MOLECULAR CHARACTERIZATION OF ISOLATES OF XANTHOMONAS CAMPESTRIS PV MALVACEARUM FROM COTTON IN SUDAN

The Bacterium Xanthomonas campestris pv malvacearum the causal agent of cotton bacterial blight was originally identified in Sudan into two races, namely pre-  Barakat and post-Barakat race. The commercial cultivated cotton varieties are virtually resistant to pre -Barakat race. The disease usually exhibited small angular necrotic leaf spots and small vein blight. Development of new symptoms like large water soaked, extended water soaked small and main vein blight and very small necrotic spots were reported to be associated with new emerging mutants of the bacterium (Ahmed et al. 2006). Sixteen isolates representing 28 isolates from different geographical regions of the main cotton growing  scheme in Sudan, Gezira scheme, were subjected to Random Amplification Polymorphic DNA (RAPD) marker based Polymerase Chain Reaction (PCR) to assess genetic diversity among isolates showing different disease symptoms. A total of 18 primers were used in which polymorphic bands were produced and accordingly they were analyzed. The results from cluster analysis based on the band patterns of the isolates resulted from repetitive PCR, showed variation and similarities among isolates and six distinct genotypic groups were detected.