Phytopathology (2017) 107, 305-312

Helvécio D. Coletta-Filho, Carolina S. Francisco, João R.S. Lopes, Christiane Muller and Rodrigo P.P. Almeida (2017)
Homologous recombination and Xylella fastidiosa host–pathogen associations in South America
Phytopathology 107 (3), 305-312
Abstract: Homologous recombination affects the evolution of bacteria such as Xylella fastidiosa, a naturally competent plant pathogen that requires insect vectors for dispersal. This bacterial species is taxonomically divided into subspecies, with phylogenetic clusters within subspecies that are host specific. One subspecies, pauca, is primarily limited to South America, with the exception of recently reported strains in Europe and Costa Rica. Despite the economic importance of X. fastidiosa subsp. pauca in South America, little is known about its genetic diversity. Multilocus sequence typing (MLST) has previously identified six sequence types (ST) among plant samples collected in Brazil (both subsp. pauca and multiplex). Here, we report on a survey of X. fastidiosa genetic diversity (MLST based) performed in six regions in Brazil and two in Argentina, by sampling five different plant species. In addition to the six previously reported ST, seven new subsp. pauca and two new subsp. multiplex ST were identified. The presence of subsp. multiplex in South America is considered to be the consequence of a single introduction from its native range in North America more than 80 years ago. Different phylogenetic approaches clustered the South American ST into four groups, with strains infecting citrus (subsp. pauca); coffee and olive (subsp. pauca); coffee, hibiscus, and plum (subsp. pauca); and plum (subsp. multiplex). In areas where these different genetic clusters occurred sympatrically, we found evidence of homologous recombination in the form of bidirectional allelic exchange between subspp. pauca and multiplex. In fact, the only strain of subsp. pauca isolated from a plum host had an allele that originated from subsp. multiplex. These signatures of bidirectional homologous recombination between endemic and introduced ST indicate that gene flow occurs in short evolutionary time frames in X. fastidiosa, despite the ecological isolation (i.e., host plant species) of genotypes.
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Link to article at publishers website
Database assignments for author(s): Helvécio Della Coletta Filho, Rodrigo P.P. Almeida, João Roberto Spotti Lopes

Research topic(s) for pests/diseases/weeds:
molecular biology - genes
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Xylella fastidiosa		Argentina
	Xylella fastidiosa		Brazil (south)
	Xylella fastidiosa	Citrus (genus)
	Xylella fastidiosa	Plum/prune (Prunus domestica)
	Xylella fastidiosa	Olive (Olea europaea)
	Xylella fastidiosa	Coffee (Coffea)
	Xylella fastidiosa	Hibiscus (crop)