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Fungi provide essential support for all communities of multicellular organisms. Fungi recycle the biomass of wood and leaves, including substances such as lignin, which other organisms may not be able to digest [1]. Underground fungal filaments called mycorrhizae extend the root systems of most plants, which form network, that interconnect that plant community.Fungi are capable of fermenting plant material, as well as being pathogenic to both plant and animal species. [1].

At the tip of a fungal hypha, the cell membrane expands by incorporating vesicles, which are generated by the endoplasmic reticulum. When the vesicle fuses, it provides phospholipids and proteins to extend its membrane surface area, which allows the cytoplasm to expand rapidly [1]. The absorption zone for hypha is right behind its tip. The absorption zone takes in nutrients from the neighboring medium. It is also important to notice that, behind the absorption zone, the older part of the hypha collect and stores nutrition as well [1]. There is an extensive number of fungal species, with each species differing in form, from the common mushrooms, fruiting bodies that can weigh several pounds, to the mycelia of pathogens and the symbiotic partners of algae in lichens. [1].

Fungi have four major phyla; such phylum includes Basidiomycota, Zygomycota, Ascomycota and Chytridiomycota.

Basidiomycetes have cells that are paired nuclei and form mushrooms. They are well known for their exceptional size and diversity of above ground fruiting bodies known as “true” mushrooms [1]. Mushrooms offer a flavorful source of protein and minerals, albeit at the risk of consuming the deadly toxins, which are produced by some species. The protein content of edible mushrooms can be as high as 25% dry weight, similar to that of whole milk (per dry weight), and includes all essential dietary amino acids [1].

It is important to note there are also Poisonous and Hallucinogenic Fungi which produce deadly poisons such as alpha-amanitin, which inhibits RNA polymerase 2. Alph-amanitin is produced by Amanita, known as “Destroying Angel”; its taste is often fatal. Other mushrooms include Portobello, which is one of the more priced mushrooms around the world [1]. Different types of mushrooms grow in different season, some grow in soil, while others such as Piptoporus grows on tree bark.

Contents

[edit] Mycophagy Throughout History

A Roman floor mosaic depicting picked edible mushrooms in a decorative bowl
A Roman floor mosaic depicting picked edible mushrooms in a decorative bowl

[edit] Ancient Times

Fungi has been used as a food source by humans for millenia. Archaeological records show edible mushroom fossils along with humans who lived approximately 13000 years ago in what is now modern day Chile [2]. A more thorough record of mushrooms as a food source can be dated back to texts written during the Han Dynasty in ancient China (206 BCE-220 CE). In ancient societies around the globe, fungi was not only prized for its medicinal properties, but it was also believed to have magical properties associated with immortality.

Emperor Wu of the Han dynasty went so far as to call for large expeditions to attempt to find these elusive mythological Fungi [3]. Fungi shared this mythical status in ancient Egypt. Hieroglyphic depictions of fungi dating back to 4500 BCE can be seen throughout the area. They can even be found in the Book of the Dead where they are described as being the "food of the Gods" [4]. The Pharaohs explicitly outlawed the consumption of fungi amongst the common populous as they were seen as only fit for royal consumption [5].

[edit] Antiquity

In Ancient Greek and Roman times, the mushroom was also a highly prized and was mainly consumed by the upper class. A particular favourite of the Emperors of Rome was the Amanite caesarea or Caesar's Mushroom, regularly on the menu at grand feasts. Unfortunately, its strong resemblance to poisonous varieties made it a relatively common and effective means of assassination. The poison's symptoms would manifest the following day and the victim would die in a week's time [6].

[edit] Mesoamerica

Of the few Mayan texts which survived the arrival of the Spanish Conquistadors, there are hieroglyphics depicting what appears to be a man outstretching an offering of a mushroom to some sort of Deity. This suggests that mushrooms were integral to religious ceremony amongst the ancient Mayan peoples [7].

Mayan deities holding mushrooms
Mayan deities holding mushrooms

[edit] Beginnings of Commercialization

Fungi was first intentionally grown as a crop around 600 CE. In the seventeenth century, mushrooms were first cultivated by the addition of spore laden manure into fresh piles of manure. In 1886 the first sterile techniques were used in order to ensure that only the desired fungi would grow on the substrate. In 1905, it was first discovered that one could produce fungi directly from tissues and not from spores themselves. These discoveries along with the prospects of indoor mushroom production paved the way for the manufacturing techniques used today for mass production [8].

[edit] Commercial Fungi Production

Mushrooms are heterotrophic in order for them to grow they must obtain all nutrients from substrates. Mushrooms must be grown on substrates that contain carbon, nitrogen, elements and vitamins. Mushrooms are cultivated inside buildings and monitored by computers.

Mushroom cultivation is broken down into 4 Phases:

Substrate Preparation:
Composting (Phase 1)
Pasteurization and conditioning (Phase 2)

Vegetative Growth Stage:
Spawn run (Phase 3)
Case run (Phase 4)

Reproductive Growth Stage:
Pinning (Phase 4)
Harvest (Phase 4)

[edit] Substrate Preparation

Phase 1 of the mushroom cultivation process is preparing compost to convert unacceptable materials to one accepted substrate by the mushrooms. Key ingredients and factors that must be included in the compost are; an accurate temperature, moisture, oxygen, pH, a specific recipe or formula, physical properties of ingredients and microorganisms [9]. The compost is usually stored in bunkers.

Phase 2 requires stricter and monitored growing conditions. Pasteurization and conditioning occur in this phase. Pasteurization is used to control unwanted organisms at a 60 °C temperature. The ideal growing conditions for phase 2 are; aerobic > 10% O2, moisture 68-70%, a loose structure, total nitrogen 2-2.2%, no ammonia, C:N ratio of 14:1, and a pH around 7.5-8 [9]. Layers which include shelves and trays or bunk (tunnels) are the system of use for storage of the phase 2 compost.

[edit] Vegetative Growth Stage

Phase 3 is the Spawn run it is the successful colonization of the phase 2 substrate by the mushroom fungus. A spawn run must have these specific requirements in order for it grow successfully; have a 20000ppm> CO2> 3000, RH> 85%, Compost temperature of 24-27°C [9]. A complete spawn run takes 14-21 days to complete.

Phase 4 is the successful colonization of the casing layer by the mushroom fungus, and an end product blend of mycelia types. This step is very important, because without this step there would be no mushroom crop. Loam soil, peat moss, and coconut noir is applied to the spawn run compost to set up conditions for mushroom formation. Once the spawn run is covered by the case layer, it must be watered very fine to a large volume of 1-1L m-1 each time to a saturation of 500L T-1 [9].

[edit] Reproductive Growth Stage

Pinning is part of stage 4. It creates conditions that stimulate the formation of primordia (pins). Pins develop when the carbon dioxide content of room air is lowered to 1000 ppm, lower compost temperature of 20 °C, and lower air temperature of 17 °C [9]. Pinning affects both the potential yield and quality of a crop and is a significant step in the production cycle.

Harvesting is the very last step in stage 4. The ideal end product is mushrooms without diseases, no scales, white bright in colour, correct proportions of cap and stem, minimal physical damage and clean without soil. The ideal conditions for harvesting are; CO2 at 1000 ppm, a compost temperature of 20 °C, air temperature of 17 °C, and a relative humidity of 85%+ [9].

[edit] Nutritional Value and Eating Mushrooms

Fungi are a significant foundation of nutrition in the food webs of many species. Edible mushrooms are found to be an excellent source of B-vitamins, Potassium, Selenium, Copper, Phosphorus, and Vitamin D; all important components to overall good health. Mushrooms are very high in protein and are exceptionally beneficial in vegetarian diets. Mushrooms found in supermarkets are, for the most part, considered safe for human consumption. This is because they are grown in controlled environments. On the other hand, there is no foolproof way of distinguishing the edibility of a wild mushroom. Some rules for discovering edible mushrooms do not apply to others, and could potentially be toxic. For example, at one point all Laetiporus (ie. ‘chicken-of-the-woods) were considered edible, but may not be edible with the presence of certain essential oils (ie. eucalyptus). Also, an edible species may have a similar resemblance to a potentially dangerous one. On that note, unfamiliar mushrooms should never be eaten without the edibility confirmed by someone with authoritative knowledge.[10]

[edit] Laetiporus sulphureus,“The Chicken-of-the-Woods”

[edit] Brief Description and Morphology

Laetiporus sulphureus is a widespread and common fungus. It is sometimes referred to as sulphur polypore or sulphur shelf due to its rich yellow pores. The underside of the fungi has a stippled appearance because it is lined with a series of tubes where its spores (3-5 per mm in size) are released. The majority of the fungus is a rich yellow to orange in colour, which tends to fade over time. [11] Laetiporus sulphurous tends to grow in a self like fashion, extending with fruiting bodies that can form up to 30 cm across. They are mostly formed by fused caps and usually do not have a central stalk, like most common fungi. [12]. They are described to have a smooth, but uneven surface, with a tough, leathery texture. The outer most margins are suitable for human consumption and will grow back; provided that there is enough nutrition in the fungi’s environment. The texture of cooked pieces is similar to that of chicken; therefore its nickname, “Chicken-of-the-woods”. [10]

[edit] Growth Cycle

Typically, Laetiporus sulphurous can be found fruiting during the late summer months to early fall. If nutrition is available for the fungi to survive, it is found to grow in a yearly cycle, fruiting in the same place for several years [12].

[edit] Habitat

Laetiporus sulphurous is a saprophyte; meaning it absorbs nutrients from the organic materials. It is mostly found growing on wood and fruiting on living trees, logs or stumps. They are, more specifically, found of conifers and hardwoods across North America. [10]

[edit] Edibility

The margins of Laetiporus sulphureus are edible, but have been found to cause gasrointestinal upsets in some individuals. It contains no serious toxins, but should be cooked and never eaten raw. A great deal of caution should be taken when consuming wild mushrooms.

[10]

Finding and cooking 'chicken-of-the-woods'

[edit] Coprinus comatus "Shaggy Mane Mushroom"

Coprinus comatus
Coprinus comatus

Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Order: Agaricales
Genus: Coprinus
Species: C. comatus

Coprinus comatus is from the genus Coprinus within the Basidiomycota, and is commonly known as "Shaggy Mane Mushroom".

[edit] Morphology

This mushroom is characterised by a long white, bell-shaped cylindrical cap which is covered in a shaggy buff, as well as tan or brown scales. This is said to resemble the appearance of a British lawyer’s wig which gave it the nickname ‘lawyer’s wig'[13]. When immature there is a ring that is seen around the stem of the mushroom, as the mushroom matures, the ring drops down the stem. Within twenty-four to forty-eight hours of maturation the gills and cap begins to self-digest, and liquefy to a black sticky substance. However this trait should not be confused with that of C. atramentarius[13]. This mushroom usually fruits in large numbers, and is frequently seen along roadsides, meadows, lawns, parks etc. It is said to be best found following the first rains of the year[13].

[edit] Edibility

This mushroom is edible, and has a robust flavor, with the best flavour being ingestion before the mushroom begins to liquefy[13]. The mushroom can still be eaten in its dissolving form, however it has a slimy texture, and is not as flavorful. This mushroom has a watery and delicate flavour, but flavour can be enhanced by boiling off the water while cooking[13].

[edit] Side Effects

Although these mushrooms are safe and edible to eat, there are very rare cases where this mushroom can react when consumed with alcoholic beverages[14]. The symptoms include[14]:

  • Red nose and ears
  • Strange metallic taste
  • Light heatedness
  • Increased heartbeat
  • Nausea

The cause of this reaction is from the toxins coprine and antabuse which interfere with alcohol metabolism. This interference causes an accumulation of acetaldehyde in the blood. Recovery from this phenomenon is usually fairly rapid, and spontaneous.

[edit] Pleurotus ostreatus – “Oyster mushroom”

Phylogeny for Pleurotus ostratus
Phylogeny for Pleurotus ostratus
Top view of wild Pleurotus ostreatus growing on a fallen hardwood log
Top view of wild Pleurotus ostreatus growing on a fallen hardwood log

[edit] Morphology

The Pleurotus ostreatus or “Oyster mushroom” can commonly be found on hardwood limbs, logs, and stumps widely distributed throughout North America, occasionally appearing on conifer wood and are a common favorite for mushroom hunters. [15]

The soft and fleshy fruiting bodies of these fungi can be identified growing in thick clusters off of the host substrate with each cap tightly overlapping the last, often possessing a short off center stalk or lacking one altogether. P. ostreatus can also be found growing in two’s or three’s, beyond the common cluster formation. [16]

The cap is dry and smooth, and can range in color considerably from light whitish grey to brown, brownish grey, bluish grey, and a blue black depending on season and temperatures. Underneath the stalk the presence of broad, thick white gills with veins between and extending down into the stalk if present can be observed, with spores often white to tinted lilac in color after moisture has escaped from the deposit. [16]

[edit] Closely Related Species

The following species are very similar in morphological characteristics, and can easily be mistaken as Pleorotus ostreatus to the untrained eye [15]:

  • Pleurotus cornucopiae
  • Pleurotus salignus
  • Pleurotus columbinus

[edit] Habitat

Pleurotus ostreatus is found widely distributed globally, with fruiting season dependent on the specific location and weather of the area.[15]

Specific considerations can be found in various North American locals such as:

  • Whitish fruiting form common on aspen wood in Lake States during the spring season, with colored form caps found on elm.
  • Rocky Mountain and Pacific Coast areas can observe the fungi growing on alder, maple, and cotton wood.
  • Irrigated sections of the West can find a gigantic form in irrigated poplar ditches.
  • East of the Great Plains it is common in the summer season to find a small white form of Pleurotus ostreatus.

[edit] Edibility

The Pleurotus ostreatus is a delicious and popular mushroom for consumption when utilized creatively during food preparation. Common practices prior to use in meals however requires the removal of the tough cap base where it merges with the stalk, and for any wild harvested P. ostreatus to be submerged in water to remove potentially hiding beetles. [15]

[edit] Agaricus brunnescens - Commercially Harvested Fungi

Phylogeny for Agaricus bisporus, the original species of Agaricus brunnescens
Phylogeny for Agaricus bisporus, the original species of Agaricus brunnescens
Agaricus brunnescens grown for commercial use in produce stores
Agaricus brunnescens grown for commercial use in produce stores

[edit] Morphology

Agaricus brunnescens is a widely popular species of Agaricales fungi in commercial growth and harvest, originally named in 1900 by Dr. Peck and published as the commonly named Agaricus bisporus in 1946. Morphologically Agaricus brunnescens is identical to the original strand Agaricus campestris that it was differentiated from except in number of spores in the basidium and cap color, of which it is now pure white in contrast to the normally browning when bruised Agaricus campestris [16].

The gills of a young fruiting A. brunnescens fungi are pink at first, and eventually darken as the spores mature to produce a chocolate brown spore print. Final distinctive features of this species is the white partial veil on the underside of the cap, leaving a ring on the upper stalk[17].

As previously mentioned another defining characteristic between the commercial A. brunnescens and closely related A. campestris found growing in the wild other than cap color is the number of spores located in the basidium. Following microscopic cellular analysis of the basidia by which cells are born, a sample of A. brunnescens will possess only 2 spores per basidium compared to the normal 4 spores per basidium in A. campestris [15].

[edit] Closely Related Species

Additional closely related species can be differentiated by the bruising color on their caps and include [15]:

  • Agaricus Silvicola and Agaricus arvensis – Yellow bruising stain
  • Agaricus silvaticus and A. subrutilescens – Red or orange bruising stain

[edit] Habitat

Although not native to North America, Agaricus brunnesces that has escaped from cultivation can be found in the wild growing in grass, especially near big cities like: Boston, New York, Philidelphia, and Washington [16].

More commonly encountered in the wild however is Agaricus campestris growing from grass, lawns, and soil containing manure often in fairy rings widely distributed globally from pastures at sea level to high mountains[16].

Fruiting season for A. brunnescens ranges from late summer into the fall depending on elevation and locality[16].

[edit] Edibility

Widely popular and commercially available mushroom due to its strong flavor and versatility of use when sautéed or added to red meat dishes, with many people preferring to harvest the wild Agaricus campestris during its more mature stages for their stronger flavor in comparison with the commercially available Agaricus brunnescens [15].

[edit] Truffles

Truffles are another example of edible fungi. There are many species of fungi that are associated with them. These are the only edible fungi in phylum Ascomycota, order Pezizales and most are in genus Tuber .[1] [2] The most popular is Tuber melanospermum, which is called a black truffle, due to the colour which is dark brown or black, rounded, and covered with polygonal wartlike protrusions, having a depression at their summit; the flesh (gleba) is first white, then brown or gray, and when mature becomes black with white veins having a brown margin [18]. They have very pleasant distinctive smell, which distinguishes them from Chinese black truffles. The price for one pound of black, French truffle is approximately $1000 compare to $30 for Chinese truffles. Their size varies from small (of a walnut) to big which is a size of fist [19].

[edit] Habitat

Truffles are associated with roots of oak trees, therefore they are found in the open woodlands on calcareous soil. Usually they are found 30 cm underground. The main truffle grounds in France are located in the south, especially in Périgord and the region of Provence–Alpes–Côte d’Azur [18]. The ground can be prepared for truffles, but since truffles are fungi, they cannot be planted. Even proper preparation of soil does not guarantee the success. The approximate time to find truffles under trees after proper soil preparation is 6 years.

[edit] Hunting for truffles

The truffle hunting is cried out by trained dogs, which find them by smell and dig them out. In the past female pigs were used to do that, unfortunately they would eat truffle immediately. The reason why only female pigs were used not male, is the fact that truffles have very similar scent to that of male pig pheromones, which made them attracted to it [18].

[edit] "False" truffles

There are "false" truffle, which are from phylum Basidiomycota, which look like black, French truffle, but they taste and smell differently. Additionally, the bearing of their spores is also different on the outside.

[edit] Different types of truffles

In addition to black truffle there are more valuable winter, white truffle (T. magnitude). Other culinary truffles include muscat black truffle (T. brumale), musky black truffle (T. brumale), Chinese black truffle (T. indicum), Himalayan black truffle (T. himalayense), summer black truffle (T. aestivum), scorzone black truffle (T. aestivum), and autumn black truffle (T. mesentericum) [18].

[edit] Truffle's parasites

Melanospora subterranea is a new species, which was described in China. Melanospora subterranea is parasitizing Chinese black (Tuber indicum) and white truffles (T. huidongense) [20].

[edit] Morchella esculenta The Common Morel

Kingdom: Fungi
Phylum: Ascomycota
Class: Pezizomycetes
Order: Pezizales
Family: Morchellaceae
Genus: Morchella
Species: M. esculenta

[edit] Brief Description

Morchella esculenta, (commonly known as common morel, morel, yellow morel, true morel, morel mushroom, and sponge morel) is a species of fungus in the Morchellaceae family of the Ascomycota.

Morchella, the true morels, is a genus of edible mushrooms closely related to anatomically simpler cup fungi. These distinctive mushrooms appear honeycomb-like in that the upper portion is composed of a network of ridges with pits between them.

The species has been named state mushroom of Minnesota, and was the first state mushroom of any state.[21][22]

Morels (Morchella spp.) are prized wild edible mushrooms. In the United States, morels are the focus of family traditions, local festivals, mycological society forays, and social media, as well as substantial commercial trade. A majority of the anglophone research on morels has been conducted in Europe and in the U.S. Pacific Northwest and Midwest. This literature provides insights into a diverse and plastic genus, but much of its biology and ecology remains a mystery.[23]

Morels can grown in urban gardens.[24]

Morels and truffles differ widely in their form and behaviour. The morels resemble mushrooms to the extent that they have a cap borne upon a central stem, whilst the truffles form solid, round balls, which grow underground. These are the edible ascomycetes. Both morels and truffles represent some of the most highly prized edible mushrooms in the world. The morels are sometimes referred to as the ‘truffles of the north’, but other popular names include ‘sponge’, ‘pine cone’, ‘corncob’, and ‘honeycomb mushroom’. They are the most popular of the springtime, edible fungi, usually occurring from late March through to mid-June, although each crop will survive only for a several days. Morels have a delicate flavour that can be overwhelmed during cooking, but delicious when eaten alone. They are normally prepared by frying in butter and can be preserved, with drying being the most popular method.

There are two kinds of morel. The true morels belonging to the genus Morchella, and the false morels or lorchels belonging to the genus Helvella. Lorchels can cause serious poisonings and should be avoided. True morels may be classified into two groups. There are the black morels, with dark to deep grey or black ridges at maturity, such as Morchella conica and Morchella elata. These usually appear slightly earlier, and are usually associated with cedar, pines, burnt areas, occasionally on dunes and in the coastal depressions between dunes.

There are a number of varieties, varying in shape and colour, sometimes regarded as separate species, ranging from yellow, with a large round head (var. rigida); ochre-yellow and small (var. rotunda); grayish brown to ochre yellow, with a rounded to conical head (var. vulgaris); blackish brown, with a rounded to conical head (var. umbrina). These occur in mixed hardwoods, especially beech, maple, old apple trees or stumps, and around dead elm trees. In the UK, morels have shown a noticeable increase in their distribution in urban areas over recent years. This is attributed to the increasing use of bark mulch in gardens. They have never been successfully cultivated until very recently and only with limited success. Attempts at cultivation in North America have involved the use of sterile masses of mycelium, or sclerotia, which are enriched by placing them on a layer of wheat or rye grain. These sclerotia are then harvested and distributed on a mixed bark and soil layer to produce the fruit bodies. However, so far the fruiting body yield has been poor, and the small size has yet to be overcome. [25]

[edit] Taxonomy and Systematics

The genus name Morchella is derived from morchel, a German word for fungus.[26]

The fungus was originally named Phallus esculentus by Carl Linnaeus in his Species Plantarum (1753),[27]. [28] and given its current name by Swedish mycologist Elias Magnus Fries in 1801.[29][30]

The M. esculenta ascocarp forms a large yellowish rounded to conical head[31] with ridges and pits. The ascocarps range 2–4 cm in width by 2–6 cm in height. The stipe ranges 2–5cm long by 1–2 cm in diameter. The lower edge of the cap is attached to the stipe and the combined ascocarp plus stipe form a continuous hollow region[Gussow and Odell]. Although it must be noted that morels show a great deal of variation ((Kellner et al. 2005; Kuo 2005; McFarlane et al. 2005; Pilz et al. 2004, 2007; Stefani et al. 2010; Weber 1995; Yoon et al. 1990))[32] [33].

[edit] Phylogeny

Considerable confusion exists in the taxonomy of Morchella because of the species considerable morphological diversity with disagreements in species identification. DNA-based phylogenetic analyses could help sort out morel taxonomy which is essential to determine morel diversity.[34]

Early phylogenetic analyses supported the hypothesis that the Morchella genus contained only a few species that exhibited a great deal of phenotypic variation[35][36]. More recent work using DNA has suggested a much more varied genus. For instance, it is suggested there are more than a dozen distinct groups of North American morels[37]. Recent molecular phylogenetic studies have revealed the existence of at least 50 species of Morchella worldwide and demonstrated a high degree of continental endemism within the genus.[38]

When suitable moisture and nutrient condistions have been reached development of young fruiting bodies begin in the form of a dense knot of hyphae. The cup-shaped hyphal knots remain underground for some time and later come up from the soil and develop into a stalked fruiting body. Because of unequal growth of the surface of the hymenium the cap of the mushroom is sponge-like or honeycomb appearance.[39]

[edit] Anatomy and Distinguishing Characteristics

There are two different classifications of true morels, the black morels and the common morels. The black morels have dark grey or black ridges at maturity such as Morchella conica and Morchella elata. The common morels have ridges that are white, ivory or dull yellowish brown such as Morchella esculenta.[25]

[edit] False Morels

Care must be taken to distinguish the true morels from the deceptive false morels (Gyromitra esculenta, Verpa bohemica and others). False morels can sometimes be eaten without any negative side effects. However, when eaten in large quantities over many days they are capable of causing severe gastrointestinal distress and or loss of muscular coordination. Gyromitra esculenta contains the toxic compound gyromitrin (acetaldehyde-N-methyl-N-formylhydrazone).[40] False morels can easily be distinguished from the true morels by looking inside the mushroom. The false morel has a cotton like substance inside the stem while the true morels are hollow. False morels are also attached at the apex of the cap and true morels are attached near the bottom of the cap.

[edit] Habitat and Distribution

Morels have been known to grow in China[41], India[34], Turkey[42][43], Israel[44][45], Mexico[44], USA [46] [47] [48], Canada[49] and Brazil[50].

Morels have a relationship with deciduous trees, evergreens and sometimes woody shrubs. In the northern hemisphere ash, sycamore, tulip tree, dead and dying elms, cottonwoods, old apple trees, pine, sassafras, beech and hickory trees are known to have a relation to the morel.[51] Yellow morels are commonly found under deciduous trees and black morels are commonly found in deciduous forests that include oak and poplar.[52] M. esculenta forms ectomycorrhizal associations with trees.[53] Some grass species seem to have a negative impact on morels.[54]

Morchella esculenta is often referred to as the "May mushroom" in North American. This is because it consistantly fruits in the month of May. It can also fruit in any month from February to July. It is usually the last of the morels to fruit in places where other species are present.[55] Their springtime fruiting may be becaue they are able to grow at low temperatures without competition.[56][57]

[edit] Ecology

Humans are not the only hunters of morels. Grizzly bears (Ursus arctos horribilis) in Yellowstone National Park Black are known to eat morels.[58]

Morels appear to prefer a disturbed forest but not flooding. For instance, M. esculenta and M. semilibera increase in mechanically disturbed soils Weber et al. (1996). Flooding seems to temporarily suppress morel fruiting Thompson (1994).[23] However, not all disturbance has a positive effect on morel fruiting. Events that affect associated trees such as heavy logging or blow-downs adversely affect morel fruiting.[23]

Morels seem to grow abundantly in fire-disturbed areas. For instance, especially large appearances of the darker mushrooms will appear after fire particularly in the Pacific Northwest of the USA (Pilz et al. 2007; Weber 1988; Weber et al. 1996; Wurtz et al. 2005).[23][59] This effect has also been observed in Israel.[60] Fire alone is insufficient to lead to abundance of ascocarps. The postfire organic layer of the forest floor (duff) must also be reduced to a thin layer.[61][54] The reason for this effect is not well understood.[62]

In addition to fire, insect infestations, tree mortality, and soil disturbance can give rise to large numbers of ascocarps. The general ordering of productivity is following disturbance is wildfire-burned forests > insect-damaged forests > healthy forests[63], (Kuo 2005; Pilz et al. 2007; Thompson 1994; Weber 1988).[23]

The abiotic factors leading to ascocarp formation production are not fully understood. However, there are some correlations between fruiting onset and temperature and available moisture. In particular, the timing of the onset of fruiting was inversely correlated with spring air and soil temperatures. In addition, the number of fruits was positively correlated with rain events (>10 mm) during the 30 d preceding fruiting. Finally, the length of the fruiting season was positively correlated with soil warming, which suggests a narrow range of favorable soil temperatures for the production of fruits.[64] The biotic factors leading to ascocarp formation production are also not fully understood. However, morels do seem to prefer associations with certain plant species such as Carya spp., Tilia americana and Ulmus americana among others.[64]

[edit] Cultivation

It is not surprising that due to the high desire for the morel's ascocarps, several attempts tried culture the fungus. Repin reported in 1901 of successful fruiting in a cave in which flower-pot cultures had been established in 1892.[65] In 1982 Ower[66] successfully cultured a Morchella esculenta ascocarp; the first reported indoor cultivation of a morel ascocarp. In 2010 Masaphy[67] reported the first successful initiation and development of a Morchella rufobrunnea ascocarp in the laboratory. The system used a soilless culture technique. After more than 100 years of work, successful cultivation of morels is still difficult.[67] Therefore, the commercial morel industry is really a harvest of wild mushrooms.[63] From a basic biology point of view, the inability to culture morels through a complete cycle including fruiting is probably responsible for the lack of reports concerning the morels' basic biology and life cycle.[68]

The inability to culture morels, their high moisture content, and their seasonal nature mean that preserving harvested morels is very important. Drying is a popular and effective method of preservation.[69] Traditionally, drying was done by exposing the morels to the sun i.e. threading the ascocarps onto string and hanging them in the sun. [70] However, solar drying is variable in both availability (e.g. climate conditions) and quality of the final product. Hence, convection dryers which can be controlled precisely might be a better option to solar.[71]

Consumers who buy dried morels will want to rehydrate them. Garcia-Pascual et al[72] studied the rehydration kinetics of M. esculenta mushrooms at different water temperatures and found that they retained 70% of their initial solids and rehydration ability was similar to other vegetables.

Although the Morchella esculenta ascocarps get a lot of attention, the mycelium is a useful product. Culturing mycelium seems to be easier. For instance, mycelium can be cultured in malt extract. Taskin et al. have cultured mycelium in detoxified loquat kernel extract and neutralized loquat kernel extract that was prepared from waste loquat kernels.[73] In addition to loquat, Taskin et al.[74]. Surprisingly, one of the best ways to cook morels is very simple, namely, gently sautee them in butter, crack pepper on top and sprinkle with salt. There are many other recipes that include breading and stuffing with vegetables and meats.[75]

Mushroom harvesting now provides a supplementary, if not primary, source of income for many people (McLain & Jones, 1997, McLain, 2000). In particular, harvesting morels from the wild is a source of income for commercial harvesters in the Pacific Northwest of the USA. Morels comprise a substantial portion of the multi–million dollar export of wild edible mushrooms to the European Community and Asia (Pilz et al. 2007)[76]. Mushrooms are recognized as a valuable forest resource as demand for wild mushrooms increases and demand for timber decreases[77].

[edit] Edibility and Nutrient Composition

According to Wahid, Sattar, and Khan (1988) Morchella esculenta's main, dry weight-based nutritional components: protein 32.7%, fat 2.0%, fibre 17.6%, ash 9.7% and carbohydrates 38.0%.[78][72] Wild samples of M. esculenta also contain several bioactive compounds such as organic acids, phenolic compounds and tocopherols. There are more polyunsaturated fatty acids than mono- and un-saturated fatty acids. Rotzoll et al.[79] identified several components of Morchella deliciosa Fr. that contribute to its sensory qualities such as “mouth feel” and umami(savory)-like taste. The components include amino acids, organic acids and a previously unknown (S)-malic acid dubbed (S)-morelid.

[edit] Toxicity

Morels contain small amounts of hydrazine[80] toxins that are removed by thorough cooking; morel mushrooms should never be eaten raw.[30] It has been reported that even cooked morels can sometimes cause mild intoxication symptoms when consumed with alcohol.[81] When eating this mushroom for the first time it is wise to consume a small amount to minimize any allergic reaction. Morels for consumption must be clean and free of decay. Morels growing in old apple orchards that had been treated with the insecticide lead arsenate may accumulate levels of toxic lead and arsenic that are unhealthy for human consumption.[82]

Raw mushrooms have a gastrointestinal irritant, but parboiling or blanching before consumption will remove it. Old fruiting bodies that show signs of decay may be poisonous.[70]

In one isolated case in Germany, six people were reported to have developed neurologic effects between 6–12 hours after consumption. The effects included ataxia and visual disturbances, and lasted up to a day before disappearing without enduring effects.[83]

Morchella esculenta and Morchella conica are well known edible morels, which seldom induce clinical symptoms. We report six persons who developed cerebellar effects 6–12 hours after consumption of these mushrooms. The symptoms were self-limited and disappeared after one day[84]

Several cases of (true) morel poisoning associated with neurological symptoms have been reported. Morels are edible mushrooms, which can be toxic when poorly cooked. This retrospective study confirms that morel ingestion may cause a NS. The neurological effects are probably toxic, as they generally occur after ingestion of large amounts. The nature of the toxin and the exact mechanism of its action are still unknown and require further analytical studies as well as experimental studies in animals.[85]

[edit] Notes and References

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