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 fescue (Festuca arundinacea) cultivars were compared in a glasshouse experiment and the effect, on those responses, of artificial infection of the tall fescue plants with two fungal endophyte (Neotyphodium coenophialum) strains was evaluated. The cultivars were Maris Kasba (MK), of Mediterranean origin, and El Palenque (EP), an Argentinian cultivar of temperate origin. The endophyte strains AgResearch isolate (AR501) and the Kentucky (KY31) wild type were compared with nil‐endophyte controls. Leaf growth rate of EP plants under water deficit was higher and leaf senescence rate lower than for MK plants ( P < 0.05). MK plants showed a greater increase in the proportion of dead leaf tissue than EP plants as water deficit increased ( P < 0.05). Stomatal conductance and lamina osmotic adjustment at low soil moisture were lower for MK than EP ( P < 0.05). Endophyte‐infected plants had a lower dry weight and tiller number, but a higher net growth rate during water deficit treatments than endophyte‐free plants ( P < 0.05). A significant cultivar × endophyte interaction ( P < 0.05) was observed for many variables studied. This implies that any new endophyte strain should be evaluated in combination with the plant genotypes with which it is likely to be associated in commercial 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 physiological effects on their tall fescue host plants.