Hymenochaetales Research Articles

Pathogenicity of South African Hymenochaetales taxa isolated from esca-infected grapevines.

Little is known about the pathogenicity and etiology of Hymenochaetales taxa associated with esca in South Africa. Ten South African Hymenochaetales taxa associated with esca in grapevine were subjected to basic enzyme assays to determine which ligninolytic enzymes were secreted by each taxon. In addition, a field trial was undertaken to determine the pathogenicity of these taxa. Twenty-seven fungal isolates and two negative controls were inoculated into wounds made on mature grapevines of the cultivars Shiraz and Mourvedre. Inoculated vines were evaluated for white rot symptoms after 24 months. The results of the enzyme assays indicated a difference in enzyme secretion among taxa and also between isolates of the same taxa. All isolates secreted cellulase and laccase, but there was a difference in isolates’ ability to secrete manganese peroxidase and lignin peroxidase. The results of the pathogenicity trial showed that all of the isolates used were capable of causing the characteristic white rot symptom in the wood. There were clear differences in susceptibility to white rot between the two cultivars tested, namely Shiraz and Mourvedre. The cultivars also differed in which taxa proved to be more virulent. On Shiraz a specific isolate of Taxon 6 (an Inonotus sp.), Phellinus sp . and Inonotus setuloso-croceus were significantly virulent. On Mourvedre, Taxon 3 (an Inocutis sp.) was significantly virulent.

Characterisation of the fungi associated with esca diseased grapevines in South Africa

During the period from 2001 to 2008, grapevines showing foliar and/or internal symptoms of esca were collected from various grape-growing regions in South Africa. Isolations were made from typical internal wood symptoms associated with esca, and fungal isolates were characterized by cultural growth patterns, morphology and phylogenetic inference. The gene regions sequenced included the internal transcribed spacers and the 5.8S rRNA gene (ITS) for the basidiomycetes and Phomopsis isolates , the partial b-tubulin and actin genes for Phaeoacremonium isolates and the partial translation elongation 1-a gene and the ITS for the Botryosphaeriaceae isolates. The fungi identified included Phaeomoniella chlamydospora and six species of Phaeoacremonium including Pm. aleophilum , Pm. alvesii , Pm. parasiticum , Pm.iranianum , Pm. mortoniae and Pm. sicilianum , of which the latter three are reported for the first time in South Africa. The following taxa were also identified: Eutypa lata , Phomopsis viticola , Phomopsis theicola , Diaporthe ambigua , Diplodia seriata , Neofusicoccum australe and N. parvum . The basidiomycete isolates were distributed over ten well supported monophyletic clades among genera of the Hymenochaetales. Two of these clades could be identified as species of Fomitiporia and Phellinus .

Biodiversity and Geographic Distribution of Basidiomycetes Causing Esca-Associates White Rot in Grapevine : A Worldwide Perspective

An overview is provided of the biodiversity, taxonomic classification and geographic distribution of basidiomycetes isolated from white rot in esca-affected grapevine all over the world. A total of 10 species have been recovered, all belonging to the Hymenochaetales and five of them of uncertain identity. Identified taxa include Fomitiporia mediterranea (Europe, Asia), F. polymorpha (North America), F. australiensis (Australia), and Inocutis jamaicensis (South America). One species, not yet formally described, is Fomitiporella vitis (South America). Uncertain taxa occur in Australia and South Africa. Existence of the fungi is widely restricted to vegetative mycelium. Fruit bodies are rare in the field and molecular data are usually necessary for differentiation.