Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/2008
Publication Date: 7/26/2008
Citation: Chen, J., Xie,, G., Han,, S., Civerolo, E.L. 2008. Variations of whole genome sequences of Xylella fastidiosa strains within the same pathotype. Phytopathology 98:535.
Technical Abstract: Xylella fastidiosa is a Gram negative and nutritionally fastidious plant pathogenic bacterium that causes almond leaf scorch disease (ALSD) and Pierce's disease (PD) of grapevine. X. fastidiosa strains from almond can be divided into two pathotypes: ALSD-PD, represented by strain M23, and ALSD-only, represented by strains M12 and Dixon. Strains from grape belong to the ALSD-PD pathotype and represented by strain Temecula-1. Limited information is available regarding the genetic variations withing the same pathotype strains. Whole genome sequence comparisons between strains M23 and Temecula-1 and between strains M12 and Dixon showed high level of genomic similarities but gene variations were noticeable. We defined that a gene was considered to be strain-specific or unique if it had no hits with an E-value=10-5 or less. With the ALSD-PD pathotype, strain M23 had 262 unique genes and strain Temecula had 30 unique genes. In contrast, 737 genes are identical with E-value=0. Although the genome sequence of strain Dixon has not been closed, comparisons between strains M12 and Dixon showed that strain M12 had 105 unique genes and strain Dixon had 203 unique genes. Similarly, 713 genes were identical with E-value=0. Among the unique genes, many of them were annotated as genes related to horizontal gene transfer. The genetic variations identified by whole genome sequence comparisons will have impact on future studies of strain differentiation, mechanisms of host specialization and genome evolution of X. fastidiosa.