Xanthomonas prunicola: an emerging pathogen of wheat in the Americas
Xanthomonas prunicola is a species first described in 2018 as a pest of nectarine (Prunus persica var. nucipersica) trees in Spain where it was also shown to be pathogenic to peach (Prunus persica) (EPPO RS 2018/128).
Recently, X. prunicola has emerged as a pathogen of wheat (Triticum aestivum) in South America and the USA. In Argentina, bacterial leaf streak symptoms have been observed on wheat in Córdoba province since 2018, with disease incidence ranging from 1 to 5%. An isolate obtained from symptomatic wheat was identified as X. prunicola by whole-genome sequencing and Koch's postulates were fulfilled. In Uruguay, surveys conducted in 61 wheat fields between 2017 and 2019 detected Xanthomonas strains causing dry necrotic lesions, later Clavijo et al. (2025) confirmed the identity of these wheat-associated strains as X. prunicola.
More recently, in July 2023, X. prunicola was identified causing bacterial leaf streak-like symptoms in a winter wheat field in Volga, South Dakota (USA). Affected plants showed necrotic and chlorotic streaks along the leaves and disease incidence was approximately 40% among 100 plants examined. The bacterium was identified by sequence analysis and pathogenicity tests reproduced leaf streak-like symptoms. The bacterium was subsequently reisolated, fulfilling Koch's postulates. This is considered the first confirmed report of X. prunicola causing disease on wheat in the USA.
X. prunicola should therefore be considered an emerging pathogen of wheat. Clavijo et al. (2025) showed that wheat-associated strains from Uruguay and the USA formed a distinct phylogenomic cluster from nectarine-associated strains. The reference strain isolated from nectarine did not cause symptoms on wheat whereas most wheat-associated strains were able to cause symptoms on peach. Wheat-associated strains may represent a new pathovar or subspecies within X. prunicola, but further studies on potential hosts are needed to confirm this.
Sources
Ahmad M, Gonzalez-Hernandez JL, Solanki S, Glover KD, Ameen G (2026) First report of Xanthomonas prunicola causing leaf streak disease on wheat (Triticum aestivum) in the United States. Plant Disease 110(1), 216. https://doi.org/10.1094/PDIS-06-25-1194-PDN
Clavijo F, Román-Reyna V, Curland RD, Dill-Macky R, Jacobs JM, Leoni C, Coimbra L, Pereyra S, Siri MI (2025) Emerging Xanthomonas prunicola strains cause bacterial leaf necrosis of wheat. Phytopathology 115(9), 1097–1108. https://doi.org/10.1094/PHYTO-02-25-0044-R
Martino JA, Fernández FD, Pozzi EA, Alberione EJ, Bainotti CT, Márquez N, Tolocka PA, Salines N, Gomez DT, Donaire GM, Conci LR, Alemandri VM (2023) First report of Xanthomonas prunicola causing bacterial leaf streaks on wheat in Argentina. Plant Disease 107(1), 212. https://doi.org/10.1094/PDIS-04-22-0886-PDN
Clavijo F, Curland RD, Croce V, Lapaz MI, Dill-Macky R, Pereyra S, Siri MI (2022) Genetic and phenotypic characterization of Xanthomonas species pathogenic in wheat in Uruguay. Phytopathology 112(3), 511–521. https://doi.org/10.1094/PHYTO-06-21-0231-R