Antioxidants in seeds of grass Festuca rubra L. as affected by the fungal symbiont Epichloë festucae.

GUNDEL, P.E.; HAMILTON, C.E.; SEAL, C.E.; VÁZQUEZ DE ALDANA, B.R.; ZABALGOGEAZCOA, I.; HELANDER, M. & K. SAIKKONEN.

Cracovia

Congreso; 7th International Symbiosis Society Congress; 2012

Symbiosis of grasses with vertically transmitted fungal endophytes can be beneficial for hosts. Whereas the alkaloid-mediated mechanism for herbivore resistance has been widely studied, underlying physiological mechanisms for increased tolerance to abiotic stress remain scarcely explored. Improved antioxidant machinery is proposed to mediate the endophyte effects positively impacting host plants under stress. We explore this hypothesis using seeds of the perennial grass Festuca rubra symbiotic with Epichloë festucae. Non-symbiotic seeds were generated by disinfecting clones of three naturally endophyte-symbiotic plants (RAB, SAN and PEN). Endophyte-symbiotic and non-symbiotic seeds were produced during 2009, 2010 and 2011 by clones planted in common garden in Salamanca (Spain). Seeds were stored at 10°C until used in antioxidant assay (2011). We tested seed and endophyte viability, and measured antioxidants of the tocopherol and glutathione family. Seed viability depended on the three-way interaction between maternal line, endophyte status and production year (P=0.014). Endophyte viability depended on the maternal line (P=0,041) and production year (P=0,003). Though contents of α-tocopherols and α-tocotrienol were affected by the three-way interaction (P<0,001), non-symbiotic seeds contained higher levels of antioxidants than endophyte-symbiotic seeds in the RAB line. Affected by the three-way interaction (P<0,001), the pattern of glutathione for RAB seeds was the opposite to that observed for tocopherols since it was higher for symbiotic than for non-symbiotic seeds. Glutathione half-cell reduction potential (EGSSG/2GSH) increased with aging (higher for seeds produced in 2009). Strikingly, although level of GSH was higher in the youngest non-symbiotic seeds (produced in 2011) of RAB, they presented the lowest seed viability. Although we did not find any clear patterns associated with endophyte symbiosis, the results indicate interaction with host genotype. Whether EGSSG/2GSH is a good predictor of seed and endophyte longevity in storage and natural conditions should be explored in seed lots differing in viability.