Assessment and utilizing sources of resistance to Fusarium wilt in oil plam (Elaeis guineensis Jacq.) Genetic resources

On a world scale, oil palm is in the process of becoming the main source of vegetable oil. Its cultivation is of vital importance for populations in West and Central Africa. However, vascular wilt, a fungal disease caused by Fusarium oxysporum f.sp. elaeidis (Foe), is one of the main factors likely to limit its production. Oil palm vascular wilt was reported for the first time in the Belgian Congo (Wardlaw, 1946 a and b), and was then observed in Nigeria (Wardlaw, 1948) and in Côte d'Ivoire (Bachy and Fehling, 1957). In the 1980s it was the most serious oil palm disease in Africa and remains potentially so. Indeed, it is endemic from Cameroon to Zaire and from Zaire to Côte d'Ivoire (Meunier et al., 1979; de Franqueville and Renard, 1990). It was reported in Brazil (Van de Lande, 1983) then in Ecuador, where that focus has now died out. In infested zones, vascular wilt can destroy 25% to 80% of oil palms depending on the type of soil and material planted (Guldentops, 1962; de Franqueville. 1984). In general, oil palm vascular wilt is a disease that occurs at a late stage in first generation plantings set up after land clearance. However, in replantings. if the previous palms expressed the disease. the new palms are faced with a strong inoculum and vascular wilt is expressed in young palms (Guldentops, 1962; de Franqueville and Renard, 1990; Renard et al., 1993, de Franqueville and Diabaté, 1995). Selecting material that is resistant to vascular wilt is currently the only satisfactory control method. This is therefore an important objective for Africa, but the material obtained needs to maintain high productivity to conserve the competitiveness of oil palm cultivation in this zone. In order to achieve such a long-term objective, it is necessary to have access to a sufficiently broad genetic base. Indeed, concentrating sources of resistance in just a few origins complicates the task of breeders who cannot carry out a sufficiently large number of generations on a perennial plant within a reasonable time span. Numerous populations have been assembled at the La Mé station (Côte d=lvoire) over the last 70 years and data on the resistance of most of them are now available. Several individuals from each population have been tested and this sample provides an idea of mean population resistance. Exploitation of the results and ways they can be used by breeders will be discussed during this presentation. (Résumé d'auteur