A UK team of wheat experts has been taking part in a worldwide 'webinar' focussing on yellow rust resistance in wheat and how to deliver genetic gain in the crop.

Angus Wheat Consultants (AWC), a specialist consultancy run by Bill Angus, from Suffolk, took part recently in the worldwide debate entitled ‘Critical reflections on delivering genetic gain in wheat’ – organised by the Borlaug Global Rust Initiative (BGRI), an organisation that fulfils a key role in helping to develop a strategy to deploy resistance genes in the most effective way.

Felix Austin, a wheat breeder with AWC, presented a key video contribution focused on the fact that wheat growing in the UK is under pressure from yellow rust because the UK climate provides a perfect environment for new races to evolve. He pointed out that while the UK was a good environment to breed resistant varieties, genetic resistance must be deployed carefully to reduce risk on farm.

“Genetic variation in UK elite lines is low as consequence of the use of a limited number of parents. Yellow rust resistance can collapse quickly and this ‘boom and bust’ cycle of variety failure has been happening for the last 40 years.

“Very high yielding feed wheats can become susceptible after just a few years following introduction, and given the narrowness of the UK germplasm, a resistance breakdown in a single variety can have a domino effect through other elite lines if the failed resistance was used regularly.

“While it is correct that yellow rust can usually be managed with good fungicide use, in field situations, two applications of a robust fungicide programme can still show high levels of yellow rust. This is a high risk scenario for the grower – and comes at a high financial cost.”

AWC have been working to monitor the yellow rust resistance in the UK and develop new resistant lines by working with Agrii, an agronomy services business. The yellow rust situation is monitored by planting tussocks of a range of varieties and lines that contain known resistance genes. This forms part of a network across the country to monitor the geographic development of new yellow rust races.

The objective was to learn from this and deploy a range of resistant lines from diverse germplasm sources that allow improvements such that ‘sons’ of widely grown lines have significantly less yellow rust. Rather than seeking out immunity, the programme is looking for robust field resistance.

Robust resistance is a trait highlighted in the germplasm of CIMMYT – the International Maize and Wheat Improvement Centre – and AWC is now working closely with it to share experiences and germplasm with good adult plant resistance both for the UK and for the developing world, and screening elite CIMMYT germplasm in a high pressure UK environment.

Using strips of susceptible varieties to increase the level of yellow rust, means there is no shortage of rust in AWC nurseries. A space was left adjacent to AWC winter sowing for drilling CIMMYT material so that their resistant lines can be evaluated to see if they will hold up to the UK’s inherent high disease pressure.

At the same time, crosses have been made between highly resistant UK lines and CIMMYT lines, as advised by pathologists from the International Bread Wheat Screening Nurseries. These crosses will determine whether resistance in germplasm comes from the same source, or if there is an opportunity to deploy novel resistance genes.

Bill Angus, managing director of AWC, concluded: “This collaboration aims to help our understanding of yellow rust races and to help farmers by creating more resistant varieties both in the UK and across the globe."