A diverse assemblage of Ophiostoma species, including two new taxa on eucalypt trees in South Africa

Abstract

Fungi in the Ophiostomatales include important pathogens of trees as well as agents of wood stain, reducing the economic value of timber. They rely on insects, such as bark beetles, for dispersal and are commonly associated with wounds on trees. Although Ophiostoma spp. have been reported from eucalypt wood chips in South Africa, very little is known about the diversity of the Ophiostomatales, or their insect associates, on plantation-grown Eucalyptus spp. The aim of this study was to consider the diversity and distribution of the Ophiostomatales infecting fresh wounds on Eucalyptus trees in the country. Additionally, knowledge regarding their association with nitidulid beetles, which have previously been shown to carry Ophiostoma spp., was sought. Surveys were conducted in five provinces where Eucalyptus spp. are commonly grown, and the fungi collected were identified using morphological comparisons and multigene sequence phylogenies. Of the 139 isolates collected, five Ophiostoma spp. were identified including O. quercus, O. tsotsi and O. tasmaniense. These were from cut stumps as well as from the nitidulid beetles Brachypeplus depressus and Carpophilus spp. In addition, two new taxa in the O. stenoceras–Sporothrix schenckii complex were identified from Eucalyptus trees infested by Phoracantha semipunctata. The two new taxa are described as O. candidum sp. nov., and O. fumeum sp. nov., respectively. The results of this study clearly show that the diversity and ecology of Ophiostoma spp. on Eucalyptus trees in South Africa is poorly understood and that further studies are required to determine the possible economic relevance of these fungi.