SPORULATION OF DIVERSE SPECIES OF FUNGI UNDER NEAR-ULTRAVIOLET RADIATION

Abstract

Cultures of 34 fungi were irradiated at 70° F under continuous exposure to near-ultraviolet light (3100–4000 Å) at 76 microwatts per cm2 for periods ranging from 3 to 10 days. Sporulation was initiated or increased in Ascochyta pinnodella, A. pisi, Alternaria chrysanthemi, A. tenuis, A. zinniae, Botrytis cinerea, Coryneum sp., Epicoccum nigrum, Epicoccum sp., Fusarium oxysporum, F. nivale, F. roseum, F. solani, Gliocladium sp., Helminthosporium avenae, Mycosphaerella pinodes, Ophiobolus graminis, Piricularia oryzae, Phoma herbarum var. medicaginis, P. trifolii, Phoma spp., Phyllosticta sp. Pyrenochaeta terrestris, Septoria tritici, Stemphyllium botryosum, S. trifolii, Wojinowicia graminis, and Verticillium albo-atrum. H. oryzae formed conidia only when irradiation was followed by a dark period. Kabatiella caulivora and H. sativum sporulated as well in darkness as under irradiation. Sclerotia of Typhula spp. produced sporophores under a 12-hour dark, 12-hour ultraviolet light cycle at 41° F. When eight ultraviolet light-sensitive species were irradiated on various media, with few exceptions sporulation was stimulated irrespective of substrate. Irradiation of fungi under near-ultraviolet and artificial daylight fluorescent lamps stimulated sporulation equally well. When, however, near-ultraviolet and blue wave lengths were filtered from daylight fluorescent lamp radiation, sporulation was absent or much reduced in most species. Irradiation of colonies on a 12-hour dark, 12-hour ultraviolet light cycle caused zoning in the majority of species. Zoning was absent in colonies cultured under continuous exposure or under darkness.