BENEFICIAL-EFFECTS OF NEOTYPHODIUM-LOLII ON THE GROWTH AND THE WATER STATUS IN PERENNIAL RYEGRASS CULTIVATED UNDER NITROGEN DEFICIENCY OR DROUGHT STRESS

Three perennial ryegrass clones infected and uninfected with Neotyphod ium lolii (formerly Acremonium lolii) were studied to determine the im pact of this endophytic fungus on plant growth and physiology under st ress conditions. Plants were grown under controlled environmental cond itions for 10 weeks and were subjected to: i) no stress (12 mM of N; n o limiting water supply); ii) N deficiency; or iii) drought stress. In the absence of stress, infected and non-infected plants of all clones showed similar growth rates. Under N deficiency (2.33 mM), infected p lants had 27% more tillers and 15% less dead leaves than uninfected pl ants, and they maintained their photosynthetic level. During drought s tress (0.7 MPa), the osmotic potential of the infected plants was 13% lower than that of uninfected plants and their tiller number was 10% g reater than that of non-infected plants at the end of the drought stre ss period. Thus, in the three clones studied, the infection results in increased tolerance of host plants to abiotic stress especially as a result of better tillering.