David Francis, The Ohio State University
Figure 1. Bacterial Spot of tomato. (a) Bacterial spot symptoms on tomato fruit. (b) Defoliation due to bacterial spot. Photo credits: David Francis, The Ohio State University.
Bacterial spot causes yield loss in tomato through reduced photosynthetic capacity and defoliation. Fruit quality is reduced indirectly due to sun-scald and directly by bacterial lesions. Bacterial spot of tomato is caused by as many as four species of Xanthomonas, including Xanthomonas euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri. In addition, at least five physiological races—T1–T5—are recognized on the basis of a hypersensitive (HR) reaction on a differential series of host genotypes. Descriptions of bacterial spot may use the species names, taxonomic groups A–D, or race designations.
|Race||Species||Molecular Phylogeny||Comments||Resistant Germplasm|
|Race T1||X. euvesicatoria||A group strains||Hawaii 7998, PI 114490|
|Race T2||X. vesicatoria||B group strains||possibly also includes X. perforans, C group strains; X. euvesicatoria, A group strains; and X. gardneri, D group strains||PI 114490|
|Race T3||X. perforans||C group strains||possibly also includes X. gardneri, D group strains||Hawaii 7981, PI 128216, PI 126932|
|Race T4||X. perforans||C group strains||LA 716, PI 114490|
|Race T5||X. perforans||C group strains|
Development of this lesson was supported in part by the National Institute of Food and Agriculture (NIFA) Solanaceae Coordinated Agricultural Project, agreement 2009-85606-05673, administered by Michigan State University. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the United States Department of Agriculture.