Control of Downy Mildew Disease of Cucumber Using Bacillus chitinosporus

A study to determine the effect of Bacillus chitinosporus on Pseudoperonospora cubensis, the causal agent of cucumber downy mildew under plastic house conditions was carried out. The optimum incubation period for bacterial bio-agent growth and metabolite production was estimated. Disease control with B. chitinosporus was effective at the optimum condition for an incubation period of 5 days. Area under diseased plants progress curve (AUDPC) was reduced by using B. chitinosporus metabolites within 35 days. A scanning electromicroscopic examination was carried out to show the effect of B. chitinosporus metabolites on sporangia and sporangiophores of P. cubensis. Twisting, loss turgor, collapsing of sporangiophores and sporangium explosion were observed after application of B. chitinosporus metabolites. Bacterial metabolites of B. chitinosporus were analyzed by gas chromatography -mass spectrophotometry (GC -MS). The efficacy of it in relation to Ridomil Gold MZ 68 WG fungicide on growth parameters was investigated. A significant increase in chlorophyll content, growth and yield parameters was observed with application of B. chitinosporus metabolites compared to control treatment. Metabolites of B. chitinosporus could be a powerful and an alternative way to chemical fungicides for controlling the downy mildew disease of cucumber.