Systematics, diagnostics and epidemiology of the fungal genus Armillaria

• Main Author: Perez Sierra, Ana
• Published: Birkbeck (University of London) 2004
• Subjects: 579.6
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406210

Species in the genus Armillaria (Fr.:Fr.) Staude are major root pathogens of woody plants. A PCR-based technique was investigated aiming to develop a rapid and accurate method for identification of Armillaria species. Armillaria taxonomy has been extensively studied in Europe, North America and Australia. However, in Africa their taxonomy remains uncertain. A. mellea and A. heimii are the main species described. Morphological characteristics, somatic incompatibility, production of basidiomata in vitro, amplified fragment length polymorphisms (AFLPs), DNA profiles generated by polymerase chain reaction (PCR) amplification and restriction fragment length polymorphisms (RFLPs) of the internal transcribed spacer (ITS) and the intergenic spacer (lGS) regions of the ribosomal RNA (rRNA) gene cluster and phylogenetic analyses were used for the characterization of Armillaria in Africa. Armillaria species were successfully differentiated using PCR-RFLP-based techniques. A new Armillaria species was found in tea plantations in Kenya with very distinct characteristics from A. heimii and A. mellea. High variability within A. heimii was observed. The possibility of this group being a complex of different species was investigated and it was concluded that it was only one species, A. heimii. The development of a suitable experimental system for the study of the pathogenicity of A. mellea, the behaviour and growth of Armillaria in different types of soils and in wood- and bark-chips were investigated. A successful experimental system was found to work with Armillaria. New methods to study the growth and spread of Armillaria in different substrates were successfully tested. There were no significant differences found in the growth and spread of A. mellea between wood- and bark-chips. However, the survival of A. mellea was more successful in deeper layers of wood-chip mulching. Mulching had no effect on the A. mellea infection process, and the risk of healthy plants being infected by colonised mulch was very low.