Cassava bacterial blight (CBB) disease is a major constraint to cassava cultivation and losses
can be extremely severe in regions where highly susceptible cultivars are grown. There is
little or no information on the genetic diversity of Xanthomonas axonopodis pv manihotis
population in Nigeria.We characterized the Xanthomonas axonopodis population in Nigeria with RandomAmplified Polymorphic DNA (RAPD) a PCR base technique. A total of 74 bacterial strainswere characterized which include six eight Xanthomonas axonopodis pv manihotis (Xam),
four Xanthomonas axonopodis pv cassavae (Xac, a yellow variant of the bacteria) and two
reference strain of Xanthomonas campestris pv malvacearum.The results obtained showed considerable differences in the pathogen population structurewith this PCR based technique. Ten clusters and five unclustered strains were identified at75% similarity coefficient on the dendrogram. The yellow variants were clustered separatelyfrom the non-pigmented strains. The Principal Component Analysis grouped the bacterialpopulation into six clusters separating the yellow variant also in cluster 4 and two unclustered strains. The diversities observed were not regionally influence or agroecologically determined.The genetic study of cassava bacterial blight presented here contributes to the understandingof the pathogen population structure in Nigeria.
