Coffee berry disease (CBD), caused by Colletotrichum kahawae, is a major constraint for Arabica coffee cultivation in Africa. The disease is specific to green berries and can lead to 60% harvest losses. In Cameroon, mixed cropping systems of coffee with other crops, such as fruit trees, are very widespread agricultural practices. Fruit trees are commonly planted at random on coffee farms, providing a heterogeneous shading pattern for coffee trees growing underneath. Based on a recent study of CBD, it is known that those plants can reduce disease incidence. To assess the specific effect of shade, in situ and in vitro disease development was compared between coffee trees shaded artificially by a net and trees located in full sunlight. In the field, assessments confirmed a reduction in CBD on trees grown under shade compared with those grown in full sunlight. Artificial inoculations in the laboratory showed that shade did not have any effect on the intrinsic susceptibility of coffee berries to CBD. Coffee shading mainly acts on environmental parameters in limiting disease incidence. In addition to reducing yield losses, agroforestry system may also be helpful in reducing chemical control of the disease and in diversifying coffee growers' incomes.

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II innovations 2017-article en prépublication d'Innovation aux pays du Sud. Une seconde partie caractérise les conditions historiques d'émergence des institutions de recherche au Cameroun. Une troisième partie analyse en quoi la structure de la production scientifique depuis 1991 répond aux besoins d'innovations du secteur agricole et alimentaire. La quatrième partie explicite les conditions d'utilisation de cette production par les sous-systèmes de l'intermédiation et de l'entrepreneuriat. Les résultats interrogent comment l'usage de la notion de SNRI peut devenir un élément d'orientation des politiques de recherche et d'innovation finalisées par le développement.

--Introduction. Plantain banana contributes to the food safety and incomes of subSaharan Africa's inhabitants. The use of healthy plants in banana plantations is an important factor for their establishment. Different methods have been developed to produce plant material free of disease, such as in vivo and in vitro multiplication. In vitro micropropagation by budding allows the production of many plants free of disease. The in vitro multiplication of banana usually takes only one shoot tip (sh t ) per sucker. However, a sucker contains many axillary buds (ax b ), whose potentialities we evaluated. Materials and methods. Our experiments related to the cultivar Big Ebanga (AAB, plantain false horn). During acclimatization under shade and in the field, we compared growth and development parameters of vitroplants resulting from the two types of explants, sh t and ax b . Plants resulting from suckers were used as control. Results. Parameters measured on the plants resulting from ax b did not present significant differences at the end of the acclimatization phase compared with the plants from sh t , except for the foliar ratio. In the same way, parameters of vegetative growth in the field and those related to the yield were not significantly different between the two types of plants, ax b and sh t . The reversion percentages of the type "false horn" towards the type "french" were 0.6% for the sh t plants and 1.2% for the ax b plants. Discussion and conclusion. Plants resulting from sh t and ax b behaved in the same manner during the acclimatization phase and in the field. The use of ax b makes it possible to increase the potentialities of in vitro production of healthy vegetable material. The reversion rate of the plants given by ax b was weak. The ax b can thus be used like explants for the micropropagation of bananas. The same experiments on other cultivars pertaining to other genomic groups will make it possible to confirm or cancel these results.