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◆ Tap into Japan's rich heritage for unique growing insights
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Development of cultivation techniques contributing to edible mushroom production in Satoyama areas
- Kazuhiko Masuno
Nagano Prefecture Forestry Research Center, 5739 Kataoka, Shiojiri City, Nagano, Japan 399-0711
Originally published in Volume 27(4) pg 122-127, 2019, Mushroom Science and Biotechnology, by the Japanese Society of Mushroom Science and Biotechnology. (日本きのこ学会誌、Vol 27(4) 122-127, 2019.一社団法人日本きのこ学会) - Abstract
To promote the production of edible mushrooms in Satoyama areas, this study examined the development of mushroom cultivation techniques and cultivars. The major achievements resulting from this research were as follows:
1. A simple inoculation method for bed-log cultivation using spawn comprising disposable chopsticks and toothpicks was devised and demonstrated for Kuritake (Hypholoma lateritium) cultivation. These methods were patented as a “mushroom inoculation method”.
2. In Kuritake mushrooms, high levels of mitochondrial DNA (mtDNA) variability may be maintained in natural populations.
3. Kuritake mycelia grow and spread in the soil using woody residues as a substrate while developing hyphal cords and rhizomorphs. In addition, a method for culturing Kuritake mycelia in nature on sterilized logs was developed. Specifically, a buried culture-bed method employing a basic knowledge of Kuritake cultivation was used in this study.
4. Mushroom genetic resources collected from wild mushrooms, such as Nameko (Pholiota microspora), Numerisugitake (Pholiota adiposa), Yamabushitake (Hericium erinaceus), and Kuritake were used to improve cultivars used in mushroom production.
Key words: Cultivation techniques, Edible mushroom, Hypholoma lateritium, Satoyama areas 1. Introduction
Mushroom production began with the utilisation of logs within forests, but nowadays, the focus has shifted to large-scale substrate cultivation methods equipped with air conditioning facilities. In large-scale production methods, efficiently producing large quantities of fruiting bodies in a short period of time is critically important. Therefore, even if new cultivation techniques for new cultivars and varieties are developed, they are less likely to be adopted if they lack efficiency.
In contrast, there are factors apart from efficiency that are also important in sustaining mushroom production in mountain villages as an industry and culture with regional characteristics. The main perspectives of the research conducted for this purpose are as follows:One is the development of mushroom cultivation techniques that do not focus solely on making a living but allow the participation of many people, in other words, establishing easy “mushroom cultivation and propagation techniques” using unused wood materials left in the satoyama areas around mountain villages and settlements.The other is the development of technologies that contribute to small and medium-sized producers centered on family labour, which is vastly different from large-scale production. Specifically, it involves the development of new varieties and cultivars of mushrooms through the collection and utilisation of mushroom genetic resources from the natural world.Based on these factors, this paper will outline the research results related to the development of cultivation techniques that contribute to the production of edible mushrooms in satoyama areas.2. Development of simple mushroom inoculation methods
In recent years, the deterioration of satoyama areas around villages has been a concern, making satoyama revitalisation a major challenge. In response, efforts have been made to develop new methods for effectively utilising satoyama for special forestry products like wild vegetables and mushrooms. As part of this effort, there has been a focus on the simplification of inoculation techniques within forests.In traditional mushroom log cultivation, electric drills are used to make holes in logs, with spawn then inoculated into these holes. Thus, if there are no portable generators, it is difficult to inoculate mushrooms in forests. To make it easy for everyone to experience the joy of mushroom cultivation and harvesting in forests, inoculation needs to be simplified. For this reason, simple inoculation methods using spawn cultivated onto disposable chopsticks and toothpicks (hereafter referred to as “chopstick spawn” and “toothpick spawn,” see Photo 1) were devised. Further, cultivation trials verified whether these devised methods could cultivate kuritake using wood obtained from periodic forest-thinning and stumps. Figure 1 shows the inoculation process using chopstick spawn, and Photo 2 shows the growth of fruiting bodies from the demonstration trial.In the log cultivation trial of kuritake (Hypholoma lateritium) using a simple inoculation method, inoculation in spring led to fruiting starting from the following fall, with the yield peaking in the second year of fruiting. Although it gradually decreased from the third year, the cumulative yield over five years amounted to 664 grams per log (Figure 2). Based on this, a model of annual yield was created, as shown in Table 1.A yield of 650 g per log over five years means that 1,000 logs can produce 650 kg of kuritake mushrooms. If the unit selling price is 1,200 yen per kg based on sample transactions, the sales amount is 780,000 yen. Deducting material and shipping costs and other expenses leaves a profit of 498,970 yen, resulting in daily labour wages of 20,039 yen (Table 2). Although this is only a calculation example, it can to some extent demonstrate the practicality of the developed technique.
- Figure 1. Inoculation process using chopstick spawn
3. Understanding kuritake traits and the development of natural propagation techniques
In the log cultivation of kuritake, fruiting bodies not only grew directly from the inoculated logs but also from the surrounding soil up to about a one-meter distance (Photo 3). At production sites, this phenomenon is called “hanare”, meaning “separation”, (hereafter called the “hanare phenomenon”). Although cultivation manuals vaguely suggest that the mycelium inside the logs spreads to the organic matter in the soil, there were no clear case studies. Therefore, in log cultivation, we carefully investigated the origin of the fruiting bodies of the hanare phenomenon and observed that the stalks of the fruiting bodies were not directly emerging from the logs but from “rhizomorphs” (root-like structures. See Photo 4). Moreover, when replication tests were conducted using sterilised log cultivation and substrate cultivation, the formation of rhizomorphs and the growth of fruiting bodies from them were confirmed in all cases (Photo 5).Additionally, culture tests and RAPD analyses were performed on isolates from fruiting bodies that grew from the hanare phenomenon, showing that fruiting bodies originating from inoculated strains can grow at points away from the logs. Observations of the hanare phenomenon revealed that kuritake has an ecological habit of forming mycelial cords and rhizomorphs to extend its reach through woody substrates in the soil, then growing fruiting bodies to spread spores.Next, in order to examine the genetic variability of 32 wild kuritake strains collected from 11 prefectures in Japan (Hokkaido, Aomori, Iwate, Akita, Yamagata, Fukushima, Gunma, Nagano, Gifu, Kyoto and Tottori), a mitochondrial DNA (mtDNA) RFLP analysis was conducted.Each of the 32 wild kuritake strains exhibited unique EcoRI and EcoRV mtDNA RFLP patterns. Based on the sum of the sizes of the restriction enzyme fragments, the size of kuritake mtDNA was estimated to be 53.4_endash_84.4 kb (average: 69.4 kb). The genetic distance values calculated between each wild strain, based on the presence or absence of restriction enzyme fragments, were significantly greater compared to those of previously studied shiitake, hiratake, and nameko mushrooms, suggesting that high variability in mtDNA is maintained in natural kuritake populations. Furthermore, there was little correlation between kuritake mtDNA variation and geographical distribution.Based on these fundamental understandings of kuritake, techniques were developed and demonstrated for inducing the natural propagation of kuritake through the burying of sterilised logs and incubated substrate blocks. Additionally, we developed kuritake cultivars that can use larch logs, a type of conifer, as well as cultivars that produce large fruiting bodies.
4. Collection, selection, and cultivar development of mushroom genetic resources
As a basis for mushroom production,we collected, selected, and developed cultivars of mushroom genetic resources of nameko (Pholiota microspora), numerisugitake (Pholiota adiposa), yamabushitake (Hericium erinaceum), and kuritake.Approximately 800 lineages of wild nameko mushrooms were collected and preserved from beech forests across Japan, from the southern region of Hokkaido to the Osumi Peninsula in Kyushu, with the cultivation characteristics of almost all strains identified. These were used to create hybrid strains, and two cultivar lineages for substrate cultivation have been registered (Photo 6). Additionally, wild strains of numerisugitake and yamabushitake were collected, selection tests were conducted, cultivation methods were examined, and cultivation techniques were developed, with selected strains registered as cultivars (Photos 7 and 8). Further, strains suitable for substrate cultivation were selected from wild kuritake strains, paving the way for kuritake substrate cultivation (Photo 9).Cultivation manuals (Photo 10) have been produced based on the techniques developed and are currently available for distribution.
5. Conclusion
The term “satoyama” was originally found in a document from 1759 called “Kiso Omizaimokukata” (“The Kiso Timber Office”) from the Nagoya Tokugawa Domain, where it was defined as “mountains close to villages or settlements (homes).” It is said that forest ecologist Tsunae Shidei resurrected this term in modern society. “Satoyama” refers to the mountains that are adjacent to villages and where people live in harmony with nature, as opposed to remote, untouched mountains.The term has come to be frequently used by locals who love nature, and nowadays, it is often used to refer not only to forests such as groves of mixed trees, pine forests, and man-made forests around settlements, but also to a broader area or region that includes grasslands, agricultural land around forests, and rivers.Mushroom cultivation began in the mountains with log cultivation, moved down to the flat countryside with substrate cultivation, and is now even conducted in large-scale factories. In recent years, even large-scale factories are facing challenges such as fierce competition between production areas and the globalisation of material procurement, prompting them to respond to a range of issues, including cost reduction and energy conservation. Meanwhile, there are many small to medium-sized producers in mountain villages engaged in log cultivation and substrate cultivation relying on family labour, revealing a dichotomy in mushroom production. The research presented here mainly contributes to the latter, but also aims to involve “locals” who do not make a living directly from mushroom production, with the goal of expanding mushroom consumption and fostering interest in forests.While the technique developed does not significantly increase mushroom production, it is gradually spreading as a mushroom production technique in satoyama areas. Furthermore, I hope that it will not only aim to increase mushroom production, but also serve as an opportunity to revitalise the entire region centered around satoyama and promote exchange between urban and rural areas through green tourism and other means. I hope to contribute to mushroom production that harnesses the characteristics of the region while promoting the dissemination of the techniques developed by this research.AcknowledgmentsI sincerely express my gratitude to Professors Masaki Fukuda and Akiyoshi Yamada of the Faculty of Agriculture at Shinshu University, the Hoshi-no-machi Usuda Wild Vegetable and Mushroom Growers Association, the Nagano Institute of Rural Industry, and JA Kamiina for their generous guidance and cooperation during the course of my research. I would also like to extend my profound appreciation to the staff of the Nagano Prefecture Forestry Center Special Products Division and Nagano Prefectural Government for their support and advice.This work was supported in part by a grant from the Agriculture, Forestry and Fisheries Research Council under the Ministry of Agriculture, Forestry and Fisheries.This English translation was done for the Japanese Exotic Mushroom Journal, and any errors in terminology, transcription, or in the presentation of the data are the responsibility of the Japanese Exotic Mushroom Journal. Please contact journal editors at jemj@salai.jp for a full list of citations and references (not translated).About the Translator: Naomi Roulston has over a decade of experience as a Japanese to English translator and specialises in food, mushrooms, nutrition and lifestyle medicine, and travel and tourism. She has a postgraduate degree in translation, is NAATI-certified, and holds a Kinoko Meister certificate from the Japan Kinoko (mushroom) Meister Association.
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