|J. Van Rensburg|
Submitted to: Mycological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2006
Publication Date: 7/1/2006
Citation: Van Rensburg, J.C.J., Lamprecht, S.C., Groenewald, J.Z., Castlebury, L.A., Crous, P.W. 2006. Characterisation of Phomopsis spp. associated with die-back of rooibos (Aspalathus linearis) in South Africa. Studies in Mycology 55:65-74. Interpretive Summary: Fungi cause billions of dollars damage to crop plants each year. Soybeans are infected with a group of fungi that cause stem and canker diseases. One of these fungi on soybeans also infects other crops including rooibos tea plants in South Africa. In this study, fungi were isolated from rooibos tea plants and characterized with regard to morphology and pathogenicity. DNA sequences were obtained from these fungi to identify them and see how closely related they were to disease-causing fungi including those on soybeans. One of the fungi that causes a disease of soybeans and also occurs on rooibos tea was given a new name. In addition these fungi were described and illustrated. This information will be useful to researchers identifying fungi causing disease on soybeans and rooibos.
Technical Abstract: Die-back of rooibos (Aspalathus linearis) causes substantial losses in commercial Aspalathus plantations in South Africa. In the past, the disease has been attributed to Phomopsis phaseoli (teleomorph: Diaporthe phaseolorum). Isolates obtained from diseased plants, however, were highly variable with regard to morphology and pathogenicity. The aim of the present study was thus to identify the Phomopsis species associated with die-back of rooibos. Isolates were subjected to DNA sequence comparisons of the internal transcribed spacer region (ITS1, 5.8S, ITS2) and partial sequences of the translation elongation factor-1 alpha gene. Furthermore, species were also compared in glasshouse inoculation trials on 8-mo-old potted plants to evaluate their pathogenicity. Five species were identified, of which D. aspalathi (formerly identified as D. phaseolorum or D. phaseolorum var. meridionalis) proved to be the most virulent, followed by D. ambigua, Phomopsis theicola, a species of Libertella and Phomopsis, respectively, and a newly described species, P. cuppatea. A description is also provided for D. ambigua based on a newly designated epitype specimen.