Enzyme polymorphism and genetic diversity in Xanthomonas oryzae pv. oryzae isolates causing rice bacterial leaf blight disease in West Africa

Abstract

Genetic diversity of 30 Xanthomonas oryzae pv. oryzae (Xoo) isolates, causing rice bacterial leaf blight disease in West Africa, was carried out using isozyme PAGE analysis. Of 13 enzyme systems evaluated, SKDH, EST and G6PH showed adequate resolution, enzyme activity and polymorphism and were used to analyze the total proteins from all the 30 isolates. The study revealed 23 isozyme loci in which SKDH produced 33.3-93.3% polymorphism, EST and G6PH equally gave 40-96.7% polymorphism within the Xoo isolates enzyme profile. These 23 isozyme loci were used to construct phylogenetic relationship cluster among 30 Xoo isolates, of which the Xoo isolates were classified into two major genetic groups (Xoo-A and Xoo-B) with two subgroups each (Xoo-A1 and Xoo-A2) and (Xoo-B1 and Xoo-B2). The 23 isozyme markers obtained clustered into 3 major groups (Gp-1, Gp-2 and Gp-3). Genetic study revealed that Gp-1 is genetically linked to the identification of Xoo-A1 genotype, Gp-2 to Xoo-A2 and Gp-3 characterized Xoo-B1 and Xoo-B2 genotypes. The distinct pattern of each isolate obtained suggests high level of genetic variation and frequent occurrence of mutants in Xoo isolates in different host cells. 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. © 2008 Academic Journals Inc.