Continuing claims made for Barley Yellow Dwarf Virus (BYDV) tolerance by plant breeding companies do hold up under the scrutiny of an independent trials’ process.

This is a strong theme that has been identified, courtesy of recent Teagasc trials.

Moreover, the varieties of winter barley concerned demonstrate this tolerance in the context of the aphid populations and the specific variants of BYDV found in Ireland.

As part of the 2026 National Tillage Conference, Teagasc Walsh Scholar, Jack Perry, provided an overview of research aimed at validating the use of tolerant winter barley varieties to manage the disease in this country.

He explained: “BYDV is transmitted into barley by aphids feeding on the crops.

"There are three BYDV species present in Ireland: BYDV MAV, BYDV PAV and BYDV PAS, with the dominant species being BYDV MAV.

Although promising tolerant varieties to BYDV have become available, Perry noted that much testing on these varieties has been carried out in relation to BYDV PAV in mainland Europe.

Teagasc BYDV trials

To quantify their effectiveness in Ireland against BYDV MAV, lab and plot scale trials have been undertaken at Teagasc’s Crops Research Centre, Oak Park.

Perry noted the four varieties on the Department of Agriculture, Food and the Marine’s recommended list "have some form of tolerance gene".

“Two of them have an Ryd2 gene and two of them have an Ryd2 + Ryd3 gene," he said.

"These genes have been well studied against BYDV PAV in mainland Europe.

Courtesy of the Teagasc study, five different winter barley cultivars were examined: one susceptible and four with tolerant genes present.

In laboratory studies, susceptible varieties had higher transmission scores than all four tolerant cultivars, which Perry highlighted was to be expected.

Findings

In the field and working off average yields from harvests in 2024 and 2025, the trial results are confirming that tolerant varieties, when left untreated with insecticide, showed lower levels of BYDV symptoms.

However, BYDV was still present within the crop.

With regard to the yield impact recorded, the Teagasc Walsh Scholar added: “Susceptible varieties that are unsprayed suffer a yield penalty of around 2t/ha, something that we expected to see.

"In cultivars with the Ryd2 genes, we see a much reduced drop in yield.

“When we examined the Ryd2 + Ryd3 cultivars, we do see a yield reduction when they are left unsprayed.

"This is only about 1t/ha and it is less than the yield penalty we see in response to susceptible cultivars treated for BYDV.”

According to Perry, the research shows "a proven reduction" in transmission efficiency in tolerant cultivars, and that these tolerant cultivars "maintain high yields despite visible BYDV symptoms".

Tolerant varieties also show a reduced yield penalty when left without an insecticide, the Teagasc Walsh Scholar said.