Given agronomy challenges, pressure on inputs and volatile markets, what are plant breeders doing to help safeguard oilseed rape’s place in the rotation? Teresa Rush and Marianne Curtis report.
Changing markets and agronomy systems are among the key drivers of Matthew Clarke’s trait-based oilseed rape breeding programme at Dekalb, the output from which includes DK Extrovert; DK Imperial, the most widely grown Clearfield variety in the UK; HOLL variety V316 OL and semi-dwarf DK Secret.
Improvements in our understanding of OSR are also helping to direct breeding efforts, says Mr Clarke, although there are some areas – light leaf spot (LLS) resistance for example – where much more work is needed to help breeders.
He says: “I see some things increasing in importance, particularly as we see a reduction in inputs and growers have less time to undergo complex management strategies and this is why Clearfield has taken off in such a big way.
“I may have been saying this for several years, but I think semi-dwarfs will have a place in the future. The yield gap has been closer and once you reach the point where there is no yield gap and you can prove this to be the case, then why would people not be growing them? They don’t lodge, they are easier to drive through and easier to treat for things such as sclerotinia because they are more determinate.”
But while more generally there are benefits to OSR becoming more determinate, there may also be costs. One area of OSR agronomy which is receiving a lot of attention is flowering, with the aim of achieving a shorter, more even flowering period to help maximise light interception by the crop.
“Short, even flowering is important in terms of management of the crop. The unanswered question is ‘What do we lose if we go down that route?’ Because oilseed rape is still virtually a weed at the moment, it has weedy characteristics and will recover from all sorts of problems almost miraculously. If we remove this capability too much in order to make a determinate crop, where might this take us?
“On the other hand there have certainly been improvements in agronomy and now we see min-till approaches and wider rows, so breeders may be more able to produce varieties which suit those systems and are a bit more determinate and easier to grow.”
One area where OSR breeders have already delivered big improvements is in disease resistance, but challenges remain.
“We’ve got the double phoma resistance in most of our varieties and this has certainly been a massive bonus to growers in the UK and throughout a lot of Europe.
“But we are constantly on guard for any idea it might be breaking down and we have potential now to take resistance a stage further. Although it is not required in the UK at the moment, the existing resistance is working well.”
Any improvements to LLS resistance are likely to come from quantitative resistance controlled by several genes, rather than major gene resistance, the latter having proved vulnerable on more than one occasion in the past.
“We can get varieties up to ratings of 7+ for LLS resistance with quantitative resistance,” says Mr Clarke.
“But there is certainly an argument in the wider breeding community as to whether we are doing the right thing with LLS. Some varieties appear to perform well in Scotland and not in the South and vice versa. There is an idea there might be different races.”
In addition, some varieties which can become heavily infected seem to be able to grow through the disease and go on to yield well.
“If you look back, varieties such as Castille were supposedly poor for LLS but you could grow it even in Scotland and you’d get good yields at the end of the day. I think it is fair to say there should be more work done on LLS as there are gaps in our understanding.”
Another agronomy area in Mr Clarke’s sights is crop establishment. “Anything we can do to make establishment more reliable would be a huge benefit. This could include influencing how seed takes in moisture. One of the problems we see quite regularly in the UK is seed takes in moisture quickly and starts to germinate and then it dries up and it’s dead. Could we get round some of these problems?”
And while the technical challenges of growing oilseed rape provides targets for plant breeders, so too do changing markets.
“I think a movement towards HOLL could happen suddenly. The Iceland announcement, where they said they were not going to use palm oil any more, means they are going to have to look for a stable oil. Conventional rapeseed oil is not all that stable,” says Mr Clarke.
Another aspect of oilseed rape quality gaining attention and which may become a lot more important in the future is protein. Research into the increasing use of OSR meal for animal and human foodstuffs is already underway in France.
“The increasing importance of local sourcing is going to have an impact on oilseed growing and the way people think about the crop.”
Clubroot, turnip yellows virus (TuYV) and verticillium wilt are among other oilseed rape diseases breeders are targeting.
Limagrain variety Amalie was the first TuYV-resistant variety to be marketed in the UK, gaining a specialist category recommendation on the 2016-17 AHDB Recommended List, while Architect, also from Limagrain, was the first TuYV-resistant hybrid to be added to the List for 2018-19.
LS Plant Breeding clubroot-resistant varieties have included Cracker, which joined the Recommended List in 2011/19 and more recently Mentor, listed currently. Crome is presently in candidate trials and further material in National List 1 trials.
LS Plant Breeding’s Theo Labuda says: “The first clubroot resistance was found in kale and we had to try and breed the resistance from kale into OSR which took many years. Once you produce a resistant variety, breeders use it to produce the next generation of clubroot resistant material, but it has always got the same basic resistance. There has been quite a lot of work in trying to bring in extra resistance genes, but it is a very long process.”
After several years of just missing out on Recommended List (RL) status for his oilseed rape varieties, independent oilseed rape breeder, Mike Pickford’s patience has shown dividends with two of his varieties, Elevation and Broadway, marketed by DLF, making the 2018/19 RL (Northern region).
Mr Pickford carries out his selection work in the north Cotswolds and says if a variety can succeed there, with its altitude, susceptibility to drought in dry weather and claggy, cold soils when wet, then it can grow anywhere.
Breeding what the farmer wants is Mr Pickford’s key objective and he believes in letting growers decide on seed rates.
“They are looking for consistency and yield potential and there is still a long way to go. Ultimately, yield potential is eight tonnes. A crop of Elevation in Suffolk did more than 7t/ha and cleaned up at 6.9t/ha.
“With good soil, the right sowing time, good growing conditions and agronomy, there is no reason why we should not be getting 5t/ha but at the moment the national average is just under 4t. Oilseed rape needs attention – particularly in the beginning.”
While maximising yield is a combination of breeding and agronomy, starting with good genetics is vital, he says.
“The main component of seed yield is the number of seeds per pod and there are big genetic differences in the number of seeds between varieties. It depends on the season but it is 20-30 seeds per pod for most conventional varieties. For Elevation I have seen seed numbers/pod of 30-plus and even up to 40.”
Looking ahead, Mr Pickford is interested in whether there are varietal differences in tolerance to cabbage stem flea beetle, which he believes has become a problem as a result of growing OSR crops too close in the rotation.
“Growing rape every two years is not on. It is too frequent. At the moment I believe all varieties can be affected by cabbage stem flea beetle but there are differences in their growth habit. You need good germination. It doesn’t matter whether plants are flat or erect, you want good establishment.”
He is also working on breeding a variety, codename P42, with a different genetic component for resistance to LLS from existing varieties, which will enter national list trials this year.
“The hope is it will offer better resistance than available currently,” says Mr Pickford.
Tolerance to turnip yellows virus (TuYV) is also receiving attention in Mr Pickford’s trials, with the aim of breeding a variety with good tolerance which is earlier maturing, taller and higher yielding than currently available.