Biological Control of White Cottony Stem Rot (Sclerotinia sclerotiorum (Lib.) De Bary) by Chitinolytic Actinomycetes under Laboratory and Greenhouse Conditions in Jordan

Previously characterized isolates of chitinomycetes were used to control white cottony stem rot disease caused by the pathogenic fungus S. sclerotiorum (Lib.) De Bary on cucumber (Cucumis sativus) under laboratory and greenhouse conditions. The actinomycetes inoculum was added to the potted soil 7days in the laboratory and 14days in the greenhouse after soil inoculation with the pathogen in pre-planting treatments. The actinomycetes isolates Ma3, Ju1 and Sa8 were found to reduce disease incidence to 0% and 20% under laboratory and greenhouse conditions, respectively. Disease severity was also reduced to zero (0) in the greenhouse and to 0.6 rating in the laboratory in contrast to 3 (dead plants) in the control. In addition, a tested non-chitinolytic isolate (Na5) reduced disease incidence to 50% and disease severity to 1.25 in the laboratory. Disease incidence and severity were also reduced to 40% and 0.8 in the greenhouse, respectively, by the same isolate. The present findings support the significance of actinomycetes as biocontrol agents against phytopathogenic fungi