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Genetic Diversity and Pathogenic Variation of Colletotrichum lindemuthianum in the Three Centers of Diversity of Its Host, Phaseolus vulgaris

August 1997 , Volume 87 , Number  8
Pages  807 - 813

D. Sicard , Y. Michalakis , M. Dron , and C. Neema

First, third, and fourth authors: Laboratoire de Phytopathologie Moléculaire, Institut de Biotechnologie des Plantes, Université Paris XI, BÂt. 630, 91405 Orsay, France; second author: Laboratoire d'Ecologie, CNRS URA 258, Université Paris VI, 7 quai St Bernard, 75252 cedex 05, France

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Accepted for publication 8 May 1997.

Population subdivision of Colletotrichum lindemuthianum, the causal agent of anthracnose, was studied in three regions located in three centers of diversity of its host, Phaseolus vulgaris. Random amplified polymorphic DNA (RAPD) markers, restriction endonuclease analysis of the amplified ribosomal internal transcribed spacer region, and virulence on a set of 12 cultivars were used to assess the genetic diversity of C. lindemuthianum strains isolated in Mexican, Ecuadorian, and Argentinean wild common bean populations. The three regions were significantly differentiated for molecular markers. For these markers, Mexico was the most polymorphic and the most distant from Ecuador and Argentina. The majority of the RAPD alleles present in Ecuador and Argentina were found in Mexico, suggesting that Andean populations have been derived from the Mesoamerican center. Pathogenicity tests on a set of 12 cultivars showed that all but one of the Mexican strains were virulent exclusively on Mesoamerican cultivars. Argentinean strains were virulent preferentially on southern Andes cultivars, and the Ecuadorian strains, except for one strain, were avirulent on all cultivars. These results suggest an adaptation of strains on cultivars of the same geographic origin. Thus, based on molecular and virulence markers, C. lindemuthianum strains isolated from wild common bean populations were divided into three groups corresponding to host gene pools.

© 1997 The American Phytopathological Society