Tall fescue aluminum tolerance is affected by Neotyphodium coenophialum endophyte

Roots of endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) exude more phenolic-like reductants than roots of endophyte-free (E-) plant s when mineral stressed. Phenolic compounds are efficient chelators of alum inum (Al) and may influence Al tolerance in many plant species. The objecti ve of our study was to determine if enhanced release of phenolic compounds by roots of E+ plants contributes to Al tolerance in tall fescue. Two clone d genotypes (DN2 and DN11) of tall fescue infected with their naturally occ urring fungal endophyte Neotyphodium coenophialum (Morgan-Jones and Gams) G lenn, Bacon and Hanlin and their noninfected isolines were grown in nutrien t solutions at 0 mu M Al(Al-) and at 640 mu M Al (Al+) under controlled env ironment conditions. Root and shoot dry matter (DM) of endophyte-infected t all fescue was greater in E+ than E- plants by 57% and 40%, respectively, w hen plants were grown without Al. Endophyte infection did not affect root a nd shoot DM of tall fescue grown with Al but relative (to Al-treatment) red uction in root and shoot DM was greater in E+ than E- plants. In response t o Al stress, more Al (47%) and P (49%) could be desorbed from root surfaces of E+ than E- plants. Aluminum concentrations in roots of E+ plants were 3 5% greater and P concentrations were 10% less than those determined in root s of E- plants. No differences in mineral concentrations were observed in s hoots, regardless of endophyte status, or Al level in nutrient solution. Ro ots of E+ plants increased pH of both Al- and Al+ nutrient solutions to a g reater extent than roots of E- plants in a 48 h interval. Our results show that more Al can be sequestered on root surfaces and in root tissues of end ophyte-infected tall fescue than in plants devoid of endophyte. Aluminum se questration was greater on root surfaces and in root tissues of E+ than E- plants of a given tall fescue genotype. Our results suggest that increased exudation of phenolic-like compounds from roots of endophyte-infected tall fescue may be directly involved in Al tolerance and serves as a mechanism f or widespread adaptability and success of endophyte-tall fescue association s.