DEVELOPMENT OF A SEMI-SELECTIVE MEDIUM FOR Xanthomonas campestris pv. musacearum

Banana bacterial wilt disease caused by Xanthomonas campestris pv. musacearum (Xcm) is a serious devastating disease of bananas in Uganda. The disease causes wilting, premature ripening of banana fruits and death of banana plants. There is limited information on the ecology and biology of the pathogen to assist in development of integrated control measures. Studies on the epidemiology of the disease have been limited by lack of a reliable detection method for the pathogen. This paper reports on the progress towards the development of a selective media for the pathogen. Using a pathogen isolate (KY44) and 8 other bacterial strains associated with the pathogen in banana tissues, soil and insect surfaces, a new medium has been developed. The semi-selective medium designated CCA contains (g L^-1): yeast extract, 1g; glucose, 1g; peptone, 1g; NH4Cl, 1g; MgSO4. 7H2O, 1g; K2HPO4, 3g; beef extract, 1g; cellobiose, 10g; peptone, 1g; agar, 14g; cephalexin, 40mg; 5-fluorouracil, 10mg and cycloheximeide, 120mg, A combination of cephalexin and 5-Fluorouracil in the media controlled most of the common bacterial strains isolated from soil and plant tissues. Results from preliminary testing for selectivity and recovery from soil and plant tissues of CCA medium using YPGA as the standard indicate that the medium is able to recover 59% of the target bacteria an is selective against 82% of the common bacterial contaminants. CCA medium is therefore a valuable tool that can be useful in epidemiological studies of Xcm pathogen.