Phytopathology (2016) 106, 1262-1269

Joubert Fayette, Richard Raid, Pamela D. Roberts, Jeffrey B. Jones, Ken Pernezny, Carolee T. Bull and Erica M. Goss (2016)
Multilocus sequence typing of strains of bacterial spot of lettuce collected in the United States
Phytopathology 106 (11), 1262-1269
Abstract: Studies on genetic diversity and recombination in bacterial pathogens are providing a better understanding of the mechanisms shaping bacterial diversity, which can affect disease control. Xanthomonas campestris pv. vitians, causal agent of bacterial leaf spot of lettuce, is a threat to the worldwide lettuce industry. We examined the genetic variation within a sample of 83 strains from California, Florida, and Ohio using multilocus sequence typing of six housekeeping genes, totaling 2.7 kb. Additionally, polymorphism in two virulence-related genes, hrpB2 and a putative glycosyl hydrolase, were examined. Based on housekeeping genes, we found three genetic groups of strains that were all able to induce the disease. These included strains collected from weeds and irrigation water that had haplotypes identical to strains from diseased lettuce. High linkage disequilibrium across the sequenced loci indicates that the pathogen is predominantly clonal but recombination has contributed to the observed sequence variation. Although there was significant genetic variation in X. campestris pv. vitians within and among sampled states, identical haplotypes were observed across all three states. This finding suggests that seedborne inoculum may contribute to the diversity of X. campestris pv. vitians in the United States. Knowledge of the genetic structure of the pathogen may be used for developing resistant lettuce varieties.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Jeffrey B. Jones, Pamela D. Roberts, Carolee T. Bull

Research topic(s) for pests/diseases/weeds:
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Xanthomonas campestris pv. vitians	Lettuce (Lactuca)	U.S.A. (SW)
	Xanthomonas campestris pv. vitians	Lettuce (Lactuca)	U.S.A. (NE)
	Xanthomonas campestris pv. vitians	Lettuce (Lactuca)	U.S.A. (SE)