Xanthomonas oryzae is a species of Proteobacteria. The major host of the bacterium is rice. The species contains two pathovars which are not European: Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae <abbr title="pathovar">pv.</abbr> oryzicola. Host resistance gene, Xa21, from Oryza longistaminata, is integrated into the genome of Oryza sativa for the broad-range resistance of rice blight disease caused by Xanthomonas oryzae pv. oryzae.