Most modern varieties have the genetic potential to deliver well over the sort of gross outputs most growers are likely to see in commercial practice.

By Rob Jones

There are eight (42%) of the 19 varieties making up three quarters of this season’s winter OSR plantings that have never been on the AHDB Recommended List.

Interestingly too, only half of the 20 varieties on the 2018/19 RL – and none of those newly-added to the List for the season – are among the most popular varieties currently in the ground.

This is the reality revealed by the latest intelligence from the industry-leading, 400-strong Kleffmann Group WOSR AMIS farmer panel, a group carefully selected to be representative of British growers.

                                                            2018 Winter OSR Variety Performance on Farm

Source: Kleffmann Group WOSR AMIS farmer panel 2019; * Figures exclude all Clearfield, clubroot and specialist oil varieties

And it’s an even more dramatic position with the hybrids that make up 11 of the 19 most popular varieties. Of these, almost two thirds have never been on the RL.

Four of this season’s five most popular conventional varieties are on the 2018/19 RL, while the fifth was a candidate not added to it. In complete contrast, four of the five most wide-grown hybrids aren’t on the List and have never even been candidates for Recommendation.

What’s more, this pattern has been remarkably consistent over at least the past five years, pre-dating the widespread growing of the Clearfield (CL) hybrids that have never been recommended but currently account for nearly 15% of total UK plantings.

So what do the best hybrid varieties have – apart from unique traits like CL – that makes them so sought after by growers, and why do so many of them fail to gain Recommended List status?

Mathew Clarke, senior breeder with Dekalb, is responsible for two varieties that have recently become grower favourites – DK Extrovert and DK Exalte. Neither of these, along with a number of others he’s helped bring to market, have ever featured on the RL.

“Of course, it’s satisfying seeing varieties like DK Expansion and DK Exsteel gaining official Recommendation,” he says. “But our breeding programme doesn’t lend itself to Listing simply because we don’t put gross output potential before anything else. Instead, we select and test for a series of traits we know to be important in farm production, doing so under the most challenging conditions. Then we take forward the best-performing of these.

“Employing no fungicides on sites with the greatest disease pressures, for instance, has been our key to developing the most robust phoma and light leaf spot resistance. Drilling later than normal and into difficult seedbeds has allowed us to identify the most vigorous-establishing and fast-developing lines. Delaying harvesting on exposed sites has been vital in securing strong resistance to pod shattering. And testing varieties widely at lower as well as standard nitrogen inputs is enabling us to develop varieties which lose less performance when nitrogen supply is restricted.”

Matthew believes this approach is why the Dekalb varieties tend not to come top of the tree in trials geared to out-and-out yield maximisation, especially when grown in small plots and to protocols designed to suit the average. “However, our parallel plot and field-scale trial work under far more typical agronomic regimes in the UK and across Europe shows they perform especially well on farm. Which is what our whole breeding effort is geared to do.”

He says the popularity and longevity of the programme’s hybrids show that this approach chimes with growers, who are prepared to try new varieties emerging from it in the absence of even RL candidature, simply because are Dekalb-bred.

It’s also evident in the independent data on the 2018 harvest gross output of more than 65 varieties in the latest Kleffmann Group WOSR AMIS farmer panel. These show mainstream hybrids out-performing conventional varieties by more than 0.3t/ha on farm (see chart above). Not only this, but the 10 Dekalb ‘Ex’ hybrids being grown – none of which were on the 2018/19 RL – enjoyed an even greater gross output advantage, at almost 0.5t/ha.

At Agrii, seed technical manager, David Leaper sees the RL as a good starting point for evaluating OSR varieties. But he and his colleagues look well beyond the information it provides in their recommendations, basing them on trial work designed as much to highlight varieties’ relative weaknesses as their inherent production potential.

“Most modern varieties have the genetic potential to deliver well over the sort of gross outputs most growers are likely to see in commercial practice,” he points out.

“So what we want to do in our trials with around 70 varieties across the country each year is identify the best from a grower’s point of view and tease out their particular agronomic strengths and weaknesses. That way we can complement the RL information with practical advice based on sound science to help growers make better variety and agronomy decisions.

“We replicate farm practice as closely as we can in our trials and drill at a standard 50 seeds/m² rates for hybrids and 70 seeds/ m² conventional varieties. This ensures we don’t discriminate against generally better-branching hybrids by sowing them too thickly and allows us to make the most meaningful comparisons of their autumn and spring growth habits and vigour.

“We find huge differences between varieties in their rate of autumn development – which isn’t measured in RL trials – enabling our growers and agronomists to match them far better to drilling slot and conditions for the best establishment,” explains David.

“This season too, we’ve seen clear correlations between levels of Cabbage Stem Flea Beetle damage and varieties’ speed of autumn and spring development. In both cases the most vigorous, faster-developing hybrids appear to have an important edge over the rest in their ability to tolerate infestations.

“We also know how important a good level of pod shatter resistance is in safeguarding yields and minimising volunteer problems. Verticillium wilt resistance is another area where we have to look beyond the RL for information. As is Clearfield variety performance and agronomy.”

ADM Agriculture head of seed, Chris Guest also looks beyond the RL to find varieties that will give his growers the year-in, year-out performance consistency they seek above everything else. Especially so in the face of the extra challenges the crop is facing from cabbage stem flea beetle.

“What we want is varieties that cope best with things like later sowing, difficult autumn or spring conditions, and slugs and pigeons as well as flea beetle rather than purely those that top the output charts when everything goes right,” he insists. “With today’s climate, we also want varieties that can survive summer storms or harvesting delays with minimal seed losses.”

Chris finds RL ratings for phoma, light leaf spot and lodging resistance valuable, and agrees that the system has the advantage of independence.

However, he finds small plot trials can be a poor predictor of how hybrids, in particular, perform on farm. This is mainly due to the fact that they need sufficient space to develop the most productive canopies and the opportunity to show the superior abilities to compensate for setbacks he knows the most robust varieties have.

“Autumn vigour and the ability to grow away from pest problems in the spring are key things we need in varieties today,” stresses Chris. “DK Exalte is a great example of a variety that has really delivered for our growers here, as well as in disease and pod shatter resistance and standing power. Yet we’d completely have missed it if we were just relying on data from the RL.

“So, we keep a close eye on what the breeding programmes we trust are coming up with, identify the varieties that have the things we’re looking for at an early stage, and work with our growers to try them out alongside their current favourites.

“At the moment we’re particularly excited by DK Exstar. It really ticks our boxes for its all-round strength and robustness. We can see it becoming another farmer favourite for these reasons.”

Output ratings immaterial in Borders

Official output ratings are not something Scottish Borders grower, David Fuller-Shapcott of Sweethope Farm just outside Kelso considers important in his OSR variety selection. Yet he’s brought in yields averaging more than 5t/ha-plus in the past and, at 4.9t/ha, his 2018 YEN crop of DK Exclaim was within the top third of entries for percentage of estimated yield potential.

Instead he looks for high oil content, strong phoma and light leaf spot resistance, stem strength and pod shatter resistance in his varieties, associating these genetic traits with reliable performance. He also prioritises varieties that suit his decidedly challenging soil conditions and particular growing regime.

“OSR always does best at low seed rates,” says David. “The last thing we want is mustard and cress. We’re after plants that are big and bushy rather than tall and tree-like. These give good light-intercepting canopies that don’t need much growth regulation.

“Hybrids like DK Expansion and DK Exclaim which are very vigorous but don’t take off too early in the spring before our ground warms up enough to provide the nutrition they need suit us well. These are important things that RL testing simply doesn’t tell us about.”

A stand-out performer?

Following in the footsteps of DK Extrovert and DK Exalte is the latest variety from the Dekalb programme, DK Exstar.

The first mainstream ‘double low’ to boast across-the-board ‘8 or greater’ ratings for phoma resistance, light leaf spot resistance, lodging resistance and stem stiffness, it has a vigorous establishment with rapid autumn development, says the breeder. It also carries pod shatter resistance, familiar mid-flowering and maturity ratings, and had an official gross output rating of 105% of controls as an RL candidate.

“DK Exstar joins our portfolio with the most complete agronomy package we’ve ever seen,” says Dekalb technical specialist, Will Vaughan-France. “Like most of our hybrids, you won’t find it on the RL. But we’re every bit as confident in its on-farm abilities as we were with both DK Extrovert and DK Exalte – which it has out-yielded by a good 0.4 t/ha at a similar 45%+ oil content in our untreated trials.

“We’ve found the variety suits a wide range of sowing dates, including later slots. Although equally vigorous in its spring growth, it doesn’t go into stem extension quite as early as some, making it especially well-suited to heavier soils and colder sites where early nutrient availability can be restricted.

“A market-leading combination of phoma stem canker and light leaf spot resistance offers flexibility in fungicide treatment, while high levels of lodging resistance and stem stiffness allow spring spray programmes to optimised for canopy structuring.

“DK Exstar is very definitely a step forward in OSR robustness and risk management,” he notes. “It has all the makings of another firm grower favourite.”