title: Spatial Genetic Structure of Coffee-Associated Xylella fastidiosa Populations Indicates that Cross Infection Does Not Occur with Sympatric Citrus Orchards.
abstract: Xylella fastidiosa, an economically important plant-pathogenic bacterium, infects both coffee and citrus trees in Brazil. Although X. fastidiosa in citrus is well studied, knowledge about the population structure of this bacterium infecting coffee remains unknown. Here, we studied the population structure of X. fastidiosa infecting coffee trees in São Paulo State, Brazil, in four regions where citrus is also widely cultivated. Genotyping of over 500 isolates from coffee plants using 14 genomic microsatellite markers indicated that populations were largely geographically isolated, as previously found with populations of X. fastidiosa infecting citrus. These results were supported by a clustering analysis, which indicated three major genetic groups among the four sampled regions. Overall, approximately 38% of isolates showed significant membership coefficients not related to their original geographical populations (i.e., migrants), characterizing a significant degree of genotype flow among populations. To determine whether admixture occurred between isolates infecting citrus and coffee plants, one site with citrus and coffee orchards adjacent to each other was selected; over 100 isolates were typed from each host plant. No signal of natural admixture between citrus- and coffee-infecting isolates was found; artificial cross-infection assays with representative isolates also yielded no successful cross infection. A comparison determined that X. fastidiosa populations from coffee have higher genetic diversity and allelic richness compared with citrus. The results showed that coffee and citrus X. fastidiosa populations are effectively isolated from each other and, although coffee populations are spatially structured, migration has an important role in shaping diversity.
authors.affiliation: First author: Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Graduate Program in Genetics and Plant Breeding, São Paulo, Brazil; first and fourth authors: Centro APTA Citros Sylvio Moreira, Cordeiropolis, São Paulo, Brazil; second author: UNESP, Campus de Ilha Solteira, São Paulo, Brazil; third author: Department of Environmental Science, Policy and Management, University of California, Berkeley.
authors.forename: Carolina S
authors.initials: CS
authors.lastname: Francisco
authors.affiliation: First author: Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Graduate Program in Genetics and Plant Breeding, São Paulo, Brazil; first and fourth authors: Centro APTA Citros Sylvio Moreira, Cordeiropolis, São Paulo, Brazil; second author: UNESP, Campus de Ilha Solteira, São Paulo, Brazil; third author: Department of Environmental Science, Policy and Management, University of California, Berkeley.
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Ceresini
authors.affiliation: First author: Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Graduate Program in Genetics and Plant Breeding, São Paulo, Brazil; first and fourth authors: Centro APTA Citros Sylvio Moreira, Cordeiropolis, São Paulo, Brazil; second author: UNESP, Campus de Ilha Solteira, São Paulo, Brazil; third author: Department of Environmental Science, Policy and Management, University of California, Berkeley.
authors.forename: Rodrigo P P
authors.initials: RP
authors.lastname: Almeida
authors.affiliation: First author: Universidade Estadual Paulista (UNESP), Campus de Jaboticabal, Graduate Program in Genetics and Plant Breeding, São Paulo, Brazil; first and fourth authors: Centro APTA Citros Sylvio Moreira, Cordeiropolis, São Paulo, Brazil; second author: UNESP, Campus de Ilha Solteira, São Paulo, Brazil; third author: Department of Environmental Science, Policy and Management, University of California, Berkeley.
authors.forename: Helvécio D
authors.initials: HD
authors.lastname: Coletta-Filho
mesh_terms: D000483:Alleles; D001938:Brazil; D002957:Citrus / Q000382:microbiology*; D040503:Coffea / Q000382:microbiology*; D014644:Genetic Variation; D023281:Genomics; D005838:Genotype; D018895:Microsatellite Repeats / Q000235:genetics; D010935:Plant Diseases / Q000382:microbiology*; D062206:Spatial Analysis; D061350:Sympatry; D044167:Xylella / Q000235:genetics* / Q000302:isolation & purification