantly decreased dry rot development, but only P. fluorescens VUPf۵۰۶, with ۷۹.۸% reduction of fungi development, and ۱۸.۵۷% prevalence, was the most effective in reduction of potato dry rot in natural conditions. Based on these results, P. fluorescens VUPf۵۰۶ can be considered as a promising alternative to chemical fungicides.

Antagonistic effects, Dry rot, PGPR, Pseudomonas., آنتاگونیست, فرمولاسیون, فوزاریوم, خراسان رضوی, سودوموناس