malvacearum Isolates Based on RAPD Markers in Sudan

Xanthomonas campestris pv malvacearum is the causal agent of cotton bacterial blight which originally identified in Sudan into two, pre- and post- Barakat races. 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 different geographical zones of the main cotton growing scheme in Sudan, Gezira scheme, were subjected to Random Amplification Polymorphic DNA (RAPD) markers to assess genetic diversity among isolates showing different disease symptoms. A total of 18 random primers were used in which polymorphic bands were produced and accordingly they were analyzed. Phylogenetic 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.