Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2010
Publication Date: 11/16/2010
Publication URL: http://handle.nal.usda.gov/10113/61449
Citation: Nunney, L., Yuan, X., Bromley, R., Hartung, J.S., Montero-Astua, M., Moreira, L., Ortiz, B. 2010. Population genomic analysis of a bacterial plant pathogen: Novel insight into the origin of Pierce's disease of grapevine in the U.S. PLoS One 5(11):e15488. Interpretive Summary: Pierce’s disease of grapevine appeared seemingly out of nowhere in 1884 in the Anaheim, California area where it wiped out a wine grape industry that had been thriving for more than 100 years at that time. The industry moved to the Napa Valley in part to escape this disease. Researchers during the last century concluded that the pathogen was native to the southeastern U.S.where it has never been possible to grow wine grapes. The hypothesis was that the pathogen had been introduced into southern California with rootstocks from the southeastern U.S. However, more recently Xylella fastidiosa, the bacterium that causes Pierce’s disease, has been found in a range of hosts in Costa Rica, including grapevine, citrus and especially coffee. We now show for the first time, through DNA sequence analysis, that the diversity of the pathogen in Costa Rica is quite high. Interestingly, the diversity of grapevine strains from the U.S. is quite low, and falls entirely within the range of diversity present in Costa Rica. Historical research has documented that coffee plants were imported into California from Costa Rica at the time of the initial outbreak of Pierce’s disease in California. Therefore the hypothesis presented is that Pierce’s disease is not native to the U.S. as has always been assumed, but instead was inadvertently introduced in the 19th century. This is of interest to students of plant pathology and the regulatory community as an example of a high consequence plant disease introduced from abroad.
Technical Abstract: Pierce’s disease of grape (PD) has long posed a serious threat to the wine industry in the United States. It is caused by infection of xylem vessels by a subspecific form of Xylella fastidiosa (subsp. fastidiosa) defined by a genetically distinct clade at least 15,000 years old (Schuenzel et al. 2005). Although generally assumed to be native to the U.S., we present genomic data suggesting that all X. fastidiosa subsp. fastidiosa in the U.S. are derived from a single introduction from Central America in the mid- to late-1800s, probably due to the importation of an infected coffee plant. This hypothesis is supported by the extensive variation seen in Costa Rican isolates of X. fastidiosa subsp. fastidiosa, whereas the level of variation found in the U.S. is consistent with radiation from a single common ancestor within the last 150 years.