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Quality of Light Required for Sporulation by Leptosphaerulina. K. T. Leath, Research Plant Pathologist, U.S. Regional Pasture Research Laboratory, Crops Research Division, ARS, USDA, University Park, Pennsylvania 16802; Phytopathology 61:70-72. Accepted for publication 10 August 1970. DOI: 10.1094/Phyto-61-70.

The effect of light quality on the sporulation of Leptosphaerulina briosiana was investigated. Cultures grown under cool-white fluorescent lamps did not sporulate when light of wavelengths shorter than 340 nanometers (nm) was excluded by filters. The generality of this requirement within the genus was determined by growing 1 isolate of L. americana, 6 of L. arachidicola, 1 of L. argentinensis, 2 of L. australis, 49 of L. briosiana, and 2 of L. trifolii under cool-white, fluorescent light, with half of each culture covered with plexiglass to exclude light of wavelengths shorter than 340 nm. One isolate each of L. arachidicola and L. briosiana sporulated normally throughout the culture. All other isolates sporulated normally in the culture half that received unfiltered light, but formed black, sterile ascostromata in the culture half from which light below 340 nm was excluded. Formation of sterile ascostromata also occurred in cultures grown in total darkness. The quality of light essential for sporulation was more precisely defined for two isolates of L. briosiana. When cultures were irradiated with narrow bands of light throughout the range of 290-340 nm, light of 310-330 nm inclusive stimulated ascospore production. No requirement for light outside this range was observed for any of the fungi tested.

Additional keywords: ascospores, fungus, photo-induction, irradiation, near-ultraviolet light.