Multilocus Variable Number of Tandem Repeat Analysis Reveals Multiple Introductions in Spain of Xanthomonas arboricola pv. pruni, the Causal Agent of Bacterial Spot Disease of Stone Fruits and Almond

PLoS One. 2016 Sep 26;11(9):e0163729. doi: 10.1371/journal.pone.0163729. eCollection 2016.

Abstract

Xanthomonas arboricola pv. pruni is the causal agent of the bacterial spot disease of stone fruits, almond and some ornamental Prunus species. In Spain it was first detected in 2002 and since then, several outbreaks have occurred in different regions affecting mainly Japanese plum, peach and almond, both in commercial orchards and nurseries. As the origin of the introduction(s) was unknown, we have assessed the genetic diversity of 239 X. arboricola pv. pruni strains collected from 11 Spanish provinces from 2002 to 2013 and 25 reference strains from international collections. We have developed an optimized multilocus variable number of tandem repeat analysis (MLVA) scheme targeting 18 microsatellites and five minisatellites. A high discriminatory power was achieved since almost 50% of the Spanish strains were distinguishable, confirming the usefulness of this genotyping technique at small spatio-temporal scales. Spanish strains grouped in 18 genetic clusters (conservatively delineated so that each cluster contained haplotype networks linked by up to quadruple-locus variations). Furthermore, pairwise comparisons among populations from different provinces showed a strong genetic differentiation. Our results suggest multiple introductions of this pathogen in Spain and redistribution through contaminated nursery propagative plant material.

Grants and funding

This work was supported by Instituto Nacional de Tecnología Agraria y Alimentaria. Project RTA-2011-00140-C03-01 (http://www.inia.es) to PLS MCM JP MML, Euphresco project (266505-FP7-ERANET Euphresco II) to PLS MCM JP APB MML, European Social Fund to PLS KB MCM JP APB CV MML OP, European Regional Development Fund to PLS KB SC MCM JP APB CV MML OP, Conseil Régional de La Réunion (http://www.regionreunion.com/fr) to KB CV OP, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) (http://www.cirad.fr) to KB CV OP, FPI-INIA grant (http://www.inia.es) Instituto Nacional de Tecnología Agraria y Alimentaria to PLS, AIP Bioressources 2012 taxonomic project to SC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.