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.
