detection of hydrogen cyanide biosynthetic gene in pseudomonas fluorescent as a control agent of rhizoctonia solani growth

in order to detect hydrogen cyanide gene and to determine pseudomonas fluorescent efficiency in producing hydrogen cyanide for controlling the growth of rhizoctonia solanipathogen (the causal agent of sugar beet root and crown rot), samples were collected from sugar beet rhizosphere in sabzevar fields. after soil sampling and purification, 31 pseudomonas spp. isolates were separated on specific pseudomonas agar f medium, and pseudomonas fluorescent strains were identified and isolated based on microbial tests. pcr results showed that three strains contained cyanide hydrogen biosynthetic gene. the qualitative evaluation of hydrogen cyanide production in microbial medium showed that all the strains were capable of producing different amounts of hydrogen cyanide. to determine the growth inhibition rate of rhizoctonia solani by pseudomonas fluorescent, the percentage of fungus growth in the presence of bacteria was calculated. among the three pseudomonas fluorescent strains, c7 showed the greatest inhibition rate and hydrogen cyanide production which can be recommended as a suitable candidate for the pathogen biocontrol.