Researchers transform the once toxic grass pea into a smart crop of the future

11 Jul 2023 --- The ancient and climate-resilient grass pea is poised to become a major future food crop following a breakthrough by UK-based researchers. The John Innes Centre will use gene editing and modern breeding methods to transform the potentially poisonous pea into a protein-rich, drought-resistant safe version that can be used across a wide range of F&B applications.

The grass pea has been historically used as an “insurance crop” that survives when other crops fail, but its widespread cultivation has been hampered because it contains a toxin that can affect malnourished people and cause the disease neurolathyrism, a condition that causes irreversible paralysis.

But now researchers are developing a non-toxic version that could be grown in many more regions worldwide and unlock a “very valuable crop.”

Using a newly available genome sequence of grass pea (Lathyrus sativus L.), the research collaboration has identified key biochemical steps that lead to the production of the neurotoxin β-L-ODAP (ODAP). 

The crop that comes with a catch
Grass pea is among indigenous species – known as orphan crops – that play a crucial role in local nutrition and livelihoods but receive little attention from breeders and researchers.

The grass pea has been historically used as an “insurance crop” that survives when other crops fail. (Credit: Phil Robinson)This could soon change, according to Dr. Anne Edwards from the John Innes Centre and one of the authors of the research.

“The genomic sequence for grass pea and the biochemical insights that occur as a result provide a breakthrough in our understanding. It offers an opportunity to develop varieties with less ODAP that are adapted to local conditions,” she tells Food Ingredients First.

“It is a crop that is resilient to drought and salination, which are important factors to ensure food security as the climate changes. Grass pea, like other legumes, can fix their own nitrogen, so they can not only grow on poor soils without the addition of nitrogen fertilizer, but it improves the soil.” 

“This is important for the environment, water quality, carbon capture and biodiversity as well as a cost consideration for the F&B industry.” 

A crisis crop in the making
Glasshouse trials at the John Innes Centre and field trials run by the International Centre for Agricultural Research in the Dry Areas ICARDA in Lebanon and Morocco and the Ethiopian Institute for Agricultural Research are already underway. These pilots will test the performance of low ODAP grass pea lines crossed with local varieties.

“As we prepare for a future of increased climate change, we are going to need crops that can cope with drought, or flooding or inundations of salt water,” continues Dr. Edwards. “Grass peas can survive such conditions better than other pulses, so now, with the genetic resources we have, there is an opportunity to develop low-ODAP varieties which have agronomic traits adapted to local conditions around the world.”

“There is a need for homegrown plant proteins and to reduce dependency on imported soya, which does not grow well in the UK.”

“The grass pea has a large potential growing area already. It could be grown in the UK.” 

Grass pea produces β-L-ODAP 
The team has traced two enzymes that interact to catalyze the last steps of ODAP biosynthesis. One of these enzymes is in many plant species involved in removing oxalate, a molecule that regulates photosynthesis and is produced by fungi as part of an attack strategy.  

In grass peas, this enzyme pathway has been repurposed, leading to the production of ODAP, which provides an alternative route to removing oxalate. 

One theory is that the toxin is produced as a kind of molecular sink to store the excess molecules used by the plant for defense or the products of essential processes such as photosynthesis. 

The possible role that this pathway plays in defending the plant means that disrupting the process may have undesirable consequences for the plant, something that the research team has to consider when using approaches such as gene editing. Grass pea is among indigenous species that play a crucial role in local nutrition and livelihoods but receive little attention from breeders and researchers. (Credit: Phil Robinson)

“We know the enzymes that lead to ODAP, but we don’t know the exact metabolic effects of disrupting the different enzymes in different ways,” explains author Dr. Peter Emmrich from the Norwich Institute for Sustainable Development.  

“The pathway leading to ODAP is important for the metabolism of other amino acids, such as cysteine and methionine, essential to the plant’s health. It should be possible to have a plant that exists without ODAP; however, we do not know all the ways the pathway helps the plant deal with its environment. So, the ideal outcome may be that you have a grass pea with less ODAP but more methionine.” 

Previously, the high level of repeat sequences in the grass pea genome meant it was difficult to identify genetic sequences that code for the enzymes behind toxin production.  

This new genome sequence means that the road map has become clearer, and the researchers are closer to adding grass pea to the list of climate-smart crops of tomorrow.

Propelling pea protein
This grass pea initiative comes on the heels of John Innes Centre’s involvement with another alternative protein project to produce “tasteless peas” in a bid to move away from the industry’s overreliance on unsustainable soy.

A significant challenge is to breed different tasteless pea varieties, as the vegetable is often associated with off-notes when used in plant-based applications.

Dr. Edwards says the next steps in the grass pea project are to unravel the earlier parts of the genetic pathway that leads to the toxin and investigate the role of the toxin in the plant, gene editing to obtain low toxin varieties and crossing these into local varieties.

“Field trials (to test the effects of heat and drought) are currently taking place on farms in Morocco and Lebanon,” she says. 

By Gaynor Selby