Archivio Journal of Plant Pathology

Abstract:

Xanthomonas campestris includes pathovars X. campestris pv. campestris, X. campestris pv. raphani and X. campestris pv. incanae, causing distinct diseases in Brassicaceae crops, ornamentals and weeds as well as on some Solanaceae crops. In Portugal, where brassica crops production has great economic importance, the presence of the first two pathovars was established. A polyphasic approach combining phenotypic, phylogenetic and genomic data was used to identify and characterize a set of 33 X. campestris isolates collected in Portugal. Pathogenicity tests on a wide host range demonstrated the presence of pathovar X. campestris pv. incanae for the first time in the country. Among X. campestris pv. campestris isolates, presence of races 4, 6 and 7 was recorded and two novel races of this pathovar, race 10 and race 11, were described. Phylogenetic relationships using gyrB gene confirmed phenotypic identification at species level and grouped X. campestris isolates in clades mostly congruent with pathovar allocation. PCR fingerprinting allowed discrimination at strain level of isolates collected from the same host species in the same year and county and revealed high levels of intra-pathovar and intra-race genomic diversity amongst Portuguese X. campestris pv. campestris isolates. Screening of eight essential virulence genes established five different partial virulence profiles, being the full set of genes present in the majority of isolates. When genomic clustering, phylogenetic positioning and virulence profiles were compared, no evident associations with race, host and county of origin were found, confirming the high levels of diversity of X. campestris pathovars in Portugal.