2 Characteristics: biology, ecology, uses, cultivation

Mycology is the study of fungi and mycologists are the people who carry out these studies. New research methods have substantially increased knowledge about the fundamental nature of fungi. Much of this research has focused on fungi that cause plant diseases. Research on edible fungi has concentrated on a small group of species that are commercially cultivated. Wild edible fungi have, until recently, been relatively ignored by science, though amateur mycologists often documented species they found in field studies, mostly in Europe or countries in which Europeans have settled.

There has always, however, been a keen interest in a small group of valuable wild edible fungi that cannot be cultivated. These include the truffles (Tuber spp.), matsutake (Tricholoma spp.) and porcini or cèpes (Boletus edulis). Their biology and ecology have been studied in some detail – a marked contrast to the many other wild edible fungi used around the world.

The consequence of this neglect is that wild edible species used in developing countries are poorly known. Some information is available from studies of close relatives in temperate regions. Russula and Lactarius occur around the world, for example, and knowledge of species in Europe can be applied with some caution and caveats to African species. The main problem is naming and recognizing species. Genera and species concepts were originally based on the narrower range of diversity found in temperate regions and these may require fundamental reappraisal as tropical species become better known.

This chapter provides a brief introduction to the larger fungi (macrofungi), with special reference to those that are edible. The use of specialist terms has been avoided where simpler alternatives are available. Field guides contain useful glossaries and there are an increasing number of Web sites that help in understanding technical terms (Chapter 6). The Dictionary of the fungi is a regularly updated text with details about all fungal genera and other information on mycology (Kirk et al., 2001).

WHAT ARE FUNGI?

Fungi are a distinct group of organisms more closely related to animals than plants. At present fungi are divided into three separate and distinct kingdoms based on an expanded knowledge of their biochemistry and genetic makeup established especially over the last 30 or so years. It is wrong and misleading to refer to fungi as “plants without chlorophyll” (FAO, 1998a).

Despite fundamental differences, fungi are often classified as plants. Understanding the taxonomic status of fungi has little apparent significance to people collecting and selling wild edible fungi, but it is of critical importance in establishing a sound and robust classification system. This ensures that when two people use the same species name they know that they are referring to the same (edible) fungus.

The classification of fungi with plants has inadvertent practical consequences. It is not always clear whether ethnobotanical studies include wild fungi, as is the case with a study from Turkey (Ertrug, 2000). Ethnomycology is the correct term that indicates fungi are involved. On a similar track, flora refers only to plants. The equivalent term for fungi is mycota. These fungal terms may be unfamiliar but their use helps to identify published information on wild edible fungi clearly that may otherwise be ignored or missed.

Structure and feeding

Fungi come in many shapes, sizes and colours (Plate 1). Macrofungus (plural: macrofungi) is a general category used for species that have a visible (to the unaided eye) structure that produces spores, such as a mushroom or truffle. These visible structures are generically referred to as “fruiting bodies”.

Fungi consist of fine threads known as hyphae, which together form a mycelium, as in the mould growing on a piece of fruit or bread. The cap of a mushroom or a bracket fungus also consists of hyphae, densely packed together to form the fruiting body. Specialized hyphae produce spores that are dispersed in a number of ways. They can be viewed en masse by placing the cap of a mushroom on a piece of white paper and covering it with a glass (Plate 3). The colour, form and way in which spores develop help to identify the fungus.

Wild edible fungi are often referred to generically as wild edible “mushrooms”. This can be confusing for a number of reasons: edible species have different forms, some with gills and some with pores, some with stems and some without (Plate 1). This book prefers the broader term wild edible fungi to reflect the diversity of forms and also to distinguish them clearly from cultivated mushrooms (Box 1).

How fungi feed

Fungi are dependent on dead and living material for their growth. They obtain their nutrients in three basic ways:

• SAPROBIC³ – growing on dead organic matter;

• SYMBIOTIC – growing in association with other organisms;

• PATHOGENIC or PARASITIC – causing harm to another organism.

The majority of wild edible fungi species are symbiotic and form mycorrhizas with trees (see below). Saprobic edible fungi are also collected from the wild but they are best known and most widely valued in their cultivated forms. Plant pathogenic fungi cause diseases of plants and a small number of these microfungi are eaten in the form of infected host material (Plate 2). The different modes of feeding are shown in Plate 2 and described briefly below.

Saprobic fungi

Fungi colonize rotting wood and organic matter found in soil. Many species cannot be seen with the naked eye (microfungi) but there are (edible) macrofungi that fruit on fallen logs and bracket fungi that grow from dead or dying parts of standing trees. Agaricus arvensis is a commonly collected wild edible species that occurs in pastures and grassy areas. Edible species of Favolus are collected from dead wood inside tropical rain forests. The wild edible fungi used by the Yanomam Indians in Brazil are all saprobic and occurred in slash and burn areas where rotting wood was present (Prance, 1984).

In the wild, the volume and value of saprobic species used as food are small by comparison with the symbiotic edible fungi, though more edible saprobic species are collected. Their overall value is much higher because they are widely cultivated: a recent figure of US$18 billion was quoted for the annual, global trade in cultivated, saprobic species (Chang, 1999; see also Table 19).

Saprobic species need a constant supply of suitable organic matter to sustain production in the wild and this can be a limiting factor in production. Shi’itake (Lentinula edodes) mushroom cultivation in one area of China is threatened by the supply of suitable tree branches from nearby forests (Pauli, 1998).

Saprobic macrofungi are also highly valued for their medicinal properties. Most are cultivated, though Ganoderma spp. (Plate 9) are also collected from the wild. The list of symbiotic macrofungi with medicinal properties is a short one, though there is some indication that they have been studied less because they cannot be cultivated (Reshetnikov, Wasser and Tan, 2001).

Symbiotic fungi

The most common form of symbiosis associated with wild edible fungi is that known as a mycorrhiza (Plate 2). Many plants depend on these fungus-root associations for healthy growth. A special type known as an ectomycorrhiza (ECM) is found on trees growing in the Taiga in the Russian Federation and the rain forest of Borneo and includes legume trees as well as conifers (Table 3). Ectomycorrhiza are typically formed by macrofungi and they include many of the key edible species that are collected in the wild, such as chanterelles (Cantharellus spp.) and Amanita species.

The mycorrhiza helps the tree to grow in nutrient-poor soils, such as the miombo woodland of central and southern Africa (Campbell, 1996). A sheath of hyphae wraps around the root. They penetrate the root structure but not the actual root cells themselves, forming a living contact between the fungus and the tree. The fungus helps the tree gather water from a wider catchment and delivers nutrients from the soil that the tree cannot access. The tree provides the fungus with essential carbohydrates.

Termitomyces contains important wild edible species. These fungi only grow in association with termites and their nests and are dependent on the organic matter brought by the insects from their feeding on trees. Although Termitomyces are saprobic, they are symbiotic with termites. Twenty edible species of Termitomyces have been recorded from Africa and Asia (Pegler and Vanhaecke, 1994). They are regularly collected and also sold (Plate 6). T. titanicus is the world’s largest edible fungus, although other species are much smaller.

Rural people have long associated the appearance of edible fungi with particular trees and have incorporated this in local names. In southern Africa, chimsuku and kamsuku both describe Lactarius spp. that grow under masuku trees (Piearce, 1981). Some edible ectomycorrhizal fungi produce their fruiting bodies underground. The best known examples are the truffles (Tuber spp.: Plate 4). Over 400 species of edible ECM have been recorded (Wang, Buchanan and Hall, 2002). There are also many ectomycorrhizal fungi which produce fruiting bodies that are not edible or are poisonous.

The production of fruiting bodies depends on a complex set of factors and in some years production can be negligible. In Botswana, 14 tonnes of Terfezia pfeilii, one of the “desert truffles”, were bought from one small community in one season; the next year only four fruiting bodies were located over a much larger area (Taylor, 2002, personal communication: Edible fungi eaten and traded in Botswana and Namibia). The lack of certainty of harvests from one year to the next makes it difficult to plan commercial exploitation and some attempts have been made to overcome this by “cultivating” key mycorrhizal species such as Tricholoma matsutake (Hall et al., 1998). Trees are successfully infected with truffles (Hall, Zambonelli and Primavera, 1998) and managed under controlled conditions in Italy (Plate 4) and elsewhere, but the time, effort and money required are only justified – assuming a good knowledge of the ecology of the fungus concerned – for the most valuable edible mycorrhizal species.

Tree species can form mycorrhizas with more than one fungus, and a fungus may associate with more than one tree. Some ECM are “native” to a region: in Madagascar an edible Russula grows on exotic eucalyptus (Buyck, 2001). Other edible ECM have been introduced and Boletus edulis is now found throughout southern Africa following the establishment of pine plantations. ECM have been most intensively studied in the past on temperate tree species but there have also been steady advances on tropical ECM in Africa (Thoen, 1993; Verbecken and Buyck, 2002).

Lichens are “self-supporting” associations between fungi and an alga or cyanobacterium and are the final example of a symbiosis that has edible properties. A lichen is a biological and not a systematic group (Kirk et al., 2001) and several valuable species are eaten by people in Europe, Asia and North America and used for other economic purposes. They are not included in this book. Further information is available from a number of sources (e.g. Richardson, 1991; Marles et al., 2000).

TABLE 3

Plant families with edible ectomycorrhizal fungi

For details of ectomycorrhizas on tropical trees, see Alexander and Hogberg (1986).

Plant pathogens and parasitic fungi

In several countries people eat plant material infected with plant pathogenic fungi. Maize cobs infected with the smut fungus Ustilago maydis are consumed in large quantities in Mexico, both fresh and canned. They are known locally as huitlacoche or cuitlacoche (Villanueva, 1997). U. maydis is a microfungus: it does not form a visible fruiting body and the only signs of its presence are a mass of dark spores (Plate 1). The cobs appear to become sweeter as the result of fungus attack (Sommer, 1995), and similar changes have been noted for the edible rust fungus Cronartium conigenum on pines in Mexico.

Other examples include: Ustilago esculenta on wild rice; Sporisorium cruenta on sorghum in China (Guozhong, 2002, personal communication: Eating Sporisorium cruenta in China); winged bean infected by Synchytrium psophocarpi in Indonesia (Rifai, 1989).

Hypomyces lactifluorum is a parasite macrofungus that grows on other macrofungi (boletes). It is eaten from Canada through to Guatemala and completes the range of ecological niches occupied by wild edible fungi.

IDENTIFICATION

Local and scientific names

Local names have been well documented in Mexico (Guzmán, 1997), China (Mao, 2000) and can be checked online for Malawi (www.malawifungi.org)4 against the equivalent scientific names. Each of these countries has a rich lexicon of names and terms (Figure 1), a sign of the importance of wild edible fungi to rural people. Some local names have been adopted more widely, particularly for valuable edible fungi. Boletus edulis is commonly referred to by its French (cèpe) or Italian name (porcino – plural porcini), and Tricholoma matsutake by its Japanese name of matsutake.

The system of scientific names aims to remove doubt about the fungus being described. A person with Cantharellus cibarius in Nepal knows they have the same fungus as someone in Mozambique, assuming both have been accurately identified. The scientific name or binomial has two parts. The first name is the genus (Cantharellus) followed by the species name (cibarius). Named varieties exist for some species but their scientific validity is often uncertain.

Local names for edible fungi are based on shape, taste and other properties that are distinctive or important to people. The lichen (Umbilicaria esculenta) and an edible fungus (Auricularia auricula-judae) have similar common names in Hunan – Yan-er (ear of a rock) and Mu-er (ear of wood) respectively. This identifies where they grow and can be collected. Mycologists are sometimes wary of local classifications because they are based on scientifically unreliable characters (Härkönen, 2002).

Local names provide important clues to the uses and importance of edible fungi to people and there is much to be gained from their study. Local names allow researchers to learn about collecting practices, to analyse markets and to talk with forest managers and others who lack formal training in science and are unfamiliar with genera and species names. Examples of ethnographic studies involving wild useful fungi are listed in Table 13. Guidelines for conducting such studies are available from a number of different sources (e.g. Alexiades, 1996).

Local and scientific classifi-cations serve two different groups of people and neither is infallible. Edible species of Boletus are not eaten in parts of the United Republic of Tanzania, for example (Härkönen, 2002), reflecting local custom rather than scientific fact. Field guides often disagree on which species are edible, either because they are cautious about recommending species that require pre-cooking or because the authors are unaware of local customs in different parts of the world.

What is clear, however, is that there are many poorly described species sold and collected for personal use in developing countries. The rate of discovery is directly related to funding for projects and the ability to draw upon mycological expertise from different countries. Work in the United Republic of Tanzania (Härkönen, Codjia and Yorou, 1995), Mozambique and Malawi (Boa et al., 2000), Burundi (Buyck, 1994b) and Benin (De Kesel, Saarimäki and Mwasumbi, 2002) emphasizes the richness of the tropical, edible mycota and how much remains to be done. In the absence of such mycological expertise local names can provide useful information, particularly if dried specimens are available for later examination.

An accurately identified specimen with a scientific name for that species ensures that any new knowledge can be reliably used. A scientific name is the most useful way of finding out whether a species is edible or poisonous, or if it has medicinal or other useful properties. An importer does not need to know if the pied de mouton from Bulgaria is Hydnum repandum since the genus contains only edible species, but an Italian buyer will pay less for the ordinary Tuber sinosum from China compared with other more valuable species. In this instance a scientific name reliably and uniquely describes the fungus in question, for which information can be gleaned from the literature.

FIGURE 1

Naming the parts of a mushroom

This example is based on a fruiting body of an Amanita.
Other genera lack a volva (the sac that encloses the expanding fruiting body)
and the ring may be absent. The English name is in bold; Spanish in capitals
followed by popular names from Ajusco and Topilejo in Mexico.

Source: adapted from Reygadas, Zamoni-Martinez and Cifuentes, 1995.

Using the current or “correct” scientific name for a fungus

The scientific names for fungi are constantly changing – an indication of how much there is still to discover about the diversity of species. New names are proposed and generic boundaries adjusted, both as the result of new discoveries and a revision of the relationships between species. When a new species is proposed it is judged against guidelines and rules drawn up and regularly revised by scientists. The correct publication of a new name does not mean that scientists agree on its taxonomic status. The boundaries between genera and species are open to different interpretations and that is why there are “preferred” rather than “correct” scientific names for fungi.

These changes and uncertainties have important practical consequences for people using wild edible fungi. People have to be aware that a species was previously known by a different name or synonym when searching for information: Termitomyces albuminosus was once known as Collybia albuminosa. Other changes are less dramatic. Lentinus edodes, or shi’itake now has the preferred name of Lentinula edodes. The older “non-preferred” name is still regularly used in publications. Opinions are still divided as to whether Coriolus species with medicinal properties should be renamed Trametes. Auricularia auricula-judae, the “preferred name”, appears variously as Hirneola auricula-judae and Auricularia auricula.

Table 4 lists the preferred names of wild edible fungi that are still commonly referred to by other names. Common spelling mistakes also appear in publications; even minor differences can cast doubt on the identity of a fungus. The Dictionary of the fungi is a standard reference that is regularly revised to list all genera of fungi (Kirk et al. 2001). Index Fungorum, an Internet resource, allows users to check the preferred or non-preferred status for species names and to find synonyms (www.indexfungorum.org). This is of considerable practical benefit, although Index Fungorum lacks the backing required to answer fully queries about which scientific name to use for wild edible fungi. This practical need has still to be addressed by the scientific community.

TABLE 4

Preferred (current or “correct”) names of economically important wild fungi

See www.indexfungorum.org for further advice and information.
+ indicates a common misspelling.

Identifying species

The genera of wild edible fungi found in tropical and subtropical climates are broadly similar to those found in the mycota of temperate regions (Lincoff, 2002). The species diversity is, however, much greater in developing countries and care must be taken when comparing specimens with the narrower range of species illustrated in the many field guides published in Europe and North America.

Edible fungi occur in two major taxonomic groups. The basidiomycetes contain the mushrooms, bracket fungi and boletes (Plate 1); the ascomycetes include truffles (Plate 4) and morels (Plate 9). There is no simple test for determining edibility. The scientific literature is the best objective source of advice, but local practices and preferences can also reveal useful information. Empirical evidence is the ultimate indication of whether or not a species is edible.

The classical method for identifying a macrofungus involves a microscopic examination of tissues, spores and sporing structures. This will at least ensure that the genus is identified. Identification of the lesser known tropical species may also require examination of reference collections (Plate 3). Useful visual clues can be obtained from photographs in field guides and there are increasing numbers of Web sites with photographs and written descriptions of species (Chapter 6). Information on Mexican NWFP provided by the Secretaría de Medio Ambiente y Recursos Naturales (2002) on the Internet includes wild edible fungi and is an excellent example of an online guide that could be developed for other regions (see www.semarnat.gob.mx).

Expert identifications can be costly, although paying for an identification does provide a guarantee of getting a response to a query (Meijer, 2001). Preserving specimens is always useful and at its simplest provides a local reference for comparing specimens. Most macrofungi are easily preserved by drying (Halling, 1996). There are special drying racks for fungi (Plate 3), but these can also be locally improvised, adopting methods used for drying fruits and other food produce. Dried specimens can, if necessary, be sent at a later date for scientific identification and should be accompanied by field notes and/or colour photographs.

Molecular tools are commonly used to identify plant pathogenic fungi and have also been applied to truffle species in order to detect which species are used in prepared foods. The practical application of these tools for identifying and characterizing edible macrofungi has still to be explored.

Sources of technical advice and support are discussed in Chapter 6.

MAJOR GROUPS OF WILD FUNGI

There are more than 200 genera of macrofungi which contain species of use to people, mostly because of their edible properties. A clear distinction is made in this book between those recorded as simply “edible” and those that are actually eaten (“food”). To include all edible species as “food” would greatly overstate the number of species consumed by people around the world. Wild fungi with medicinal properties are also valued by rural people in several countries, though this is of secondary importance.

The major genera of wild edible fungi are described in Table 5, with brief notes on medicinal species. The genera of wild edible fungi can be divided into two categories: those containing species that are widely consumed and often exported in significant quantities, such as Boletus and Cantharellus; and those with species that are eaten widely, usually in small amounts, and rarely if ever traded beyond national boundaries. Annex 1 summarizes the general importance of wild edible fungi by country while Annexes 2 and 4 list individual species.

Medicinal mushrooms

Medicinal mushrooms are attracting greater scientific and commercial interest, prompted by a renewed awareness of the use of such material in traditional Chinese medicine (Table 17). The International Journal of Medicinal Mushrooms began publication in 1999 and is an important source of information for this expanding field of research (Wasser and Weis, 1999b). See Chapter 4 for further discussions about the health benefits of medicinal mushrooms.

TABLE 5

Important genera of wild fungi with notes on uses and trade

Information obtained mostly from developing countries. See www.wildusefulfungi.org for more details of individual records for species and countries. “Food” signifies confirmed use of species; “edible” is a noted property without confirmed consumption. The total number of edible species is the sum of the two. Use refers to country of origin and not countries of export. “Medicinal” (‘med.’) is a noted property and does not confirm use of species for health reasons. Edible species may have medicinal properties and therefore the total number of species in bold may be less than the sum of individual uses. See Lincoff (2002) for distribution of major groups of edible fungi around the world.

TABLE 6

Fungi with conflicting reports on edibility

Ceremonial aspects

The ceremonial and religious roles played by wild fungi in different cultures are closely associated with hallucinogenic properties. This has attracted much scientific and personal interest, particularly in Mexico (Davis, 1996; Riedlinger, 1990). Globally this use of wild fungi is of minor or no relevance to most countries.

EDIBILITY AND POISONOUS FUNGI

Many macrofungi are not worth eating or are simply inedible. This worthless group of species – as defined by their edibility – significantly dwarfs the very small number of toxic or poisonous species, of which there are only a very few that can kill. Yet it is also true that this very small group of lethal species has significantly shaped attitudes to eating wild fungi, creating potential barriers to wider marketing in many places.

Knowing the scientific name of a fungus provides a good indication of its edibility. In some cases the genus alone will suffice; all known Cantharellus species are edible (though not equally tasty). On the other hand, Amanita contains both exquisite edible and deadly poisonous species. The only reliable guide to edibility is the knowledge that someone has eaten a particular type – and survived. Local practices and preferences are therefore another useful source of information.

There are conflicting reports in field guides about edibility. Some recommend eating species that others reject as poisonous. People from eastern Finland regard the false morel, Gyromitra esculenta, as a culinary delicacy once it has been carefully pre-cooked. Guides in the United States and elsewhere state emphatically that the fungus is poisonous and should not be eaten. Other examples of conflicting advice are summarized in Table 6.

What species are eaten?

A total of 1 154 edible and food species have been recorded from 85 countries (Table 1). The species eaten in one country or region often differ from nearby areas and in some cases there are dramatic changes in tradition. The Mesoamerican tradition of eating wild edible fungi continues from Mexico to west Guatemala then is absent from much of Honduras and Nicaragua, even though both contain forest areas that in theory support production of edible fungi.

The number of species eaten is sometimes only a fraction of those available. Only 15 of the 284 edible species in Armenia are regularly eaten (Nanaguylan, 2002, personal communication: Edible fungi in Armenia). In two districts of Turkey, 12 out of a possible 29 edible species were collected and eaten (Yilmaz, Oder and Isiloglu, 1997). The reasons for these different patterns of use are not always clear but there is a trend of less frequent use as people move away from the land. Rural people in Guatemala have a positive yet informed approach to eating wild fungi which people living in cities lack (Lowy, 1974). Educated people living in towns in Malawi lose the strong local traditions that rural communities maintain and even acquire a suspicious attitude towards wild fungi (Lowore and Boa, 2001).

In parts of the United Republic of Tanzania boletes are thought to be poisonous (Härkönen, Saarimäki and Mwasumbi, 1994a). In Colombia there is no apparent tradition of eating wild fungi in the Andean regions, though they occur widely (Franco-Molano, Aldana-Gomez and Halling, 2000). Tricholoma matsutake was of little local interest in Sichuan, China (Winkler, 2002) prior to Japanese demand that stimulated an export trade in the late 1980s and appears to have prompted wider local consumption. A similar event took place in the Pacific northwest, though with Tricholoma magnivelare (Redhead, 1997). This was collected and eaten by Japanese settlers in the 1930s (Zeller and Togashi, 1934) but at the time this did not arouse much, if any, local interest.

Poisonous species

A review of poisoning incidents in official and informal publications shows that the frequency of such events and the effect on humans are overall less than that suggested by attendant publicity (Logemann et al., 1987). During the search for information on wild edible fungi, about 170 poisonous species were noted. Most are either related to edible species or confused with them. There are, of course, real dangers in collecting and consuming poisonous fungi, but these should be seen against the wider background of millions of people collecting and eating wild fungi safely on a regular basis.

Several popular and highly esteemed edible species are poisonous when raw. Few people eat them in this condition and risks of poisoning are in reality small. Poisonous mushrooms vary in their effects from mild stomach and digestive upsets to more serious problems such as liver damage. The solutions to these potential risks include providing local advice on which species to collect and which ones to avoid (Plate 3) and publicity campaigns that highlight potentially poisonous species on posters. Mr Sabiti Fides, a trader in Malawi, took a more direct route by eating mushrooms in front of his customers (Box 3).

In southern Africa roadside sellers only offer “safe species” (Ryvarden, Piearce and Masuka, 1994) and most market places are a reliable means of obtaining known, edible wild fungi. Problems can occur with “contamination” in markets but such incidents are most uncommon (see Table 8).

Finland has trained mushroom advisers covering all rural areas (Härkönen, 1998; Härkönen and Järvinen, 1993). The svamp “police” based in some town centres in Norway help collectors identify edible species, and there are similar schemes in other countries.

Poisonings are associated with a number of events:

• young children collecting indiscriminately and eating raw mushrooms;

• immigrants arriving in a new country and wrongly identifying a local species that turns out to be poisonous;

• food shortages and economic hardship force people to hunt for food;

• different physiological responses to an “edible” fungus.

Mexicans living in California have eaten Amanita phalloides – a poisonous species not found at home – thinking it was the edible Volvariella volvacea (Plate 2). The guide for edible mushrooms in Israel is written in Hebrew and Russian (Wasser, 1995), following the arrival of over one million Russians in the 1990s and their strong tradition of collecting wild edible fungi. One Russian was poisoned when he too mistook a poisonous species for an edible species known from his home country (Hazani, Taitelman and Sasha, 1983). Other reports suggest a certain recklessness amongst Russians in choosing which species to collect and eat (Matsuk, 2000).

Some people eat Laetiporus sulphureus without any ill-effects while others feel ill. The suggested reason is that physiological responses by people differ but there could also be different strains of the fungus, which differ in chemical composition. Little is known about this particular feature for poisonous or potentially poisonous species.

A summary of well-publicized incidents of widespread poisoning is given in Table 7. There has been a spectacular rise in poisonings and deaths in Ukraine in the last decade. Various reasons have been given, including a dramatic economic downturn and the desperate search for food5 or produce to trade in local markets.

Regular reports of poisonings in the United States appear in the journal McIlvainea (e.g. Cochran, 1987). These incidents are insignificant by comparison with the thousands of people who collect and consume wild fungi without any reported problems. Millions of other people around the world also regularly eat wild edible fungi without any ill-health effects, and it is important to keep a sense of perspective when reviewing the reported incidents of poisoning.

TABLE 7

Incidents of large-scale poisoning caused by consumption of wild fungi

ns – not stated.

* Sum calculated using an estimated ratio of ten poisoned to each person who dies,
to account for those years where people died but the number of people poisoned and who recovered were not stated.

Contamination of wild edible fungi

The Chernobyl accident in Ukraine in the 1980s prompted investigations of radioactive materials in sources of wild food and particularly wild edible fungi. Broader concerns about the accumulation of heavy metals and pollutants by macrofungi have also been expressed.

A study of radiocaesium intake via consumption of wild fungi in the United Kingdom concluded that intake depended more on the species eaten than the weight consumed (Barnett et al., 2001). Mycorrhizal fungi had a significantly greater radioactivity compared to saprobic or parasitic species. Consumption of wild edible fungi in the United Kingdom is small by comparison with other countries but the study gives a general indication of the potential health risks.

One reported case of contamination concerned the accidental mixing of potentially poisonous wild species with wild edible fungi imported by the United States (Gecan and Cichowicz, 1993). Such events are rare, however, and there are no known instances of this causing any damage to human health in Europe.

CULTIVATION OF EDIBLE FUNGI

There are nearly a hundred species of fungi that can be cultivated (Annex 4). All are saprobic. Commercial markets are dominated by Agaricus bisporus, Lentinula edodes and Pleurotus spp. (Table 18) and these account for nearly three quarters of the cultivated mushrooms grown around the world (Chang, 1999). The major cultivated species are grown on a variety of organic substrates, including waste from producing cotton and coffee. The technologies are well established and successful mushroom industries have been established in many countries. There has been a huge increase in production in the last ten years, mostly as a result of increased capacity in China.

Reports from Africa (Mshigeni and Chang, 2000), Mexico (Martínez-Carrera et al., 2001) and Amazonia in Brazil (Pauli, 1999) suggest that mushroom cultivation offers economic opportunities as well as nutritional and health benefits. Small-scale cultivation takes place throughout China and could provide a suitable model for technology transfer. The cultivation of the paddy straw fungus (Volvariella volvacea) is integrated with rice production in Viet Nam. Wherever saprobic species are cultivated they require a steady supply of raw materials. The expansion of shi’itake production in Qingyuan, China (“the mushroom capital of the world”) led to a serious depletion of local forests that supplied the wood on which to grow this edible fungus (Pauli, 1998).

The number of saprobic species being cultivated is steadily increasing and information and practical advice are readily available (Stamets, 2000). Ectomycorrhizal fungi can also be “cultivated”. Trees are inoculated with truffle fungus that must then infect the roots and form the ectomycorrhizae. The trees are carefully tended to encourage production of the truffles (Plate 4). Methods for “cultivating” truffles are constantly being refined and improved (Hall et al., 1998a).

PLATE 1

TYPES OF MACROFUNGI

Edible fungi come in many shapes and sizes. There are no consistent features (or tests) that distinguish them from poisonous varieties. Examples are from Malawi and photos by Eric Boa, unless stated otherwise.

PLATE 2

HOW FUNGI GROW: mycorrhizas, saprobes and pathogens

Fungi obtain their food symbiotically, as saprobes or parasites (pathogens). There are edible macrofungi in each category. The most valuable wild species are ectomycorrhizal, a form of symbiosis. Ectomycorrhizal roots have a distinct though varied appearance. It is unusual to see them clearly in situ. Many saprobic macrofungi are edible. Few pathogens are eaten. All examples are from Malawi unless stated otherwise. All photos by Eric Boa.

PLATE 3

WHICH FUNGI ARE EDIBLE? IDENTIFYING SPECIES

Edible species can be identified using local and scientific knowledge. Neither system is infallible: local practices are based on empirical evidence of edibility, though local beliefs may falsely exclude edible species. A scientific name provides access to published information on properties, but conflicting advice may exist. Used together, local and scientific knowledge are a powerful guide to properties of wild fungi. All photos by Eric Boa unless stated.

3.1 (left) This French pharmacy offers local assistance in identifying edible species	3.2 (right) The second oldest publication on wild edible fungi from China. It includes descriptions of ‘species’ and would have been a useful reference book. (photo: Warren Priest)
3.3 (left) Paul Kirk documents a field collection from Malawi. Each specimen is given a reference number and described before being dried, and thus preserved for further examination.	3.4 (right) Spore print of Hypholoma fasciculare, a poisonous species. The upper print is after leaving the cap for several hours; the one below for less than an hour. Spore colour helps to distinguish similar genera but not to species.
3.5 (right) Alessandra Zambonelli of the University of Bologna with a unique collection of truffle specimens from around the world. Collections are vital reference sources for identifying fungi and naming new species.	3.6 (left) Dried examples of truffles are carefully labelled and stored in the collection.

³ Saprophyte describes a plant that feeds by external digestion of dead organic matter.

⁴ All Web pages have been viewed in 2003.

⁵ “I had never seen people (in central Lviv) not only rummaging in dustbins, but putting valuable scraps of food from them directly into their mouth – even in the collapsed societies such as Georgia and Moldova.” (Almond, 2002).