Distribution of Xanthomonas oryzae pv. oryzae DNA modification systems in Asia

Abstract

The presence or absence of two DNA modification systems, XorI and XorII in 195 strains of has oryzae pv. oryzae collected from different major rice- growing countries of Asia was assessed. All four possible phenotypes (XorI+ XorII+, XorI-XorII+, XorI- XorII+ and XorI- XorII-) were detected in the population at a ratio of approximately 1:2:2'.2. The XorI+ XorII+ and XorI- XorII+ phenotypes were observed predominantly ha strains from southeast Asia (Philippines, Malaysia, and Indonesia), whereas strains with the phenotypes XorI-XorII- and XorI+ XorII- were distributed in south Asia (India and Nepal) and northeast Asia (China, Korea, and Japan), respectively. Based on the prevalence and geographic distribution of the XorI and XorII systems, we suggest that the XorI modification system originated in northeast Asia and was later introduced to southeast Asia, while the XorII system originated in southeast Asia and moved to northeast Asia and south Asia. Genomic DNA from all tested strains of X. oryzae pv. oryzae that were resistant to digestion by endonuclease XorII or its isoschizomer PvuI also hybridized with a 7.0-kb clone that contained the XorII modification system, whereas strains that were digested by XorII or PvuI lacked DNA that hybridized with the clone. Size polymorphisms were observed in fragments that hybridized with the 7.0-kb clone. However, a single hybridization pattern generally was found in XorII+ strains within a country, indicating clonal maintenance of the XorII methyltransferase gene locus. The locus was monomorphic for X. oryzae pv. oryzae strains from the Philippines and all strains from Indonesia and Korea.

Source or Periodical Title

Applied and Environmental Microbiology

ISSN

992240

Page

1663-1668

Document Type

Article

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