Oilseed rape One third of crops at
risk from rape virus • Virus no longer confi ned only to hotspots • Crops can suff er 30% yield penalty • Genetic resistant varieties important
G
rowers should select rape va- rieties carefully after a survey confi rmed that one third of sus-
ceptible UK crops are infected with Turnips Yellows Virus (TuYV). Transmitted by aphids, TuYV can result in a 30% yield penalty where high levels of infection occur early in the crop’s life. It is believed that 70% of peach potato aphids (Myzus persi- cae) carry the virus.
Plant breeder Limagrain has been monitoring TuYV levels in non-resist- ant or susceptible crops since 2015. Leaf samples are taken both in spring and autumn – and tested using the standard Elisa test. “We’ve mapped the incidence of
TuYV from the UK to Ukraine and seen it build over the years,” says Lim- agrain marketing manager William Charlton. “We’re getting to a situation where TuYV is now endemic across Europe, and no longer confi ned to hot- spots.”
Infection levels
Samples were taken from 26 locations across the British Isles. Results from this spring’s sampling confi rm that one third of all the UK’s non-resistant oil- seed rape crops sampled were infect- ed with TuYV. As expected, high rates of infection of 66-80% were reported in south-east England. But the highest rates of in-
fection – as much as 81-100% – were reported on farms across the Midlands. High levels of infection were detect- ed as far north as the borders, and as far west as Wales. One third of non-re- sistant rape crops were infected across Yorkshire, Lincolnshire, Shropshire and Wales. “Five years ago we would not have seen these cases in the north and west, which just goes to show how TuYV is becoming increasingly widespread, and is now endemic in the UK rape crop, irrespective of region.”
Risk factors
The link between high numbers of aphids in the autumn and correspond- ing levels of infection is clear, explains Mr Charlton. Infection usually occurs in September to October when aphids are still fl ying, he adds.
“The earlier a crop is infected, the more severe the symptoms tend to be with a harsher yield penalty as the plants have less seeds or pods. Early drilled crops that are more open, cor- responding with mild autumnal con- ditions, are at the highest risk.” Aphid numbers have increased because controlling them has become harder with the loss of neonicotinoid seed treatments. Getting the timings right for sprays is diffi cult, so TuYV inoculum is building up in the envi- ronment.
“Once an aphid is infected, it is in- fected for life, “ says Mr Charlton. “If an uninfected aphid feeds on an infect- ed plant, the aphid becomes infected and so the cycle continues – producing fewer side branches, pods, and seeds per pod.”
Hard to detect
Even severe symptoms can be hard to spot, so TuYV often goes undetect- ed. Combined with the loss of neon- icotinoids, this can make it particu- larly hard to diffi cult to control early infection.
TuYV is increasingly widespread, says Will Charlton
40 ANGLIA FARMER • JULY 2021
The value of genetic resistance to TuYV has been proven since Lim- agrain launched TuYV resistant va- riety Amalie in 2014, says Mr Charl- ton. Initially, resistance came with a
LG Anarion is
resistant to clubroot as well as TuYV
Clubroot variety offers pod shatter resistance
A new rape variety is being off ered to growers looking for Turnip Yellows Virus (TuYV) resistance and pod shatter protection in club-root infected areas. LG Anarion is Limagrain’s fi rst clubroot resistant variety
to off er high yields. Available to UK growers for the coming season, it is an exciting development, says Will Charlton, the company’s arable marketing manager. “Possession of these traits provides much needed on-
farm security to growers who are looking to improve their profi ts from oilseed rape, in areas that have until now, been challenging as a result of clubroot.” Clubroot typically causes losses of 0.3t/ha for every 10%
of plants aff ected. In Limagrain breeding trials, LG Anarion yielded 11% more than clubroot variety Alasco – further closing the yield gap associated with clubroot resistance. LG Anarion also off ers pod shatter resistance; a trait
which has recently been added to the recommended list. This can help secure yields and prevent untimely seed losses when weather is inclement later in the season. Other traits stacked into LG Anarion include the RLM7
phoma resistance gene. This provides resistance scores of 7 or 8. Breeding data suggests ratings of 6 for light leaf spot, 6+ for phoma and good tolerance to verticillium.
Turnips yellows virus is now endemic in the UK
“
yield lag, but innovative breeding has since overcome this. Today, hybrid and convention-
al TuYV-resistant varieties top the AHDB Recommended List – confi rm- ing the value of genetic resistance as a way to protect crops against heavy yield losses from the virus. Varieties carrying TuYV resistance rely less on insecticides, adds Mr Char- lton. In high-risk regions, as much as 80% of the total rape area is drilled with resistant varieties. “Genetic re- sistance is by far the best way forward.”
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