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Molecular Plant Pathology

Molecular Taxonomy of Colletotrichum Species Causing Anthracnose on the Malvaceae. J. A. Bailey, IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, BS18 9AF, United Kingdom; C. Nash(2), L. W. Morgan(3), R. J. O’Connell(4), and D. O. TeBeest(5). (2)(3)(4)IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol, BS18 9AF, United Kingdom; (5)Department of Plant Pathology, University of Arkansas, 217 Plant Science Building, Fayetteville 72701. Phytopathology 86:1076-1083. Accepted for publication 8 July 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/Phyto-86-1076.

The taxonomic status of isolates of Colletotrichum (C. gossypii; C. gossypii var. cephalosporioides; C. gloeosporioides f. sp. malvae, including BioMal; and C. malvarum) from cotton, Lavatera trimestris, Malva pusilla, and Sida spinosa was studied. For a representative sample of these isolates, conidial morphology and differentiation, their affinity for the lectin Bauhinia purpurea agglutinin (BPA) and a monoclonal antibody (UB 20), and the nature of their infection hyphae were assessed in association with an analysis of rDNA sequence data. The results revealed that all the isolates from L. trimestris, M. pusilla, and S. spinosa, including BioMal and several other samples of C. gloeosporioides f. sp. malvae, were forms of the C. orbiculare aggregate species. All these isolates produced straight-cylindrical conidia that bound BPA and UB 20 and remained aseptate after germination. The similarity of these isolates to other forms of the C. orbiculare species aggregate was confirmed by examination of their initial infection process and by restriction analysis of their rDNA. Analysis of isolates from cotton showed that they were similar to each other and to several forms of C. gloeosporioides. Thus, it is probably not appropriate to regard C. gossypii as a species distinct from C. gloeosporioides. The suitability of the C. orbiculare species aggregate for studies on the molecular basis of host specificity is discussed.