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.

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Germination bioassays performed with conidia obtained from young lesions overcome most drawbacks encountered with ascospore germination bioassays and could be considered as a new reference method for fungicide resistance monitoring in this species. Different steps are proposed, from sampling to microscopic examinations, for the implementation of this technique.

-Introduction. The susceptibility of banana fruit to crown rot and anthracnose, the two main banana post-harvest diseases, is influenced by many pre-harvest abiotic factors. Mycosphaerella leaf spot diseases (MLSD) of bananas are biotic pre-harvest factors, which have an influence on fruit physiology. The fruit's susceptibility to post-harvest diseases may also be influenced by foliar diseases caused by M. fijiensis, responsible for black leaf streak disease (BLSD), and M. musicola, which causes sigatoka disease (SD). The aim of our study was to determine the influence of these biotic pre-harvest factors on banana fruit's susceptibility to crown rot and anthracnose. Materials and methods. A disease severity gradient was established in two experimental fields (Cameroon for BLSD and Guadeloupe for SD) where, at the flowering stage, six different levels of MLSD severity were selected. Fruit susceptibility was determined through necrotic surface assessments after artificial inoculation by Colletotrichum musae on the 3rd hand of harvested bunches. Results and discussion. BLSD significantly influenced banana sensitivity to crown rot (P < 0.001) but only had a slight effect on the development of anthracnose (P = 0.041). SD had no effect (P > 0.05) on banana susceptibility to either post-harvest disease. These results are discussed with emphasis on the influence of variations in the source-sink ratio on fruit physiology. The influence of BLSD on crown rot disease suggests the need to take into account the management of these foliar diseases for an alternative control method of post-harvest diseases through integrated pest management programs.Cameroon / Guadeloupe / Musa / fruits / Mycosphaerella fijiensis / Mycosphaerella musicola / black sigatoka / black leaf streak disease / anthracnoses / crown rots Impact de l'extension de la maladie des raies noires sur la sensibilité des bananes aux maladies post-récolte.Résumé -Introduction. La sensibilité des bananes aux maladies post-récolte (pourriture de couronnes et anthracnose) est influencée par plusieurs facteurs abiotiques pré-récolte. Les maladies foliaires de bananes sont des facteurs biotiques pré-récolte causés par Mycosphaerella fijiensis pour la maladie des raies noires (MRN) et M. musicola, pour la maladie de Sigatoka (MS). Ces maladies foliaires pourraient avoir une influence sur la physiologie du fruit. L'objectif de cette étude a été de déterminer l'influence de ces facteurs biotiques pré-récolte sur la sensibilité du fruit à la pourriture de couronnes et à l'anthracnose. Matériel et méthodes. Un gradient de sévérité de la maladie a été établi dans deux parcelles expérimentales (Cameroun pour la MRN et Guadeloupe pour MS). À la floraison, six niveaux différents de sévérité de ces maladies foliaires ont été sélectionnés. La sensibilité du fruit a été déterminée en évaluant la surface de couronnes nécrosée après inoculation artificielle des fruits de la 3e main du régime par Colletotrichum musae. Résultats et discussion. La MRN a influencé significativem...