Morphological Mulation of Koji Molds (Asp. oryzae) by Irradiation of Ultraviolet Ray

Abstract

The present investigation has been carried out with the object to determine whether or not the S- and F-types obtained by natural variation reverse to the parent (the X-type).
Morphological characteristics of the induced mutants obtained has also been studied.
(1) Ultraviolet rays have been irradiated to the S- and F-types obtained by natural variation of Asp. oryzae. aX.
(2) The S- or F-type has been obtained from the parent S-type, and the S-, F- or X-type from the parent F-type, These mutants have proved to be the same as the natural variants mentioned in (1) above.
(3) The mutants that have been obtained from the S-type are as follows: 1. Normal 2. Restricted 3. Sterile 4. Nitrate non-assimilative 5. “Nitratophobe” 6. Heavy 7. Olive 8. Brown 9. Albino 10. Floccose 11. Yeast and 12. Maroon-exudate.
The mutants that have been obtained from the F-type are as follows: 1. Normal 2. Restricted 3. Sterile 4. Nitrate nonassimilative 5. “Nitratophobe” 6. Normal (S) 7. Restriced(S) 8. Brown 9. Yellow and 10. X.
Of the above-mentioned mutants these which are not described by IGUCHI⁽²⁾ are Yeast and Maroon exudate.
A new kind of mutant that does not grow even on such media as koji-agar and malt-extract-agar has also been found.
(4) The conidia ofthe S- and F-type which aye natural variants are of comparativly uniform size. As to the induced mutants, the conidia of the mutants from the S-type, expect for “Nit-ratophobe”, Brown and Floccose, are comparatively similar in size to those of the parent. Those of the mutants from the F-type are generally rich in variety of sizes.
(5) The shape and size of each organ which are used as the standards for the classification of Asp. oryzea strains have been found to be remarkably changed by ultraviolet ray irradiation.