Armillaria - Naratake

This edible mushroom belongs to the family Tricholomataceae, order Acaridiomycetes. Its cap is 5-12 cm long and round to flat. Its cap is candy-colored or light yellowish brown, with dark fine burrs in the center and radial streaks around the edge. It has yellowish-white folds that hang down from the stem. The stem has a brim, and the lower part is blackish. Its spore print is white. It emerges from early summer to late autumn and is distributed all over the world. It is popular as an edible fungus in many countries, and in Japan it has many local names such as Orimiki, Boribori, Sawamotashi, Habakitake, and Asinaga. It usually grows in clusters at the base of standing or dead trees. Armillaria arvensis is also known as a tree pathogen, killing forest trees, fruit trees, and garden trees. There are over 600 types of trees that are affected by this. This condition is called armillaria disease, and the fungus invades through the roots and attacks the cambium layer beneath the bark. Shiny, black, root-like bundles of mycelium are formed beneath the bark of trees that have died from armillaria disease, allowing armillaria to survive for many years. Due to this characteristic, in Europe it has the common name "shoe string mushroom." Leafless orchids such as Acanthurus maximus and Akebia japonica live in symbiosis with the Armillaria fungus, forming special mycorrhizae and surviving with the help of the fungus. It has also been reported that the flesh or mycelium at the base of fresh armillaria stems sometimes emits a weak light.

[Imaseki Rokuya]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

担子菌類、マツタケ目キシメジ科の食用キノコ。傘は5～12センチメートル、丸形から平らに開く。傘の色は飴(あめ)色ないし淡黄褐色で、中心部に暗色の細かいささくれを帯び、周辺部には放射状の筋(すじ)がある。ひだは黄白色で、茎に垂生。茎にはつばがあり、つばから下は黒みを帯びる。胞子紋は白い。発生期は初夏から晩秋で、世界各地に分布する。多くの国で食菌として親しまれ、日本では、オリミキ、ボリボリ、サワモタシ、ハバキタケ、アシナガなど多数の地方名がある。普通、立ち木や立ち枯れした木の根元に束になって群生する。ナラタケは樹木の病原菌としても知られ、林木、果樹、庭木などを枯らす。その対象となる木は600余種にも上る。これをならたけ病といい、菌は根から侵入して樹皮の下の形成層を侵していく。ならたけ病で枯れた木の樹皮下には、黒色で光沢のある根状菌糸束が形成され、これによってナラタケは長い年月生き延びていく。この特徴からヨーロッパには靴の紐茸(ひもたけ)shoe string mushroomのような俗名がある。また、オニノヤガラ、ツチアケビなどの無葉緑のランは、ナラタケ菌と共生して特殊な菌根をつくり、ナラタケ菌に助けられて生活する。なお、新鮮なナラタケの茎の根元の肉または菌糸は、ときに弱い発光性を示すという報告がある。

［今関六也］

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