Multilocus Sequence Typing of Xylella fastidiosa Causing Pierce's Disease and Oleander Leaf Scorch in the United States

• Published in: Phytopathology 2010-06, Vol.100 (6), p.601-611
• Main Authors: Yuan, Xiaoli, Morano, Lisa, Bromley, Robin, Spring-Pearson, Senanu, Stouthamer, Richard, Nunney, Leonard
• Format: Article
• Language: English
• Subjects: accuracy; bacterial diseases of plants; Bacterial plant pathogens; Bacterial Typing Techniques; Biological and medical sciences; DNA, Bacterial - genetics; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; genetic polymorphism; genetic techniques and protocols; Genetic Variation; genome; Genome, Bacterial; geographical variation; host plants; host range; housekeeping genes; loci; microbial genetics; molecular sequence data; multilocus sequence typing; Nerium - microbiology; Nerium oleander; nucleotide sequences; oleander leaf scorch; Phytopathology. Animal pests. Plant and forest protection; Pierce's disease; Plant Diseases - microbiology; plant pathogenic bacteria; Recombination, Genetic; Selection, Genetic; Sequence Analysis, DNA; strain differences; strains; Xylella - classification; Xylella - genetics; Xylella fastidiosa
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-100-6-0601

Using a modified multilocus sequence typing (MLST) scheme for the bacterial plant pathogen Xylella fastidiosa based on the same seven housekeeping genes employed in a previously published MLST, we studied the genetic diversity of two subspecies, X. fastidiosa subsp. fastidiosa and X. fastidiosa subsp. sandyi, which cause Pierce's disease and oleander leaf scorch, respectively. Typing of 85 U.S. isolates (plus one from northern Mexico) of X. fastidiosa subsp. fastidiosa from 15 different plant hosts and 21 isolates of X. fastidiosa subsp. sandyi from 4 different hosts in California and Texas supported their subspecific status. Analysis using the MLST genes plus one cell-surface gene showed no significant genetic differentiation based on geography or host plant within either subspecies. Two cases of homologous recombination (with X. fastidiosa subsp. multiplex, the third U.S. subspecies) were detected in X. fastidiosa subsp. fastidiosa. Excluding recombination, MLST site polymorphism in X. fastidiosa subsp. fastidiosa (0.048%) and X. fastidiosa subsp. sandyi (0.000%) was substantially lower than in X. fastidiosa subsp. multiplex (0.240%), consistent with the hypothesis that X. fastidiosa subspp. fastidiosa and sandyi were introduced into the United States (probably just prior to 1880 and 1980, respectively). Using whole-genome analysis, we showed that MLST is more effective at genetic discrimination at the specific and subspecific level than other typing methods applied to X. fastidiosa. Moreover, MLST is the only technique effective in detecting recombination.