Effect of Epichloe fungal endophyte symbiosis on tall fescue to cope with flooding-derived oxygen-limited conditions depends on the host genotype

Background and aims There is little information about the role of fungal endophytes on plant performance under oxygen-limited conditions. This study aimed to investigate the effect of Epichloe endophyte symbiosis on tall fescue responses to oxygen stress in a greenhouse experiment. Methods The experiment was conducted with seven air-filled porosity levels in a sandy loam soil using genotypes (75C and 75B) of tall fescue (Festuca arundinacea) infected with and without endophytic fungus Epichloe coenophiala (E+ and E-, respectively). Growth and physiological variables were determined to characterize plant response to oxygen-limited conditions, after nine-month application of the treatments. Results The results showed that E+ 75B plants benefited from endophytic symbiosis in all air-filled porosity levels, showing a higher plant biomass, better water status and lower catalase and ascorbate peroxidase activity than E- 75B plants. In contrast, a reverse trend was observed for the genotype 75C. The E- plants also coped with poor aeration by forming adventitious roots at the soil surface, aerenchyma formation within the root tissue, and increased alcohol dehydrogenase activity. Conclusions The presence of endophyte improved the genotype 75B performance under anaerobic conditions, while endophyte had an adverse effect on the performance of genotype 75C. This is probably due to incompatibility between Epichloe endophyte and genotype 75C. Epichloe endophyte is likely to decrease the flooding-induced oxidative stress and prevented the over-accumulation of reactive oxygen species in the genotype 75B. Epichloe endophyte probably maintained oxidative conditions around the roots, and consequently, E+ plants required lower level of flooding-tolerance mechanisms.