Induction of 'Gigas' Forms of Penicillium Notatum by Treatment with Camphor Vapour

Abstract

CAMPHOR has been reported by Bauch1 to be effective in inducing polyploidy in fungi. Thaysen and Morris2 succeeded in producing a giant strain of Torulopsis utilis by treatment with camphor vapour. It was therefore determined to test the effect of camphor vapour on Penicillium notatum strain N. R. R. L. 1978 B. The procedure was to add different, amounts of camphor to flasks each containing 25 ml. of sterilized 3 percent malt agar. The agar was then poured into Petri dishes of 100 mm. diameter. The cultures on the plates to which 75 mgm. of camphor had been added showed a distorted growth. Conidial formation was delayed but after twenty-two days some spores were formed. When these were examined microscopically, some of the spores were found to be larger than the others, whereas spores from control cultures were uniform in size. Spores from the treated and control cultures were plated out on malt agar by the dilution method. There were no macroscopic differences between the colonies from the control and treated samples. When examined for spore size, however, thirty colonies from the control series were found to have spores of the same size, whereas, out- of forty-four colonies from the treated samples, thirty-five were like the controls, five had spores larger than the controls and four had a mixture of large and average sized spores. Isolations were made from these large-spored colonies and 'gigas' lines established. Fig. a shows spores from a normal line and Fig. b spores from a gigas line, three months after isolation and after being subcultured four times. The change thus appears to be permanent. Camphor treatment has been shown to induce polyploidy in higher plants3, and since pollen grain size has been found to be a useful criterion of polyploidy, it is probable that the 'gigas' forms with larger spores in Penicillium are polyploids.