Screening of more than 60 advanced breeders materials across a number of sites shows that even tolerant modern hybrids with their superior ability to compensate for environmental stresses typically lose 22% of their yield when nitrogen inputs fall from 180 kg/ha to 120 kg/ha. While the least tolerant lines suffer yield losses of 25% or more, however, the most tolerant lose just 15% or less, opening up the prospect of substantial variety improvements through breeding.
“Breeding varieties with a high output potential isn’t difficult,” explained Monsanto’s European head of breeding, Jean-Pierre Despeghel to visiting growers and specialists from the UK, Ireland, Nordics and Baltics at the company’s Boissay breeding headquarters in the Paris basin. “But the whole focus of our work is to combine this potential with the greatest performance ability under less-than-ideal conditions. This is far more challenging.
“We want varieties that perform consistently well from site to site and year to year; varieties that deliver the best margins as well as yields and oil contents; and varieties that lose the least possible output when conditions are sub-optimal.
“More than 30 years of oilseed rape breeding experience across Europe have taught us that the best hybrids have a much greater capacity to compensate for a whole range of environmental stresses than pure lines.
“We’ve been able to extend this resilience significantly in recent years by introducing vigorous establishment, double phoma resistance, pod shatter resistance and low biomass traits into our Dekalb hybrids To these we are currently adding robust light leaf spot and even stronger phoma resistance. And, with our latest studies, we’re actively working to build-in extra nutritional stress tolerance too.”
As well as providing valuable additional yield protection against growing climatic variability, Jean-Pierre Despeghel and his Monsanto breeding team see their emphasis on breeding for stress tolerance alongside output as vital in securing the future of European oilseed rape production in the face of current and future legislative and economic pressures.
Foremost amongst these are greater restrictions on nitrate and pesticide use for environmental protection, the progressive loss of plant protection products through the re-registration process, and increasing growing costs.
They stress that, on average, winter oilseed rape costs more to grow per hectare than any other European field crop with the exception of grain maize. What is more, they can only see input costs continuing to rise with an increasing area under OSR and intensity in the rotation as well as output expectations. This will make varieties producing more from less increasingly sought-after.
Screening parent materials and testing developing hybrids in parallel under high stress as well as standard breeding environments is the best way of ensuring the progress they seek, the study tour was told by OSR breeder, Laurent Verdier.
At the same time, he pointed out that it allows them to identify the characteristics responsible for high output resilience so they can build on them to greatest effect by both conventional and marker-assisted breeding and selection.
“Employing no fungicides on sites with the greatest disease pressures has been instrumental in enabling us to develop robust varietal resistance,” he said. “Delaying harvesting on particularly exposed sites has been vital in securing pod shatter resistance; growing nurseries in the most extreme continental locations in ensuring high levels of winter hardiness, and drilling later than normal and into difficult seedbeds in pinpointing the most vigorous-establishing lines.
“We’ve always appreciated the impressive powers of recovery oilseed rape possesses and we’ve long recognised the superiority of hybrids in this respect. But only by strictly limiting nitrogen inputs on a number of breeding sites are we seeing just how widely high output hybrids differ in their ability to tolerate nutritional stress. This has opened some very exciting doors for future variety development.
“Our studies suggest environmental stress tolerance is linked to a superior capacity for branching in general and branching from low down on the stem, in particular,” reported Laurent Verdier. “A capacity which depends on a number of essential hormonal factors – primarily those involved in apical dominance.
“We are well-advanced in developing hybrids which combine the highest possible output under optimal nitrogen levels with the least output penalties when nitrogen supply is seriously constrained. Added to continued developments across a range of other yield-protecting traits, we are confident these will be able to deliver the increasing levels of crop sustainability European growers will need for the future.
“The fact that the capacity to compensate can only be fully exploited where plant populations are not too high underlines the need for appropriate agronomy as well as variety choice in making the most of the more and more resilient high output hybrids we are breeding,” he added.