LG Seeds - 12th June 2015
With reports of very high TuYV infection levels being recorded from across the country, many oilseed rape growers will be considering their options for the coming season to manage for what is considered it be the most important, yet least understood, viral disease in oilseed rape, Turnip yellows virus (TuYV).
Presenting the results from a nationwide survey at Cereals, Dr John Walsh of Warwick University who headed up the research on behalf of breeders Limagrain UK, warned that levels of TuYV infection are as high as he has ever seen. “Results from across the country are showing worryingly high levels of infection with some hotspots of infection showing levels as high as 72% infection!”
“Generally, these hotspots are where you would expect due to the large areas of oilseed rape grown, however the levels of infection are much higher than they have been for the last few seasons with Yorkshire and East Anglia at around 72% infection, and some surprises such as 64% infection in Somerset. “
Alan Dewar, of Dewar Crop Protection, believes that these high incidences have come about as a result of the high numbers of aphids flying last autumn. “Last autumn many oilseed rape crops were drilled early, it was also the first autumn without neonicotinoid seed treatments and whilst there are insecticides available there are some issues around timing and duration of control as well as developing resistance to pyrethroids and primicarb which can severely impede fully effective control.”
The timing of infection of TuYV from aphids has a significant influence on the levels of infection and subsequent yield – studies from the University of Warwick has confirmed that the earlier the infection the greater the yield loss. “So this year we could be looking at some fairly significant yield losses,” says Dr Vasilis Gegas, senior oilseed rape breeder with Limagrain.
“However, the difficulty with TuYV is that it is difficult to identify and often yield losses will be attributed to other factors. However in trials with high levels of virus, resistant varieties could out yield non-resistant varieties by 10-15%, demonstrating the value of resistance in protecting yield,
Looking ahead to next autumn and what this means for the oilseed rape crop, Mr Dewar urges growers to strongly consider the role that varietal resistance can play.“The most exciting news for OSR growers this autumn is that the variety Amalie has proven itself to be completely resistant to TuYV and I am confident with this claim having had some testing done myself,” he says.
“I visited a farm in Debenham, Suffolk and was shown a field of Amalie which the farmer felt was not showing any symptoms of TuYV in comparison to a neighboring field of a non-resistant variety, so I sent 10 leaves of both the Amalie and also the leaves from the non-resistant variety to Rothamsted for ELISA testing – the results confirmed that there susceptible OSR variety had 70% infection but there was no virus whatsoever in the Amalie!”
“It’s not often in this industry that you get good news like this and it’s very important that growers pay attention to these findings and make use of the varietal resistance that is available.”
“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. Amalie can yield up to around 10% more than non-resistant varieties in the presence of TuYV infections.
Agronomically the variety offers sound agronomics and robust disease resistance ratings, with a 7 for LLS and 8 for phoma, so with no obvious weaknesses there is a serious case for growers to consider making it part of their OSR cropping this season.