Joanne E. Taylor

Fungi, aflatoxins, and cyclopiazonic acid associated with peanut retailing in Botswana.

Peanuts are important food commodities, but they are susceptible to fungal infestation and mycotoxin contamination. Raw peanuts were purchased from retail outlets in Botswana and examined for fungi and mycotoxin (aflatoxins and cyclopiazonic acid) contamination. Zygomycetes were the most common fungi isolated; they accounted for 41% of all the isolates and were found on 98% of the peanut samples. Among the Zygomycetes, Absidia corymbifera and Rhizopus stolonifer were the most common. Aspergillus spp. accounted for 35% of all the isolates, with Aspergillus niger being the most prevalent (20.4%). Aspergillus flavus/parasiticus were also present and accounted for 8.5% of all the isolates, with A. flavus accounting for the majority of the A. flavus/parasiticus identified. Of the 32 isolates of A. flavus screened for mycotoxin production, 11 did not produce detectable aflatoxins, 8 produced only aflatoxins B1 and B2, and 13 produced all four aflatoxins (B1, B2, G1, and G2) in varying amounts. Only 6 of the A. flavus isolates produced cyclopiazonic acid at concentrations ranging from 1 to 55 microg/kg. The one A. parasiticus isolate screened also produced all the four aflatoxins (1,200 microg/kg) but did not produce cyclopiazonic acid. When the raw peanut samples (n = 120) were analyzed for total aflatoxins, 78% contained aflatoxins at concentrations ranging from 12 to 329 microg/kg. Many of the samples (49%) contained total aflatoxins at concentrations above the 20 microg/kg limit set by the World Health Organization. Only 21% (n = 83) of the samples contained cyclopiazonic acid with concentrations ranging from 1 to 10 microg/kg. The results show that mycotoxins and toxigenic fungi are common contaminants of peanuts sold at retail in Botswana.

Fungal endophytes of Proteaceae, with particular emphasis on Botryosphaeria proteae

Fungal endophytes occurring in leaves and stems of three species of Proteaceae,Protea cynaroides, Leucospermum cordifolium andLeucadendron salignum×laureolum were investigated on farms in three locations in the Western Cape province of South Africa. The aims of this study were to determine ifBotryosphaeria proteae, a fungus that has been recorded from leaf spots ofProtea spp., was mostly restricted to leaf tissue, and whether it could occur as an endophyte in different members of Proteaceae. In this studyB. proteae was routinely isolated inProtea andLeucospermum, although it was not a dominant taxon and did not occur inLeucadendron. Botryosphaeria proteae occurred mostly in leaves, rather than stems, suggesting that it is not important as a stem canker pathogen.

A phylogenetic analysis of Mycosphaerellaceae leaf spot pathogens of Proteaceae

Many plant pathogenic foliicolous fungi recorded on Proteaceae hosts in South Africa are reminiscent of members of the Mycosphaerellaceae and their anamorphs. However, these fungi are often unusual and specific to the Proteaceae, and have proved difficult to classify in the past. To address this issue, a phylogenetic analysis of the ITS-1, 5.8S and ITS-2 DNA sequence data was performed to determine relationships between members of the Mycosphaerellaceae and some taxa apparently unique to the Proteaceae. Results from this study have confirmed Batcheloromyces to be affiliated to the Mycosphaerellaceae. Within Mycosphaerella, Batcheloromyces was also shown to be distinct from Stigmina, which clustered separately from Pseudocercospora. The separation between Mycosphaerella and Teratosphaeria (anamorph Trimmatostroma) was shown to be artificial, which was further supported by several Trimmatostroma species clustering within Mycosphaerella. From these data it is concluded that Teratosphaeria should be reduced to synonymy under Mycosphaerella, and that Trimmatostroma represents yet another additional anamorph of Mycosphaerella.

Biodiversity in the Cape Floral Kingdom: fungi occurring on Proteaceae.

The South African Cape Floral Kingdom is the worlds smallest and most diverse plant Kingdom, but is greatly under threat from urbanisation and agriculture. It covers only 90000 km2 and has a Mediterranean climate. This area has a long history of botanical studies, but little research has been undertaken on the associated fungi. Therefore, a biodiversity study of the fungi has been initiated. The catalyst for this study has been the diversity of unusual fungi encountered whilst studying the fungal pathogens of Proteaceae. These pathogens include species, or entire genera of fungi that are specific to genera of Proteaceae. The diversity and uniqueness of the Proteaceae pathogens may indicate a similar diversity in saprobic fungi in this unusual habitat. Therefore, microfungi associated with genera of Proteaceae in various habitats are being systematically sampled over a two-year period. The initial results of this study are presented.

Rhynchostomatoid fungi occurring on Proteaceae

A new ascomycete fungus, with long-necked perithecia having central ostioles and striate ascospores, was isolated from flowerheads of Protea burchellii and P. laurifolia in South Africa and is described here as Rhynchostoma proteae sp. nov. Sequence data obtained from the small-subunit ribosomal DNA (SSU nrDNA) place this fungus with 100% bootstrap support in a clade containing the type species of Rhynchostoma, R. minutum. A similar fungus with verruculose ascospores also was observed on a member of the Proteaceae from Australia, Lomatia polymorpha, which is described here as Rhynchomeliola lomatiae sp. nov. These two species are illustrated and contrasted with a third species from Proteaceae, Rhynchomeliola australiense, known from Grevillea in Australia.

Morphological variation and cultural characteristics of Coniothyrium leucospermi associated with leaf spots of Proteaceae

During an examination ofConiothyrium collections occurring on Proteaceae one species,C. leucospermi, was repeatedly encountered. However, it was not always possible to identify this species from host material alone, whereas cultural characteristics were found to be instrumental in its identification. Conidium wall ornamentation, which has earlier been accepted as crucial in species delimitation is shown to be variable on host material, making cultural comparisons essential. Using standard culture and incubation conditions,C. leucospermi is demonstrated to have a wide host range in the Proteaceae. In addition, microcyclic conidiation involving yeast-like budding from germinating conidia and hyphae in culture is newly reported for this species.

Two new species of Pseudohalonectria from palms

AbstractTwo new species, Pseudohalonectria eubenangeensis and P. palmicola, are described from palms in rainforests in north Queensland, Australia. The new species are compared with the known speci...

Batcheloromyces species occurring on Proteaceae in South Africa.

Batcheloromyces spp. are dematiaceous hyphomycetes which cause leaf spots on members of the Proteaceae in South Africa. The leaf spots are non-necrotic and composed of numerous sporodochial conidiomata. Conidiogenesis is holoblastic with percurrent, enteroblastic proliferation producing conidiogenous cells with ragged and irregular annellations. Brown, verrucose, aseptate and multiseptate conidia are produced. Conidia produced percurrently, can remain adhered to each other in fragile chains, disarticulating to produce aseptate conidia or, in some cases, they remain as multiseptate conidia where further schizolytic cleavage, at the delimiting septa, may or may not occur. This paper compares Batcheloromyces with the morphologically similar Stigmina, discusses the current members of Batcheloromyces and introduces the new species B. leucospermi.

Lasiosphaeria and a similar new genus from palms

Lasiosphaeriaceous ascomycetes from palms are discussed in this paper and three new species,L. alexandricola, L. alexandrae andL. chapmanii, are described. Three species are excluded fromLasiosphaeria, L. nematospora, L. rufula andL. tephrocoma, and the transfer ofL. subambigua toCercophora is noted. A new genus,Arecacicola, is introduced to accommodate a distinctive taxon from palms.Arecacicola is characterized by ascomata immersed in a sparse stroma consisting of hosts cells filled with fungal hyphae. The ascomata do not ultimately become erumpent. The ascospores lack apical spines, and the asci do not possess an apical ring. A key to lasiosphaeriaceous taxa from palms is provided.