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Assessment of the host status of ornamental rutaceous species to Xanthomonas citri pathovars causing Citrus Bacterial Canker. [O.20]

Licciardello G., Pruvost O., Robene I., Cubero J., Redondo C., Caruso A., Licciardello C., Caruso P., Catara V.. 2017. In : 15th Congress of the Mediterranean Phytopathological Union: Plant health sustaining Mediterranean ecosystems Abstracts book. Cordoba : MPU, p. 57-57. 15th Congress of the Mediterranean Phytopathological Union, 2017-06-20/2017-06-23, Cordoba (Espagne).

Xanthomonas citri pv. citri IXcc) and X. citri pv. aurantifolii (Xca), are causal agents of Citrus Bacterial Canker ICBC) a severe disease that requires costly control measures and primarily causes defoliation and fruit blemish and drop. Xcc and Xca are quarantine pathogens for UE, net known to occur in the Mediterranean region. The probability of their entry, via import of ornamental rutaceous plants, through bath the commercial trade and passenger pathways, is rated as likely by EFSA (2014). To provide useful information for the pest risk assessment, 25 ornamental rutaceous plants in the genera Atalantia, Balsamocitrus, Clausena, Eremocitrus, Glycosmis, Melicope, Microcitrus, Murraya, Vespris, not covered by Directive 2000/ 29EC, as well as Citrus and Fortune/la, were tested for resistance to Xcc (pathotype A, A*, Aw) and Xca (pathotype Band C) strains in controlled environment by a detached leaf assay. Nine plant species were presumptively classified as non-host, among them Murraya paniculata. Only M. ovatifoliolata and Eremocitrus glauca were susceptible to all pathotypes. The remaining species were susceptible at least to one of the pathotype A strain. Bacterial population densities ranged from 103 to 106 cfu mL-1 and 107 to 109 cfu mL-1 in plants showing HR or no response and typical CBC lesions, respectively. Crystal violet staining showed aggregation of citrus canker strains on M. paniculata leaf similar to that on citrus species but different to that found for a non-citrus Xanthomonas. Moreover, a de novo sequencing of M. paniculata genome, already completed, will serve for RNAseq studies on bath Murraya species.

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