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Xanthomonas arboricola comprises a number of economically important fruit tree pathogens classified within different pathovars. Dozens of nonpathogenic and taxonomically unvalidated strains are also designated as X. arboricola, leading to a complicated taxonomic status in the species. In this study, we have evaluated the whole-genome resources of all available Xanthomonas spp. strains designated as X. arboricola in the public databases to refine the members of the species based on DNA similarity indexes and core genome-based phylogeny. Our results show that, of the nine validly described pathovars within X. arboricola, pathotype strains of seven pathovars are taxonomically genuine, belonging to the core clade of the species regardless of their pathogenicity on the host of isolation (thus the validity of pathovar status). However, strains of X. arboricola pv. guizotiae and X. arboricola pv. populi do not belong to X. arboricola because of the low DNA similarities between the type strain of the species and the pathotype strains of these two pathovars. Thus, we propose to elevate the two pathovars to the rank of a species as X. guizotiae sp. nov. with the type strain CFBP 7408T and X. populina sp. nov. with the type strain CFBP 3123T. In addition, other mislabeled strains of X. arboricola were scattered within Xanthomonas spp. that belong to previously described species or represent novel species that await formal description., Iran National Science Foundation Grant/Award Number: 99017084 Shiraz University Iranian Ministry of Science and Technology. University of Tehran Grant/Award Number: 1400-223

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La importancia de las enfermedades causadas por bacterias fitopatógenas en España se ha ido incrementando exponencialmente desde la detección, a finales de la década de 1990, de diversas bacteriosis emergentes y reemergentes que han tenido serias repercusiones económicas hasta la detección, desde 2016, de distintos focos deXylella fastidiosaen varias Comunidades Autónomas. Por ello, la Junta Directiva de la Sociedad Española de Fitopatología (SEF) consideró que existía una gran demanda de un libro español de texto o de consulta que recopilara información actualizada sobre estas enfermedades. Este tratado, actualmente único internacionalmente, pretende cubrir ese hueco y ofrecer información proporcionada por 52 expertos bacteriólogos. El libro incluye 48 capítulos que pretenden ofrecer una revisión científica actualizada, pero también realista y práctica, sobre las bacterias fitopatógenas y las enfermedades que ocasionan. Consta de seis capítulos generales introductorios, 13 sobre los géneros de las bacterias seleccionadas y 29 sobre las enfermedades de mayor importancia actual para la agricultura española y también de las que representan una amenaza potencial. La lectura de los distintos capítulos nos lleva a profundizar en el complejo patosistema que constituye cada bacteriosis, su etiología, diagnóstico, epidemiología y control. Cada problema bacteriano se trata con rigor académico, por lo que este texto sirve como fuente básica de conocimiento tanto para profesores como para estudiantes, pero también para técnicos y profesionales de la Sanidad Vegetal, así como para todos los actores que intervienen en la cadena de valor agrícola, desde la producción hasta la comercialización.

Background Xanthomonas arboricola pv. pruni (Xap) causes bacterial spot of stone fruits and almond, an important disease that may reduce the yield and vigour of the trees, as well as the marketability of affected fruits. Xap lies within the Xanthomonas genus, which has been intensively studied because of its strain specialization and host range complexity. Here, we summarize the recent advances in our understanding of the complexities of Xap, including studies of the molecular features that result after comparative phenotypic and genomic analyses, in order to obtain a clearer overview of the bacterial behaviour and infection mechanism in the context of the X. arboricola species. Taxonomic status Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Xanthomonadales; Family Xanthomonadaceae; Genus Xanthomonas; Species X. arboricola; Pathovar pruni. Host range and symptoms Xap infects most Prunus species, including apricot, peach, nectarine, plum and almond, and occasionally cherry. Symptoms are found on leaves, fruits, twigs and branches or trunks. In severe infections, defoliation and fruit dropping may occur. Distribution Bacterial spot of stone fruits and almond is worldwide in distribution, with Xap being isolated in Africa, North and South America, Asia, Europe and Oceania. It is a common disease in geographical areas in which stone fruits and almonds are grown. Xap is listed as a quarantine organism in several areas of the world. Genome The genomes of six isolates from Xap have been publicly released. The genome consists of a single chromosome of around 5 000 000 bp with 65 mol% GC content and an extrachromosomal plasmid element of around 41 000 bp with 62 mol% GC content. Genomic comparative studies in X. arboricola have allowed the identification of putative virulence components associated with the infection process of bacterial spot of stone fruits and almond. Disease control Management of bacterial spot of stone fruits and almond is based on an integrated approach that comprises essential measures to avoid Xap introduction in a production zone, as well as the use of tolerant or resistant plant material and chemical treatments, mainly based on copper compounds. Management programmes also include the use of appropriate cultivation practices when the disease is already established. Finally, for the effective control of the disease, appropriate detection and characterization methods are needed for use in symptomatic or asymptomatic samples as a first approach for pathogen exclusion. USEFUL WEBSITES: https://gd.eppo.int/taxon/XANTPR; http://www.cost.eu/COST_Actions/ca/CA16107; http://www.xanthomonas.org.

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espanolLa aparicion de Xylella fastidiosa en 2017 en la peninsula iberica ha provocado una preocupacion creciente en Comunidades Autonomas como Aragon, con una superficie importante de cultivos sensibles a la bacteria y de gran importancia economica. En este articulo se estima el impacto economico de una potencial infeccion de X. fastidiosa en Aragon bajo dos escenarios: presencia no confirmada (situacion actual) y presencia confirmada. El trabajo recopila la informacion de costes publicos que se estan asumiendo en la Comunidad Autonoma como consecuencia de la puesta en marcha de medidas cautelares para impedir la entrada y dispersion de la bacteria, y estima los costes privados y publicos que conllevaria la aparicion de X. fastidiosa en plantaciones de cultivos lenosos y alfalfa, viveros y encinar trufero. Asimismo, presenta un mapa de riesgo de infeccion por comarcas agrarias. Los resultados muestran que los costes privados por provincia y cultivo oscilan entre 745 y 5.193 €/ha en regadio y entre 136 y 3.407 €/ha en secano. Los costes totales (publicos y privados) por brote de infeccion ascienden a 600.000 € en caso de afectar a una explotacion comercial de lenosos, a lo que habria que anadir 31.958 €/ha en caso de que quedara afectado un vivero y entre 500 y 90.000 €/ha en caso del encinar trufero EnglishThe appearance of Xylella fastidiosa in 2017 in the Iberian Peninsula has caused growing concern in regions such as Aragon, with a large area of crops sensitive to bacteria and of great economic importance. The aim of this paper is to estimate the economic impact of a potential infection of X. fastidiosa in Aragon under two scenarios: unconfirmed (current situation) and confirmed presence. The information on private and public costs is collected to evaluate the economic impact of the implementation of preventive measures to avoid the introduction and spread of X. fastidiosa in woody crops, alfalfa fields, nurseries and truffle-oaks plantations. Also, a map of potential infection risk by agricultural regions is shown. The results show that private costs per province and crop range between 745 and 5,193 €/ha in irrigated land and between 136 and 3,407 €/ha in dry land. The costs per infection outbreak amount to 600,000 € in the case of affecting woody crops, to which 31,958 €/ha would have to be added if a nursery was affected and between 500 and 90,000 €/ha in case of a truffle-oaks plantation

Operational capacity of real-time PCR and loop-mediated isothermal amplification (LAMP) diagnostic assays for detection of Xanthomonas arboricola pv. pruni was established in a ring-test involving four laboratories. Symptomatic and healthy almond leaf samples with two methods of sample preparation were analyzed. Kappa coefficient, sensitivity, specificity, likelihood ratios and post-test probability of detection were estimated to manage the risk associated with the use of the two methods.

Background: Xanthomonas arboricola pv. pruni (Xap) causes bacterial spot of stone fruits and almond, an important disease that may reduce the yield and vigour of the trees, as well as the marketability of affected fruits. Xap lies within the Xanthomonas genus, which has been intensively studied because of its strain specialization and host range complexity. Here, we summarize the recent advances in our understanding of the complexities of Xap, including studies of the molecular features that result after comparative phenotypic and genomic analyses, in order to obtain a clearer overview of the bacterial behaviour and infection mechanism in the context of the X. arboricola species. Taxonomic status: Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Xanthomonadales; Family Xanthomonadaceae; Genus Xanthomonas; Species X. arboricola; Pathovar pruni. Host range and symptoms: Xap infects most Prunus species, including apricot, peach, nectarine, plum and almond, and occasionally cherry. Symptoms are found on leaves, fruits, twigs and branches or trunks. In severe infections, defoliation and fruit dropping may occur. Distribution: Bacterial spot of stone fruits and almond is worldwide in distribution, with Xap being isolated in Africa, North and South America, Asia, Europe and Oceania. It is a common disease in geographical areas in which stone fruits and almonds are grown. Xap is listed as a quarantine organism in several areas of the world. Genome: The genomes of six isolates from Xap have been publicly released. The genome consists of a single chromosome of around 5 000 000 bp with 65 mol% GC content and an extrachromosomal plasmid element of around 41 000 bp with 62 mol% GC content. Genomic comparative studies in X. arboricola have allowed the identification of putative virulence components associated with the infection process of bacterial spot of stone fruits and almond. Disease control: Management of bacterial spot of stone fruits and almond is based on an integrated approach that comprises essential measures to avoid Xap introduction in a production zone, as well as the use of tolerant or resistant plant material and chemical treatments, mainly based on copper compounds. Management programmes also include the use of appropriate cultivation practices when the disease is already established. Finally, for the effective control of the disease, appropriate detection and characterization methods are needed for use in symptomatic or asymptomatic samples as a first approach for pathogen exclusion. USEFUL WEBSITES: https://gd.eppo.int/taxon/XANTPR; http://www.cost.eu/COST_Actions/ca/CA16107; http://www.xanthomonas.org.