Features for Evaluating and Selecting a Mushroom Strain

The strain of mushroom, its unique personality—mannerisms, sensitivities, yield expressions—is the foundation of any mushror m farm. When a strain goes bad, production precipitously declines, typically followed by a proliferation of disease organisms.Therefore, cultivators must continuously scrutinize new strains to find candidates worthy of production. Once a strain has been

Figure 95. Grain spawn 3 days and 8 days af: inoculation. Visible recovery of spawn two days after inoculation is considered good, one day is considered excellent.

developed, multiple back-ups are made in the form o test tube slants. Test tube slants insure long term storage for future use. The cold stor age of test tube slants limits the rate of cell divisions, protecting the Stain from mutation and senescence factors.

Although this list is not all inclusive, and can be expanded by any knowledgeable cultivator, it reveals much about the goals cultivators ultimately seek in bringing a strain into culture. However, the following list arises from a uniquely human, self-serving perspective: creating food for human consumption. From an ecological perspective, this list would be considerably altered.

1. Recovery The time for a mushroom strain to recover from the concussion of inocu-

Figure 96. Healthy mushroom mycelium running through cardboard.

lation. This is often referred to as "leap off. * Oyster and Morel strains are renowned for their quick "leap off' after transfer, evident in as short as 24 hours. Some strains of mushrooms show poor recovery. These strains are difficult to grow commercially unless they are re-invigo rated through strain development and/or media improvement

2. Rate of growth Strains differ substan dally -n their rate of growth at all stages of the mushroom growing process. Once the mycelium recovers from the concussion of inocul?' on, the pace of cell divisions quickens Actively growing mycelium achieves a mycelial momentum, wh; ;h. if properly managed, can greatly shorten the colonization phase, and ultimately the production cycle.

The fastest of the species described in this book has to be the Morels. Their mycelia typically covers a standard 100 x 15mm.petndish in 3-5 days at 75° F. (24° C.). Oyster strains, under ihe same conditions typically take 5-10 days depending on the size of the transfer and other factors All other conditions being the same (i. e. rate of inoculation, substrate, incubation environment) strains taking more than 3 weeks to colonize nutrified agar media, grain or bulk substrates are susceptible to contamination. With many strains, such as Oyster and Shiitake, a sufficient body of knowledge and experience has accumulated to allow valid comparisons With strains relatively new to mushroom science, benchmarks must first be established.

3. Quality of the Mycelial Mat Under 'ideal conditions, the mycelial mat expands and thickens with numerous hyphal branches. The same mycelium under less than perfect conditions, casts a mycelial mat finer and less dense. Its "hold" on the substrate is loose. In this case, the substrate, although fully colonized, falls apart with ease. In contrast, a mycel um properly matched with its substrate forms a mat tenacious in character. The substrate and the mycelium u"'fy together, requiring considerable strength to rip the two apart This is especially true of colonies of Oyster, King Strophara and PsUocybe mushrooms.

Some specks of mushrooms, by nature, form weak mycelial mats. This is especially true of the initially fine mycelium of Morels. Pholioia nameko, the slimy Nameko mushroom, generates a mycelium considerably iess tenacious thanLentinula edodes, the Shiitake mushroom, on the same substrate and at the same rate of inoculation. Once a cultivator recognizes each species' capacity for forming a mycelial network, recogi iiing what is a"strong" or"weak" mycei'Um becomes obvious.

4. Adaptability to single component, formulated and complex substrates Some strains are well known for their adaptability to a va-

Figure 97. Photoiropic response of rsilocybe cubensis to light

riety of substrates. Oyster and King Stropharia are good examples. Oyster mushrooms, native to woodlands, can be grown on cereal straws, corn stalks, sugar cane bagasse, coffee leaves, and paper (including a multitude of paper byproducts). These species' ability to utilize such a spectrum of materials and produce mushrooms is nothing short of amazing Although most strains can grow vegetatively on a wide assortment of substrates, many are narrowly specific in their substrate requirements for mushroom production.

5. Speed of colonization to fruiting Here, strains can fall into two sub-categories. One group produces mushrooms directly after colo nization This group includes the Oyster mushrooms (Pleurotus pulmonai ius, some warm weather P. ostreatus strains), L;on's Manes (Hericium ennaceus) and the Paddy

Straw (Volvariella volvacea) mushrooms Others, like theWoodlovers (Hypholoma capnnides and H. sublaieritium) require a sustained rest-ingperiod after colonization, sometimes taking up to several weeks or months before the onset of fruiting.

6- Microflora Dependability/Sensitivity Some gourmet and medicinal mushroom spe cies require a living community of microorganisms. The absence of critical microflora prevents the mycelium from producing a fruitbody. Hence, these species will not produce on sterilized substrates unless microflora are introduced. The King Stropharia (Stropharia rugcso-annulata), Zhu Ling (Polyporus umbellatus), and the Button Mushroom (Agaricus brunnescens) are three examples Typically, these species benefit from the application of a microbially enirched soil or "casinj layer.

The Blewitt, Lepista nuda, has been suggested by other authors as being a microbially dependent species. However, I have successfully cultivated this mushroom on sterilized sawdust apart from any contact with soil microorganisms The Blewitt may fall into an intermediaie category whose members may not be absolutely dependent on nf roflora for mushroom production, but are quick to fruit when pa;red with them.

7. Photosensitivity The sensitivity of mushrooms to light is surprising to most who have heard that mushrooms like to grow in the dark. In fact most of the gourmet and medici nal mushrooms require, and favorably react to, light. The development of mushrooms is af fectedby light in two ways. Initially, primordia form when exposed to light. Even though thou sands of primordia can form in response to brief light exposure, these primordia will not develop into normal looking mushrooms unless light is sustained. V "thout secondary exposure to light postprimordiaformation. Oyster mushrooms, in particular, malform. Their stems elongate and the caps remain undeveloped. This re sponse is similar to that seen in high C02 environments. In both cases, long stems are produced. Th;; response makes sense if one considers that mushrooms must be elevated above ground for the caps and subsequently forming spores to be released. Oyster, Shiitake and Reishi all demonstrate strong photosensitivity

8. Requirement for cold shock The classic initiation strategy for most mushrooms calls for drastically dropping the temperature for several days With many temperate mushroom strains, the core temperature of the substrate must be dropped below 60-65° F. (15-18° C.) before mushroom p imordia v "11 set. Once formed, temperatures can be elevated to the 70

80° F (21-27° C.) range. This requirement is particularly critical for strains which have evolved in temperate climates, where distinct seasonal changes from summer to fall precedes the wild mushroom season. Because of their cold shock requirement, growing these strains during the summer months or, for instance, in southern California would not be advisable. Strains isolated from subtropical or tropical climates generally do not require a cold shock. As a rule, warm weather strains grow more quickly, fruiting in half the time than do their cold-weather cousins. Experienced cultivators wisely cycle strains through their facility to best match the prevailing seasons, tnus minimizing the expense of heatL.g and cooling.

9. Requirement for high temperature Many warm weather strains wi 11 not produce at cooler temperatures. Unless air temperature is elevated above the minimum threshold for trig-

Figure 98. Photctropic response of two strains of Gonoderma lucidum to light.

gering fruiting the mycelium remains in stasis, what cultivators term "over-vegetation." Volvariella volvacea, the Paddy Straw Mushroom, will not produce below 75° F. (24° C.) and in fact, most strains of this species die if temperatures drop below 45° F. (7.2° C.).Pleurotus pulmonarius, a rapidly growing Oyster specie^ thrives between 75-85° F. (24-29°C.) and is not prevented from fruiting until temperatures drop below 45° F. (7° C.). With most temperature-tolerant strains, higher temperatures cause the mushrooms to develop more quickly. Another example is Pleurotus citrinopileatus, the Golden Oyster, which fruits when temperatures exceed 65° F. (18° C.).

10. Number and distribution of primordial sites For every cultivator, the time before and during primordia formation is one of high anxiety, expectation and hope. The change-over from vegetative colonization to this earliest period of mushroom formation is perhaps the most critical period in the mushroom life cycle. With proper environmental stimulation, the cultivator aids the mushroom organism in its attempt to generate abundant numbers of primordia. Aside from the influences of the environment and the host substrate, a strain's ability to produce primordia is a genetically determined trait. Ideally, a good strain is one that produces a population of numerous, evenly distributed primordia within a short time frame.

11. Site-specific response to low carbon dioxide levels As the mycelium digests a substrate, massive amounts of carbon dioxide are produced, stimulating mycelial growth but preventing mushroom formation.The pronounced reaction of mycelium to generate primordia in response to lowering carbon dioxide gives the cultivator a powerful tool in scheduling fruitings. Strains vary in their degree of sensitivity to fluctuations in carbon dioxide.

Mushroom cultivators who grow Oyster mushrooms in plastic columns or bags desire strains that produce primordia exactly where holes have been punched. The holes in the plastic become the ports for the exodus of carbon dioxide. At these sites, the mycelium senses the availability of oxygen, and forms primordia. This response is very much analogous to the mushroom mycelium coming to the surface of soil or wood, away from the C02 rich environment from within, to the oxygenated atmosphere of the outdoors, where a mushroom can safely propel spores into the wind currents for dispersal to distant ecological niches. With strains super-sensitive to carbon dioxide levels, the cultivator can take advantage of this site-specific response for controlled cropping, greatly facilitating the harvest.

12. Number of primordia forming vs. those maturing to an edible size. Some strains form abundant primordia; others seem impotent Those which produce numerous pri-mordia can be further evaluated by the percentage of those forming compared to those developing to a harvestable stage. Ideally, 90% of the primordia mature. Poor strains can be described as those which produce primordial populations where 50% or more fail to grow to maturity under ideal conditions. Aborted primordia become sites of contamination by molds, bacteria and even flies.

13. Number of viable primordia surviving for 2nd and 3rd flushes Some strains of Oyster and Button mushrooms, especially cold-weather varieties, form the majority of primordia during the first initiation strategy. Many primordia lay dormant, yet viable, for weeks, before development. After the first flush of mushrooms matures and is harvested, the resting primordia develop for the second and subsequent flushes.

J4. Duration between 1st, 2nd and 3rd flushes An important feature of any mushroom strain is the time between "breaks" or flushes. The shorter the period, the better. Strains char acterized by long periods of dormancy between breaks are more susceptible to exploitation by insects and molds. By the third flush a cultivator should have harvested 90% of the potential crop. The sooner these crops can be harvested, the sooner the growing room can be rotated into another crop cycle. The rapid cycling of younger batches poses less r~k of contamination

15. Spore load factors Over the years, the white Button mushroom, Agaricus brunnes-cens, has been genetically selected for small gills, tl ick flesh, and a short stem. In dcmg so, a fat mushroom with a thick veil covering short gills emerged, a form that greatly extended shelf life. As a general rule, once spores have been released in mass, the mushroom soon decomposes. Hence, strains that are not heavy spore producers at the ime of harvest are attractive to cultivators. Additionally, the massive release of spores, particularly by Oyster mushrooms, is an environmental hazard to workers within the growing rooms and is taxing on equipment- I nave seen, on numerous occasions, the spores from Oyster mushrooms actually clog and stop fans running at several hundred rpms, ruining their motors.

Another mushroom notorious for its spore load is Reishi, Ganoderma lucidum. Within the growing rooms, a rust colored spore cloud forms, causing similar, although less severe, allergic reactions to those seen with Oyster mushrooms. Rather than emitting spores for just a few days, as with most fleshy mushrooms, the woody Ganoderma generates spores for weeks as it slowly develops.

16. Appearance: form; size; and color of

Figure 99. I photographed this unsavory package directly after purchasing it from a major grocery store chain. Mushrooms in this condition, if eaten, cause extreme gastro-intestinal discord. This is the "sajor-caju" variety of Pleurotus pulmonarius also known as the Phoenix Oyster mushroom, and has been a favorite of large scale producers. Subsequent to harvest, hundreds of primordia soon form on the decomposing mushrooms.

Figure 99. I photographed this unsavory package directly after purchasing it from a major grocery store chain. Mushrooms in this condition, if eaten, cause extreme gastro-intestinal discord. This is the "sajor-caju" variety of Pleurotus pulmonarius also known as the Phoenix Oyster mushroom, and has been a favorite of large scale producers. Subsequent to harvest, hundreds of primordia soon form on the decomposing mushrooms.

the harvestable mushrooms Every cultivator has a responsibility to present a quality product to the marketplace. Since gourmel mushrooms are relatively new, national standards have yet to be set in the United States for disting :shing grades. As gourmet mushrooms become more common, the public is becoming increas:ngly more oisc~ ninating,

What a cultivator may lose in yield from picking young mushrooms is offset by many benefits.Young mushrooms are more flavorful, lighter fleshed, often more colorful, and ship and store longer than older ones. Crop rotation, with much less associated spore load, is 'ike-

124 EVALUATING A MUSHROOM STRAIN

wise accelerated through the harvest of adoles cent forms. Diseases are less likely and consistency of production is better assured.

One general feature is common to all mushrooms in determining the best stage for picking: the cap margin. Cap margins reveal much about future growth. At the youngest stages the cap margin is incurved, soon becoming decurved, and eventually flattening at maturity. In my opinion, the ideal stage for harvest is midway between incurved and decurved. During this period, spore release is well below peak production. Since the gills are protected by both the curvature of the whole mushroom as well as adorning vei. remnants (as in Shiitake), the mushrooms are not nearly as vulnerable to damage For more information, please consult Chapter 23.

17. Duration from storage to spoilage: Preservation An important aspect of evaluating any strain is its ability to store well. Spoilage is accelerated by bacteria which thrive under high-moisture stagnant air conditions. A delicate balance must be struck between temperature, air movement, and moisture to best prolong the storage of mushrooms.

Some species and strains are more resistant to spoilage than others. Shiitake mushrooms store and ship far better, on the average, than Oyster mushrooms. Some Oyster mushrooms, especially the slow-forming cold weather strains, survive under cold storage longer than the warm weather varieties. In either case, should spores be released and germinate, bacterial infection quickly sets in.

18. Abatement of growth subsequent to ftarvesf Yet anotherfeature determining preservation is whether or not the mushrooms stop growing after picking. Many mushrooms continue to enlarge, flatten out, and produce spores long after they have been harvested. This is especially distressing for a cultivator picking a perfect-looking young specimen one day only to find it transformed into a mature adult the next day. This continued growth often places growers and distant distributors into opposing viewpoints concerning the quality of the product. Strains of Pleurotus pulmonarius, especially the so-calledliPleurotus sajor-caju" is one such example. I like to describe this strain of Oyster mushrooms as being "biologically-out-of control." (See Figure 99.)

19. Necrosis factors and the protection o f dead tissue from competitors After a mushroom has been picked tissue remnants become sites for attack by predator insects and parasitic molds. Some species, Shiitake for instance, have a woodier stem than cap. When Shiitake is harvested by cutting at the base of the stem, the stem butt, still attached to the wood substrate, browns and hardens. As the stem butt dies, a protective skin forms. This ability to form a tough outer coat of cells protects not only the left-over stem remnant from infestation, but also prevents deep penetration by predators. Since most Pleurotus ostreatus strains are not graced with this defense, extreme caution must be observed during harvest so no dead tissue remains. The "sajor-caju" variety of Pleurotus pulmonarius is surprising in its ability to reabsorb dead tissue, even forming new mushrooms on the dead body remnants of previously harvested mushrooms.

20. Genetic stability/instability Since all strains eventually senesce, genetic stability is of paramount concern to every cultivator. Signs of a strain dying are its inability to colonize a substrate, produce primordia, or develop healthy mushrooms.Typical warning signs are a delay in fruiting schedules and an increasing susceptibility to disease. These symptoms are a few of many which suggest strain senescence.

21. Flavor Strains of the same species differ substantially in flavor. The cultivator needs to be sensitive to customer feedback. Americans favor mildly flavored mushrooms whereas the Japanese are accustomed to more strongly flavored varieties. Pleurotus c;*rinopileatus, the Golden Oyster mushroom, is extremely astrin-ent until thoroughly cooked, a good example that flavor is affected by the length of cooking. Generally speaking, younger mushrooms are better-flavored than older ones. The King Stropharia, Stropharia rugoso-annulata, is a good example, being exquisitely edible when young, but quickly losing flavor with maturity. Shiitake, Lentinula edodes, has many flavor dimensions. If the cap surface was dry before picking, or cracked as in the so-called"Donko" forms, a richer flavor is imparted during cooking Although the cracking of the cap skin is environmentally induced, the cultivator can select strains whose cap cuticle easily breaks in response to fluctuating humidity.

22. Texture The stage at harvest, the duration and temperature of cooking, and the condiments with which mushrooms are cooked all markedly affect textural qualities. Judg" g the best combination of texture and flavor is a highly subjective experience, often influenced by cultural traditions. Most connoisseurs prefer mushrooms that are slightly crispy and chewy but not tough. Steamed mushrooms are usually limp, soft and easily break apart, especially if they have been sliced before cook« ng By tearing the mushrooms into pieces, rather than cutting, firmness is preserved. These attributes play an important role in the sensual experience of the mycophagist.

23.Aroma Few expediences arouse as much interest in eating gourmet mushrooms as their aroma. When Shiitake and Shimeji are stir-fried, the rich aroma causes the olfactory senses to dance, setting the stage for the taste buds. Once paired with the experience of eating the aroma signature of each species is a call to arms (or "forks") for mycophagists everywhere. My family begins cooking mushrooms first when preparing dinner. The aroma undergoes complex transformations as water is lost and the cells are tenderized. (Please refer to the recipe; n Chapter 24.)

24, Sensitivity to Essential Elements: Minerals and Metals Gray Leatham (1989) was one of the first researchers to note that nanograms of tin and nickel were critical to successful fruitbody formation in Shiitake. Without these minute amounts of tin and nickel, Sh" ake mycelium is incapable of fruiting. Manganese also seems to play a determinate role in the mushroom life cycle. Many other minerals and metals are probably essential to the success of the mushroom life cycle Since these compounds are abundant in nature, cultivators need not be concerned about the" addition to wood-based substrates. Only in the designing of "artificial" wood-free media, does the cultivator run the risk of creating an environment lacking in these essential compounds.

25. Ability to Surpass Competitors An essential measure of a strap's performance is its ability to resist competitor fungi, bacteria and insects. Strains can be directly measured by their ability to overwhelm competitor molds, especially Trichoderma, a forest green mold, which grows on most woods On thoroughly ster ized substrates, a mushroom strain may run quickly and without hesifr :on. Once a competitor is encountered, however, strains vary substantially in their defensive/offensive abilities Oyster mushrooms (Pleurotus ostreatus) for instance, are now recognized for their nema-tode-trapping abilities. I have even witnessed Sciarid flies, attracted to aromatic Oystermyce-lium, alighting too long, and becoming stuck to the aerial mycelium. The degree by which flies are attracted to a particular Oyster mushroom strain can be considered a genetically determined trait—a feature most cultivators would like to suppress

26. Nutritional Composition Mushrooms are a rich source for amino acids (proteins), minerals and vitamins. The percentages of these compoundscarcvary between strains. Substrate components contain precursors which can be digested and transformed into tissue to varying degrees by different strains. This may explain why there is such a variation in the protein analysis of, for instance, Oyster mushrooms. The analyses are probably correct. The strains vary in their conversion efficiencies of base substrate components into mushroom flesh.

27. Production of Primary and Secondary Metaholites A strain's ability to compete may be direcily related to the production of primary and secondary metabolites. All fungi produce extracellular enzymes that break down food sources. Myriads of metabolic by-products are also generated. These extracellular compounds are released through the cell walls of the mycelium, enabling the digestion of potential food sources. Enzymes, such as ligninase which breaks down the structural component in wood, are extremely effective in reducing complex carbon chains, including carbohydrates and hydrocarbons.

Secondary metabolites usually occur well after colonization. A good example is the yellow fluid, the exudate, frequently seen collecting at the bottom of aged spawn containers. Pleurotuss^.,

Stropharia rugoso-annulata, and Ganoderma lucidum are abundant producers of secondary metabolites, especially complex acids and cthylene-related products.These metabolites forestall competition from other fungi and bacteria.

28. Production of Medicinal Compounds Bound within the cell walls of mushrooms are chains of heavy molecular weight sugars, polysacharrides. These sugars compose the structural framework of the cell. Many mushroom polysacharrides are new to science and are named for the genus in which they have been first found, such as lentinan (from Shiitake, Lentinula edodes), flammulin or "FVP" (from Enokitake, Flammulina velutipes), grifolin or grifolan (from Maitake, Grifolafrondosa), etc. Research inAsia shows that these cell wall components enhance the human immune system. Cellular polysaccharides are more concentrated, obviously, in the compact form of the mushroom than in the loose network of the mycelium. In traditional Chinese pharmacopeia, the sexually producing organ—in this case the mushroom—has long been viewed as a more potent source for medicine than from its infertile representations.

Cell components other than polysaccharides have been proposed to have medicinal effects. Strain selection could just as well focus on their molecular yields. Precursors in the substrate may play determinant roles in the selective production of these components when matched with various strains. (Please refer to Chapter 21.)

CHAPTER 15

rain spawn is the next step in the exponential expansion of mycelial mass. The intent and purpose of grain spawn is to boost the mycelium to a state of vigor where it can be launched into bulk substrates. The grain is not only a vehicle for evenly distributing the mycelium, but also a nutritional supplement. Whole grain is used because each kernel becomes a mycelial capsule, a platform from which mycelium can leap into the surrounding expanse. Smaller kernels of grain provide more points of inoculation per pound of spawn. Millet, a small kernel grain, is used by many large spawn producers because end-users like its convenience. Most small scale, gourmet mushroom growers utilize organically grown rye or wheat grain. Virtually all the cereal grains can be used for spawn production. Every spawn maker favors the grain which, from experience, has produced the most sat'¿factory results.

The preferred rate of inoculation depends upon many factors, not the least of which is cost. If a cultivator buys spawn from a commer-

Lcial laboratory, the recommended rate is often between 3-7% of substrate mass. What this means is that for every 1000 lbs. of sub

2 in

igi e - 0. he progressive colonization cf sterilized grain by mushroom mycelium incubating in recyciea w skey bottles, "lis ingenius Tl;ai grower inoculated the centers via a removable tube.

strate (dry weight), 30-70 lbs. of spawn (wet, weight) is suggested. Since grain spawn is ijj: ^ ally around 50% absolute moisture, this rati inoculation would be equivalent to 1. 5-3 ifW of dry spawn/dry substrate

Cultivators who generate tfeir own spawn frequently use a 8-15% rate of moist spawn/dry substrate, or by this example 80 -150 lbs. of fresh spawn per 1000 lbs. This increased rate of spawning accelerates colonization, narrows the window of opportunity for competitor invasion, and boosts yields. Clearly, those making their own spawn have an advantage over those buying spawn from afar.

One major drawback of high spawning rates is increased thermogenesis. the heating up of the substrate as the mycelium overwhelms it. Anticipating and controlling thermogenesis is essential for success.This subject will explored in detail later on

Of the many cereal grains used for creating S° spawn, rye grain is the most popular. Wheat, milo, sorghum, corn, and millet are also uti-uS lized. There are tuo approaches for preparing grain spawn The first is to submerge grain in a cauldron of boiling water. After an hour of boiling (or steeping), the saturated grain is drained of water (discarded) and scooped into awaiting spawn containers. Fitted with a lid having a 1/3 to 1/2 in. hole and lined w;th amicroporous filter disc, the grain-filled jars are sterilized in a pressure cooker. This method is widely used and recommended by many because even moisture absorption and consistency is assured

The second method calls for first placing dry grain into glass spawn jars, adding the recommended amount of water, preferably hot. and allowing the jars |o sit overnight- The jars are capped with lids, complete with a 3/8 to 1/2 in. hole and fitted underneath with a microporous

Figure 101. One method for preparing grain spawn is to simply pour dry grain into glass jars, add water, allow to sit overnight, and then sterilize. Advantages of this method ars: one-step process; less fuel consumption; and less handling. One disadvantage is uneven water absorption.

filter disc. By allowing the grain to soak for 1224 hours, the heat resistant endospores of bacteria germinate and become sensitive to heat sterilization. Before use, the filter d;scs should be soaked in a weak (5%) bleach solution to dislodge and disinfect any imbedded contan in ants. The next day, th° jars are shaken by striking them against a rubber tire, or similar surface, to mix together the more moist and drier grain kernels. Once shaken, they are promptly placed into the sterilizer. The advan tage of this method is that it is a one-step procedure, A case can be made that starches and other nutrients are preserved with this method since the water is not discarded. Proponents of the first method argue that not only is their start ing material cleaner, but this second technique causes the grrins to have an uneven moisture content. The reader must decide which is most suitable. Neither method, ir. my opinion, merits endorsement over the other.

With excess water, grain kernels explode, exposing the nutrients within and making them more susceptible to contamination. Exploded grain kernels also cause clump:ng and sites of depressed gas exchange, environments wherein bacterir proliferate. The shape of the intact grain kernel, with its protective outer surface, selectively favors the filamentous mushroom mycelium and produces a spawn that separates readily upon shaking.

Suitable Containers for Incubating Grain Spawn:

16 fl oz. mineral spring water bottles, quart masor 'ars, liter bottles

Vi gallon jars

1 gallon jars

2 i/2 gallon jars

Polypropylene plastic bags

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