Sustainable oats varieties with genes capable of fighting stem rust have been developed: CDL-111 and CDL-167.

The team of specialists has developed special varieties of oats that can be crossed with prestigious commercial varieties in order to strengthen them with new genetic sources of resistance to crown rust caused by the fungus named Puccinia coronata f. sp. avenae.

Crown rust of oats is a worldwide problem and can lead to a loss of up to 50 percent of grain yield in unprotected crops.

An announcement about the creation of resistant oats varieties with embryo plasm in May 2024 issue of the Journal of Plant Registration, named CDL-111 and CDL-167, was the result of over 25 years of research, including embryo plasm screening, plant genetic mapping, selection, and evaluation in various trials.

"Almost all oat varieties with rust resistance carry only one or two resistance genes (often referred to as seedling resistance genes) to a specific form of crown rust," explains Shahryar Kianian, co-author of the article in the journal and chief researcher of the ARS Cereal Disease Lab in St. Paul, Minnesota.

However, the crown rust fungus is a genetically diverse pathogen capable of rapidly evolving into new forms known as races. This evolution occurs so quickly that the average productive life of an oat variety with resistance ranges from three to five years, requiring producers to use chemical fungicides in traditional production systems.

If the fungus is not stopped, it infects the lower leaves and sometimes the spikes of susceptible oat plants, forming round or oval pustules filled with orange spores that can spread by wind or rain. Leaf damage leads to a reduction in photosynthesis and disruption of sugar transport from leaves to grains, resulting in shriveled grains and reduced nutritional value.

The team focused their breeding effort on a "genetic stack" of oat varieties using a strategy called "gene pyramiding." The essence of this strategy was to cross cultivated oat varieties with wild relatives, including wild oats (a rare variety usually considered a weed) possessing adult plant resistance genes.

"Adult plant resistance provides oats with a certain level of immunity, although not complete," Kianian explains. "In this case, the selection pressure on the pathogen decreases, leading to its alteration, and the plant is not heavily damaged, allowing it to continue yielding crops and providing grains for farmers."

Overall, the team has created plants resulting from the crosses that carry three adult plant resistance genes to crown rust. They then conducted testing on these plants starting from 2020. This included growing plants in fields where buckthorn, a secondary host of crown rust and a source of its spread, is present. In areas with high disease intensity, two varieties of plants showed more resistance, namely CDL-111 and CDL-167.

Now, the resistant oat varieties have been multiplied for seed production, which can be used in new variety development programs under a material transfer agreement from ARS, as reported by Kianian. This is necessary to ensure the effectiveness of genetic crosses with commercial oat varieties, regardless of their level of resistance to crown rust.

Meeting this requirement, breeders can deliver a double blow to the crown rust fungus by using elite oat varieties adapted to specific regions that possess not only rust resistance at an early growth stage but also adult plant resistance, the researcher concludes.

"We also provide molecular markers associated with these three genes to help select plants carrying them," concluded Kianian, who worked with Eric Nazareno and Kevin Smith from the University of Minnesota, Melanie Caffe from the University of South Dakota, Roger Kasper from ARS, as well as Howard Rines and Marti Carson, who were also research participants.

Source: www.ars.usda.gov.

Photo: Anna Medvedeva, AgroXXI.ru.