BIO-CONTROL OF POTATO BACTERIAL WILT CAUSED BY Ralstonia solanacearum ISOLATED FROM DIFFERENT SOURCES

Abstract

Seventeen pathogenic isolates of brown rot pathogen were collected from field soil, potato tubers, weeds and irrigation water at major potato districts in Egypt. Isolates recovered produced pink, or light red, colour with whitish margin on tetrazolium chloride medium (TZC) indicated possible virulent Ralstonia solanacearum pathogenic isolates. Pathogenicity test revealed the ability of the isolates to cause wilt symptoms in potted potato plant and three leaved tomato seedlings. Morphological, physiological and biochemical tests were used in identification. The biovar determination was made using for oxidization of disaccharides (maltose, lactose, and cellobiose) and confirmed the identity to R. solanacearum, race 3, biovar II equivalent to phylotype II, sequevar 1. A polymerase chain reaction (PCR) confirmed the identity of highest virulent isolates from tuber (T6) and from water (W11) to R. solanacearum. The application of biological agents Pseudomonas fluorescens, Bacillus subtilis, Pseudomonas aeruginosa and Trichoderma spp. decreased R. solanacearum infected plants and caused greater decrease in severity.