Driving OSR resilience with precision breeding

Precision breeding techniques

Precision breeding techniques are driving the development of new oilseed rape varieties with greater resilience and better yield stability for growers. We take an exclusive look at Europe’s leading oilseed rape improvement programme.

The precision breeding being pioneered across the Dekalb network is a huge step on from traditional breeding methods that focus on selecting and crossing the best material available, according to OSR development lead, Fabien Poree, of Bayer’s breeding facility in Boissay, France.

The new “rapid-cycling, design-led hybrid development” approach focuses on understanding how oilseed rape genetics interact with the soil, water, pests, disease and other characteristics of production environments, and designing genomes that make the most of them.

Mr Poree believes such techniques are the best way of building the greater environmental resilience oilseed rape growers need in a constantly evolving process, to keep-up with environments that are changing more rapidly than ever.

“All the environmental and performance information we gather from testing materials across more than 50 very different UK, Nordic and continental locations is continually adding to our vast database of detailed genetic profiles.”

In turn, this informs the artificial intelligence-led hybrid “engine” – essentially a massive database and set of algorithms – the team uses to predict the optimum genetic combinations that will perform best in specific environments.

Stable performance

Yield stability across sites and years is a key driver behind the work, stresses Dekalb’s Boissay-based breeding programme lead, Julien Binet.

“Major differences between lines in this important characteristic are allowing us to prioritise genetics that offer yield stability, as much as just yield maximisation.

"Genetic finger-printing and thorough testing across all our germplasm means we are identifying and utilising whole blocks of genes associated with superior performance under particular conditions, rather than just individual traits.

“Our process is one of continued cycling and testing to redefine the most valuable genetic combinations.

"That way, we are always designing and producing the most consistent, high output varieties for the future.”

The Dekalb breeding engine takes full advantage of the work of discovery plant health scientist, Maria Arce and her colleagues charged with developing increasingly robust disease and pest resistance and tolerance traits. Again, data is their biggest resource and sophisticated models their most important tools.

“We have active programmes identifying the genetics that offer the greatest protection against cabbage stem flea beetle, Phoma, light leaf spot, verticillium and sclerotinia amongst other biotic challenges,” she says.

“Rather than just focussing on individual genes here, much of our work is on building-up strong bases of quantitative resistance, involving large numbers of genes working together.

“Stacking major genes is all very well and may deliver short-term advantages, but it puts particular selection pressure on the organisms targeted. The whole genomes we are developing have far more durable all-round defences.”

Building the genetic package

Precision breeding is taking Dekalb’s history of pioneering traits, such as double Phoma resistance (in which the major Rlm7 gene is protected against breakdown by a raft of minor genes), several steps further.

Amongst other things, it enables a number of plant growth and development characteristics, such as vigorous development before winter and rapid spring regrowth, that aid crop recovery from a range of setbacks, to be reliably incorporated into the genetic package.

“At the same time, we are substantially widening the genetic separation of our pools of male and female parent lines – all of which, we must remember, came from the same ancestors only around half a century ago,” notes UK breeder, Matthew Clarke.

“This enables us to maximise the genetic variation we are working with, and the 1+1=3 effect of hybrid vigour, which increases with the genetic distance between parents.”

The complex Brassica napus genome, with no less than eight copies of some genes, provides a tremendous resource to improve the level and resilience of crop performance. While hybrid programmes have accelerated rates of gain over the past two decades, their potential has arguably been limited by a reliance on the traditional ‘cross-select and-prove’ approach and a narrower than ideal diversity of parent lines.

New varieties coming

The Dekalb team accepts the complete transformation of their breeding efforts has meant something of a hiatus in bringing varieties forward in the past year or so. However, as well as opening the door to far broader genetic progress, it promises to significantly cut the cycling time from one generation of varieties to the next, from its current five years, while at least doubling rates of genetic gain.

“We have a strong pipeline of hybrids coming forward over the next two years,”

concludes Mr Poree. “And, with the first varieties from our new programme due to enter national testing from 2024, we confidently expect them to be providing growers with as much of a step forward in performance as Excalibur, DK Extrovert and DK Exalte did in their time.”

Unravelling the genetics of resilience

Understanding the genetics behind several key plant development stages, to make winter oilseed rape more resilient to the changing climate, is the focus of a major five-year UK research effort.

BRAVO (Brassica, Rapeseed and Vegetable Optimisation) brings together the John Innes Centre (JIC), Rothamsted Research, the Universities of Aberystwyth, Nottingham, Warwick and York, Bayer and other industry specialists.

“Up to now, most breeding has concentrated on the most responsive varieties for maximum potential under the best conditions,” explains JIC-based BRAVO project manager, Dr Rachel Wells.

“But what we really need for stability are varieties that perform well overall, but are less responsive to environmental variation.”

BRAVO project findings so far include: 

• Late autumn and early winter temperature variation has one of the greatest climatic influences on oilseed rape yield stability, with Castille genetics standing out as some of the most yield stable and least temperature sensitive

• Providing they are frost tolerant, earlier flowering varieties could be advantageous in allowing the longest pod-fill with the least vulnerability to high summer temperatures and drought

• The pollen viability of some lines is noticeably less affected by cold and heat than others

• There is plenty of variation between lines in ovule number, early pod abortion and seed development

• Early vigour is more dependent on the environment under which seed is produced than seed size, with warm temperatures and lack of stress during seed set particularly Important

While it is too early to define specific traits that make the most resilient oilseed rape varieties, the BRAVO researchers have no doubt the understanding they are gaining about the genetics of key transitions has great potential to build extra resilience into the crop – whether through reduced sensitivity to key stresses or a greater ability to recover from them.

“The work we are doing is revealing the genetic fundamentals behind the way brassicas respond to the most important environmental triggers,” Dr Wells concludes.

“Marry this understanding with today’s genetic technologies and I’m confident our industry will be able to breed much greater tolerance to important climatic, pest and disease stresses, into oilseed rape in the coming decade.”

Tolerance to nitrogen stress

The particular nitrogen stress tolerance of two current Dekalb TuYV-resistant hybrids has stood out in restricted fertilisation trials for the second year in a row, with both varieties showing valuable improvements over the leading N-Flex hybrid control, and the trial average.

The replicated, three-site 2021/22 studies conducted under farm regimes show the gross outputs of six top performing EX and competitor hybrids averaging between 3.9 t/ha and 4.1 t/ha, and falling by an almost identical 0.7 t/ha when total nitrogen rates were cut from 180 kg/ha to 100 kg/ha.

A more realistic 40 kg/ha reduction to 140 kg/ha led the average gross output reduction to almost halve to 0.36 t/ha.

There was much greater variation between the varieties here, though, with DK Excited and DK Exposé the only varieties to lose noticeably less output than the average, at 0.17 t/ha and 0.27 t/ha respectively.

In contrast, the gross output of the least nitrogen stress tolerant variety in the trial was reduced by nearly 0.5 t/ha, and even the leading hybrid with the N-Flex nitrogen use efficiency trait lost 0.42 t/ha.

This article is an extract from CropFocus magazine, if you would like to sign up for the next issue please sign up here