Characterization of Armillaria isolates from tea (Camellia sinensis) in Kenya

Abstract

Armillaria is a primary root rot pathogen of tea (Camellia sinensis) in Kenya. The main species presently described in this country are A. mellea and A. heimii. A survey covering fourteen districts of Kenya was carried out and forty-seven isolates of Armillaria collected. Cultural morphology, rhizomorph characteristics, somatic incompatibility and features of basidiomata were used to characterize the isolates, together with molecular analysis based on randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR), restriction fragment length polymorphism (RFLP) of the internal transcribed spacer (ITS) and the intergenic spacer (IGS) regions and sequence of the IGS region. It can be concluded that two Armillaria species were present and they were different from A. mellea. The first group was morphologically similar to A. heimii but this was contradicted by the molecular data, suggesting that A. heimii could be a complex of several species. The second group was different from the first and morphological and molecular data strongly suggest that it could be a new Armillaria species.

• Armillaria
• IGS
• ISSR
• ITS
• RAPD
• RFLPs
• phylogeny

We thank Dr. J-J Guillaumin and Mr. P Desray of UMR INRA, Clermont-Ferrand, France, for their generous donation of isolates and for their helpful advice and support. We also thank Dr. C. Prior and Dr. R. Cook of the Royal Horticultural Society (RHS), UK; Dr. J. Nicklin and Prof. P. Bridge of the School of Biological and Chemical Sciences, Birkbeck College, London; and Dr. Francis N. Wachira of the Department of Botany, Tea Research Foundation of Kenya, for their support and helpful comments on the manuscript. Dr. B. Spooner and Prof. P. Bridge of the Royal Botanical Gardens at Kew, UK kindly gave us access to Armillaria material from the Herbarium. Dr. B. Henricot of the RHS helped with the phylogeny.