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Molecular Plant Pathology

DNA Restriction Fragment Length Polymorphisms in Mycosphaerella Species That Cause Banana Leaf Spot Diseases. J. Carlier, Centre de Coopération International en Recherche Agronomique pour le Développement (CIRAD)/Departement Fruits Legumes et Productions Horticoles (FLHOR), Laboratoire de Pathologie Végétale, BP 5035, 34032 Montpellier; X. Mourichon(2), D. González-de-Léon(3), M. F. Zapater(4), and M. H. Lebrun(5). (2)(4)Centre de Coopération International en Recherche Agronomique pour le Développement (CIRAD)/Departement Fruits Legumes et Productions Horticoles (FLHOR), Laboratoire de Pathologie Végétale, BP 5035, 34032 Montpellier; (3)CIRAD/Analyse du Genome des Plantes Tropicales (AGETROP), 34032 Montpellier; Present address: CIMMYT, Lisboa 27, Apdo. Postal 6-641, 06600 México, D. F. México; (5)Institut de Génétique et Microbiologie, Université de Paris-Sud, CNRS-URA 1354, Bât. 400, 91405 Orsay, France. Phytopathology 84:751-756. Accepted for publication 5 April 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-751.

Restriction fragment length polymorphisms (RFLPs) of leaf spot pathogens of bananas, Mycosphaerella spp., were examined with low-copy nuclear DNA probes isolates from a M. fijiensis cosmid library. The two related fungi, M. musicola and M. fijiensis, displayed different RFLP patterns and hybridization intensities, suggesting considerable interspecific genetic divergence. The synonymy of M. fijiensis var. difformis with M. fijiensis was supported because RFLP patterns were similar and did not reflect morphological variations between these fungi. Fifty-seven isolates of M. fijiensis with different geographic origins were assayed for RFLPs. The highest level of genetic diversity in this pathogen was found in Southeast Asia, the region where it probably originated according to the chronological spread of M. fijiensis in the world. In other areas, isolates formed genetically homogeneous groups specific for each region (Africa, Pacific islands, and Latin America). Such geographical differentiation suggests that there was limited introduction of M. fijiensis into each of these regions.