Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 12/31/2016
Publication Date: 12/31/2016
Citation: Chen, J., Van Horn, C., Wallis, C.M. 2016. Study the taxonomy of Xylella based on whole genome sequences. CDFA Pierce's Disease Control Program Research Symposium. p. 189.
Technical Abstract: Members of the genus Xylella cause diseases on many economically important crops in the Americas, including Pierce's disease (PD) of grapevine in U.S., and citrus variegated chlorosis (CVC) disease in Brazil. In the past decade, Xylella-caused diseases from outside the Americas, such as pear leaf scorch disease in Taiwan and olive quick decline syndrome in Italy, have emerged. All Xylella strains are phenotypically characterized as being nutritionally fastidious, such that physiological and biochemical tests are of limited use for strain detection and identification. Next generation sequencing technology allows for rapid acquisition and analysis of draft genome sequences. Using draft genome sequences, average nucleotide identity (ANI) values may be used for taxonomic placement of Xylella strains and for species definition. Recently, a new species, Xylella taiwanensis, has been established. The ANI values between X. taiwanensis and X. fastidiosa were 83.4-83.9%, significantly lower than the bacterial species threshold of 95%. Interestingly, ANI analyses also drew a defined line among X. fastidosa subsp. fastidiosa, X. fastidosa subsp. multiplex, and X. fastidosa subsp. pauca, suggesting that ANI value, along with sequence similarity of other genes/sequences including 16S rRNA gene and 16S-23S ITS, could be useful for subspecies analysis.