Résumé
Coffee leaf rust (CLR), a pathogenic disease that results in premature leaf fall and significant yield loss, has become a major concern in coffee-growing regions, especially in Central and South America, after recent intense epidemics. CLR is caused by the basidiomycete fungus Hemileia vastatrix Berk. et Br., an obligate parasite, which infects new leaves via dispersed urediospores. While there is evidence of biochemical responses of susceptible Coffea varieties to H. vastatrix invasion, these responses occur too late rendering them ineffective. An important system component that has not been thoroughly investigated is the leaf morphology of both coffee plants and shade trees, which may have a potential coordinated role in CLR incidence and severity on a plot-scale. We hypothesize that (1) coffee leaves with enhanced toughness traits, reduced stomatal density, and greater leaf inclination angle will negatively affect CLR; and (2) shade trees with closed canopy architecture and lower leaf inclination angles in the lower canopy stratum will strongly reduce rain throughfall kinetic energy (TKE) thus moderating H. vastatrix invasion. Preliminary results suggest that coffee leaf traits have variable effects on CLR severity, differing between shade management systems, which are similarly reflected in the TKE variability within the shade tree stratum. These preliminary findings advance our understanding of non-chemical resistance measures available in agroecological systems, which may lead to more sustainable and more economical options to battle CLR and pathogen invasions in general. (Texte intégral)