Better disease resistance ramps up rape protection

New genetic resistances to two serious and costly diseases affecting oilseed rape could be available to growers in the next few years, say breeders DSV.

Breeder DSV says its Phoma Blocker trait – a new genetic mechanism for resistance to phoma stem canker in Europe – is already included in varieties going through UK testing, with enhanced clubroot resistance CRE1 close behind.

Phoma stem canker in rape costs UK growers some £100m annually in lost yields and disease management, says Simon Kröger, DSV’s leader for product management in oilseed crops.

“Resistance to phoma results in better and longer lasting plant health with better lodging resistance as well as a longer and undisturbed assimilation process that supports growth through tough climate conditions such as early summer drought.

“It also underpins optimum harvest date and can lead to higher yields as well as reducing the general level of phoma spores in the field.”

The main genetic disease resistance mechanism for many years has been RLM7, which is seen as an industry standard. But Mr Kröger says there is growing evidence it is becoming less effective.

In DSV trials in Dyngby in Denmark, for example, on a scale of 0-10 with 0 being excellent resistance and 10 being high susceptibility to Phoma, varieties without any qualitative resistance showed an average score of 7.5 with a range of 6.5 to 8.5.

Wider range

Varieties with the RLM7 gene showed a wider range of phoma susceptibility scores – from 4 to 9 – but of real concern is that the average was the same 7.5 as varieties with no disease resistance at all, says Mr Kröger.

“When you consider 53% of oilseed rape varieties on the 2023/24 AHDB Recommended List for the UK rely on RLM7 as the mainstay of their protection against this yield-robbing disease, clearly this is a very worrying situation.”

RLMS provides some hope DSV Phoma Blocker adds a much-required extra layer of future-proofed security, believes Mr Kröger. “At the heart of Phoma Blocker is LepR1 – a completely new type of genetic mechanism for phoma resistance in Europe.

“While LepR1 by itself has been shown to have the best resistance to the most common phoma strains in field trials across Europe, we believe it is most effective when used in conjunction with other disease resistance traits.

“DSV Phoma Blocker is made up of LepR1 with RLM7 and this combination achieved an average of score of just 2.3 in the Dyngby trials – compared to the 7.5 for RLM7 by itself.”

But the real advantage is that DSV now has varieties featuring all three different phoma resistance mechanisms: RLM7, RLMS and LepR1. These can be rotated in the field to minimise major breakdown of any one type of resistance, adds Mr Kröger.

This has taken phoma resistance in rape several stages on, he adds. DSV already has Phoma Blocker varieties moving through the UK testing process, with the first of these set to be commercially available in 2024.