Ancient roots of wheat virus resistance discovered

The DNA sequence of a wheat gene responsible for resistance to a devastating virus has been discovered, providing vital clues for managing more resistant crops and maintaining a healthy food supply.

Wheat crops in the Americas, Asia, Europe and Africa are frequently ravaged by wheat yellow mosaic virus, so there is a high demand for wheat varieties or cultivars that can resist this virus.

Published today in Proceedings of the National Academy of Sciencesthe study found that the resistance gene came from an ancient Mediterranean wild plant related to wheat.

The study’s lead researcher at the University of Melbourne, Dr Mohammad Pourkheirandish, said: “This finding could aid in the development of more resistant wheat cultivars, increase crop yields and reduce the use of harmful fungicides. It also highlights the need to preserve biodiversity to protect food supplies. .”

WYMV reduces grain yield by up to 80%, resulting in significant economic losses. The virus is hosted and transmitted by a soil fungus that colonizes the roots of wheat plants, discolors wheat leaves and stunts plant growth.

Microscopic fungal spores containing WYMV can live in soil for up to a decade. While fungicides can kill spores and stop transmission, fungicide treatment is neither cost effective nor environmentally sustainable.

“The viable alternative is to breed or genetically modify WYMV-resistant wheat,” Dr Pourkheirandish said.

“Before this research, we knew that a dominant gene called Ym2 reduced the impact of WYMV on wheat plants by more than 70%, but we did not understand how the gene achieved this.”

The research team used a technique called positional cloning to locate the Ym2 gene on a common wheat chromosome and discovered that its DNA sequence codes for a protein of the type known as NBS-LRR. These proteins are “gatekeepers” that detect pathogens and trigger an immune response in plants.

“Now that we know the DNA sequence of the gene, we can select lines carrying Ym2 by simply analyzing DNA from a small piece of leaf, even without the virus inoculation step,” said the Dr Pourkheirandish.

“It will also facilitate the search for Ym2 variants in wild relatives of wheat, which may provide superior disease resistance for further crop improvement.”

Modern wheat’s DNA is chimeric, which means that its genetic material comes from several ancestral plants through natural interbreeding, or hybridization, followed by selective breeding by humans.

By comparing DNA sequences of related species, the researchers found that Ym2 in modern common wheat derives from an ancient wild plant called Aegilops sharonensis, native to eastern Mediterranean countries. A similar gene is present in Aegilops speltoides, another wild ancestor of bread wheat.

“These wild species would have interbred with cultivated wheat at some point and transmitted the genetic resistance that is now so commercially critical,” Dr Pourkheirandish said.

“Ancestral wild plants are a rich source of useful traits, like disease resistance, that plant breeders and geneticists can harness to protect modern crops and maintain a healthy food supply, including breads, pastas, noodles, couscous, pastries, cakes and other wheat. products that many of us depend on and enjoy.”