Characterization of an new variant of Xanthomonas citri subsp. citri which triggers a host-specific response

CHIESA, M.A. ET AL

PHYTOPATHOLOGY

AMER PHYTOPATHOLOGICAL SOC

Año: 2013 vol. 103 p. 555 - 564

0031-949X

Citrus is an economically important fruit crop that is severely afflicted by Asiatic citrus bacterial canker (CBC), a disease caused by the phytopathogen Xanthomonas citri ssp. citri (X. citri). To gain insight into the molecular epidemiology of CBC, a total of 42 Xanthomonas isolates were collected from a range of Citrus species across seventeen different orchards in Tucuman, Argentina; and subjected to molecular, biochemical and pathogenicity tests. Analysis of genome-specific X. citri markers and DNA polymorphisms based on rep-PCRs showed that all 42 isolates belonged to X. citri. Interestingly, pathogenicity tests showed that one isolate, which shares more than 90% genetic similarity to the reference strain X. citri T, has host range specificity. This new variant of X. citri ssp. citri, named X. citri AT, which is deficient in xanthan production, induces an atypical non-cankerous chlorotic phenotype in Citrus limon and C. paradisi and weak cankerous lesions in C. aurantifolia and C. clementina leaves. In C. limon, suppression of canker development is concomitant with an oxidative burst; xanthan is not implicated in the phenotype induced by this interaction, suggesting that other bacterial factors would be involved in triggering the defense response.