The virulences of three isolates of Eusarium o.xysporum f.sp. elaeidis from West Africa were compared with that ofa Brazilian isolate. The Brazilian strain was more virulent and caused disease in all oil-palm lines tested, even those which had been selected for resistance to. and were generally unaffected by, African strains. Differential interactions between hosts and isolates ofthe pathogen could have serious implications for selection of breeding material and for the extension of oil-palm cultivation in South America.

Fusarium wilt (Fusarium oxysporum f.sp elaeidis) is the most serious disease of oil palm in Africa. Control measures are dependent upon breeding for resistance, but the lack of a rapid screen for resistance and lack of understanding of the underlying resistance mechanisms has constrained breeding programmes. A novel petiole infusion technique is reported that exploits the ability of the majority of petiole cells to express disease resistance or susceptibility. A clear correlation was found between disease resistance or susceptibility of six clones and external symptoms and fungal colonization in petioles. Antifungal compounds accumulated in resistant but not in susceptible clones in response to inoculation; there was also some evidence of preformed antifungal compounds in resistant clones. Further investigation of resistance mechanisms can be undertaken using this model system. The use of this novel technique, both as a potential rapid replacement for current nursery selection methods (time reduced from 8 months to 8 days) and as an assessment of resistance in individual field palms, is discussed.*