Xanthomonas citri pv. citri Findings in Citrus Fruits Imported in the Netherlands

Abstract

Xanthomonas citri pv. citri and pv. aurantifolii are responsible for citrus bacterial canker. The trade of citrus fruit is recognized as one of the seven X. citri pv. citri introduction pathways. Under the current European Union phytosanitary measures, the likelihood of these X. citri pathovars being introduced into the Mediterranean region via infected fruit is rated as unlikely. To closely monitor the commercial trade flow of citrus fruit, imported lots that contained fruits with citrus bacterial canker symptoms were quarantined, and a sample was sent for laboratory analysis. Survey results revealed the presence of viable and highly pathogenic X. citri pv. citri isolates in 97 infected lots between 2013 and 2022, whereas X. citri pv. aurantifolii was never found. These X. citri pv. citri-infected lots primarily concerned Citrus latifolia (64), C. hystrix (17), and C. grandis (11) fruits, mainly from South America but also from several Asian countries. Additionally, a genetic characterization of these X. citri pv. citri isolates demonstrated that, although they originated from different countries, years, and Citrus species, they were all highly related, with average nucleotide identity scores ranging from 99.98 to 100%. These intercepted lots containing symptomatic citrus fruits due to the presence of X. citri pv. citri underlines the importance of continued vigilance by both the exporting and importing countries. Import inspections of the citrus fruit trade flow for the presence of citrus bacterial canker symptoms and subsequent laboratory testing remain significant tools for assessing the long-distance dispersal of X. citri pv. citri.