Studies on the Natural Variation of Koji-molds (Aspergillus oryzae and Asp. sojae)

Part 3. Studies on the Mechanism of Natural Variation based on Heterocaryosis

Abstract

1. Anastomosis occurs between variants and between different strains of Koji-molds.
2. Anastomosis takes place often between conidia, between germ-tubes and between mature .hyphae, accompanied by vigorous nuclear division and nuclear migration through connecting tube or fusion bridge.
3. When the constant types S and F are grown together in mix-culture, they produce intermediate type X. In pedigree-culture..by successive single spore method of the X-type, they again separate into all 3 types, namely, X, S, and F.
4. The constant type or homo-type S and F or conidia are comparatively uniform in sizes and leave 1-4 nuclei.
The conidia of inconstant type or hetero-type X, which occur by mix-culture, are rich in variety of sizes and multiiiucleate.
5. By mix-culture between different strains of Koji-molds, they also give rise to an interstrainic dicaryophytic hybrids.
6. From the above facts and the findings hetherto reported ⁶⁾ it may be concluded that the natural variations of Koji-Molds (Asp. oryzae and Asp. sojae) is to greater extent responsible to the heterocaryosis. And the resultant heterocaryosis produce generally conidia of much greater diameters than those of the parent strains, a phenomenon similar to heterosis, through, which the heterocaryosis are very easily detectable.