Disease-resistant genes key to safeguard crops

Corn, rice, wheat, potato, soybean: these are some of the so-called staple crops, providing the bulk of our calories. But as global agriculture becomes more homogenised, the risk of disease wiping out an entire crop becomes greater.  

That’s why Australian, British and US scientists have developed a new way of identifying and cloning disease-resistant genes in the wild cousins of these plants, giving scientists a faster, cheaper way to address potentially devastating infections. 

“We have found a way to scan the genome of a wild relative of a crop plant and pick out the resistance genes we need, and we can do it in record time,” says Brand Wulff, of the John Innes Centre, Britain, and a lead author of the study. 

“This used to be a process that took 10 or 15 years and was like searching for a needle in a haystack.” 

As proof of concept, the researchers use a system dubbed AgRenSeq (which stands for “association genetics with R gene enrichment sequencing”) to identify and clone four genes in a wild wheat strain that are resistant to the stem rust pathogen. The work was conducted in just months.{%recommended 7953%}  

“We have perfected the method so that we can clone these genes in a matter of months and for just thousands of dollars instead of millions,” Wulff says. 

The work appears in a letter in Nature Biotechnology.

Stem rust is a particularly damaging disease that strikes wheat, causing the plant to stop producing grain. It has been responsible for famines across thousands of years, experts say. 

More recently, in the 1950s, a stem rust outbreak ruined 40% of the US crop. Then, in 2007, a black stem rust outbreak hit parts of Africa and the Middle East, prompting famine concerns. 

In addition, modern agricultural strains of staple grains, including wheat, are less diverse and less resistant to disease due to breeding, the scientists behind the AgRenSeq system point out.  

Working off the findings that genetic traits are often correlated into subsequences of genetic code, known as k-mers, the team identified sequences associated with disease-resistance.  

They designed “a sequence capture bait library” so they could scan for these k-mers.  When they find the resistant code in wild species, they can replicate it and use it to fortify domesticated crops. This process can be duplicated for different species and diseases. 

“The work in wild wheat is being used as a proof of concept, preparing the way for the method to be utilised in protecting many crops which have wild relatives including, soya bean, pea, cotton, maize, potato, wheat, barley, rice, banana and cocoa,” the authors write. 

Hopefully, this technique will help protect the world’s food supply from disease, they write. 

“If we have an epidemic, we can go to our library and inoculate that pathogen across our diversity panel and pick out the resistance genes. Using speed cloning and speed breeding we could deliver resistance genes into elite varieties within a couple of years, like a phoenix rising from the ashes,” Wulff says.