Most of us in mushroom industry got used that spawn just exists. UMDIS Mushroom Information Agency asked Nikodem Sakson to share the history – how different strains were developed and spawn suppliers appeared.
“The fact that it is possible to copy mushroom strains without respecting the rights of their creators has inhibited the breeding of new mushroom strains for many years. In previous years, a number of attempts were made to protect the ownership rights of new strains without success. Only Amycel took up the challenge of protecting its original strains. This mainly applies to the Heilroom brown strain with quite a large effect. Work on the development of their strains was undertaken in France by Euromycel E-58 Premium and in Poland by Spyra F 1 GP. In the latter case, the aim of the breeding work is to obtain a strain that gives best yield on the substrate produced in Poland; straw and chicken manure.
A serious obstacle in the breeding of new strains is the rejection of the possibility of obtaining them through genetic engineering as a product not acceptable for human consumption. In my opinion, this limitation may disappear and completely new strain of mushrooms may be created as an industrial raw material for production materials used for utility products. This is a potentially likely effect of the purchase of Labmert by Ecovative. As a consequence, this may result in the appearance of new strains of mushrooms cultivated on the market.
For young and middle-aged mushroom growers, spawn and the strains used in its cultivation are something natural and accessible. However, this state, the cultivation of heterozygous strains, as well as the grains and artificial carriers of mycelium for reproduction in compost, are consequences of changes that have taken place in the last 40 years.
Industrial spawn is a specific component of mushroom cultivation technology. It is a source of mushroom mycelium. It determines the course of cultivation, primarily the speed of colonization and sensitivity to the quality of compost. It affects yield, appearance, and quality of fruit bodies, as well as behavior during cultivation. That is why so much attention is paid to selecting the strain and the spawn producer. It has a long tradition and is associated with companies that produce spawn.
The production of commercial spawn was initiated by mushroom farms initially for their own needs and then developed as an independent type of activity. The best examples are American companies such as Amycel, Lambert, and Sylvan. In the past, having their own strain with characteristics expected on the market, such as higher yields and better quality, was one of the important elements of competition in the mushroom market. In Europe, mushroom cultivation started its development in France. The main producers of spawn there were Somycel and Le Lion.
Production of commercial spawn involves several types of activities that take place in the process:
- Breeding new strains: This involves a complex set of measures based on selection and crossbreeding to find mycelium with desired characteristics. Initially, breeding led to the creation of stable strains. The breakthrough role in selection was played by the Dutch Mushroom Research Station and G. Fritsche (1980), who utilized the heterosis effect, where a strain obtained by crossing two parental pairs surpasses the parents. Today, almost all strains are hybrid. The supply of strains on the market is not only the result of our own breeding work but can also come from licensing. Sometimes, new strains are protected by patents.
- Conservative breeding (maintenance of genetically fixed characteristics of a given breed) and preparation of material for the production of commercial mycelium. Cultivated mushroom mycelium must have reproduction characteristics. The problem with mushrooms is that mycelium can change its characteristics during reproduction. The starting point for the production of commercial mycelium is the mycelium stored in our own bank of varieties and strains, from which the parent mycelium is created, which must be tested for consistency of characteristics. After testing, the parent mycelium is propagated several times, and each propagation is called a line. Such propagation is carried out up to 10 times and is referred to as successive lines. The more successive lines are propagated, the greater the risk of degeneration of fruit bodies and loss of vigor; the speed of mycelium growth in compost. The mycelium introduced onto the commercial mycelium carrier can be in the form of solid grains, a hyphal fragment, or liquid.
- Production of commercial spawn: Commercial spawn takes the form of granules for easy sowing, and the material used includes grain cereals, mycelial granulated or synthetic material, and synthetic spawn. Carriers of various diameters are selected.
Initially, grain spawn was produced on large grains because the mycelium survived in them in the presence of elevated ammonia content in the compost during inoculation. It is also produced on small grains such as millet since modern composts do not pose such a threat, and small grains provide more starting points for substrate colonization. The faster the colonization, the potentially higher yields and greater resistance to competing fungi. Currently, the choice of grain size depends more on marketing. The production process involves the following stages: grain sterilization, cooling, filling of containers (currently only plastic bags with a special design, featuring a filter), and pasteurization. After cooling, the mycelium is seeded in sterile conditions, and the carrier is allowed to colonize on shelves. Sylvan developed a method of inoculating liquid mycelium and a device for mixing it with the carrier. Once the carrier is fully colonized, the commercial spawn is allowed to mature for two weeks in a refrigerated chamber, after which the bags are selected and packaged in cardboard boxes.
Synthetic spawn is designed to accelerate substrate colonization by 1-2 days.
The history of the origin and use of commercial spawn has seen achievements scattered over time:
- Spawn on cereal grains: Initially, sterilized phase II medium served as the carrier for mycelium. Growth took place in cylinders from which walnut-sized portions were extracted and planted on the substrate at a certain density. In 1931, the technology for producing granulated spawn was developed, and spawn from cylinders gradually became obsolete and is no longer produced today.
- Breeding hybrid strains: The selection of mushroom mycelium began with strains that could reproduce in natural conditions, sharing a common origin and characteristics that distinguished them from other organisms of the same species. In the 1980s, Dr. G. Fritze at the Mushroom Experimental Station in Horst, Netherlands, developed hybrid strains that could no longer reproduce naturally, leading to the disappearance of white button mushroom varieties within a short period, followed by a decline in established brown mushroom varieties after a few years. The breeding work resulted in the creation of two hybrid strains designated as Horst U3, characterized by small fruit bodies that are easy to form and have relatively low demands, and Horst U-1, which is difficult to form with large fruit bodies but requires high-quality compost and microclimate support.
The next step involved developing intermediate strains through the crossbreeding of the aforementioned strains, referred to as U-2. These strains are characterized by medium-sized fruit bodies, relatively easy formation, and compatibility with less quality compost, but require effective microclimate control for pins growth. Strains from the U-3 group, specifically Somycell 516, became the basis for success in Polish mushroom cultivation in the 1990s, being the best strain for small fruit bodies suitable for processing. Strains from the U-1 group are not currently sold or cultivated. Currently, the Hauser A-15 strain serves as the basis for cultivating intermediate mushroom varieties. After purchasing this manufacturer, it is referred to as Sylvan A-15. This is the first strain grown on a large scale for the fresh market in Poland. Currently, primarily intermediate strains closer to U-1, with less spontaneous fruiting and better quality, are being cultivated. The following strains are represented in the market with their economic share: Sylvan 737, Euromycel E-58, Spyra F1, Amycel TRIPLEX X, Italspawn F-599, Kanmycel 55, and A-15 strains – Sylvan A-15 and Kanmycel 53, among others. The latest strain that closely resembles U-1 and is being introduced is Exxcalibur Amycel, which exhibits better fruiting body quality and less spontaneous pinning. Excessive pinning remains a problem for many mushroom producers, necessitating manual separation of small fruit bodies during the first flush to allow for elongation over time and generation formation.
Amycel Heirloom currently dominates among brown strains. The appearance of this strain led to the disappearance of established strains in cultivation and the emergence of hybrid strains among other mycelium producers.
3. New carrier forms, such as liquid mycelium and mycelium on synthetic carriers, aim to accelerate compost colonization. Commercial liquid mycelium did not meet expectations in practice and is not utilized. On the other hand, mycelium on synthetic carriers, known as fast spawn, emerged to improve substrate colonization in cultivation tunnels. Mycelium on this medium starts growing immediately after inoculation, enabling the compost to grow faster by 1-2 days. This results in better tunnel utilization, longer colonization, increased yields, and the yield depends on the mycelium’s mass. Another advantage of using this mycelium is its reduced susceptibility to green mold contamination, as the rapid growth and colonization by the mushroom mycelium limits or eliminates the development of competitive green mold species.
The mentioned part discusses the problems faced by mushroom producers related to the mycelium:
- Threat of disease transmission: The most significant concern at present is the periodic appearance of symptoms caused by the MVX virus and the resulting losses. In the past, the La France virus caused substantial damage, leading to progressive deformities and the death of fruit bodies. However, the MVX viruses belong to a different group and have different biology and mechanisms of loss, causing browning of caps and yield loss. The extent of losses depends on the level of viral contamination in the substrate and the stress imposed on the mushrooms during cultivation. However, it is not entirely fair to blame all the responsibility on the mycelium.
- Degeneration: This refers to two groups of generations. The first is known as stroma, which involves excessive mycelial growth that is difficult to suppress. The second group is characterized by developmental abnormalities in fruit bodies, such as clustered or fused fruit bodies and absence of gills. However, such symptoms have not been observed recently.
- Yield disruptions: In recent times, another symptom of yield loss has emerged, although it has only occurred once and is unlikely to be repeated.
The unresolved problems related to mycelium are as follows:
- Lack of breeding disease-resistant strains: The main problem in the emergence of MVX infection is the genetic similarity of the cultivated mushroom strains today. All U-2 Intermediate strains are so closely related that there are minimal genetic differences, mainly related to yield and certain quality traits such as dry matter content. This puts the entire harvest of these strains at risk of losses from these viruses. In other cultivated crops like tobacco and tomatoes, resistant varieties have been developed. It remains unclear whether this direction of selective breeding will be pursued in mushroom cultivation as there is no available information on this matter.
- Lack of direction for selection considering the challenges posed by technological advancements in cultivation.
- Adaptation of mycelium strains to the expected automation of harvest collection: Currently, the minimum diameter of fruit bodies that can be handled by harvesting robots is 2.5 cm. This necessitates thicker skins on fruit bodies that are resistant to surface imprints. The main challenge lies in achieving fruit body formation without the need for manual separation. It is expected that strains will have a tighter structure and be more difficult to pin, allowing for more compact fruit bodies. Does Exxcalibur bring us closer to meeting these expectations? Cultivation technology without manual shelf separation already exists, involving the growth of less spontaneous strains at a casing height of 2.5 cm.
- Need for improved utilization of high-quality substrate created through the potential of U-1 large hybrid group mycelium: Standardization of substrate is expected, which would enable the cultivation of U-1 group strains. Whether such strains will be included in the breeding programs of individual companies remains to be seen.
In conclusion, it is worth considering whether we will produce and consume mycelium itself. This is possible because the nutritional and flavor properties of mycelium in the substrate are similar to those of the fruit body. This was observed at the Lambert Ecovative Spawn and Substrate booth, as the production of mycelium for household purposes can also be beneficial for its use as food”.
You can ask Nikodem Sakson for private consulting on mushroom, comost, casing production.
UMDIS Mushroom Information Agency provides consultations on mushroom growing and picking in Europe, organizes study tours. Also you can place advertisement on this media web-site. Contact us for more information: [email protected], +380935690941 (WhatsApp, Viber, Telegram).