CHARACTERIZATION OF A SINGLE CLONAL LINEAGE OF FUSARIUM-OXYSPORUM F-SP ALBEDINIS CAUSING BAYOUD DISEASE OF DATE PALM IN MOROCCO

Bayoud, the Fusarium wilt of date palm, was first detected in southern Morocco (Draa Valley), after which it spread to most of the Moroccan palm groves. To assess whether the epidemic results from the spread of a single virulent clone, 42 isolates of Fusarium oxysporum f. sp. alb edinis were collected from several cultivars of wilted palms at differ ent locations in Morocco; two isolates were included from Algeria, whe re the disease also occurs. The isolates were tested for vegetative co mpatibility group (VCG), restriction fragment length polymorphism (RFL P), and random amplified polymorphic DNA (RAPD). No polymorphism was o bserved either in RFLP studies on mitochondrial DNA or in RAPD analysi s, and all strains belonged to a single VCG (0170). Sequences homologo us to the DNA transposable element Fot1 were found in the genome of th e F. oxysporum f. sp. albedinis strains. Repetitive DNA patterns were produced when EcoRI-digested DNA of the isolates was probed with Fot1; 23 distinct hybridization patterns were established among the 44 isol ates. Of these patterns, 4 accounted for more than 50% of the isolates , 1 was found twice, and 18 were represented by a single isolate each. Common hybridization patterns were found in the Moroccan palm groves surveyed; the two Algerian isolates had a pattern that also was found in the Draa Valley. Cluster analysis grouped most of the F. oxysporum f. sp. albedinis strains at a genetic distance of 0.11. Such dose gene tic relationships between the isolates provides evidence that Moroccan F. oxysporum f. sp. albedinis populations may belong to a single clon al lineage that originated in Moroccan palm groves and eventually reac hed the Algerian eases.