The effect of light on conidial germination and appressorial formation of Colletotrichum graminicola
Windelborn, Jane E. Cerda (Jane Elizabeth Cerda)
MetadataShow full item record
A hyphal tip isolate of Colletotrichum graminicola was used in an investigation of the effects of light intensity on spores during germination and differentiation and the effects of the exposure of the culture to light at various periods during sporulation. Slant cultures, grown on oatmeal agar, were exposed to 80 foot candle fluorescent light for day lengths of 0, 12, or 24 hours. Cultures exposed to continuous or intermittent light were indistinguishable from each other. Cultures grown in complete darkness were, however, quite different in that the development, of normal spores was delayed about 3 days. The abundance of spores produced in the light-grown cultures by the seventh or eighth day, indicated by salmon-colored masses on the surface of the culture, was not present in the dark- grown cultures until 16 days post-inoculation. Spores from dark-grown cultures germinated to form irregular germ tubes. Conidial suspensions in distilled water were exposed to light intensities of 0, 6, 33, 115, 240, 300, 600, 700, 800, 1500, and 2000 foot candles. There was no appreciable difference in germinability or appressorium formation among these treatments. Spores ex- posed co light during specific time intervals during the first 24 hours after hydration did show some responsive periods to light. These results, however, were highly variable among different runs of the same experiment . The age of the culture was explored as a possible variable in these, experiments,, Spores from cultures grown 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 21 days were tested for differences in response to light during sporulation and germination. This factor did have an effect on spore germination and appressorium formation, but further tests would be needed to determine whether, within the 1-3 week period, culture age was truly a significant factor.