SUPPRESSION OF RHIZOCTONIA-SOLANI DAMPING-OFF DISEASE OF CUCUMBERS INAUTOCLAVED SOILS AMENDED WITH BENEFICIAL MICROORGANISMS

Impact studies on a mixture of beneficial bacteria Pseudomonas fluores cens strain CHAO and some strains of hyperparasitic Trichoderma spp. f ungi were carried out under glasshouse conditions in three separate ex periments. The trials were conducted in glasshouse cabins at 75-80% re lative humidity, with a 16/8 h light/dark cycle and temperature of 22/ 18 degrees C. A considerable high suppression efficiency of damping-of f disease of cucumbers was observed in Rhizoctonia solani was observed at a mixture of both microorganisms in treatments with some fungal st rains and/or bioformulations, respectively. Some treatments revealed q uite high inconsistency in their suppressive efficiency of dumping-off disease of cucumbers within three experiments conducted separately be cause of a complexity of inter actions between plants and all microorg anisms involved. In some treatments with fungal antagonists alone (wit hout addition of Pseudomonas fluorescens CHAO) a higher suppressive ef ficiency was found as compared to the treatments with mixtures. In tre atments with bioformulation. Trichodex alone and/or when treated with a mixture of bacteria, root growth depression and/or a toxic effect on cucumber plants was observed.