CULTURAL PROPERTIES OF RE-DIKARYOTIZED ST OCKS OF OIDIUM OCCURRING INTHE CULTIVATION OF THE DIKARYOTIC MYCELIUM OF PHOLIOTA-NAMEKO

Monokaryotic mycelia were isolated from oidia occurring in the cultiva tion of the dikaryotic mycelium of Pholiota nameko (T. Ito) S. Ito adn Imai, and re-dikaryotized stocks were obtained with the di-mon mating of the original dikaryon and the isolated monokaryon. The cultural pr operties of 22 re-dikaryotized stocks were examined to confirm that th e phenotype of these stocks returned to that of the original dikaryon. For nine re-dikaryotized stocks, a ''flat'' colony occupied more than 30% of the mycelium area on the PDA (potato-dextrose-agar) plate medi um. The ''flat'' colony appeared identical to that observed in the myc elium of the undesirably changed stocks isolated from the cultivator's media. Among re-dikariotized stocks, nine showed more than 85% declin es in yields and more than 25 days of retardations in the harvesting o f fruiting bodies, as compared with the original dikaryon, and one of them did not form any fruiting bodies. The undesirably changed stock d id not appeare from the dikaryotic mycelia isolated from oidia. This f act indicated that changes in the nucleus or cytoplasm occurred in re- dikaryon at the time of oidia formation or re-dikaryotization, and/or original cells which formed oidia already were changed. Therefore, the re exists the possibility that these changes were concerned with the p henomena of undesirable changes in the yields of fruiting bodies.