Demo Field tour part 2 – Searching for new BYDV resistance

Wheat varieties from across the world are being screened for new sources of barley yellow dwarf virus resistance to reinforce the Bdv2 gene that is currently used in RAGT’s Genserus varieties.

While the trait has shown no signs of breaking down in more than 20 years of commercial use in Australia and decades of breeding work at RAGT, Lee said it made sense to protect it.

The Bdv2 gene is derived from intermediate wheatgrass by repeated backcrossing – it is not present on the wheat genome. However, some conventional (non-Bdv2) varieties appear to have more natural tolerance to BYDV than others, so this screening trial is widening the search to find the very best.

Two near-identical lines of every wheat are being compared, one with the Bdv2 gene, the other without. All have been inoculated with virus-bearing aphids. Bdv2 lines whose partners without the trait escape serious infection will be taken forward for further assessment.

Other genes derived from the same wheatgrass as Bdv2 are also being examined under the same system.

“We know these can confer useful resistance, so we have included these as single genes and all possible combinations,” Lee said.

“Ultimately, perhaps in 10-12 years, we will end up with commercial varieties with a complex polygenic base of BYDV resistance.”

Standout performance from Genserus wheats in BYDV trials

The effectiveness of BYDV resistance in RAGT’s Genserus wheats has been graphically illustrated in trials this season.

They have thrived even under the intense BYDV pressure that left many conventional varieties showing reddening and dwarfing symptoms that are certain to cause significant yield loss.

Twenty September-sown wheats have been put to the test in the two-replicate trial – eight BYDV-resistant varieties and a range of commercial ones. All received Recommended List-protocol fungicide and PGR treatments, but no insecticide.

Plots were inoculated with BYDV-infected aphids, some during the autumn, some during autumn and spring and some in spring only.

All Genserus plots look level and green across the trial, regardless of when they were inoculated. These include hard feed wheat RGT Grouse and its likely successor RW42265, plus new breadmaker RGT Goldfinch, up for recommendation this autumn, and RW42396, an early sowing, very clean, hard feed variety in National List trials.

“There is no dwarfism and no discoloration or loss of photosynthetic area in any of the Genserus varieties,” Lee observed.

A few of the conventional (susceptible) varieties have tolerated BYDV relatively well, but many others have suffered, including RGT Illustrious and Crusoe.

“Champion also takes a lot of colour although it doesn’t suffer from too much dwarfing, but Gleam, Extase and SY Cheer detest BYDV,” he noted. “They are full of colour and dwarfed badly.”

Symptoms are similar in the autumn- and spring-inoculated plots, although the most susceptible varieties appear even more affected and are heading for a serious yield hit.

Results from last year’s trial, which was autumn and spring inoculated, showed RGT Grouse outyielded Champion by 8.3%, worth an extra £173/ha with grain at £180/t. RGT Grouse also outyielded Skyscraper, by almost 15%, similar to the two preceding years. In the same trial RGT Goldfinch outyielded Extase by 14% and Skyfall by 11%.

Spring damage

In this season’s spring-inoculated plots, some susceptible varieties have suffered less stunting than earlier-inoculated plots, but not all. “Extase is still badly affected, and there seems to be just as much leaf discoloration across the board,” said Lee.

“I’ve seen what damage can be done by spring BYDV infections in Ireland, but how many farmers spray for aphids in the spring? They don’t.

“The results here beg the question: What value is there in drilling late if you do get spring infection? The aphids in this trial weren’t put in until the last week of February and the BYDV they’ve transmitted has still caused significant damage.

“Genserus varieties take away all those headaches. They offer season-long control of BYDV, so you don’t need to worry about getting the sprayer out in a wet autumn, or applying and timing often-multiple sprays when you can travel. And you don’t have to worry about resistance and you’re not going to kill beneficials – it’s a hugely positive PR story for UK farming.”

To read the following article of Demo Field tour please click here.