Impact of AR37, a selected Epichloë endophyte, on Italian ryegrass yield performance across regions in New Zealand

Abstract

The selected Epichloë endophyte strain AR37 first became commercially available in 2007 in New Zealand cultivars of perennial ryegrass (Lolium perenne), before being extended into shorter-term ryegrass cultivars. In 2012, the cultivar Asset was the first commercially available Italian ryegrass (L. multiflorum) with the options of AR37 and endophyte-free. Over the past 10 years, the use of Epichloë endophytes in shorter-term ryegrass cultivars has expanded, with more than 10 hybrid (L. boucheanum, syn. L. hybridum) or Italian ryegrass cultivars with a selected Epichloë endophyte option now available.

The National Forage Variety Trials (NFVT) evaluates commercial and pre-commercial ryegrass cultivars within New Zealand through the New Zealand Plant Breeding and Research Association. The diploid Italian ryegrass cultivar Asset has been evaluated in 15 of these trials with AR37 and without endophyte, varying in duration from 12 to 18 months. To understand the effect in production that Epichloë endophyte AR37 provides in Asset Italian ryegrass, these trials were analysed for seasonal and total dry matter yield nationally and by region.

Asset with AR37 endophyte demonstrated increased production over no endophyte, with the combined multisite analysis showing an 11% increase in dry matter yield in the first summer post sowing, and a 14% increase in dry matter yield in the second autumn (P<0.05). The four trials located in the Upper North Island displayed the greatest benefits of AR37, with a 9% mean increase in dry matter yield over the period from sowing to the end of the first summer. In three of these four trials, AR37 had a significantly greater dry matter yield in the summer and second autumn.

Of the 11 trials located in the Lower North Island and Upper South Island, there were no seasons that differed significantly in the combined seasonal analysis within each region. In an analysis of the individual trials, two of the four Lower North Island trials had significantly greater dry matter production with AR37 in summer and the second autumn than without endophyte. In the Upper South Island, three of the seven trials had significantly greater dry matter yield for AR37 in both the summer and in total production over an 18-month period.

The results confirm that AR37 endophyte in Asset Italian ryegrass provided equal or greater total dry matter yield over without endophyte across all trials within 12 to 18 months, giving confidence that endophyte can have a positive impact on Italian ryegrass dry matter yield. While this work did not investigate the specific factors contributing to the benefits of endophyte, future work would help validate how Epichloë endophyte supports the resilience of shorter-term ryegrasses under varied environments within regions and seasons.