Our scientists are using gene editing to selectively change the DNA of endophytes within ryegrass to improve plant protection and reduce harm to livestock. 


Epichloë endophytes occur naturally in some grasses, such as those used to feed livestock on New Zealand farms. While some types of endophyte can be harmful to livestock, selected endophytes introduced to varieties of grass offer benefits such as deterring insect pests from feeding on the grasses, while minimising any negative health effects.

The addition of selected fungi called Epichloë endophytes to ryegrass has saved New Zealand billions of dollars over the past 30 years, and now gene editing technology could provide even greater benefits through targeted changes to these endophytes. AgResearch scientists, with partners PGG Wrightson Seeds and Grasslanz Technology, supported by funding from the government, have been researching how the use of gene editing tools to change the DNA of endophytes might generate further gains on top of the considerable progress achieved to date by conventional selection.

Linda Johnson, AgResearch Science Group Manager.

Financial benefits

One non-edited commercialised endophyte alone, AR37, has been estimated to contribute $3.6 billion to the economy through the life of its patent. These naturally occurring endophytes live inside ryegrass and form a mutually beneficial relationship with the grass. Natural substances released by the endophytes deter insect pests from eating the ryegrass and improve plant growth and persistence, which collectively results in a reduced need for chemical pesticides and increases efficiencies in milk and meat production for New Zealand’s pasture-based agricultural industries. 

The challenge has always been that some endophytes that protect ryegrass against pests also produce toxins that can be harmful to the livestock which feed on the ryegrass, causing heat stress or a disease called ryegrass staggers.

Our science

Over the past few decades scientists and the seed industries have successfully harnessed selected endophytes to add to ryegrass that have brought this billion-dollar benefit, but efforts have continued to identify other endophytes that may further maximise the benefits and minimise the negative effects. AgResearch scientists have now identified targeted changes to the DNA of selected endophytes via gene editing, resulting in either greater plant protection or less harm to livestock. Without intervention, the toxic effect of compounds from some endophytes for livestock is expected to worsen as a result of climate change. The gene editing of organisms is tightly regulated in New Zealand, and to date has only been undertaken in specialised containment facilities. Specific approval is required for field testing in the open or the release of gene edited organisms.

Australasian collaboration

AgResearch and its partners have launched field trials in Australia, where ryegrass containing these gene edited endophyte strains is being tested in the open. 

Seed is first being produced in Victoria to allow three sets of field trials to be planted in spring 2024 in both Victoria and New South Wales. These agronomy trials will be evaluated over a period of three years. The trials will be in locations where the ryegrass is likely to come under pressure from insect pests that is similar to New Zealand conditions.

The aim of these Australian trials is to gather data to ascertain the value and effectiveness of these gene edited endophytes ahead of a potential application to field test the ryegrass containing gene edited endophytes in New Zealand. Research is also continuing in containment in New Zealand to further understand the potential and effects of the gene editing.

Beyond the potential to reduce harm to animals while deterring pests with less chemical use, and adding to the resilience of the ryegrass, it is thought that gene editing could also add to the persistence of the ryegrass, meaning less resowing of pastures and improved sustainability. Additional potential environmental benefits will also continue to be explored 




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