Neotyphodium lolii, a Fungal Leaf Endophyte, Reduces Fertility ofLolium perenneExposed to Elevated UV-B Radiation

Plants ofLolium perenne, grown with and without the balansoidfungal leaf endophyteNeotyphodium lolii, were exposed to threeultraviolet radiation treatments at an outdoor facility in theUK for 172 d. Plants were exposed to either (a) a 30% elevationabove the ambient erythemally-weighted level of UV-B (280–315nm) radiation under banks of cellulose diacetate filtered fluorescentlamps that also produce UV-A (315–400 nm) radiation (UV-B+A);(b) elevated UV-A radiation alone under banks of polyester filteredlamps; or (c) ambient levels of solar radiation under banksof unenergized lamps. The fertility of plants grown withN. loliiwassignificantly reduced by the elevated UV-B+A exposure. After172 d, these plants produced 70% fewer spikes, 75% fewer seeds,71% lower total weight of seed and 78% fewer seeds per g d.wt of plant tissue than plants colonized byN. loliiwhich wereexposed to ambient radiation. There was no discernible effectof elevated UV-B+A exposure on the fertility of endophyte-freeplants. Plants irradiated with UV-B+A developed 14% thickerleaves than those exposed to ambient radiation. Those whichwere irradiated with elevated UV-A alone produced seeds thatwere 20% heavier than plants exposed to ambient levels of radiation.Plants grown withN. loliihad 7% thicker leaves, 4% thicker stembases and 7% fewer tillers than those grown without it. Thefresh mass of tillers of plants grown withN. loliiwas 11% greaterthan those of endophyte-free plants, owing to their higher moisturecontents. These results suggest that the fertility ofL. perennecolonizedbyN. loliiin the natural environment could be deleteriouslyaffected by elevated fluxes of UV-B radiation associated withstratospheric ozone depletion and that this may affect the populationdynamics of the species.Copyright 1998 Annals of Botany Company Fungal leaf endophyte,Neotyphodium lolii, perennial ryegrass (Lolium perenne), stratospheric ozone depletion, UV-B radiation.