Seed Varieties: Look beyond traditional traits for improving OSR productivity

Much of the gap between the production potential of many modern OSR varieties revealed by official trials and the consistency of their performance in the field can be explained by their vulnerability to less than ideal conditions at any stage in the season, suggests Matthew Clarke of Dekalb. 

“With ever-increasing workload pressures and far more variable weather we have to cope with these days, it’s becoming more and more difficult to give every crop just the right establishment conditions, slug and pigeon protection, fungicide spray timing and harvest management, to name but a few crucial agronomic considerations. 

“It really isn’t surprising many varieties are failing to live up to their initial promise in carefully-controlled, small scale trials.”

Mr Clarke’s experience in developing some of the most widely-grown varieties – Castille and Excalibur – convinces him the way to overcome this dilemma is to look beyond traditional traits such as lodging resistance, stem stiffness and stem canker/ light leaf spot resistance to characteristics with particular practical relevance to modern OSR growing conditions.

Factors include establishment vigour to enable reliable drilling into mid-September and under more challenging seedbed conditions; spring vigour to give the most effective recovery from pigeon damage and frost kill; crop manageability to give the greatest leeway in spraying for disease control and growth regulation; and harvestability for the most rapid, trouble-free combining with the least possible seed loss.

Variety choice

“Together with improved marketability to deliver the highest and most stable gross outputs of the right oil specification, improvements in these characteristics are key to the more reliable and valuable oilseed rape varieties we need these days,” he says.

 “Excalibur made everyone aware of the value of establishment vigour last autumn. While many other varieties failed to cope with late-sowing under difficult conditions, it proved OSR could be successfully established from mid-September sowings across much of the country.

It really isn’t surprising many varieties are failing to live up to their initial promise in carefully controlled, small scale trials.

Matthew Clarke

“This can be very helpful in relieving workload pressures where there are large acreages to plant as well as giving more time for pre-planting weed control and improving the effectiveness of propyzamide.

It is vital to appreciate autumn vigour is not a characteristic of all hybrid varieties, says Mr Clarke.

“As many growers found to their cost in the past year, some hybrids can be very disappointing in the speed and strength with which they get their feet down ahead of the winter.

“While the best hybrids are generally better than the best pure lines for this characteristic, growers need to be careful with their variety choices.

“The same is true of the separate character of spring vigour, which relates to the ability of varieties to grow away from the winter.

“As well as this difference, it’s easy to mistake earliness of stem extension for spring vigour. What we really want to do is compensate for pigeon or frost damage with a variety that builds extra leaves and vegetative structure, rather than just shooting upwards into its reproductive phase at the earliest opportunity.

“In addition to creating a far better performance base, this makes the crop inherently more robust and better able to handle lodging challenges.

“Rather than going by vigour scores, which can be highly subjective and vary widely between different assessors, good autumn and spring vigour can best be ensured by selecting varieties under difficult conditions in breeding trials. These can then be tested widely in challenging environments,” he says.

Flexibility

In terms of manageability, relative shortness is a great virtue when it comes to spring and early summer spraying.

It allows very much more flexibility in the timing of growth-regulating fungicides, which is especially valuable with large acreages to manage.

Accompanied by a good strength of stem, it means crops are far less likely to lodge in summer storms.

Low biomass hybrids such as DK Secure give a new choice to growers in situations where this characteristic is highly desirable.

Good disease resistance is also an important component of manageability. “Low biomass is undoubtedly a widely-sought characteristic, but relatively tall varieties that respond well to the best management are also valued by many.

For growers across the bulk of England, these do need to have good stem canker resistance. 

Again, this makes the timing of sprays less critical and lodging less of a concern.

“Light leaf spot resistance is more important for northern growers. There is a broad spectrum of resistance or high

level of tolerance to these and other important brassica diseases in variety backgrounds, in both cases to guard against major resistance breakdowns, and increasingly important pathogens like sclerotinia, club root and verticillium.”

Mr Clarke also prioritises varieties’ speed and ease of harvest and low seed loss risk.

Alongside a manageable height for direct combining and good straw strength, he sees evenness of ripening, tolerance to pod shatter and varieties with a range of maturities as especially valuable in this context.

“Traits like evenness and pod shatter may be difficult to measure, but we are able to build on observable differences in pure lines and hybrids in both respects in our programme,” he says.

Bringing forward these additional management characteristics takes time and invariably means compromises to achieve the best all-round improvement.

“However, with advanced hybrid breeding allowing us to use heterosis to boost output, while introducing new traits of value far more rapidly than in the past, we are successfully moving beyond traditional traits in our breeding to deliver increasingly valuable commercial grower returns,” says Mr Clarke.

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