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Characterization of a Single Clonal Lineage of Fusarium oxysporum f. sp. albedinis Causing Bayoud Disease of Date Palm in Morocco. Abdelaziz Tantaoui, Laboratoire de Phytopathologie, Institut National de la Recherche Agronomique (INRA), B.P. 533 Marrakech, Morocco; Mohamed Ouinten(2), Jean-Paul Geiger(3), and Diana Fernandez(4). (2)(3)(4)Laboratoire de Phytopathologie, Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM), B.P. 5045, 34032 Montpellier Cedex 1, France. Phytopathology 86:787-792. Accepted for publication 23 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/Phyto-86-787.

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. albedinis were collected from several cultivars of wilted palms at different locations in Morocco; two isolates were included from Algeria, where the disease also occurs. The isolates were tested for vegetative compatibility group (VCG), restriction fragment length polymorphism (RFLP), and random amplified polymorphic DNA (RAPD). No polymorphism was observed either in RFLP studies on mitochondrial DNA or in RAPD analysis, and all strains belonged to a single VCG (0170). Sequences homologous to the DNA transposable element Fot1 were found in the genome of the 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 isolates. 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 close genetic relationships between the isolates provides evidence that Moroccan F. oxysporum f. sp. albedinis populations may belong to a single clonal lineage that originated in Moroccan palm groves and eventually reached the Algerian oases.

Additional keywords: genetic diversity, Phoenix dactylifera, population structure.