Determination of effects of local plant growth promiting rhizobacteria on white mold disease agent [Sclerotinia sclerotiorum (Lib.) de Bary]

This study was carried out to determine the effects of rhizobacteria isolates, which were obtained from the soil rhizosphere in tomato production areas of Tokat and have the strong abilities to dissolve phosphorus and reduce nitrogen, on the white mold disease agent Sclerotinia sclerotiorum (Lib.) de Bary. In the study, ten rhizobacteria isolates of the genus Pseudomonas were used. In the in vitro study, the tested bacterial isolates suppressed the mycelial growth of S. sclerotiorum by 65.49-88.25%. Isolates with a high inhibition rate on mycelial growth were also effective on the viability of the sclerotia of the pathogenic fungus. Five bacterial isolates caused complete loss of sclerotia viability. According to the result of the in vitro studies, bacterial isolates with strong effects on the pathogenic fungus were selected and assayed in pot studies under greenhouse conditions. In pot studies, single treatments with Pseudomonas chlororaphis (R-7) and the dual treatments with Pseudomonas brassicacearum + Pseudomonas chlororaphis (R-3 + R-7) were the most effective against white mold disease. On the contrary, it was determined by pot study that bacterial isolates were not effective on plant growth in cucumber. The results of this study show that these rhizobacteria can be used in the biological control of S. sclerotiorum. In addition to the in vitro and in vivo studies, it is necessary to determine the performances of rhizobacteria isolates, which had the highest effect on white mold disease, in greenhouses and field conditions.