Genetic Analysis and Molecular Identification of Virulence in Xanthomonas oryzaepv.oryzaeIsolates

Bacterial leaf blight (BLB) of rice is a very destructive disease worldwide and is caused byXanthomonas oryzaepv.oryzae(Xoo).The aimofthepresentstudywastoexamineiftheXoovirulence pathotypes obtained using phenotypic pathotyping could be confirmed using molecular approach. After screening of 60 Operon primers with genomic DNA of twoXooisolates (virulent pathotype,Vr, and mildly virulent pathotype,MVr), 12 Operon primers that gave reproducible and useful genetic information were selected and used to analyze 50Xooisolates from 7 West African countries. Genetic analysis revealed two majorXoovirulence genotypes (Mta andMtb)withMtahaving two subgroups (Mta1andMta2).Mta1(Vr1) subgroup genotype has occurrence in six countries and Mta2(Vr2) in three countries whileMtbgenotype characterized mildly virulence (MVr)Xooisolates present in five countries. The study revealed possible linkage and correlation between phenotypic pathotyping and molecular typing ofXoovirulence.Xoo virulence genotypes were known to exist within country and there was evidence ofXoopathogen migration between countries. Durable resistance rice cultivars would need to overcome bothMtaandMtb Xoovirulence genotypes in order to survive after their deployment into different rice ecologies in West Africa