An overview of Aspergillus ( Hvphomycetes ) and associated teleomorphs in southern Africa

An overview is given of literature concerning the genus Aspergillus Link and its teleomorphs. Chaetosartorya Subram.. Emericellu Berk. & Broome. Eurotium Link. Fennelliu B.J. Wiley & E.G. Simmons, Neosartorya Malloch & Cain and Sclerocleista Subram. encountered in the Republic of South Africa. Botswana. Lesotho. Mozambique. Namibia. Swaziland. Transkei and Zimbabwe up to 1993. The information is grouped under headings that indicate the field of research, namely general mycology, plant pathology, human pathology, animal and insect pathology, industrial relevance and secondary metabo­ lites and mycotoxins. An alphabetical list of recorded Aspergillus species is provided and the relevant host or substrate is given together with a literature reference, while the fungal nomenclature has been updated. All the Aspergillus species that are regarded as common have been reported from southern Africa. No in-depth research has been done here on this group, except for chemical work on mycotoxins.


INTRODUCTION
'Species of the great group Aspergillus form a very considerable percentage of all the mould colonies en countered in the cultural examination of foodstuffs, of soil and of miscellaneous materials' (Thom & Church 1926).
Economically and ecologically Aspergillus is a very important group, not only because of its ubiquitous nature, but it also has the ability to grow under a wide range of conditions (Domsch et al. 1980).There are probably few substrates that cannot be colonized and degraded.These fungi also synthesize an extraordinary variety of metabo lites with biological activity (Raper & Fennell 1973).Profitable and advantageous applications of Aspergillus can be found in the production of antibiotics, antifungal substances, vitamins and organic acids, in the preparation of oriental foods, the use of various species in physiologi cal experiments and testing of fungicides as well as in genetic work (Kozakiewicz 1989).Aspergilli also have a deleterious impact: some members of the genus are plant pathogens (Raper & Fennell 1973: Gorter 1977).there are well-known human (Martin & Berson 1973) and animal pathogens (Neitz 1965), many are mycotoxin producers (Frisvad 1989) and they contribute greatly to spoilage (Kozakiewicz 1989).
The genus name Aspergillus dates back to Micheli.who used the term because of the similarity between the conidial head and a holy water sprinkler called an aspergill (Raper & Fennell 1973).The development of the taxonomy of Aspergillus is described in detail by Raper & Fennell (1973).Christensen & Tuthill (1985) and Kozakiewicz (1989).
The first comprehensive work on the genus Aspergillus was by Thom & Church (1926) and the second revision of this work is the monograph currently used for Asper gillus identifications (Raper & Fennel 1973).These authors recognised 132 species and separated them into 18 groups.In an update by Samson (1979).he accepted another 34 taxa and nomenclaturally separated the asexual from the sexual states.
A shortcoming of the work of Raper & Fennell (1973) is the fact that both anamorph and teleomorph species are treated under the anamorph genus.Aspergillus.The nomenclatural separation of the anamorph from the teleomorph.as incorporated by Benjamin (1955), was not accepted by Raper & Fennell (1973).Benjamin (1955) selected the previously published generic names.Eurotium Link.Emericella Berk, and Sartorya Vuill.for the teleo morph ic states.The typification of 190 taxa of Aspergillus was investigated by Samson & Gams (1985) and adjust ments were made to meet the rules of the International Code of Botanical Nomenclature, giving teleomorphic names priority over anamorphic ones.The taxonomic work of Horie (1980).Gams & Samson (1985) and Bothalia 24,2 (1994) Kozakiewicz (1989) further contributed to our knowledge of the group.
Various authors have studied specific groups of the genus: Al-Musallam (1980) did a revision of the black Aspergilli, Christensen (1982) revised the A. ochraceus group and Kurtzman et al. (1986) and Klich & Pitt (1988) differentiated between species in the A. flavus group.Horie (1980) and Kozakiewicz (1989) used ascospore and conidial ornamentation as an aid to identification.
More sophisticated methods such as DNA relatedness (Kurtzman et al. 1986), mycotoxin production (Klich & Pitt 1988;Frisvad 1989), API-Zym strips (Jain & Lacey 1991) and genetic similarity studies (Peterson 1992) have been used with success in Aspergillus identification.Sam son & Pitt (1985Pitt ( . 1990) described the use of nucleic acid relatedness, serological methods, exocellular polysac charides, enzyme electrophoresis, ubiquinone systems and DNA and RNA studies for the same purpose.Their find ings confirm the value of a multidisciplinary approach to fungal taxonomy in general, including that of Aspergillus.
A major contribution to Aspergillus taxonomy has been made by the workshops on Aspergillus and Penicillium systematics (Samson & Pitt 1985, 1990) as well as the formation of the Subcommission on Penicillium and Aspergillus Systematics under the International Commis sion on Taxonomy of Fungi (Samson & Pitt 1990).This paper is an overv iew of publications dealing with all aspects of Aspergillus in South Africa, Botswana, Lesotho, Mozambique.Namibia.Swaziland, Transkei and Zimbabwe.Literature is grouped under headings indicat ing the scope of the research and is in chronological order.A list of recorded species is appended in which isolates in the dried collection (PREM) as well as the culture col lection (PPRI) of the National Collection of Fungi were included.Culture collections donated to the Mycology Unit as well as catalogues of international culture collec tions were consulted tor additional information.No at tempt has been made to verify published data, the identity of Aspergillus isolates or any other information.Names of fungi and hosts or substrates are given exactly as in the original text.

General mycology
The first entry' of an Aspergillus in the National Col lection of Fungi is A. glaucus Link (PREM 701-see checklist), collected by J.H.T.  (Doidge 1950).In all probability this specimen represents the first record of an Aspergillus in southern Africa.
Aspergillus isolates are often listed in general fungal surveys.Cohen (1950) studied soil fungi and recorded three Aspergillus species.Doidge (1950) listed 19 species of Aspergillus.Many of these species names are no longer in use.The mycoiogical Herbarium of the Timber Re search Laboratory, connected to the Transvaal Chamber of Mines, had a collection of over 1 400 timber-deteriorat ing fungi, mostly obtained underground.Many of these isolates had been identified overseas by Thom and the CBS (see checklist).Fortunately, Doidge (1950) listed these fungi, including the Aspergilli, as the original infor mation and lists could not be traced.
Ascosporic Aspergillus spp.present in the collection of the University of the Witwatersrand were discussed by Swart (1959).Five Aspergillus spp., four of which were new records for South Africa, were isolated from forest soil in Zululand (Eicker 1969).The majority of fungi iso lated from Zululand soil belonged to the Fungi Imperfecti, with Aspergilli well represented (Eicker 1970a), and dis tributed evenly in vertical profiles of these soils (Eicker 1970b).In a paper dealing with the occurrence, isolation and identity of thermophylic fungi, Eicker (1972) indi cated that A. fumigatus Fresen.can grow and sporulate at temperatures ranging from 20°C to 50°C. A. japonicus Saito was present in three of the four Eucalyptus leaf litter horizons (Eicker 1973).From savanna soil of the Transvaal 16 species of Aspergillus were isolated (Eicker 1974), and most of these were deposited in IMI (see checklist).Few isolates of Aspergillus were found on litter of Panicum coloration L. (Eicker 1976).In the western Transvaal, seven species of Aspergillus were found in the soil of an Acacia karroo community (Papendorf 1976).Bezuidenhout (1977) found nine Aspergillus spp.among Hyphomycetes associated with the grass, Cenchrus ciliaris L. Hyaline amerospores, including those of Asper gillus, were found to make up 4.5% of the aerospora above an Eragrostis curvula (Schrad.)Nees pasture (Van der Merwe et al. 1979).Gorter (1979) compiled a checklist of fungi recorded in South Africa up to 1977: the original publications are listed here.A. clavatus Desm.was found to be present in 45% of industrial malt samples, while A. flavus Link com prised about 25% of the fungi found on commercial malt (Rabie & Liibben 1984).Roux (1985) isolated five Asper gillus spp.from a Karoo pasture. A. carbonarius (Bainier) Thom has been recorded on Eucalyptus (Lundquist & Baxter 1985) and Aspergillus spp.were found on Pinus (Lundquist 1987).Aspergillus spp.were the dominant fungi isolated from the bare patches on the Giribes plains in Namibia, making up 21% of fungi isolated (Eicker et al. 1982).but no ex planation could be given for this phenomenon.Allsopp et al. (1987) isolated fungi associated with roots of proteaceous seedlings and recorded A. duricaulis Raper & Fennell and A. uni lateral is Thrower from South Africa tor the first time.A. ficuum (Reichardt) Hennings and A. ustus (Bainier) Thom & Church were found to be endophytes in grass (De Villiers 1989).Aspergillus spp.were commonly isolated from indigenous stored seed (Isaacs & Benic 1990).Watson et al. (1990) found among others, A. terreus in the gut of dune dwelling lepismatids.but neither the role nor the effect of these fungi could be determined.Conidiogenesis of A nigerTiegh. w as studied by Tiedt (1992).Verwoerd (1929) indicated A. niger as the cause of disease of onions and pomegranates in the winter rainfall area.Rosselet (1953) used A. niger as test organism in determining available potassium in lowveld soil, and later (Rosselet 1955) to determine levels of potassium, mag nesium and phosphorus in citrus orchards as well as in virgin soil.This method is based on the assumption that elements available to micro-organisms will be available to plants.These references possibly have more relevance to plant nutrition than to plant pathology.Doidge & Van der Plank (1936) indicated A. niger and Aspergillus spp. as a cause of rot on stored citrus fruit.A. carhonarius, A. niger and A. ochraceus group were listed as plant pathogens by Doidge et al. (1953).A. niger was found to comprise 6 % of fungi in citrus orchard soil whereas in virgin soils A. fumigatus was one of the dominant species.The latter species was rarely isolated from citrus soil (Martin I960).Four species of Aspergillus contributed to the decay of litchi fruit, according to Roth (1963) whereas A. niger has been isolated from banana hands (Roth & Loest 1965).Van der Westhuizen & Bredell (1972) found several Aspergillus species on high quality maize, A. flavus, A. niger and A. sydowi (Bain.& Sart.)Thom & Church being among the most prevalent ones.Stored lucerne seed was found to yield only a few Aspergillus spp.and no increase during storage was reported (Marasas & Bredell 1973).An index of plant pathogens (Gorter 1977) listed A. flavus and A. niger.

Plant pathology and seed deterioration
According to Bornman (1978) a large proportion of seeds of Welwitschia mirabilis (Hwk.f.) are sterile and this situation is aggravated by A. niger.This fungus infests the inflorescence, rendering more than 99% of all seeds infertile.This same fungus has also been listed in con nection with post-harvest decay of mangoes (Wehner et al. 1981).Aspergillus contamination of both stored seed and seedlings of maize is high: members of the A. glaucus group are often isolated and it is suggested that some Aspergillus spp.may be seed-transmitted (McLean & Berjak 1987).
Various Aspergillus species were isolated from the roots of Medicago spp.. but they were not pathogenic (Lamprecht et al. 1988).Steinke et al. (1990) found that Aspergillus spp.deteriorated both Avicennia and Hruguiera leaves but they made up less than 12% of isola tions.This group of fungi occurred in less than 10% of sorghum grain (Bosnian et al. 1991).A. niger commonly occurred in citrus soil but did not have a pronounced an tagonistic effect on various fungal pathogens of citrus (Botha & Wehner 1990).Four Aspergillus spp.were recorded to be antagonistic to Rhizoctonia solani by Weideman et al. (1990).Aspergillus spp.did not pose problems on stored homoiohydrous seeds (Mycock & Berjak 1990).My cock et al. (1990) found that A. flavus var.columnaris Raper & Fennell can infect maize seedlings and survive in the maturing plant, and Mycock & Berjak (1992) found that hot water treatment of maize seed decreased internal Aspergillus counts from 61% to 5%.Healthy chicory roots were inoculated with Aspergillus spp.isolated from in fected roots, but the fungi had no detrimental effect (Prinsloo et al. 1991).

Human pathology
Species of Aspergillus are indicated as pathogens worldwide in various aspects in the pathology of humans and of other mammals and insects.In the case of humans information is grouped below according to the effect of the fungus.Thiel (1986) as well as Marasas (1988) con sidered foodbome mycotoxins such as aflatoxin.produced by A. flavus to be of great medical relevance.

Aspergilli as allergens
Members of this genus have allergenic qualities and the first southern African report in this regard is a surv ey done by Ordman & Etter (1956).They found that Asper gillus spp.made up only 0.7% of airborne fungi in Johan nesburg and show ed no seasonal incidence.A later surv ey (Ordman 1963) indicated the same tendencies, with similar results obtained for Windhoek (Ordman 1970).Patients w ith positive precipitins to Aspergillus had these to either A. fumigatus or A. niger.; the antigens were prepared locally (Benatar et al. 1980).Patients of certain population groups were found to be more allergic to A. fumigatus than others (Joubert et al. 1988).Ten per cent of allergic children in the Western Cape were sensitive to Aspergillus spp.when positive skin tests were done, whereas 12% tested positive to this fungus when IgE responses w ere used (Potter et al. 1991)

Aspergilli and cancer
In an appraisal of liver cirrhosis and hepatoma in the local population.Isaacson (1966 > came to the conclusion that liver cell necrosis can be a result of A. flavus toxicosis rather than of infective hepatitis.Purchase & Vorster (1968) suggested that aflatoxin M found in milk also had a carcinogenic effect.Gilman (1972) conducted a comprehensive surv ey into fungal contamination of food in the Eastern Transvaal and Swaziland and the findings supported an association be tween mycotoxins in the diet and incidence of liver cancer.Various Aspergillus spp.were recorded and aflatoxin was found to be more prevalent in groundnut products than in maize.Peers et al. (1976) found a significant correlation between ingested aflatoxin and the incidence of primary liver cancer in Swaziland.Aspergillus was present in 3.3% of samples from the low rate area and 6.7% samples from the high rate area of an oesophageal cancer area in Transkei (Marasas et al. 1981).The correlation of high risk of exposure to aflatoxin and the hepatitis B virus to hepatocellular carcinoma has been indicated (Brcssac et al. 1991).but is beyond the scope of this overv iew.The above-mentioned references arc merely representative of this subject; more were traced but they did not refer to a specific fungus.Bothalia 24,2 (1994) Aspergillosis, keratitis and otitis Cases of infection by Aspergillus are often associated with degenerative disorders.Jacobs et al. (1965) found that pulmonary aspergillosis was extremely rare in all race groups in South Africa and they described a single case.Martin & Berson (1973) gave a comprehensive account of fungal diseases in southern Africa, listing cases of aspergilloses: various Aspergillus spp.were considered responsible for 69 cases of diseases of the ear.
Two cases of aspergillosis of the skin were recorded by Findlay et al. (1971) and in both cases the organism involved was A. fumigatus, while Caro & Dogliotti (1973) described a similar case.Block & Young (1977) indicated the value of early diagnosis of opportunistic fungal infec tions and again referred to A. fumigatus.They also found that the use of membrane filter blood cultures gave better results than serological methods.This same fungus was responsible for four cases of pneumonia described by Kallenbach et al. (1977).Bak & Wagenveld (1983) discussed the treatment of otitis where one of the organisms causing problems was A. niger.A. fumigatus as well as an uniden tified Aspergillus sp. was found to cause fatal fungal pneumonia in heart transplant patients (Cooper et al. 1983).A case report of paranasal sinus aspergillosis was given by Glass et al. (1984) but no fungus was indicated.Pulmonary aspergillosis caused by A. fumigatus compli cated pneumonia and was the cause of death of an other wise healthy patient (Lewis et al. 1985).
Aspergillus spp.were identified in four cases of fungal keratitis that responded well to miconazole treatment (Fitzsimons & Peters 1986).In the area where Mseleni joint disease is found, 41% of homegrown groundnuts were contam inated by Aspergillus (M arasas & Van Rensburg 1986).A. stromatoides Raper & Fennell was found to cause a fatal sino-orbital infection (Sacho et al. 1987), while A. niger was isolated from a patient with a fatal brain abscess (Berkowitz et al. 1987).Govender et al. (1991) reported five cases of A. fumigatus infection of the spine and found that the patients responded well to antifungal drugs.Prinsloo (1960) tound that A. parasiticus Speare in fected brown locusts both in the laboratory and in the field.Neitz (1965) indicated A. fumigatus as an enzootic pathogen in various birds, having obtained some of this information by personal communication.Prozesky et al. (1971) gave an account of A. fumigatus infection of scaly weavers.An outbreak in a colony of these birds kept at Onderstepoort is described: fortunately, the indicated treat ment quickly put an end to the morbidity and deaths.Nesbit (1986) described aspergillosis of a piglet but no causative organism could be isolated.

Industrial relevance
The first record of Aspergilli mentioned in an industrial sense was by Van der Bijl (1920) who studied deteriora tion of sugar by fungi.Isolates were sent to Thom in America and his full report is included in Van der Bijfs publication.The production of the enzyme invertase by micro-organisms such as A. niger and A. terreus Thom was influenced by various factors and these were indi cated.In the dairy industry Aspergillus spp.were reported by Davel & Neethling (1930) to be troublesome.Purchase & Vorster (1968) tested milk samples for the presence of aflatoxin M, as this mycotoxin may be carcinogenic: 21 samples were tested and five gave positive results.A prob lem with sticky molasses meal was addressed 'by Roth (1968) who tested many micro-organisms, among others seven species of Aspergillus, to render the product more free-flowing.
When fungi tound on cheese were tested for toxicity, all isolates of A. ustus were found to be toxic to ducklings, but no mycotoxins were detected in the cheese (Luck et al. 1976).Likewise, no aflatoxin was detected in cheese or milk powder but 23% of milk samples tested positive (Luck & Wehner 1979).
Aspergillus spp.were found to be more prevalent on grapes infected by Botrytis than on healthy ones (Le Roux et al. 1973).Using three different techniques, Eicker (1977) isolated thermophylic fungi, including A. fumi gatus, from mushroom compost.Fungal growth on wetblue leather is a common occurrence and Russell (1981) tested various fungicides by using fungi including Asper gillus spp.isolated from this substrate.
Relative cellulytic activity of 14 species of Aspergillus was also determined, when mesophilic fungi on compost was studied (Eicker 1980).Various casing materials for mushroom production were evaluated by Smit (1984) and Aspergilli were encountered during microbiological evaluation.Thermotolerant fungi, namely A. fumigatus and an Aspergillus sp., were grown on spent sulphite liq uor from a pulp mill (Pretorius 1993a, b, c).The potential for single cell protein production, the growth charac teristics ol these fungi and three reactor configurations were discussed.

Secondary metabolites and mycotoxins
Species of Aspergillus a n d Penicillium are potent secondary metabolite and mycotoxin producers (Frisvad 1989).The use of secondary metabolite profiles in the identification of these species is well established and these substances are the subject of ongoing research (Samson & Pitt 1985;Frisvad 1989;Samson & Pitt 1990).
In the early 1960's aflatoxin, a metabolite of A. flavus and A. parasiticus, was discovered and soon found to be highly carcinogenic (Raper & Fennell 1973).Previously Thom & Church (1926) had already indicated that grain contaminated with A. flavus could be poisonous to cattle and swine.As a result of these findings, research in secon dary metabolites and mycotoxins became a high prioriiv world-wide.Rabie e t al. (1964) indicated that A. amstelodami (L.Mangin) Thom & Church had a toxic effect on poultry and rabbits.The fungus proved to be lethal to rabbits and reduced the growth of ducks.The work done subsequently by Scott (1965) attracted inter national attention.He investigated the toxigenicity of fungi obtained from various commercial products: 46 fun gal strains belonging to 22 species caused the death of ducklings in only 14 days.Of these, 12 species belonged to the genus Aspergillus.Five of these Aspergillus spp.also had a detrimental effect on mice and rats.
Rabie et al. (1965) found that A. wentii Wehmer was toxic to experimental animals, but the toxin was not iden tified.Rabie & Terblanche (1967) compared the influence of temperature on two A. wentii isolates with variable toxicity.The toxins were characterized and found to be mildly toxic to ducklings (Rabie et al. 1986).
Van Warmelo (1967) investigated the correlation be tween the incidence of toxicity of stock feeds and certain fungal species.Aflatoxin was found in only five of the 39 samples in which A. flavus was detected.Van Warmelo et al. (1968) found that aflatoxin can accumulate in maize naturally infected with A. flavus and that moisture and temperature affect this process.
Holzapfel et al. (1966) showed that sterigmatocystin was produced by fungi other than A. versicolor (Vuill.)Tiraboschi and found that three out of five strains of A. nidulans (Eidam) Wint.caused rapid deaths in ducklings.A. niger was the most frequent fungus found on dried fruits and nuts.Wehner & Rabie (1970) indicated that maize on which A. niger as well as A. flavus was grown had a detrimental effect on ducklings.
The production of ochratoxin by A. ochraceus Wilhelm is well documented (Kellerman et al. 1988).The structure of the mycotoxin has been determined by Van der Merwe et al. ( 1965a, b), and Purchase & Theron (1968) illustrated the acute toxicity of this fungus to rats.(Rabie et al. 1977).The latter was a local isolate, producing a low quantity of sterigmatocystin.The effect it had could have been partly due to other toxins such as ausdiol.which were not tested for.
A. clavatus produced a tremorgenic substance which had a lethal effect on cattle and sheep (Kellerman et al. 1976).This fatal substance was produced by the fungus when it was grown on malt sprouts as well as on sorghum beer residue (Kellerman et al. 1984).In both cases the toxin involved was unknown.The mycotoxins cytochalasin E and K were isolated from an isolate of A. clavatus (Steyn et al. 1982).The tremorgenic and lethal effect of A. clavatus was illustrated with photographs by Coetzer et al. (1985) and a similar report was given by Kellerman et al. (1988).Dutton & Westlake (1985) tested agricultural com modities for fungi and their toxins.They found A. flavus and A. parasiticus in 22% of the samples whereas 27.2% of samples yielded aflatoxin B1 and often also B2.G1 and G2.Westlake & Dutton (1985) reported on the in cidence of mycotoxins in the broiler industry and found that aflatoxin may depress growth rates and could play a role in poultry diseases.Rabie (1986) reviewed contamination of foods by toxigenic fungi and mycotoxins and discussed law-enfor cement problems.Rheeder et al. (1990) warned that Aspergillus on maize grain should be monitored as it poses a mycotoxological threat.Liibben (1992) tested various isolates of fungi obtained from oats and wheat for toxicity and found that several Aspergillus isolates tested positive.All isolates that proved to be toxic in the above research are indicated in the appended checklist with an asterisk (*) preceding the reference.
Mutagenic activity of various secondary metabolites of Aspergillus spp.has been indicated by Wehner et al. (1978).Wehner et al. (1979a. b) and Kfir et al. (1986).Extracellular enzyme production of Aspergillus spp. was studied by McLean et al. (1985): A. flavus and A. candidus Link were found to be prolific enzyme producers.HPLC determinations of aflatoxin B and G in groundnut seed, indicated a 79.1% presence of A. parasiticus and 20.9% of A. flavus (Labuschagne & Wehner 1990).McLean et al. (1990) found that aflatoxin B1 is toxic to callus tissue of maize.
The large number of references concerning work of a chemical nature, is beyond the scope of this overview.However, the following works serve as general references.A symposium on mycotoxins (Anon. 1965) treated various aspects of aflatoxin.Purchase & Theron (1967) gave a comprehensive review of work on mycotoxins in South Africa.Steyn (1980) summarised studies on secondary metabolism, highlighting contributions by South African scientists.The sixth International IUPAC Symposium on Mycotoxins and Phvcotoxins (Steyn & Vleggaar 1986) was held in South Africa and two local papers on aflatoxin were included.An update on the mycotoxins produced by Aspergillus spp., is included in the work of Frisvad (1989).

DISCUSSION
The 25 commonly encountered species of Aspergillus (Domsch et al. 1980) have all been recorded from southern Africa, although of the estimated 170-200 described Aspergilli (Christensen & Tuthill 1985), only 72 or about 40% of species with Aspergillus anamorphs have been traced and included in the checklist.Forty per cent of all described Aspergillus spp.have been recorded from single locations or are restricted in geographic dis tribution (Christensen & Tuthill 1985): so many probably do not occur here.This may explain why such a relatively low percentage of Aspergillus species have been recorded from southern Africa.
It may be concluded that southern Africa, with its v aried climatic regions and some of the oldest geological formations in the world, may be a source of Aspergillus species differing from those already known.Most records of Aspergilli here have been from foodstuffs, and little information is available concerning the ecological adap tation of members of this genus to the diverse conditions in this country.It is significant that on the arid Giribes Plain of Namibia, the dominant genus isolated from soil in the perplexing bare patches has been Aspergillus (Eick er et al. 1982).Unfortunately there is no indication how many, if any. of those isolates were difficult to identify and were consequently lumped under the heading *Asjht- Bothalia 24,2 (1994) gillus spp.'The same may be true for other surveys such as those of Eicker (1969Eicker ( , 1970Eicker ( , 1974) ) and Papendorf (1976), where unidentified Aspergilli were listed.A survey of various ecological niches may prove to be a taxonomically rewarding undertaking and may yield potentially useful but as yet undescribed species.
South African isolates of Aspergillus have been men tioned by authorities such as Thom &Church (1926), andRaper &Fennel (1973)  Although no local scientist has made a major contribu tion to the taxonomy of this group, much attention has been paid to the detection and characterisation of mycotoxins, and South Africans have become world leaders in this field.A large number of references con cerning aflatoxin, a metabolite of A. flavus a n d A. parasiticus, are available, but these have not been treated here as they do not refer to specific fungal isolates.The same goes for other mycotoxins such as austocystins, ochratoxin and sterigmatocystin.It is of interest that ochratoxin A, B. and C were characterised in South Africa ( Van der Merwe et al. 1965a, b), and their toxicity deter mined (Purchase & Theron 1968), but the toxins themsel ves have never been isolated here (Mantle & McHugh 1993).Eicker (1975) found that A. aculeatus had an an tagonistic effect on both Staphylococcus and Candida.Shortly afterwards a secondary metabolite of this fungus, namely aculeacin A. was found to have strong activity against filamentous fungi, as well as yeasts (Mizuno et al. 1977).There may be other members of the group with similar undetected beneficial characteristics.
Species of Aspergillus such as A. ochraceus K. Wilh., A. niger and A. terreus, but especially A. parasiticus, are known insect pathogens (Domsch et al. 1980).Isolates from arthropods have been recorded in southern Africa (Prinsloo 1960), but their potential as agents in biological control has not been investigated.Aspergillus spp.are chemically very active and may even be valuable in the control of plant pathogens.
The value of sophisticated chemical methods employed by many Aspergillus taxonomists (Samson & Pitt 1985, 1990) as well as that of electron microscopy (Kozakiewicz 1989)
who described A. cristatus Raper & Fennell on the basis of an isolate 'received in 1954 from the CBS as H. Swart 168 isolated by H. Swart, S. Africa'.Neither the authors of this fungus name, nor the CBS catalogue (see checklist), indicated a substrate or locality for this isolate.Swart's (1959) writings however, stated that his specimen No. 168 was isolated from mangrove soil, collected on the island of Inhaca off Maputo [Louren^o Marques], Mozambique.