No known vector.
Method | Detail | NAPIS Survey Method |
---|---|---|
Visual | Collect symptomatic leaf samples. For a preliminary indications of seed infection, look for bacterial streaming (Singh and Rao, 1977). | 3031 - General Visual Observation |
Amber colored bacterial exudates on surface of lesions with bacterial leaf streak.
Bacterial leaf streak is seen as narrow, dark-greenish, water-soaked, interveinal streaks of various lengths on the leaf blades. The lesions enlarge and turn yellow orange to brown and coalesce. The lesions then turn grayish white and die. There are no symptoms on seeds with bacterial leaf streak.
In the early stage of disease, the symptoms are similar to narrow brown leaf spot. At the later stage, when the streaks have coalesced, symptoms of bacterial blight and bacterial leaf streak are similar. The shape of the edges of the lesions differs; straight in leaf streak and wavy in leaf blight. X. oryzae pv. oryzicola may be distinguished from X. oryzae pv. oryzae by colony morphology in typical isolates, strong starch and gelatin hydrolysis, and by biochemical and molecular methods.
Pathogenicity: Isolates can be tested for pathogenicity on susceptible rice cultivars. For X. oryzae pv. oryzicola use 30-45 day old IR24 or IR50 (International Rice Institute) or local popular varieties with known susceptibility to bacterial leaf streak. Leaf clipping and spray inoculation methods are available for inoculations (Kauffman et al., 1973; Cottyn et al., 1994; EPPO, 2007). Nino-Liu et al. (2005) inoculated plants by dipping them in bacterial mixture and incubating in a growth chamber. Symptoms developed a 6-day period. Xie and Mew (1998) used inoculum that came from seed and leaves sediments that had the bacterium using a washing procedure. The leaves were then placed on water agar and pricked with a needle that was dipped in the tissue sediments. Fatty Acid Profiles: Fatty acid profiles allow identification at the genus level only (Swings et al., 1990), so this analysis is not recommended a diagnostic method. Molecular: Leach et al. (1990) used a repetitive DNA sequence (pJEL101) to distinguish X. oryzae pv. oryzae from other pathovars and species of Xanthomonas. Kang et al. (2008) developed a specific PCR detection system (targets a membrane fusion protein gene) for X. oryzae pv. oryzicola. Real-time PCR: Zhao et al. (2007) developed a real-time PCR to detect X. oryzae pv. oryzae and can distinguish it from X. oryzae pv. oryzicola. Liao et al. (2003) developed a real-time PCR that can distinguish the two pathovars. Computational Genomics/Multiplex PCR: Lang et al. (2010) used a computational genomics pipeline to compare sequenced genomes of Xanthomonas species to identify regions for development of highly specific diagnostic markers. A suite of primers were selected to monitor different loci and to distinguish the rice bacterial blight and leaf streak pathogens. A subset of primers were combined into a multiplex PCR to accurately distinguish the two rice pathogens in a geographically different collection from other xanthomonads and other plant pathogenic and plant-or seed associated bacteria.
Xanthomonas oryzae is on the Select Agent List.
If you are unable to find a reference, contact STCAPS@usda.gov. See the CAPS Pest Datasheet for all references.