146 EFFECTS OF RADIATION ON FUNGI 



tions of short wavelengths, however, have been used to produce 

 heritable mutations with many biological materials, as is well 

 known, and a voluminous literature on this subject exists. Rela- 

 tively few studies have been made of induction of heritable mu- 

 tations in fungi. Dickson (1932, 1933) exposed malt-agar cul- 

 tures of Mucor gevevensis, Phy corny ces blakesleeamts, and the 

 ascospores of seven species of Chaetomium to X-rays for 50 min- 

 utes at a distance of 26 cm. Changes in color and amount of 

 mycelium were induced in colonies arising as subcultures from the 

 irradiated materials, and these changes were manifest by sector- 

 ing. Stevens (1930) obtained sectoring in cultures of Glomerella 

 c'nigulata exposed to ultraviolet radiation. Greaney and Machacek 

 (1933) exposed cultures of Hehninthosporhnn sativum to a mer- 

 cury-arc lamp (110 volts, 60 cycles) for 4 minutes on each of 3 

 successive days. During exposure the cultures were placed at a 

 distance of 35 cm from the arc. As a result of this treatment a 

 saltant having hyaline mycelium and almost colorless conidia ap- 

 peared. In all these cases the saltants remained constant in sub- 

 cultures through succeeding- generations. 



Lockwood and associates (1945) irradiated 217 isolates of Asper- 

 gillus t err ens with, ultraviolet rays, and as a consequence 141 were 

 changed morphologically. Among the 76 that were unchanged 

 morphologically, 59 were found capable of producing more ita- 

 conic acid than the parent strains. None of the 141 strains that 

 were altered morphologically, on the other hand, was found cap- 

 able of this increased production of itaconic acid. 



Emmons and Hollaender (1939) irradiated the dermatophyte, 

 Trichophyton mentagrophytes, and thereby induced the produc- 

 tion of mutants. This organism lacks a sexual stage, and conse- 

 quently the investigators were unable to make a genetical analy- 

 sis of the mutants. By use of Neurospora cr asset [Sansome et al. 

 (1945)], however, it was found that two types of mutants could 

 be induced, one of which was caused by chromosomal aberration. 

 They varied dosage and intensity and noted that increase in in- 

 tensity resulted in increase in mutation rate. At low dosage there 

 was a straight-line relationship between increase in mutation rate 

 and increase in energy. 



