Effects of the endophyte Epichloe festucae var. lolii of perennial ryegrass (Lolium perenne) on indicators of oxidative stress from pathogenic fungi during seed germination and seedling growth

To determine whether infection by a fungal endophyte of the genus EpichloA << has a modifying influence on pathogenic fungal stress, endophyte-infected (E+) and endophyte-free (E-) seeds of perennial ryegrass (Lolium perenne), inoculated with the ryegrass pathogens Alternaria alternata, Ascochyta leptospora, Bipolaris sorokiniana, Curvularia lunata and Fusarium avenaceum were used for germination experiments and quantification of oxidative stress. Four measures of oxidative stress were used: malonaldehyde (MDA) content, peroxidases (POD) and superoxide dismutase (SOD) activity, and proline content. MDA content, an indicator of membrane lipid peroxidation damage, was significantly lower in E+ seedlings than in E- seedlings under stress from the test fungi. POD activity of E+ seedlings exposed to A. alternata, B. sorokiniana and C. lunata was significantly higher than similarly challenged E- seedlings. SOD activity of E+ seedlings was significantly higher than E- seedlings after exposure to A. alternata, B. sorokiniana, C. lunata and As. leptospora. Proline content of E+ seedlings exposed to the five pathogens was significantly higher than E- seedlings. Interestingly, these effects were present in the absence of disease symptoms apart from some root browning of E+ and E- seedlings exposed to B. sorokiniana. The results of this study showed that the seed-borne endophyte E. festucae var. lolii has potential to enhance establishment of perennial ryegrass by providing protection against pathogenic fungi during the critical early stages of seed germination and subsequent growth.