Characterization of Armillaria Isolates from Tea (Camellia sinensis) in Kenya

Abstract

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.

Characterization of Armillaria heimii from Africa

“…This possible A. fuscipes taxon (Coetzee et al ., 2000; Otieno et al ., 2003) was differentiated from A. heimii from other African countries by differences in the sequence of the intergenic spacer (IGS) region of the ribosomal RNA gene cluster that could be determined by polymerase chain reaction and restriction fragment length polymorphisms (PCR‐RFLP) of the IGS region. The second species described by Otieno et al . (2003) was considered a new Armillaria species.…”

Armillaria species on tea in Kenya identified using isozyme and DNA sequence comparisons

“…Results of this study using isozyme analyses, RFLP patterns and comparisons of DNA sequence data showed that Armillaria from diseased tea bushes in Kenya represent three distinct groups. These results are in agreement with previous investigations that have found a variety of Armillaria groups in Kenya (Mwangi et al ., 1989, 1994; Mohammed et al ., 1994; Otieno et al ., 2003b; Pérez‐Sierra et al ., 2004). In the present study, these groups are referred to as Kenyan groups I, II and III.…”

“…(2000a) available in TreeBase (matrix number M859, study number S566). IGS‐1 sequence data for isolates CMW15584 and CMW15585, used in this study, were previously published by Otieno et al . (2003b).…”

“…This has motivated the use of molecular‐based studies to identify and classify isolates. Recent studies using analyses of pectic enzymes, DNA sequences, and RFLP and AFLP profiles have suggested that several species other than those previously recognized may be present in Africa (Mwenje & Ride, 1996, 1997; Coetzee et al ., 2000a; Mwenje et al ., 2003; Otieno et al ., 2003b; Pérez‐Sierra et al ., 2004).…”

“…Armillaria fuscipes encompassed isolates previously characterized and referred to as A. heimii (Coetzee et al ., 2000a). The separation of the lineages, reflecting A. fuscipes and A. heimii , into species, and the application of the names to identify them subsequently evoked considerable debate (Otieno et al ., 2003b; Pérez‐Sierra et al ., 2004). Recently, Coetzee et al .…”