title: High-resolution mapping of the recombination landscape of the phytopathogen Fusarium graminearum suggests two-speed genome evolution.
abstract: Recombination is a major evolutionary force, increasing genetic diversity and permitting efficient coevolution of fungal pathogen(s) with their host(s). The ascomycete Fusarium graminearum is a devastating pathogen of cereal crops, and can contaminate food and feed with harmful mycotoxins. Previous studies have suggested a high adaptive potential of this pathogen, illustrated by an increase in pathogenicity and resistance to fungicides. In this study, we provide the first detailed picture of the crossover events occurring during meiosis and discuss the role of recombination in pathogen evolution. An experimental recombinant population (n = 88) was created and genotyped using 1306 polymorphic markers obtained from restriction site-associated DNA sequencing (RAD-seq) and aligned to the reference genome. The construction of a high-density linkage map, anchoring 99% of the total length of the reference genome, allowed the identification of 1451 putative crossovers, positioned at a median resolution of 24 kb. The majority of crossovers (87.2%) occurred in a relatively small portion of the genome (30%). All chromosomes demonstrated recombination-active sections, which had a near 15-fold higher crossover rate than non-active recombinant sections. The recombination rate showed a strong positive correlation with nucleotide diversity, and recombination-active regions were enriched for genes with a putative role in host-pathogen interaction, as well as putative diversifying genes. Our results confirm the preliminary analysis observed in other F. graminearum strains and suggest a conserved 'two-speed' recombination landscape. The consequences with regard to the evolutionary potential of this major fungal pathogen are also discussed.
authors.affiliation: MycSA, INRA, Université de Bordeaux, 33882, Villenave d'Ornon, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Laurent
authors.affiliation: The Roslin Institute, University of Edinburgh, Midlothian, EH25 9RG, UK.
authors.forename: Christos
authors.initials: C
authors.lastname: Palaiokostas
authors.affiliation: MycSA, INRA, Université de Bordeaux, 33882, Villenave d'Ornon, France.
authors.forename: Cathy
authors.initials: C
authors.lastname: Spataro
authors.affiliation: MycSA, INRA, Université de Bordeaux, 33882, Villenave d'Ornon, France.
authors.forename: Magalie
authors.initials: M
authors.lastname: Moinard
authors.affiliation: MycSA, INRA, Université de Bordeaux, 33882, Villenave d'Ornon, France.
authors.forename: Enric
authors.initials: E
authors.lastname: Zehraoui
authors.affiliation: The Roslin Institute, University of Edinburgh, Midlothian, EH25 9RG, UK.
authors.forename: Ross D
authors.initials: RD
authors.lastname: Houston
authors.affiliation: MycSA, INRA, Université de Bordeaux, 33882, Villenave d'Ornon, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Foulongne-Oriol
mesh_terms: D005670:Fusarium / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics / Q000502:physiology; D016681:Genome, Fungal / Q000235:genetics*; D005838:Genotype; D008540:Meiosis / Q000235:genetics / Q000502:physiology
keywords: Gibberella zeae; RAD-seq; crossover rate; dense genetic linkage map; genotyping-by-sequencing; meiosis