Tarbiat Modares University Journal of Agricultural Science and Technology 1680-7073 14 6 2012 11 01 The Use of a Gamma-irradiated Mutants of F. solani f.sp. phaseoli with Reduced Pathogenicity for the Biological Control of Fusarium Root Rot of Bean (Phaseolus vulgaris) in Field Conditions 1415 1423 15177 EN H. Ahari Mostafavi Nuclear Science and Technology Research Institute, Agricultural Medical and Industrial Research School, Karaj, Iran. S. M. Mirmajlessi Department of Plant Protection, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran. N. Safaie Department of Plant Protection, College of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran. V. Minassyan Department of Plant Protection, College of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran. H. Fathollahi Nuclear Science and Technology Research Institute, Agricultural Medical and Industrial Research School, Karaj, Iran. H. R. Dorri Ministry of Agriculture, Tehran, Islamic Republic of Iran. S. M. Mansouripour Nuclear Science and Technology Research Institute, Agricultural Medical and Industrial Research School, Karaj, Iran. Journal Article <em>Fusarium solani </em>wasisolated from diseased roots of common bean (<em>Phaseolus vulgaris</em>) grown in fields which were severely infected with Fusarium root rot of bean in Markazi Province of Iran. Specific PCR primer pairs were used for the identification and verification of <em>F. solani</em> (Mart.) f.sp. <em>phaseoli</em> (Burkholder) W.C. Snyder and N.H. Hans. Spore suspensions of <em>F. solani </em>f.sp.<em> phaseoli</em> were subjected to gamma irradiation at 130 Gy using Cobalt-60, and 700 mutants were generated. All 700 mutagenized colonies were tested in the greenhouse for reduced pathogenicity. One mutant (M23) showed the best expected reduction of Fusarium root rot and was chosen to be tested as a biocontrol agent in field experiments. Different concentrations of avirulent mutant (avr-M23) were used against Fusarium root rot in the infested field and their effects on the yield of bean plants were evaluated. The biocontrol effect of avr-M23 on Fusarium root rot was significantly improved with increasing its concentration from 10³to 10⁹conidia ml^-1. Best yields (no. of pods per plant and 100-seed weight) were obtained at concentrations of 10⁶ and 10⁹conidia ml^-1. This study confirms that avr-M23 can be used as a biocontrol agent to protect bean plants from Fusarium root rot under field conditions. https://jast.modares.ac.ir/article_15177_46c5976b94ffe3389fe63bed55f9cc8f.pdf