Characterization of a variant of Xanthomonas citri subsp. citri that triggers a host-specific defense response

CHIESA, M. A.; ORNELLA, L.; ROESCHLIN, R. A.; FAVARO, M. A.; DELGADO, N. P.; SENDÍN, L. N.; ORCE, I. G; PLOPER, L. D; VOJNOV, A. A.; VACAS, J. G.; FILPPONE, M.P.; CASTAGNARO, AP.; MARANO, M.R.

PHYTOPATHOLOGY

AMER PHYTOPATHOLOGICAL SOC

Año: 2013 p. 555 - 564

0031-949X

Citrus is an economically important fruit crop that is severely afflictedby Asiatic citrus bacterial canker (CBC), a disease caused by the phytopathogenXanthomonas citri subsp. citri (X. citri). To gain insight into themolecular epidemiology of CBC, 42 Xanthomonas isolates were collectedfrom a range of Citrus spp. across 17 different orchards in Tucumán,Argentina and subjected to molecular, biochemical, and pathogenicitytests. Analysis of genome-specific X. citri markers and DNA polymorphismsbased on repetitive elements-based polymerase chain reactionshowed that all 42 isolates belonged to X. citri. Interestingly, pathogenicitytests showed that one isolate, which shares >90% genetic similarityto the reference strain X. citri T, has host range specificity. This new variantof X. citri subsp. citri, named X. citri AT, which is deficient in xanthanproduction, induces an atypical, noncankerous chlorotic phenotype inCitrus limon and C. paradisi and weak cankerous lesions in C. aurantifoliaand C. clementina leaves. In C. limon, suppression of canker developmentis concomitant with an oxidative burst; xanthan is not implicatedin the phenotype induced by this interaction, suggesting that other bacterialfactors would be involved in triggering the defense response.