MORE THAN half of all winter wheat varieties have been shown to be resistant to yellow rust at the young-plant stage in an important 2021 survey.

The UK Cereal Pathogen Virulence Survey (UKCPVS) in its annual update on varietal resistance conducted on AHDB Recommended Lists (RL) varieties, showed that the latest screens found that a majority of varieties tested were resistant at an early stage.

Growers should use this information, alongside the RL (adult plant) disease resistance ratings, to adapt spray programmes in 2022, particularly at the T0 spray timing, the reported concluded.

Dr Charlotte Nellist, UKCPVS' project lead at NIAB, said: “The pathogen that causes yellow rust is complex – some varieties are susceptible to the disease when plants are young but go on to develop some level of resistance after early stem extension.

"However, if young plants are susceptible and the RL disease resistance rating is also low, crops will require closer monitoring for active rust over the winter period.”

The screens use five pathogen isolates selected by UKCPVS to best represent the diversity in the yellow rust population at the time of testing. A variety is classified as susceptible at the young-plant stage if it is sufficiently susceptible to any one isolate.

Charlotte said: “The 2010s saw large changes in the UK yellow rust population, resulting in numerous reductions in resistance, at both the young-plant and adult-plant stages. For example, only three varieties were recorded as having young-plant stage resistance in 2016.

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"Since then, the situation has improved somewhat, with over half of the varieties screened in 2021 classed as resistant during these early growth stages,” she added.

Relatively few yellow rust samples were received by the UKCPVS team in 2021, with 155 samples sent in (from 54 varieties and 19 counties) – around half the number recorded in 2020. This was probably due to this year’s cool, dry spring, which helped reduce wheat yellow rust pressure. Similarly, for brown rust, only 10 samples were received.

Charlotte said: “It is important to send in material, irrespective of the disease pressure. It helps us provide a regional snapshot of the pathogen population and serves as a basis for early warnings of population change.

"While we cannot test every sample, we do preserve and archive all isolates, which provides an essential reference library for pathogen virulence research.”

The latest cereal pathogen developments, both in the UK and globally, will be in focus at the annual UKCPVS stakeholder meeting on March 2, 2022.