Résumé
Coffee wilt is a vascular disease caused by Fusarium xylarioides Steyaert, which is the conidial stage of Gibberella xylarioides Hem. and Saccas. CWD can be very destructive to coffee trees (Figure I.II), leading to total loss of investment It was first reported in 1927 on Coffea liberica var. dewevrei (formerly C. liberica type excelsa, Davis et al., 2006) plantations in the Central African Republic (CAR) (Figueres, 1940). It progressively destroyed this crop during 1930s to 1950s in other Central African countries i.e. Cameroon (Guillemat, 1946; Fraselle, 1950; Saccas, 1951; Muller, 1997). During the same period, it destroyed C. canephora in Ivory Coast, causing serious losses and disappearance of some local varieties (Delassus, 1954). In contrast several varieties of C. canephora imported from DRC between 1914 and 1933 exhibited some level of field resistance, which was later confirmed by artificial inoculation (Meiffren, 1961). Meiffren (1961) also reported apparent differences for the same materials planted in different areas of the region, i.e. certain Coffea liberica and C. canephora varieties showing resistance in Ivory Coast were completely susceptible in CAR, suggesting the resistance was either being influenced by environmental conditions or there were different physiological races of the pathogen in different localities of this region. Fraselle (1950) reported CWD attack on C. canephora at Yangambi in the DRC in 1948 and subsequently the disease became a serious problem in many parts of the country. In 1957 similar symptoms were reported on C. arabica in Ethiopia (Lejeune, 1958). C. canephora resistant varieties identified in the DRC were used for replanting within the DRC and Ivory Coast (Saccas, 1956; Meiffren, 1961). In Cameroon the disease was eliminated by rigorous systematic uprooting (Muller, 1997) of the C. dewevri plantations. These strategies proved to be successful as the disease had declined drastically by the end of the 1950s and it eventually disappeared from Cameroon and Ivory Coast and probably DRC and CAR. The disease remained affecting C. arabica in Ethiopia and it is doubtful if any of these strategies were applied. In 1980s a new large scale outbreaks of CWD were reported on C. canephora in the north-east of DRC (Flood & Brayford, 1997), from where it spread rapidly to affect this crop in Uganda (1993) and north-west Tanzania (1997). Chemical control is considered ineffective. Moreever currently, no commercial varieties resistant to the disease are available and it is not recommended to replant on an infected soil. The main objective of this project was to develop a global strategy to fight the disease, based on durable resistance and adapted to the smallholder's agro systems and to the conditions prevailing in Africa. A multidisciplinary approach was developed to reach this objective with. The findings of this work are of fundamental importance to the future management of CWD and in safeguarding the livelihoods of millions of smallholder coffee farmers across the African continent. (Résumé d'auteur)