Matthew Clarke, Dekalb UK & Nordics OSR Breeder
Breeding varieties with a high output potential isn’t difficult. But combining this potential with the greatest performance ability under less-than-ideal conditions is far more challenging.
Monsanto has identified major differences in the ability of high output winter OSR hybrids to tolerate nutritional as well as other environmental stresses.
Our screening of more than 60 advanced breeders’ materials across a number of sites has revealed that even tolerant modern hybrids with their superior ability to compensate for environmental stresses typically lose 22% of their yield when nitrogen inputs are cut from
180 kg/ha to 120 kg/ha.
While the least tolerant lines suffer yield losses of 25% or more, however, we’ve found the most tolerant lose just 15% or less, opening up the prospect of substantial improvements through breeding to further boost the resilience and reliability of winter OSR.
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.
Employing no fungicides on sites with the greatest disease pressures has been instrumental in enabling us to develop robust varietal resistance. In the same way, delaying harvesting on particularly exposed sites has been vital in identifying 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 the clear 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; a capacity which depends on a number of 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 – whether intentionally or in challenging seasons.
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