Characterization of Xanthomonas arboricola pv. pruni from Prunus spp. orchards in Western Balkans

The present study provides a new insight into the existing Xanthomonas arboricola pv. pruni (Xap) bacterial population originating from peach and apricot in two Western Balkans countries (Serbia and Montenegro). Multilocus sequence typing and analysis of the sequences of nine housekeeping genes revealed homology between the tested Xap strains as well as with the European population of this bacterium. The tested strains share the same haplotype (Haplotype I) with the Xap strains from Italy, France, Spain, United States, Australia and Brazil. The revealed single nucleotide change (G ↔ C) in the sequences of the gyrB1 gene differentiates Haplotype I from Haplotype II (Xap from South Korea, New Zealand, Argentina and Uruguay). The detached‐leaf bioassay results confirmed differences in virulence between strains originating from peach and apricot towards Prunus armeniaca (apricot), indicating host specialization of the apricot strain towards this host. For the first time, immunity of P. fruticosa (European ground cherry) to Xap was established. According to the AUDPC, PCA and cluster analysis, other Prunus spp. were classified as having low susceptibility (P. mahaleb, P. cerasus and P. avium), as susceptible (P. domestica) and as highly susceptible (P. persica, P. dulcis, P. cerasifera and P. spinosa). Xap strains were also found to be susceptible to 10 tested antibiotics. This study provides valuable knowledge on the Xap population from stone fruit grown in the Western Balkans region as well as the source of immunity, which could serve as a starting point for breeding Prunus cultivars and could be used as the main control strategy. Peach and apricot Xanthomonas arboricola pv. pruni (Serbia and Montenegro) compose a genetically homogeneous group with European population; host specialization of the apricot strain and Prunus fruticosa immunity were determined.