While turnip yellows virus (TuYV) incidence in OSR has reached its highest level ever this season – yields can be protected by genetic resistance, according to ongoing trials.

Annual monitoring of TuYV infection in the UK’s oilseed rape crop has shown that 84% of non-TuYV resistant crops were infected in early spring 2019, the highest level ever recorded.

However, despite this, TuYV resistant varieties – Aspire, Aurelia and Ambassador – have recorded some of the highest yields in independent trials.

TuYV is spread by the peach potato aphid (myzus persicae) and can impact yields by as much as 30% in highly infected situations and oil content by 3%, whilst increasing levels of glucosinolates and erucic acid.

Since 2016, Limagrain UK and industry partners, Agrii, Openfield and AICC, have been monitoring levels of TuYV in crops across the UK. Leaf samples were taken in the spring and autumn and tested using the Elisa standard test.

“Results from this springs sampling confirm that almost all sites had an infection rate between 81-100%. Many of these sites are in regions where you would expect infection levels to be high, such as in the south-east, however what is noticeable is that we are now seeing sites in Scotland and south-west with these very high levels of infection,” said Dr Vasilis Gegas, Limagrain’s OSR European portfolio manager.

“Three years ago, we wouldn’t have seen these levels in the west, which shows how TuYV is becoming increasingly widespread and is endemic in the UK OSR crop, irrespective of region.”

Harvest results from trials conducted by AICC in West Wittering, show that there was a 0.4-0.5t/ha yield advantage from varieties with TuYV resistance against those with none.

“Limagrain’s conventional variety, Aspire, performed very well, as did Aurelia and Ambassador. In this trial, Aspire yielded 6.7t/ha; that’s a yield bonus over the 6t/ha from the non-TuYV resistant variety; Campus. Aurelia was just behind, yielding 6.4t/ha,” said Peter Cowlrick, director in CCC Agronomy.

In a second trial in Suffolk, the trend was the same. Aurelia managed a top yield of 6.1t/ha, with Campus producing around 5.6t/ha. Ambassador yielded just below 5.9t/ha and Aspire 5.86t/ha.

“What these results show is that with varieties such as Aspire, Aurelia and Ambassador, there is no longer the yield drag once associated with TuYV resistance, in fact, it’s quite the opposite.”

“In the south-east, where the risk of TuYV infection is very high, on some farms, almost 80% of the crop entering the soil will be TuYV resistant varieties. These varieties also play an important role in IPM, as there is less reliance on insecticides,” added Mr Cowlrick.