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Trunk disease fungal pathogens reduce olive production globally by causing cankers, dieback, and other decline-related symptoms on olive trees. Very few fungi have been reported in association with olive dieback and decline in South Africa. Many of the fungal species reported from symptomatic olive trees in other countries have broad host ranges and are known to occur on other woody host plants in the Western Cape province, the main olive production region of South Africa. This survey investigated the diversity of fungi and symptoms associated with olive dieback and decline in South Africa. Isolations were made from internal wood symptoms of 145 European and 42 wild olive trees sampled in 10 and 9 districts, respectively. A total of 99 taxa were identified among 440 fungal isolates using combinations of morphological and molecular techniques. A new species of Pseudophaeomoniella, P. globosa, had the highest incidence, being recovered from 42.8 % of European and 54.8 % of wild olive samples. This species was recovered from 9 of the 10 districts where European olive trees were sampled and from all districts where wild olive trees were sampled. Members of the Phaeomoniellales (mainly P. globosa) were the most prevalent fungi in five of the seven symptom types considered, the only exceptions being twig dieback, where members of the Botryosphaeriaceae were more common, and soft/white rot where only Basidiomycota were recovered. Several of the species identified are known as pathogens of olives or other woody crops either in South Africa or elsewhere in the world, including species of Neofusicoccum, Phaeoacremonium, and Pleurostoma richardsiae. However, 81 of the 99 taxa identified have not previously been recorded on olive trees and have unknown interactions with this host. These taxa include one new genus and several putative new species, of which four are formally described as Celerioriella umnquma sp. nov., Pseudophaeomoniella globosa sp. nov., Vredendaliella oleae gen. & sp. nov., and Xenocylindrosporium margaritarum sp. nov. [ABSTRACT FROM AUTHOR]

Nineteen Phaeoacremonium species are currently known in South Africa. These have been reported from grapevines, fruit trees, fynbos twig litter and arthropods. In other countries some of these Phaeoacremonium species are also known from hosts such as European olive, quince and willow that commonly occur in the Western Cape Province of South Africa, where most South African records of Phaeoacremonium have been made. The aim of this study was to investigate the species diversity and host-range of Phaeoacremonium in the Western Cape Province of South Africa by characterising 156 isolates collected from 29 woody hosts. Phylogenetic analyses of combined actin and beta-tubulin datasets allowed for the identification of 31 species among the 156 isolates, including 13 new species and 3 known species that had not been recorded in South Africa previously. The new Phaeoacremonium species include P. album, P. aureum, P. bibendum, P. gamsii, P. geminum, P. junior, P. longicollarum, P. meliae, P. oleae, P. paululum, P. proliferatum, P. rosicola and P. spadicum. All previous records of P. alvesii in South Africa were re-identified as P. italicum, but both species were recovered during this survey. A total of 35 described Phaeoacremonium species are now known from South Africa, more than double the number reported from any other country. This high diversity reflects the high diversity of indigenous flora of the Cape Floral Region, a biodiversity hotspot mainly situated in the Western Cape Province. Paraphyly and incongruence between individual phylogenies of the actin and beta-tubulin regions complicated species delimitation in some cases indicating that additional phylogenetic markers should be investigated for use in Phaeoacremonium phylogenies to prevent misidentifications and the introduction of vague species boundaries. [ABSTRACT FROM AUTHOR]

Cell suspension cultures of Vitis vinifera cv. Dauphine berries were used to study the response to the vascular pathogen, Eutypa lata, in comparison with a biological control agent, Trichoderma atroviride, that was previously shown to be effective in pruning wound protection. The expression of genes coding for enzymes of the phenylpropanoid pathway and pathogenesis-related (PR) proteins was profiled over a 48-h period using quantitative reverse transcriptase PCR. The cell cultures responded to elicitors of both fungi with a hypersensitive-like response that lead to a decrease in cell viability. Similar genes were triggered by both the pathogen and biocontrol agent, but the timing patterns and magnitude of expression was dependent on the specific fungal elicitor. Culture filtrates of both fungi caused upregulation of phenylalanine ammonia-lyase ( PAL), 4-coumaroyl Co-A ligase ( CCo-A) and stilbene synthase ( STS), and a downregulation of chalcone synthase ( CHS) genes. The pathogen filtrate caused a biphasic pattern in the upregulation of PAL and STS genes which was not observed in cells treated with filtrates of the biocontrol agent. Analytical assays showed significantly higher total phenolic content and chitinolytic enzyme activity in the cell cultures treated with the T. atroviride filtrate compared to the pathogen filtrate. These results corresponded well to the higher expression of PAL and chitinase class IV genes. The response of the cell cultures to T. atroviride filtrate provides support for the notion that the wound protection by the biocontrol agent at least partially relies on the induction of grapevine resistance mechanisms. [ABSTRACT FROM AUTHOR]

Background and Aims The application of Trichoderma species on grapevine pruning wound surfaces reduces wound infection from trunk pathogens that cause grapevine decline. The aim of this study was to determine the efficacy of pruning wound treatments containing Trichoderma as influenced by the time of pruning and time of application following pruning. Methods and Results Cultivars Chenin Blanc and Cabernet Sauvignon were pruned early and late in the winter season, respectively, corresponding to the break from the winter dormancy period and the normal pruning time for these cultivars. After pruning, the wounds were treated immediately, 6, 24, 48 or 96 h after pruning with either T. atroviride or T. harzianum. Colonisation of grapevine pruning wounds by the Trichoderma spp. was dependent on the physiological state of the vines as well as the weather conditions at pruning. In dormant vines, colonisation remained high from immediate application up to 48 h after pruning. In vines at break of dormancy, colonisation was highest at 6 and 24 h after application. Natural wound infection was higher in wounds pruned in late winter compared with that in early winter. Conclusions Applying the biocontrol agent 6 h after pruning consistently resulted in a high incidence of Trichoderma spp. in both cultivars at either early or late pruning regardless of vine physiological state or the weather conditions. Significance of Study Pruning early in the season in combination with the application of Trichoderma spp. pruning-wound agents approximately 6 h after pruning can significantly reduce wound infection by trunk pathogens. [ABSTRACT FROM AUTHOR]

Antibiosis has been shown to be an important mode of action by Trichoderma species used in the protection of grapevine pruning wounds from infection by trunk pathogens. The major active compound from Trichoderma isolates known to protect grapevine pruning wounds from trunk pathogen infection was isolated and identified. The compound, a 6-pentyl- α-pyrone (6PP), was found to be the major secondary metabolite, by quantity, which accumulated in the culture filtrate of T. harzianum isolate T77 and the two T. atroviride isolates UST1 and UST2. Benzimidazole resistant mutants generated from these isolates also produced 6PP as their main secondary metabolite, except for a mutant of T77 that had lost its ability to produce 6PP. The isolates UST1 and UST2 were co-cultured with the grapevine trunk pathogens Eutypa lata and Neofusicoccum parvum in a minimal defined medium and a grapevine cane-based medium ( GCBM). Co-culturing UST1 with N. parvum induced 6 PP production in the minimal defined medium and the GCBM. The production of 6 PP by UST2 was induced in the GCBM, while co-culturing with the two trunk pathogens either reduced or had no effect on 6 PP production. Mycelial growth and ascospore/conidia germination of E. lata, N. australe, N. parvum and Phaeomoniella chlamydospora were inhibited by 6 PP in a concentration-dependent manner. The results show that the presence of N. parvum and grapevine wood elicits the production of 6 PP, suggesting that this metabolite is involved in Trichoderma-pathogen interactions on grapevine pruning wounds. [ABSTRACT FROM AUTHOR]

Esca disease of grapevine is a complex trunk disease consisting of several symptoms, one of which, white rot, has been found to be caused by various basidiomycetes within the order Hymenochaetales. During recent surveys of esca-related pathogens in South African vineyards, several unidentified basidiomycetes were isolated from white rot occurring in diseased vines. A new Fomitiporia species, F. capensis, is described based on fruit body morphology and combined internal transcribed spacer (ITS) and large-subunit (LSU) phylogeny, where it forms a clearly delineated and well-supported clade. Morphologically, F. capensis is similar to F. punctata in that both species essentially lack setae. Fomitiporia capensis, F. punctata and F. aethiopica produce similarly sized basidiospores but differ in terms of host range, pore size and, possibly, fruit body shape. Phylogenetically, F. capensis appears to be related to F. tenuis, though morphologically, the species differ significantly in that F. tenuis has smaller pores and smaller basidiospores. Fomitiporia capensis was found to occur widely as vegetative mycelium throughout the Western Cape Province, though fruit bodies were scarce in comparison. A vineyard with fruit bodies was also found in Limpopo in the north east of the country. Fruit bodies were found growing on the underside of the cordon of living vines displaying external symptoms typically associated with esca, or general decline and dieback symptoms together with internal white rot. [ABSTRACT FROM AUTHOR]

The generalist ascomycete fungus Eutypa lata causes Eutypa dieback of grapevine ( Vitis vinifera) worldwide. To decipher the cosmopolitan distribution of this fungus, the population genetic structure of 17 geographic samples was investigated from four continental regions (Australia, California, Europe and South Africa), based on analysis of 293 isolates genotyped with nine microsatellite markers. High levels of haplotypic richness ( R = 0·91-1) and absence of multilocus linkage disequilibrium among loci supported the preponderance of sexual reproduction in all regions examined. Nonetheless, the identification of identical multilocus haplotypes with identical vegetative compatibility groups, in some vineyards in California and South Africa, suggests that asexual dispersal of the fungus among neighbouring plants could be a rare means of disease spread. The greatest levels of allelic richness ( A = 4·89-4·97) and gene diversity ( H = 0·66-0·69) were found in Europe among geographic samples from coastal areas surrounding the Mediterranean Sea, whereas the lowest genetic diversity was found in South Africa and Australia ( A = 2·78-3·74; H = 0·49-0·57). Samples from California, Australia and South Africa, which had lower genetic diversity than those of Europe, were also characterized by demographic disequilibrium and, thus, may represent founding populations of the pathogen. Low but significant levels of genetic differentiation among all samples ( DEST = 0·12, P = 0·001; FST = 0·03, P = 0·001) are consistent with historical gene flow preventing differentiation at continental scales. These findings suggest that global, human-mediated spread of the fungus may have resulted in its current global distribution. [ABSTRACT FROM AUTHOR]

Black foot disease of grapevines is a decline and dieback disease caused by a soilborne pathogen complex including Cylindrocarpon liriodendri, C. macrodidymum, Campylocarpon fasciculare and Campyl. pseudofasciculare. These pathogens cause primary infections of roots and basal ends of grafted cuttings in nursery soils. Thirteen fungicides were screened in vitro for mycelial inhibition of these pathogens. Prochloraz manganese chloride, benomyl, flusilazole and imazalil were the most effective fungicides tested, and were subsequently included in semi-commercial field trials. Basal ends of grafted cuttings were dipped in various chemical and biological treatments prior to planting in open-rooted nurseries. Black foot pathogens were not isolated from grafted cuttings prior to planting. Additional treatments involved soil amendments with Trichoderma formulations and hot water treatment of dormant nursery grapevines. Field trials were evaluated after eight months. Isolations from uprooted plants revealed low levels of black foot pathogens in the roots of untreated control plants, and significantly higher levels in basal ends of rootstocks. The incidence of black foot pathogens, as well as that of Petri disease pathogens, was not significantly and/or consistently reduced by the majority of chemical or biological treatments. However, these pathogens were not isolated from uprooted plants that were subjected to hot water treatment. It is therefore recommended that hot water treatment of dormant nursery plants be included in an integrated strategy for the proactive management of these diseases in grapevine nurseries. [ABSTRACT FROM AUTHOR]

Several hyphomycetes were recently isolated from asymptomatic or symptomatic vascular tissues of grapevines showing Petri disease symptoms in South Africa. In most cases, their status as pathogens was unknown and pathogenicity studies were, therefore, conducted to determine their potential as decline pathogens. The fungi included Acremonium cf. charticola, Acremonium cf. ochraceum, Cadophora luteo-olivacea, Phialemonium cf. curvatum, Pleurostomophora richardsiae, Phaeoacremonium (Pm.) krajdenii, Pm. parasiticum, Pm. subulatum, Pm. venezuelense and Pm. viticola. Of these, Pm. parasiticum and Pm. viticola have been associated with Petri disease symptoms, although their pathogenicity has not been tested. Phaeomoniella (Pa.) chlamydospora and Pm. aleophilum, known to be involved in Petri disease and esca, were included as positive controls. Pathogenicity studies were conducted in glasshouse experiments where grapevine rootstocks were artificially inoculated, as well as in the field. Data obtained after 3 months from a glasshouse trial were difficult to interpret, due to the small lesions and similarity in disease expression among different species. However, Pa. chlamydospora produced the largest lesions and was by far the most aggressive pathogen. To supplement the glasshouse trial, grapevine trunks and pruning wounds of Vitis vinifera cv. Periquita were artificially inoculated in the field. Field trials, rated after 14 months, confirmed Pa. chlamydospora to be the most aggressive pathogen, since it produced the largest trunk and pruning wound lesions. Furthermore, it was re-isolated more frequently than any of the other fungi, especially from the pruning wounds. All the fungi were able to infect, colonise and produce lesions statistically different to those caused by the water control and the non-pathogen in the field trial. [ABSTRACT FROM AUTHOR]

Little information is presently available on the disease aetiology and epidemiology of the fungi involved in the decline of young vines. To address this question, four rootstock-scion combinations, originating from three commercial nurseries in the Wellington area of the Western Cape Province of South Africa were investigated during the 1999/2000 season. The first isolations were made in September from callused cuttings prior to planting in nurseries. After planting, asymptomatic rooted cuttings were selected from nurseries after 3, 6 and 9 months. Isolations were made from the roots, rootstock, grafting union and scion. Isolations from callused cuttings prior to planting clearly demonstrated that primary pathogens associated with Petri disease, such as Phaeomoniella chlamydospora and Phaeoacremonium spp. were already present in the apparently healthy rootstock propagation material as endophytes. However, Cylindrocarpon spp., which cause black foot disease, rarely occurred in propagation material at this time. Species of this genus were isolated at higher percentages later during the season. Less than 1% of the plants were infected with Cylindrocarpon spp. before planting in the nursery (October), whereas 50% or more of the plants were infected at the end of the season (June). These findings suggest that the low percentage survival of vine plants observed in recent years is partly due to infected propagation material, and to new infections established in nurseries. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the study "Grapevine Trunk Diseases: Complex and Still Poorly Understood," published in "Plant Pathology."

The presence of Phaeomoniella chlamydospora and Phaeoacremonium spp., the causal organisms of Petri disease of grapevine, in canes of rootstock vines in four mother blocks was determined monthly by means of isolations from the basal and fourth internodes. The canes were generally free from fungal, yeast and bacterial infection with only 2.4% of the total number of isolated xylem segments colonised. Basal internodes exhibited three-fold higher levels of infestation. The incidence of Pa. chlamydospora and Phaeoacremonium spp. was extremely low (< 0.2%) in the symptomless canes sampled from these rootstock mother vines. This emphasises the need for more sensitive detection techniques to be used for phytosanitary evaluation and research. [ABSTRACT FROM AUTHOR]