Farming UK - 23rd April 2015
Carried out by Dr John Walsh of Warwick University on behalf of breeders Limagrain UK, the survey which will be completed by the end of May, will provide a comprehensive indication of Turnip Yellows Virus (TuYV) infection hotspots across the country. TuYV is thought to be the most important, yet least understood viral disease in oilseed rape.
“Overall results so far are showing generally high levels of infection across the three regions that have been tested as part of a PhD project led by Dr Walsh; results from the south of England have detected incidences of as high as 80%, in Somerset incidences of up to 74% and in Yorkshire incidences of up to 72%, whereas in Cardiganshire we found incidences of up to 46%.”
“We will have the final results of this extensive survey at the Cereals Event in June.”
“What we do know is that high levels of TuYV infection can lead to substantial yield penalty as we very clearly saw in many areas in continental Europe last year. In locations with high levels of virus, resistant varieties could out yield non-resistant varieties by 10-15%,” says Dr Vasilis Gegas, senior oilseed rape breeder with Limagrain.
William Compson, oilseeds product manager with Limagrain, recognizes that the problem with TuYV is that you don’t usually see the symptoms until spring. “Early symptoms of TuYV are expressed by intense purpling of the leaves; later symptoms of interveinal yellowing and reddening of leaf margins are not usually expressed before stem extension and can easily be confused with other stress symptoms and nutritional deficiencies, which is why the effect of the virus is underestimated.”
Looking ahead to next autumn and what this means for the oilseed rape crop, Mr Compson notes that whilst foliar insecticides such as Plenum, can offer some solution to the aphid problem, there is widespread resistance to pyrethroids and primicarb to consider.
“This means that variety choice will be even more critical than ever and will require a change in mind set where resistance and agronomics play an increasingly crucial role in order to protect yield,” he says.
Amalie remains the only commercially available oilseed rape variety with resistance to TuYV on the market, and the variety was re-submitted as a candidate in the 2014-2015 HGCA RL trials based on this trait.
Amalie is a conventional OSR variety that offers a gross output similar to the widely grown variety, DK Cabernet. “However, our own trials using untreated seed over the last four years have clearly shown that where TuYV is present, Amalie can yield up to around 10% more than non-resistant varieties,” says Mr Compson.