With Clearfield varieties gaining renewed interest, the focus is shifting firmly onto performance as well as flexibility. CPM looks at LG Calvin CL to understand how breeding, agronomy and on-farm experience are combining to shape the next phase of OSR development.
“Yield is critical but it must be delivered alongside good establishment and overall agronomic security.” CORETTA KLOEPPEL-WOODS
by Charlotte Cunningham
For any grower, the decision to introduce a Clearfield oilseed rape variety rarely comes without reason. More often than not it’s driven by a specific rotational challenge – a field where brassica weeds, volunteers or legacy issues have become difficult to manage through conventional approaches.
While Clearfield has historically been seen as a compromise on the yield front, recent breeding progress is beginning to change that perception… Enter LG Calvin CL – a Clearfield hybrid variety aiming to shift the dial, bringing together herbicide tolerance with a fully loaded agronomic package and competitive yield.
For Coretta Kloeppel-Woods, who heads up winter OSR breeding at Limagrain’s Rothwell site, that shift reflects a deliberate focus on developing varieties that are not only productive, but also consistent and resilient within UK growing conditions.
“We’re breeding specifically for a maritime climate – so that’s the UK, but also northern Europe,” she explains. “Everything starts here, from the initial crosses through to the early stages of hybrid development, which means we’re selecting material under the same kind of conditions growers are facing in the field.”
That local focus is important she adds, not least because OSR performance is increasingly dictated by how well varieties cope with variability – whether that’s drilling conditions, pest pressure or weather extremes.
“With Calvin, we were very much focused on what farmers require now,” says Coretta. “Yield is critical, but it must be delivered alongside good establishment and overall agronomic security. One aspect that stands out is its autumn vigour, which helps to give the crop a strong start and supports consistency later on.”
Establishment remains a key battleground for OSR, particularly where drilling windows are tight or conditions are less than ideal. As such, traits that help crops to establish quickly and evenly continue to carry significant weight within breeding programmes, believes Coretta.
Alongside this, there’s an increasing emphasis on resilience traits and longer-term risk mitigation, she adds. “We’re putting a lot of effort into areas such as cabbage stem flea beetle resilience.
“Even if pressure isn’t as high in all regions now, it’s something growers still want confidence in. At the same time, we’re looking ahead at potential disease threats and making sure we’re prepared for those.”
That forward-looking approach is essential given the time lag between initial breeding work and commercial release. “It can take close to a decade to bring a variety to market,” she notes. “So we have to consider what challenges growers might face in the future, not just what they’re dealing with today.”
Advances in breeding technology are also playing an increasing role in that process, with genomic selection, drone imaging and phenotyping tools helping to refine decision-making and accelerate progress.
For Florentina Petrescu, OSR and sunflower product manager for Limagrain UK and Ireland, Calvin represents a point where breeding progress and market demand are beginning to align more closely.
“We’ve seen a clear increase in interest in Clearfield varieties, largely because growers are dealing with more brassica weed pressure,” she explains. “That’s driving demand for solutions that allow them to retain OSR in the rotation without compromising on crop performance.”
Historically, that compromise has often been a sticking point, with Clearfield varieties perceived as offering flexibility at the expense of yield or agronomic strength. However, that balance is shifting, believes Florentina.
“On the AHDB Recommended List, Calvin is delivering a gross output of 94% for the UK – making it the highest yielding Clearfield tolerant variety,” she says. “Importantly, that performance is consistent across regions which is key given the variability we see between seasons.”
Consistency across the UK remains a critical consideration, particularly where data sets can be limited and growers are looking for reassurance that a variety will perform reliably across different conditions, suggests Florentina.
Alongside yield, the variety brings a comprehensive agronomic package. “It combines turnip yellows virus resistance with pod shatter resistance, which are both important traits,” she highlights. “You also have strong autumn and early spring vigour, shorter plant height and good stem stiffness, all which contribute to overall performance.”
Disease resistance is another factor where the variety stands out within the Clearfield segment. “It has one of the strongest light leaf spot scores (6) available in this sector. As a key disease for many growers, having that level of resistance provides additional security within the programme,” says Florentina.
Considered together, these traits are designed to provide a balanced approach, combining flexibility with the agronomic performance typically associated with conventional hybrids.
From a technical standpoint, one of the most significant developments has been the extent to which Clearfield varieties are now closing the gap on conventional material. According to Limagrain’s Liam Wilkinson, that shift has been central to the renewed interest in the system.
“A few years ago, when OSR prices were lower, it was more difficult to justify Clearfield because of the perceived yield penalty and higher input costs,” he says. “Now, with stronger crop values and improved genetics, that calculation has changed.”
As a result, Clearfield is increasingly being viewed not just as a niche solution, but as a practical option for managing specific challenges within the rotation, believes Liam.
“It allows growers to bring problem fields back into production; particularly where there are issues with brassica weeds, volunteers or fields coming out of certain stewardship or contract situations.”
A key part of that is the flexibility offered by the herbicide system, adds Liam. “You have the option to clean up fields post-emergence once you know you have an established crop,” he says. “That reduces reliance on pre-emergence programmes and gives growers more control over how they manage those situations.”
Importantly, Calvin combines that flexibility with a full agronomic package, points out Liam. “It brings together traits like pod shatter resistance, TuYV resistance and good disease scores, but without sacrificing yield. Structurally, it’s also slightly shorter and more compact (152), which helps in exposed conditions.”
With a lodging resistance score of 7.9 and stem stiffness of 8, the variety is designed to stand well, even where crops are subject to wind or variable weather.
And from a management perspective, Liam emphasises that integration into existing systems should be straightforward. “It doesn’t require a different approach compared with other hybrids, Growers can manage it in the same way, but with the added benefit of Clearfield chemistry when it’s required.”
Beyond the field, the role of Clearfield within wider rotation planning is also evolving, particularly as market dynamics shift. For Beckii Gibbs of United Oilseeds, that broader context is an important part of the conversation.
“Calvin continues to stand out as a strong option for growers considering Clearfield technology. As the highest-yielding Clearfield hybrid on the RL this year, it brings a high level of agronomic security, including turnip yellows virus resistance and pod shatter resistance.
“It’s a particularly valuable choice where brassica weeds are a challenge, offering a practical solution within the rotation.”
At the same time, external market pressures are shaping how growers approach variety selection, adds Beckii. “Clearfield remains an important tool where growers are following HEAR production. With some uncertainty around the future of the UK HEAR market, we expect the Clearfield segment to remain relevant as growers look to manage risk and maintain flexibility.”
This article was taken from the latest issue of CPM. Read the article in full here.
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