[Breeding experiments with "59c", a mushroom strain with new type of fruit body : I. Increase of yield]

1. The paper deals with the cultivation and breeding of a mushroom strain which produces fruit bodies of an entirely new type. The fruit bodies have neither stalk, nor cap, nor gills but are in the form of a clump which can weigh up to 1,8 kg. They possess an excellent aroma and can be sliced and fried like cutlets or be used by the soup industry. In addition to this, they do not require picking as frequently as the strains with normal fruit bodies. 2. One of the negative characteristics of this strain, known as 59c, is its small total yield. The first attempts at breeding were mainly concerned with raising the yield because a certain yield is essential if a strain is to be commercially viable. 3. By continuous propagation using tissue cultures and selection (i. e. propagation were made with fruit bodies from tissue-cultures with the best yields), the yield was increased from 35% of normal strains in the 1st tissue culture propagation to 105% in the 4th tissue culture propagation. 4. However, as a rule, the tissue cultures decreased in yield and formed fruit bodies similar to those of a pooryielding prototype, Type 59b. 5. The decline in yield and the appearance of the prototype can be explained by concentration of the hereditary factors of Type 59b in the mycelium of the 59c type. The first fruit body of the c-type, formed spontaneously in a cultivation bed spawned with 59b, was propagated by tissue culture and presumably still contained nuclei with hereditary factors of the type 59b. They propagated themselves in the course of the mycelium growth. 6. Fruit bodies which could be classified as between types 59b and 59c produced both 59c forms, and 59b forms, as well as intermediate ones after tissue culture propagation. It is probable that they received their form by a certain numerical proportion of the nuclei with the hereditary factors for 59b and 59c. 7. Attempts to maintain the high yield of 59c at a constant level (elimination of the 59b-nuclei) and to improve the quality of the fruit bodies are initiated.