Antioxidants in Festuca rubra L. seeds affected by the fungal symbiont Epichloe festucae

Vertically transmitted fungal endophytes can be beneficial for host grasses. While the alkaloid-mediated mechanism for herbivore resistance has been widely studied, underlying physiological mechanisms for increased tolerance to abiotic stress remain scarcely explored. In this study we used three maternal lines of perennial grass Festuca rubra to examine the role of antioxidants in endophyte-mediated effects on seed viability over long-term storage. Uncolonized plants (E-) were generated by removing the endophyte from ramets of naturally endophyte-colonized (E+) plants. The E + and E- ramets were planted in a common garden in Salamanca, Spain. Seeds produced in 2009, 2010 and 2011 were harvested at maturity, dried and stored at 10 A degrees C until 2011 when we tested seed and endophyte viability, and measured antioxidants. Seed viability and alpha-tocopherol antioxidant were negatively affected by the endophyte in two maternal lines. In these same lines, the endophyte viability was lowest at the longest storage time. In the maternal line that showed the highest negative effect of endophyte on seed viability, the pattern of glutathione was opposite to that observed for tocopherols since it was higher for E + than for E- seeds. In all maternal lines, the glutathione half-cell reduction potential (E-GSSG/2GSH) and % glutathione disulphide (GSSG) increased with storage time but there was no clear pattern associated with endophyte symbiosis. Whether these parameters are good predictors of seed and endophyte longevity in storage and natural conditions should be further explored.