xanthomonas oryzae xanthomonas oryzae xanthomonas oryzae is a species of bacteria. the major host of the bacterium is rice. xanthomonas oryzae scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: xanthomonadales family: xanthomonadaceae genus: xanthomonas species: x. oryzae binomial name xanthomonas oryzae(ishiyama 1922) swings et al., 1990 pathovars xanthomonas oryzae pv. oryzae xanthomonas oryzae pv. oryzicola the species contains two pathovars, neither of which is native to europe: x. o. pv. oryzae and x. o. pv. oryzicola. xanthomonas oryzae epidemics can cause yield losses ranging from 2-74%, and the bacteria can be carried on rice seeds, causing further disease spread. the host resistance gene, xa21, from oryza longistaminata, is integrated into the genome of oryza sativa for its broad-range resistance to rice leaf blight caused by x. o. pv. oryzae.