Genetic map unveiled to help fight 'wheat cancer'

XI'AN — Chinese scientists have unveiled the world's first genetic map tracking wheat resistance to the devastating yellow rust disease, representing a significant breakthrough that promises more durable wheat resistance and decreased pesticide dependency.

Their research, which was published in the Nature Genetics journal on July 23, was jointly led by the Northwest Agriculture and Forestry University and the Chinese Academy of Sciences' Institute of Genetics and Developmental Biology. It provides breeders with an unprecedented gene navigation tool, the university told Xinhua on July 25.

Yellow rust, which is caused by the Puccinia striiformis f. sp. tritici (Pst) pathogen, is often termed "wheat cancer". It mutates rapidly, generating a new prominent pathotype every five years and causing roughly 10 percent of global wheat yield loss annually, according to Kang Zhensheng, an academician at the Chinese Academy of Engineering and a professor leading NWAFU's plant immunity team.

Breeding resistant cultivars is crucial to managing this disease, Kang said.

"For the first time, this study systematically reveals the genomic selection signatures and epidemiological characteristics of wheat-Pst interactions over the past century, as well as the co-evolutionary dynamics between resistance genes and pathogen races," Kang said.

The team spent five years conducting a comprehensive analysis using variome data from 2,191 wheat accessions around the world, as well as over 47,000 yellow rust response records from multiple environments and pathogen races.

Using these resources, they identified 431 yellow rust resistance loci, constructing a genome-wide map of yellow rust resistance genes. Carefully analyzing the 559 candidate genes associated with yellow rust resistance, the team successfully cloned three novel resistance genes corresponding to the identified loci.

Gene Yr5x, a novel allele, demonstrates resistance to multiple Pst races, highlighting the potential for allelic variation in broadening resistance spectra.

Gene Yr6/Pm5 confers dual resistance to both yellow rust and Blumeria graminis f. sp. tritici, which is a powdery mildew, uncovering a novel mechanism for broad-spectrum disease resistance in crops.

Additionally, gene YrKB (TaEDR2-B) confers broad-spectrum rust resistance without yield penalty.

The identification of such "elite" haplotypes that combine resistance with desirable agronomic performance is a major step forward, according to the research team.

"This map is a rich resource for resistance gene deployment in wheat breeding programs," said Han Dejun, a professor at NWAFU.

He noted that the identified combinations of resistance genes could significantly prolong the effective lifespan of resistant wheat varieties.

Unlike current varieties, which typically lose resistance within three to five years due to pathogen evolution, the new genes could retain their efficacy for over a decade and potentially longer, he added.

Wheat breeding lines carrying these cloned genes are now undergoing field trials across major wheat-growing regions both at home and abroad. This advancement provides robust scientific support to cut pesticide use and strengthen global food security against this persistent threat, according to the research team.

Xinhua