Identification of Pythium carolinianum causing 'root rot' of cotton in Egypt and its possible biological control by Pseudomonas fluorescens

A severe root rot disease of cotton caused by Pythium carolinianum was diag nosed in a cotton field in Beni-Musa village, 20 km southwest of El-Minia c ity, Egypt, during the summer of 1996. This was the first reported isolatio n of this fungus in Egypt. In the light of the importance of the cotton ind ustry in Egypt, research was initiated to develop a biocontrol agent agains t Pythium carolinianum. In vitro agar plate technique identified a Pseudomo nas fluorescens strain that was highly antagonist to Pythium carolinianum. Subsequent plant growth experiments establish that substantial disease cont rol could be obtained by applying Pseudomonas fluorescens to the soil. Opti mal control was obtained by mixing the bacteria with the soil rather than b y dipping the cotton roots in the bacterial suspension immediately before p lanting. Disease was more severe in autoclaved soil than in nonsterile soil .