Pasture biotechnology update: AgResearch reports on three pasture programmes

AgResearch is working with partners to use genetic modification and gene editing technologies to enhance pasture that forms the foundation of our livestock farming industries in New Zealand.

Gene editing and genetic modification technologies can be used to change the DNA of a living organism, such as a plant or animal, through either inserting, replacing, or deleting genetic material.

Opportunities from these technologies include greater farm productivity, better animal health and improved environmental results that may include reduced greenhouse gas emissions and less nitrogen loss that has the potential to contaminate waterways. Work is underway to understand the potential benefits of these technologies and to ensure that those benefits outweigh any potential risks.

In this newsletter, we provide the first in a series of six monthly updates on the progress of three pasture programmes that are currently underway; either indoors in containment in New Zealand or in field trials offshore.

Gene edited endophytes

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.

To provide context, 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.

Over the past few decades scientists and the seedindustries 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.

Accordingly, 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.

High Metabolisable Energy (HME) Ryegrass

A modified ryegrass that could reduce environmental impacts while boosting animal nutrition and farm productivity is expected to be fed to livestock for the first time next year to obtain an initial gauge of potential benefits.

AgResearch scientists have been working over many years with the support of the government and commercial partners Grasslanz Technology, PGG Wrightson Seeds and DairyNZ, to develop the High Metabolisable Energy (HME) ryegrass.

This is being done by adding and modifying two plant genes to increase lipid content in the leaf and enhance photosynthesis in the plant under some conditions.

The purpose is to increase the nutritional quality of ryegrass to drive greater productivity, but the research also suggests environmental benefits such as reduced nitrogen loss that can contribute to waterway contamination, and reduced emissions of greenhouse gases, methane and nitrous oxide.

Current research suggests that methane reductions of 10 to 15 per cent may be achievable but the animal feeding trials are still to be undertaken to definitively test this.

For nitrous oxide, the opportunity is the improved animal nutrition leading directly to a reduction in urinary nitrogen excretion, resulting in reduced emissions and lower nitrate leaching; as well as the potential for reductions due to the HME plants influencing composition of the soil microbes leading to benefits in the nitrogen cycle.

Growing of HME Ryegrass and the required research has taken place indoors in contained conditions in New Zealand, according to regulations in place around genetically modified organisms. However, it has also been grown in regulated outdoor growing trials in the United States.

Planning is now underway for a trial that is expected to start late next year, in which lambs will be fed both the HME ryegrass and a control ryegrass. To enable this, work is now underway to grow enough of the ryegrass in contained glasshouses in New Zealand that can be ensiled (preserved) for feeding to the lambs when the trial begins.

Scientists expect the trial to provide insights on methane emissions and urinary nitrogen excretion. Further confirmation in cattle will need to be performed in outdoor trials, most likely in Australia at a later date.

The programme team earlier this year applied to Australia’s Office of the Gene Technology Regulator (OGTR) for permission to conduct growing trials in Australia.

Through the course of the application process with OGTR, it emerged that additional detailed analysis would be required on a specific issue for the application to proceed and be successful. The issue relates to an allergen (known as sesame oleosin) that may be present and could be released in the pollen of the ryegrass.

While AgResearch testing demonstrated that sesame oleosin is not expressed in the pollen of HME Ryegrass, a more rigorous test was required by OGTR. Given the timeframe and complexity associated with this more detailed test, the team reached the view that the best course was to withdraw the application to the OGTR and resubmit at a later stage.

The intention is to further reduce any future risk by replacing the sesame oleosin with an alternative that has no known allergenic properties.

The scientists are currently working on refining the composition of the ryegrass, based on a rice component rather than sesame, to support a further application for field trials and potential commercialisation of the ryegrass in Australia.

Results from the feeding trial commencing next year will guide next steps for the development of the HME Ryegrass programme and inform the potential for future commercialisation.

High Condensed Tannin White Clover

High Condensed Tannin (HiCT) white clover has been modified to boost the level of condensed tannins present.

Condensed tannins occur naturally in the flowers of white clover and in other species such as grapes, tea and many other components of the human diet.

In white clover they offer significant promise for reducing environment impacts from livestock farming while improving both animal health and production.

AgResearch scientists are working with partners PGG Wrightson Seeds and Grasslanz Technology to genetically modify white clover — an important component of pastures in New Zealand — with a gene taken from another species of clover to enable expression of condensed tannins in the leaves of the white clover.

The modification made by the scientists essentially flicks a “molecular master switch” which increases the condensed tannins content to meaningful levels in white clover leaves.

The results seen to date in containment in New Zealand suggest reductions in methane emissions; and nitrogen leaching, in excess of 15 per cent are potentially achievable.

Consumption of the white clover with increased condensed tannins is also expected to reduce the occurrence of a condition known as bloat that can be fatal for both sheep and cattle. It may also reduce the internal parasite burden for livestock.

In addition to the modified white clover bred and grown in contained conditions in New Zealand, three years of field trials have been completed in the United States where regulations controlling the testing of genetically modified plants differ to those in New Zealand.

The levels of condensed tannins expressed in the HiCT white clover grown in USA was consistent with what was seen in the plants grown in containment in New Zealand.

Subsequent cycles of breeding and growing in containment in New Zealand have demonstrated that modified HiCT white clover with commercially acceptable yield and persistence can be generated.

Permission has now been granted for further field trials in Victoria, Australia, for a period for up to four years, and the first field trial was recently planted.

Further steps will see selection of plants for seed multiplication in Australia, as the partners look ahead to animal feeding trials and the potential for commercialisation of the HiCT white clover in the next few years.

Source:  AgResearch

Author: Bob Edlin

Editor of AgScience Magazine and Editor of the AgScience Blog