Dedicated breeding work is helping to ensure a pipeline of oilseed rape varieties continues to set new standards – despite the challenge of cabbage stem flea beetle.
With rape more difficult to grow, developing varieties that better stand up to flea beetle is a priority. But higher yields remain key too, with nitrogen utilisation efficiency also an important area of development work.
Three years of challenging weather – ranging from dry conditions at sowing to last year’s record-breaking wet autumn – have highlighted the resilience of modern rape varieties, says Sarah Hawthorne, of plant breeders DSV.
“The inherent high vigour of modern hybrids undoubtedly has much to do with this, but the focus on developing varieties with deep taproots and large branching root architectures has also really come into its own in recent years.”
Turnip Yellow Virus (TuYV) resistance has also helped growers mitigate the impact of the yield robbing disease. With little effective chemistry now available, genetic resistance is the only viable way to control TuYV-carrying aphids.
Evidence is growing that such varieties are able to handle abiotic environmental stresses much better than other non TuYV resistant varieties which has also contributed to their yield stability, says Ms Hawthorne.
“Features such as better resistance to light leaf spot and RLM7+ multigene resistance to phoma stem canker and physical traits such as pod shatter resistance also mean the latest ‘triple layer’ varieties are better than anything that has gone before.”
DSV breeders are already focusing on varieties with better drought and heat survival – as well as faster root growth – to protect against oxidative stress when under stagnant water, Ms Hawthorne adds.
“Building on the success of our triple-layer oilseed rape varieties, DSV quad-layer varieties are now being introduced adding even greater production resilience and reliability for growers.
“Depending on the variety and its application, the fourth layer can vary to include characteristics such as verticillium wilt tolerance, clubroot resistance or Clearfield technology added to the mix.”
There are currently two new DSV quad-layered varieties entering the UK testing system. The first is a high output hybrid oilseed rape featuring multi-gene phoma stem canker, TuYV, pod shatter and clubroot resistances.
“With clubroot an increasing problem in the Borders and Scotland this will be a variety particularly relevant to the North of the country, although there are signs that the disease is becoming an issue across the UK now.
“The second of these is a Clearfield variety which features phoma stem canker resistance together with TuYV and pod shatter resistance.
“This will sit well alongside the other layered varieties in the Clearfield portfolio and the incorporation of TuYV resistance will reduce dependency on insecticides to control the vector of what is becoming a significant disease in the UK.”
Many UK growers are starting to see that Clearfield technology adds significant benefits to oilseed rape production over the expected better control of pernicious brassica weeds, says Ms Hawthorne.
“The Clearfield system of Imazamox herbicide and oilseed rape varieties resistant to it has made reliable control of problem weeds such as charlock, runch and hedge mustard a reality in recent years.
“The system’s efficacy is such that even fields that have been out of production for many years due to large burdens of these weeds, can be made suitable for oilseed rape once more.
“Furthermore, many growers had identified the high cost of pre-emergence weed control from metazachlor-based products as being one of the most expensive elements of their establishment management.”
The added flexibility Clearfield provides around early weed control strategies means the technology can also be used help fine-tune time of drilling and reduce competition during establishment, she adds.
“The DSV varieties Plurax CL and Phoenix CL have proved very popular in recent years by combining Clearfield functionality with yields rivalling some of the highest outright yielders on the RL, but the new quad layer varieties will lift the bar even higher.
“It might be a few years before growers have the confidence to build the UK OSR area back up to the levels before the Neonicotinoid ban, but modern varieties continue to give them the best opportunity to benefit from this valuable crop.”