Effect of Neotyphodium Lolii on the Freezing Tolerance of Lolium Perenne.

The fungal endophyte Neotyphodium lolii has a mutualistic relationship with perennial ryegrass (Lolium perenne) and offers several benefits including decreased insect herbivory and increased tolerance to drought stress. In northern climates perennial ryegrass is utilized because of its quick establishment and excellent wear tolerance. However, the lack winter hardiness in perennial ryegrass inhibits long- term stand persistence in cold climates. There is little information published on the effect of endophytes on the winter hardiness of perennial ryegrass. The objective of this experiment was to determine if the presence of endophytes has an effect on the freezing tolerance of perennial ryegrass. Freezing tolerance has been shown to correlate well with winter hardiness and can be determined in a controlled artificial environment. Twenty randomly-selected endophyte-infected genotypes from the cultivar Arctic Green were clonally propagated to produce sufficient plant material for the study. Half of the plants were then treated with the systemic fungicide propiconazole to kill most of the viable endophyte. Both of the resulting populations (endophyte-infected and endophyte free) were tested to confirm the presence of absence of endophyte and then subjected to a freezing test using a programmable freezer. Freezing tolerance was determined by the population’s lethal temperature 50 (LT50), the temperature at which 50% of the population dies. Preliminary results suggest that endophyte infection in Arctic Green results in a small, but significant increase in freezing tolerance. Future tests using more diverse ryegrass accessions infected with endophyte will be used to determine the effects of multiple endophyte strains on perennial ryegrass freezing tolerance.