Résumé
WP1 Breeding for durable resistance. Some Coffea eugenioides genotypes were collected by Coffee Research Foundation in the forests of Mt. Elgon (Kenya); no CBD could be observed in situ; these genotypes still have to be tested. Some resistance was found in Ethiopian germplasm from Cameroon, it has to be confirmed. In order to confirm the results of earlier hypocotyl tests conducted at Cirad, seeds of 25 Colombian Catimor and Sarchimor lines were send to Kenya and Cameroon for field establishment in CBD infested zones. Some Resistant x Susceptible F2 progenies derived from well identified resistant individual trees have been prepared and established in the field during the last joint Research Project funded by the EC. They will be used to study the inheritance of resistance, especially in hybrids derived from Ethiopian entries. No material was available for tests in Year 1. Another study, on inheritance of the resistance found in Timor Hybrids, has been postponed due to bad germination of seeds. Search for markers of resistance is still pending availability of F2 seeds. WP2 Host x Pathogen interaction. The tree-to-tree variation within entries often seen as homogeneous was highlighted by the few tests conducted. However enough replications are necessary to confirm the presence of interaction, moreover to identify the genotypes (Coffee and Fungus) responsible for that interaction. The achievement of proper ring tests is thus conditioned by the availability of seeds. It is proposed, for a better co-ordination of results, that all partners simplify their tests results into 5 classes of susceptibility (0 to 4) and calculate a mean grade by dividing the weighted total by the total number of seedlings. WP3 The pathogen. 29 Isolates were collected by CRF in various regions of Kenya, and from resistant varieties. Tests were initiated both at CRF and at CIRAD to check their aggressiveness. They will have to be confirmed by further replications. A collection of isolates was also made in Rwanda in a germplasm collection. A complementary study of the diversity (morphology, aggressiveness, molecular biology) of the fungus is pending the availability of isolates collected in the wild on Coffea eugenioides. Indeed this species may be the initial host of the disease before it spread to C. arabica. WP4 Epidemiology. A thorough study of the evolution of the disease and of crop losses was made in Cameroon. Three sites were chosen, with two varieties on one of the sites. Half the trees are under shade, the others in full sunshine, with some variation due to the presence of banana trees. Three branches per tree were monitored. The analyses are not completed yet. The same trees will be monitored for 4 years. In Kenya the sites for a similar study were earmarked but the study will start in Year 2. Search for antagonistic micro flora started in Kenya. Antagonistic effects were detected in the lab. The multiplication of these microorganisms will start next year. Meanwhile at CIFC it was evaluated the antagonistic effect of the extract Gal-02 from the fungus Ganoderma sp. on CBD isolates. The conidia germination of some isolates was significantly inhibited in vitro by the extract Gal-02, while for others the results were not conclusive. However, the conidia germination of all the C. kahawae isolates tested was inhibited in vivo. The differentiation of melanized appressoria of the different CBD isolates was also inhibited by Gal-02, both in vitro and in vivo. In what concerns the percentage of hyaline appressoria, the results of the in vitro and in vivo studies were not coincident. Even in the in vivo studies, contradictory results were obtained for the some isolates, in the different experiments. So, apparently it seems that Gal-02 had no effect in the appressoria melanization. (Résumé d'auteur)