Isozyme fingerprinting and differentiation of Xanthomonas oryzae pv. oryzae (Xoo) isolates, causing rice Bacterial Leaf Blight (BLB) disease in West Africa, was carried out. Of 13 enzyme systems screened, Glucose 6-phosphate dehydrogenase (G6PH) showed adequate resolution and enzyme activity. Thus total proteins from all the 30 isolates were then analyzed using G6PH. This enzyme system was potentially useful as they differentiate all the 30 Xoo isolates studied. The study revealed 40-96.7% polymorphism in G6PH loci within the Xoo enzyme profile. These polymorphic isozyme loci were used to construct phylogenetic relationship cluster dendrogram among the 30 Xoo isolates. All the 30 Xoo isolates were classified into two major genetic groups (Xoo-A and Xoo-B) with five subgroups. Xoo-A possibly covers 46% and Xoo-B 54% of BLB population across West Africa. This study suggests the emergence of subgroup genotypes possibly the result of mutations and interactions amongisolates and strains that originally made up Xoo-A and Xoo-B genotypes. The isozyme fingerprint defined for each race of Xoo could be useful for epidemiological surveys, disease diagnoses and in the identification of new virulent strains, isolates and their origin. This information could be useful in rice breeding programs aiming at development of durable Xoo resistant rice cultivars to different rice ecologies and localities in West Africa.
A. Onasanya, M.M. Ekperigin, Y. Sere, F.E. Nwilene, J.O. Ajele and G. Oboh, 2007. Isozyme Fingerprinting and Genetic Differentiation of Xanthomonas oryzae pv. oryzae Isolates as Revealed by Glucose 6-phosphate Dehydrogenase (G6PH) Analysis. Biotechnology, 6: 357-363.