Morphological and physiological effects of water deficit and endophyte infection on contrasting tall fescue cultivars

Morphological and physiological responses to water deficit of two tall fesc ue (Festuca arundinacea) cultivars were compared in a glasshouse experiment and the effect, on those responses, of artificial infection of the tall fe scue plants with two fungal endophyte (Neotyphodium coenophialum) strains w as evaluated. The cultivars were Maris Kasba (MK), of Mediterranean origin, and El Palenque (EP), an Argentinian cultivar of temperate origin. The end ophyte strains AgResearch isolate (AR501) and the Kentucky (KY31) wild type were compared with nil-endophyte controls. Leaf growth rare of EP plants u nder water deficit was higher and leaf senescence rate lower than for MK pl ants (P < 0.05). MK plants showed a greater increase in the proportion of d ead leaf tissue than EP plants as water deficit increased (P < 0.05). Stoma tal conductance and lamina osmotic adjustment at low soil moisture were low er for MK than EP (P < 0.05). Endophyte-infected plants had a lower dry wei ght and tiller number, but a higher net growth rate during water deficit tr eatments than endophyte-free plants (P < 0.05). A significant cultivar x en dophyte interaction (P < 0.05) was observed for many variables studied. Thi s implies that any new endophyte strain should be evaluated in combination with the plant genotypes with which it is likely to be associated in commer cial practice. MK-KY31 and EP-AR501 associations appeared to tolerate short -term water deficit more effectively than other associations studied. There was evidence that the two endophyte strains studied had different physiolo gical effects on their tall fescue host plants.