Neotyphodium lolii, a Fungal Leaf Endophyte, Reduces Fertility of Lolium perenne Exposed to Elevated UV-B Radiation

Plants ofLolium perenne, grown with and without the balansoid fungal leaf endophyteNeotyphodium lolii, were exposed to three ultraviolet radiation treatments at an outdoor facility in the UK for 172 d. Plants were exposed to either (a) a 30% elevation above the ambient erythemally-weighted level of UV-B (280–315 nm) radiation under banks of cellulose diacetate filtered fluorescent lamps that also produce UV-A (315–400 nm) radiation (UV-B+A); (b) elevated UV-A radiation alone under banks of polyester filtered lamps; or (c) ambient levels of solar radiation under banks of unenergized lamps. The fertility of plants grown withN. loliiwas significantly reduced by the elevated UV-B+A exposure. After 172 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 were exposed to ambient radiation. There was no discernible effect of elevated UV-B+A exposure on the fertility of endophyte-free plants. Plants irradiated with UV-B+A developed 14% thicker leaves than those exposed to ambient radiation. Those which were irradiated with elevated UV-A alone produced seeds that were 20% heavier than plants exposed to ambient levels of radiation. Plants grown withN. loliihad 7% thicker leaves, 4% thicker stem bases and 7% fewer tillers than those grown without it. The fresh mass of tillers of plants grown withN. loliiwas 11% greater than those of endophyte-free plants, owing to their higher moisture contents. These results suggest that the fertility ofL. perennecolonized byN. loliiin the natural environment could be deleteriously affected by elevated fluxes of UV-B radiation associated with stratospheric ozone depletion and that this may affect the population dynamics of the species.