Genetic Diversity of avrBs-like Genes in Three Different Xanthomonas Species Isolated in Korea

Plant-pathogenic bacteria including Xanthomonas spp. carry genetic diversity in composition of avirulence genes for interaction with their host plants. Previously, we reported genetic diversity of avirulence genes in X axonopodis pv. glycines. In this study, we determined genetic diversity of five avirulence genes, avrBs1, avrBs2, avrBs3,avrBs4, and avrRxv, in three other Xanthomonas species isolated in Korea by genomic southern hybridization. Although Korean races of X campestris pv. vesicatoria that were isolated from year 1995 to 2002 had the same avirulence gene patterns as those that already reported, there was race shift from race 3 to race 1 by acquisition of avrBs3 genes. X campestris pv. campestris isolated from Chinese cabbage, but not from cabbage or radish, carried two avrBs3 genes, and one of them affected HR-eliciting ability of this bacterium in broccoli. X oryzae pv. oryzae carried eight to thirteen avrBs3 gene homologs, and this bacterium showed dynamic changes of resistance patterns in rice probably by losing or obtaining avrBs3 genes. These results indicate that avrBs3 gene is more diverse in Xanthomonas spp. than other four avirulence genes and also host ranges of these bacteria can be easily changed by loss or acquisition of avrBs3 genes.