title: Long-distance wind-dispersal of spores in a fungal plant pathogen: estimation of anisotropic dispersal kernels from an extensive field experiment.
abstract: Given its biological significance, determining the dispersal kernel (i.e., the distribution of dispersal distances) of spore-producing pathogens is essential. Here, we report two field experiments designed to measure disease gradients caused by sexually- and asexually-produced spores of the wind-dispersed banana plant fungus Mycosphaerella fijiensis. Gradients were measured during a single generation and over 272 traps installed up to 1000 m along eight directions radiating from a traceable source of inoculum composed of fungicide-resistant strains. We adjusted several kernels differing in the shape of their tail and tested for two types of anisotropy. Contrasting dispersal kernels were observed between the two types of spores. For sexual spores (ascospores), we characterized both a steep gradient in the first few metres in all directions and rare long-distance dispersal (LDD) events up to 1000 m from the source in two directions. A heavy-tailed kernel best fitted the disease gradient. Although ascospores distributed evenly in all directions, average dispersal distance was greater in two different directions without obvious correlation with wind patterns. For asexual spores (conidia), few dispersal events occurred outside of the source plot. A gradient up to 12.5 m from the source was observed in one direction only. Accordingly, a thin-tailed kernel best fitted the disease gradient, and anisotropy in both density and distance was correlated with averaged daily wind gust. We discuss the validity of our results as well as their implications in terms of disease diffusion and management strategy.
authors.affiliation: CIRAD, UMR BGPI, Montpellier, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: Rieux
authors.affiliation: INRA, UR546 Biostatistics and Spatial Processes (BioSP), Avignon, France.
authors.forename: Samuel
authors.initials: S
authors.lastname: Soubeyrand
authors.affiliation: CIRAD, UMR BGPI, Montpellier, France.
authors.forename: François
authors.initials: F
authors.lastname: Bonnot
authors.affiliation: INRA, UR546 Biostatistics and Spatial Processes (BioSP), Avignon, France.
authors.forename: Etienne K
authors.initials: EK
authors.lastname: Klein
authors.affiliation: Centre Africain de Recherches sur Bananiers et Plantains (CARBAP) - Njombe, Cameroon.
authors.forename: Josue E
authors.initials: JE
authors.lastname: Ngando
authors.affiliation: Bayer CropScience AG, Monheim, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mehl
authors.affiliation: CIRAD, UMR BGPI, Montpellier, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Ravigne
authors.affiliation: CIRAD, UMR BGPI, Montpellier, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Carlier
authors.affiliation: CIRAD, UPR Systèmes de culture bananiers plantains ananas, Montpellier, France.
authors.forename: Luc
authors.initials: L
authors.lastname: de Lapeyre de Bellaire
mesh_terms: D000465:Algorithms; D001203:Ascomycota; D005658:Fungi; D015233:Models, Statistical; D010935:Plant Diseases / Q000382:microbiology; D010944:Plants / Q000382:microbiology*; D013172:Spores, Fungal; D014919:Wind