Characterization of a variant of Xanthomonas citri ssp. citri which triggers a host-specific defense response

M. A. CHIESA, F. SICILIANO, LEORNELLA, R. ROESCHLIN, A. FAVARO, N. PINO, L. SENDÍN, G. ORCE, D. PLOPER, A. VOJNOV, J. GADEA, P. FILIPPONE, A. CASTAGNARO, M. MARANO

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 phyto- pathogen Xanthomonas citri subsp. citri (X. citri). To gain insight into the molecular epidemiology of CBC, 42 Xanthomonas isolates were collected from a range of Citrus spp. across 17 different orchards in Tucumán, Argentina and subjected to molecular, biochemical, and pathogenicity tests. Analysis of genome-specific X. citri markers and DNA polymor- phisms based on repetitive elements-based polymerase chain reaction showed that all 42 isolates belonged to X. citri. Interestingly, pathogeni- city tests showed that one isolate, which shares >90% genetic similarity to the reference strain X. citri T, has host range specificity. This new variant of X. citri subsp. citri, named X. citri AT, which is deficient in xanthan production, induces an atypical, noncankerous chlorotic phenotype in Citrus limon and C. paradisi and weak cankerous lesions in C. auranti- folia and C. clementina leaves. In C. limon, suppression of canker devel- opment is concomitant with an oxidative burst; xanthan is not implicated in the phenotype induced by this interaction, suggesting that other bac- terial factors would be involved in triggering the defense response.