Molecular analysis of the major Phytophthora species on cocoa

doi:10.1111/j.0032-0862.2004.00980.x

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Wiley InterScience

Plant Pathology

Volume 53 Issue 2, Pages 209 - 219

Published Online: 28 Apr 2004

Published on behalf of the British Society for Plant Pathology

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Molecular analysis of the major Phytophthora species on cocoa

A. A. Appiah ^ab‡, J. Flood ^b , S. A. Archer ^a and P. D. Bridge ^c *†§

^a Department of Biology, Imperial College, Silwood Park, Buckhurst Road, Ascot SL5 7PY; ^b CABI Bioscience, UK Centre, Bakeham Lane, Egham TW20 9TY; and ^c Mycology Section, Royal Botanic Gardens, Kew, Surrey TW9 3AH and School of Biological & Chemical Sciences, Birkbeck College University of London, Malet Street, London WC1E 7HX, UK

*To whom correspondence should be addressed.

†E-mail: pdbr@bas.ac.uk

‡Present address: Department of Molecular & Cell Biology, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK.

§Present address: British Antarctic Survey, NERC, High Cross, Madingley Road, Cambridge CB3 0ET, UK.

KEYWORDS

interspecific variation • rDNA-ITS region • RFLPs

ABSTRACT

The internally transcribed spacer (ITS) regions of the ribosomal RNA (rRNA) gene cluster of 161 isolates of Phytophthora species involved in pod rot, stem canker and leaf blight of cocoa were analysed to determine inter- and intraspecific variation in this disease complex. The species P. palmivora, P. megakarya, P. capsici, P. citrophthora and P. nicotianae could all be clearly distinguished by PCR amplification of the ITS region followed by restriction analysis with HaeIII, HinfI, PvuII and AluI. This method provided a relatively rapid identification procedure for these species, and was able to distinguish isolates that had previously been misidentified by morphological methods. Sequence analysis showed that the four main cocoa-associated species formed two distinct groups, one comprising P. capsici and P. citrophthora, and the other P. palmivora and P. megakarya. Detailed sequence analysis and comparison with published literature suggested that P. capsici isolates from cocoa may be closely related to P. tropicalis, a species recently described from Cyclamen and Dianthus.