Impact of selected Epichloë endophyte on perennial ryegrass yield performance across regions in New Zealand

Abstract

Over the past couple of decades selected Epichloë endophytes have been vital to farmers and the economy in New Zealand, with AR1 and AR37 being two of the frontier and foundational ryegrass endophyte strains. These endophytes produce different alkaloid profiles which defines the scope of pest resistance afforded by them to the host grass and suitability for use in different areas of New Zealand. Data collected by the New Zealand Plant Breeding and Research Association as a part of the National Forage Variety Trials provide information to understand the yield advantages that endophyte can have in regions with different insect and environmental limitations. The analysis focused on the impact of AR37, AR1 and without endophyte in a diploid perennial ryegrass cultivar (cv. Ceres ONE⁵⁰) evaluated in 20 trials throughout New Zealand.

There were significant regional and seasonal endophyte effects, with the greatest benefits being consistent with when insect and abiotic pressures were expected to be the greatest. AR37 had the broadest level of increased yield while AR1 still offered yield advantages over no endophyte in many cases. Dry matter yield did not differ between AR37 and AR1 at a national level except for autumn, or regionally except for the Upper North Island. The benefit of AR37 was seen to the greatest extent in the Upper North Island, with a 33% and 51% yield advantage over AR1 and without endophyte respectively. For the Upper South Island both AR37 and AR1 gave a significant increase in DM yield over without endophyte for annual dry matter yield.

There were individual trials in which AR1 and without endophyte gave inadequate protection, resulting in pasture failure, others in which insect pests or other stressors are likely to have impacted yield without causing pasture failure, and some where there was little differentiation between selected endophyte and without endophyte. This highlights the wide variation that can be observed on individual farms across New Zealand and the role that selected endophyte plays in creating resilient pastures.