Diversity of Xanthomonas campestris Isolates from Symptomatic Crucifers in New York State

To assess the diversity of Xanthomonas campestris spp. infecting crucifers in New York, 154 isolates were collected over 10 years across the state. The goal was to determine if isolates of the pathogen were overwintering in New York and serving as primary inoculum in subsequent years, or if novel isolates were entering the state each year. Pure cultures of isolates were characterized using multilocus sequence analysis (MLSA), a greenhouse pathogenicity assay, repetitive element-polymerase chain reaction (Rep-PCR) using the BOX-A1R primer, and enzyme-linked immunosorbent assay. The MLSA scheme proved to be more efficient than Rep-PCR for a large sample population and for comparison with global isolates. X. campestris isolated from crucifers in New York comprised of X. campestris pv. campestris and X. campestris pv. raphani, with X. campestris pv. raphani being predominately isolated from transplants. Evidence for unique haplotypes persisting on the same farm for several years due to improper seedbed rotations was documented in addition to novel haplotypes being spread throughout states through infected transplants and seed. Rep-PCR confirmed the high diversity of X. campestris and was used to generate 15 unique fingerprint patterns from isolates collected in the first 5 years. A worldwide comparison of isolates suggests that the X. campestris pv. campestris population appears to be very homogenous with dominant haplotypes persisting for extended periods and being globally disseminated.