New Wheat Gene Yr88 Explains 86% of Resistance to Stripe Rust

28 September 2026, New South Wales, Australia: Researchers at the University of Sydney’s Plant Breeding Institute in Cobbitty, New South Wales, have mapped a new wheat gene that provides strong resistance to stripe rust, also known as yellow rust, one of the most damaging fungal diseases affecting wheat crops worldwide. The gene, named Yr88, explains about 86 percent of the variation in resistance to a specific strain of the rust pathogen tested in the study, according to results published online August 5, 2026 in the journal Theoretical and Applied Genetics by a team led by Professor Robert Park. The researchers cautioned that the resistance is not durable on its own and can eventually be overcome by new strains of the fungus, meaning breeders will need to combine it with other resistance sources rather than rely on it alone.

Stripe rust, caused by the fungus Puccinia striiformis f. sp. tritici, produces yellow orange, powdery pustules on wheat leaves that reduce the plant’s ability to photosynthesize and fill grain. In seasons with cool, moist weather during the growing period, it can cut yields significantly across major wheat regions including Australia, the western United States, East Africa, and South Asia, including India and Pakistan. The fungus is also notorious for evolving new strains, called pathotypes, that can overcome resistance genes bred into commercial wheat varieties, forcing plant breeders into a continuous cycle of finding and deploying new sources of resistance.

Mapping a Gene From a Cross of Two Wheat Lines

To find Yr88, the researchers crossed a resistant wheat line called Kazouria Taliani with a susceptible line called Avocet S, then grew out 95 resulting plant lines, each carrying a different, fixed combination of genes from the two parents. This type of population, known as a recombinant inbred line population, lets researchers statistically link specific stretches of the wheat genome to a trait of interest, in this case resistance measured in mature, adult plants rather than young seedlings. The team tested the population against a defined stripe rust pathotype, a laboratory shorthand describing exactly which known resistance genes that particular fungal strain can and cannot get past.

To pinpoint the resistance gene’s location, the researchers used a genotyping method called targeted genotyping by sequencing, which reads DNA at close to 2,000 specific points scattered across the wheat genome, combined with statistical mapping approaches including identity by descent modeling and bulked segregant analysis, a technique that compares the genetic markers of resistant and susceptible plants grouped in bulk. This combination of tools pointed to a single major region on the short arm of chromosome 2D that had not previously been linked to adult plant stripe rust resistance, which the team designated Yr88.

The 86 percent of resistance variation explained by Yr88 makes it an unusually strong single-gene effect, but the researchers classified it as “race specific” resistance, meaning it protects against pathotypes that lack the matching ability to overcome it, rather than the broader “slow rusting” or durable type of resistance that tends to hold up against a wider range of the pathogen’s evolving population. History suggests race specific genes used alone are eventually defeated as new pathotypes emerge and spread. For that reason, the study’s authors recommend that breeders combine, or “stack,” Yr88 with previously known durable, slow rusting resistance genes such as Yr18 and Yr29 in the same variety. This pyramiding strategy, layering multiple resistance genes with different mechanisms into one wheat line, is the standard approach breeders use to slow down a pathogen’s ability to defeat resistance entirely, because the fungus would need to overcome several genetic barriers at once rather than just one.

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