SYMBIOSIS WITH NEOTYPHODIUM-UNCINATUM ENDOPHYTE MAY INCREASE THE COMPETITIVE ABILITY OF MEADOW FESCUE

Infection with the endophyte Neotyphodium uncinatum (Gams, Petrini & S chmidt) Glenn, Bacon, Price & Hanlin may influence drought resistance and competitive ability of meadow fescue (Festuca pratensis Huds.). We determined endophyte-related effects on some growth and physiological characteristics in one clone of meadow fescue. In a growth chamber ex periment, meadow fescue and orchardgrass (Dactylis glomerata L.) were planted in pots as monocultures or binary mixtures, competing in the r oot systems. One group of plants was adequately watered to maintain th e original pot weight (control). The other group was subjected to a gr adually imposed water stress, defined as soil water deficit, during 25 d (stressed plants). After rewatering, plants were allowed to regrow for 3 wk. Endophyte infection increased shoot and root dry weight by 3 3 and 70%, respectively, in control meadow fescue plants, and by 24 an d 69% in stressed plants. Infected (E+) plants had significantly great er competitive ability than noninfected (E-) plants when grown in E-/E + binary mixture. In binary mixtures with orchardgrass, the competitiv e abilities of E-and E+ plants were reduced relative to that of E-and E+ plants grown as monocultures. In response to water stress, stomatal conductance was lower in Ef than in E-plants, regardless of root comp etition. Noninfected plants could not completely recover in leaf water potential when exposed to root competition with infected plants or or chardgrass. The greater competitive ability of E+ plants was related t o improved root and shoot growth and enhanced drought resistance. Infe ction with N. uncinatum could confer a competitive advantage to the me adow fescue clone.