Adaptations of endophyte-infected cool-season grasses to environmental stresses: Mechanisms of drought and mineral stress tolerance

Cool-season grasses infected with Neotyphodium spp. endophytes have an extr aordinary impact on the ecology and economy of pasture and turf. A range of adaptations of endophyte-infected grasses to biotic and abiotic stresses h as been identified but mechanisms of these adaptations are not clearly unde rstood. In this review, we present recent research progress on endophyte-re lated mechanisms affecting abiotic (drought, mineral) and selected aspects of biotic stress tolerance in cool-season gasses. Endophytes induce mechani sms of drought avoidance (morphological adaptations), drought tolerance (ph yiological and biochemical adaptations), and drought recovery in infected g asses. Mineral nutrition (nitrogen, phosphorus, calcium) affects production of ergot alkaloids, thus understanding mechanisms involved in mineral econ omy of endophyte-infected gasses will help in developing management practic es to reduce forage toxicity to livestock. Previous research resolved the r ole of endophyte in nitrogen (N) economy of tall fescue. We identified two endophyte-related mechanisms in tall fescue operating in response to phosph orus (P) deficiency. The mechanisms are altered root morphology (reduced ro ot diameters and longer root hairs) and chemical modification of the rhizos phere resulting from exudation of phenolic-like compounds. These mechanisms were shown to benefit endophyte-infected plants grown under P deficiency. We also report a mechanism of aluminum (Al) sequestration on root surfaces in endophyte-infected tall fescue, which appears to be related to exudation of phenolic-like compounds with Al-chelating activity. Understanding mecha nisms of abiotic stress tolerance in endophyte-infected grasses is essentia l for continued improvement and persistence of grasses for a range of appli cations, e.g., forage for semi-arid areas or cover plants for soil renovati on.