NEOTYPHODIUM LOLII, A FUNGAL LEAF ENDOPHYTE, REDUCES FERTILITY OF LOLIUM-PERENNE EXPOSED TO ELEVATED UV-B RADIATION

Plants of Lolium perenne, grown with and without the balansoid fungal leaf endophyte Neotyphodium lolii, were exposed to three ultraviolet r adiation treatments al an outdoor facility in the UK for 172 d. Plants were exposed to either (a) a 30% elevation above the ambient erythema lly-weighted level of UV-B (280-315 nm) radiation under banks of cellu lose 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 radi ation under banks of unenergized lamps. The fertility of plants grown with N. lolii was significantly reduced by the elevated UV-B+A exposur e. After 172 d, these plants produced 70 % fewer spikes, 75 % fewer se eds, 71 % lower total weight of seed and 78 % fewer seeds per g d, wt of plant tissue than plants colonized by N. lolii which were exposed t o ambient radiation. There was no discernible effect of elevated UV-BA exposure on the fertility of endophyte-free plants. Plants irradiate d with UV-B+A developed 14% thicker leaves than those exposed to ambie nt radiation. Those which were irradiated with elevated UV-A alone pro duced seeds that were 20 % heavier than plants exposed to ambient leve ls of radiation. Plants grown with N, lolii had 7 % thicker leaves, 4 % thicker stem bases and 7 % fewer tillers than those grown without it . The fresh mass of tillers of plants grown with N. lolii was 11 % gre ater than those of endophyte-free plants, owing to their higher moistu re contents. These results suggest that the fertility of L. perenne co lonized by N. lolii in the natural environment could be deleteriously effected by elevated fluxes of UV-B radiation associated with stratosp heric ozone depletion and that this may affect the population dynamics of the species. (C) 1998 Annals of Botany Company.