Xanthomonas hortorum

{{Short description|Species of bacterium}}

{{Speciesbox

| image = Xanthomonas leaf spot.png

| image_caption = Leaf spot on English ivy plant, caused by Xanthomonas hortorum

| genus = Xanthomonas

| species = hortorum

| authority = Vauterin et al. 1995

}}

Xanthomonas hortorum is a plant pathogen. It includes the following pathovars:

• pv. hederae, common ivy and possibly other Araliaceae
• pv. taraxaci, Pelargonium peltatum
• pv. carotae, wild carrot
• pv. pelargonii, Kazakh dandelion
• pv. vitians, bacterial leafspot and headrot of lettuce, using the neopathotype of LMG 938
• pv. cynarae, formerly Xanthomonas cynarae, pathogenic on artichoke{{cite journal |last1=Morinière |first1=Lucas |last2=Burlet |first2=Alexandre |last3=Rosenthal |first3=Emma R. |last4=Nesme |first4=Xavier |last5=Portier |first5=Perrine |last6=Bull |first6=Carolee T. |last7=Lavire |first7=Céline |last8=Fischer-Le Saux |first8=Marion |last9=Bertolla |first9=Franck |title=Clarifying the taxonomy of the causal agent of bacterial leaf spot of lettuce through a polyphasic approach reveals that Xanthomonas cynarae Trébaol et al. 2000 emend. Timilsina et al. 2019 is a later heterotypic synonym of Xanthomonas hortorum Vauterin et al. 1995 |journal=Systematic and Applied Microbiology |date=July 2020 |volume=43 |issue=4 |pages=126087 |doi=10.1016/j.syapm.2020.126087}}
• pv. gardneri, formerly Xanthomonas gardneri and briefly X. cynarae pv. gardneri, bacterial leafspot of peppers and tomatoes (pathotype also causes BLS on lettuce surprisingly)

The species was originally defined in 1995 as a grouping of pathovars hederae, taraxaci, carotae, pelargonii from Xanthomonas campestris, and the lettuce-infecting part of X. c. pv. vitians. (X. c. pv. vitians was found to consist of two genetic groups, only one of which causes disease on lettuce.)