CSIRO researchers have successfully engineered wheat plants that form symbiotic relationships with nitrogen-fixing bacteria, similar to how legumes like soybeans fix atmospheric nitrogen through root nodules.

If this technology can be commercialised, it could reduce wheat’s dependence on synthetic nitrogen fertilisers, which account for significant greenhouse gas emissions and represent major costs for grain farmers.

The research, published in a leading plant biology journal, demonstrates that wheat plants with modified root systems can form nodule-like structures where bacteria convert atmospheric nitrogen into forms the plant can use.

Dr. Michelle Watt, who leads the project, said achieving nitrogen fixation in cereal crops has been a goal of agricultural research for decades. “Legumes evolved this capability over millions of years. We’re essentially installing that same machinery into wheat through synthetic biology, though our version is much simpler.”

Nitrogen is essential for plant growth, but most plants can’t use atmospheric nitrogen directly. They depend on nitrogen compounds in soil, either from natural decomposition or synthetic fertilisers.

Synthetic fertiliser production consumes about 1-2% of global energy and produces substantial CO2 emissions. Agriculture applies roughly 100 million tonnes of nitrogen fertiliser globally each year, much of which ends up in waterways or volatilises into the atmosphere rather than being used by crops.

Enabling cereal crops to fix their own nitrogen would reduce fertiliser requirements and associated environmental impacts. Even partial nitrogen fixation that reduces fertiliser needs by 30-40% would be valuable.

The CSIRO approach involves several genetic modifications. First, wheat plants were engineered to produce chemical signals that attract nitrogen-fixing bacteria to roots. Second, root cell development was modified to allow bacteria to colonise specialised structures. Third, plants were given genes that suppress immune responses against the bacteria.

This required introducing about 15 genes from legumes and other sources into wheat’s genome. That’s technically challenging because genes need to be expressed at the right levels, in the right tissues, and at the right developmental stages.

The engineered wheat doesn’t form proper nodules like legumes. Instead, bacteria colonise modified lateral roots where they fix nitrogen. The nitrogen fixation rates achieved so far are modest, about 20-30% of what legumes achieve. But that’s sufficient to reduce fertiliser needs significantly.

Field trials are scheduled for 2026 at several Australian grain-growing regions. These will test whether nitrogen fixation works in real agricultural conditions rather than controlled greenhouse environments, and whether it provides meaningful yield benefits without fertiliser application.

One concern is whether the engineered plants will be productive enough. Nitrogen fixation requires substantial energy, and plants must divert resources from growth to support bacterial symbionts. In legumes, this trade-off is worthwhile, but poorly engineered cereal systems might reduce yields rather than increase them.

The field trials will address this by comparing engineered wheat with and without fertiliser application to conventional wheat with standard fertiliser rates. If engineered wheat yields match conventional wheat without fertiliser, that represents a successful outcome even if yields don’t increase.

Regulatory approval will be challenging. The engineered wheat contains genes from multiple source organisms and would be classified as a genetically modified organism in most jurisdictions. Australia has relatively streamlined GMO approval processes, but export markets vary widely in their acceptance of GM crops.

Some Asian countries that import Australian wheat have restrictions on GMOs that could complicate market access. Grain industry groups are working with regulators in key markets to establish whether nitrogen-fixing wheat would be acceptable, but answers won’t be clear for several years.

Public acceptance is another consideration. While GM crops are widely grown globally, consumer resistance persists in some markets. Whether nitrogen-fixing crops face more or less resistance than other GM crops depends partly on how the technology is framed and perceived benefits.

Environmental groups have mixed reactions. Some welcome reduced fertiliser use and associated environmental benefits. Others oppose genetic engineering on principle or worry about unintended ecological consequences if nitrogen-fixing genes spread to wild relatives of wheat.

That latter concern is probably minimal because wheat has few wild relatives in Australia, and most grain-growing regions are far from native grasslands. Still, gene flow is a standard concern with any GM crop that requires risk assessment.

The economic case for nitrogen-fixing wheat depends heavily on fertiliser prices. When nitrogen fertiliser is cheap, farmers have little incentive to adopt alternatives. When prices spike, as they did in 2021-2022, interest in alternatives increases dramatically.

Farmers would also need to use bacterial inoculants to ensure nitrogen-fixing bacteria colonise the engineered wheat. This is similar to current practices with legumes, where farmers buy rhizobium inoculants. But it adds complexity and cost compared to conventional wheat.

Whether seed companies will develop and commercialise nitrogen-fixing wheat depends on market demand and regulatory pathways. The technology is still at least 5-7 years from potential commercialisation, assuming field trials succeed and regulatory approval proceeds smoothly.

CSIRO is also applying similar approaches to other cereal crops including rice and maize. Rice is particularly interesting because it’s grown in flooded conditions where nitrogen fertiliser runoff is a major environmental problem. Nitrogen-fixing rice could substantially reduce water pollution in rice-growing regions.

The synthetic biology field is advancing rapidly, with new gene editing and genetic engineering tools enabling increasingly sophisticated modifications. What seemed impossible a decade ago is now routine for many applications.

Whether society embraces these capabilities in agriculture remains contentious. The scientific community largely supports biotechnology as a tool for improving sustainability and food security. But public debates about GMOs remain polarised, and regulatory processes vary widely between countries.

The nitrogen-fixing wheat project represents ambitious goals for synthetic biology: fundamentally altering plant metabolism to provide environmental benefits while maintaining crop productivity. Whether it succeeds will influence perceptions about what’s possible and acceptable in agricultural biotechnology.