Hybrid oilseed rape varieties have been available in the UK for about 20 years, but it is only now their true potential is starting to be realised, according to the Bayer CropScience UK seeds business manager Adrian Cottey.
Outlining the merits of Fencer, the company’s latest addition to the HGCA Recommended List, Mr Cottey said he expected hybrids would follow the same development path as maize.
Early maize hybrids had provided steadily increasing yields. “But it was only after a decade or so of understanding and sorting out the germplasm, getting it organised and knowing what to cross that hybrids really kicked off with maize.”
Since then yields had risen markedly and growers had continued to buy hybrid seed even though its price had kept increasing. Only during the subsequent stages of the crop’s development had breeders been able to invest in making the most of specific traits, he said.
Oilseed rape hybrids were still in the equivalent first phase of development. “We’re quite excited by our early hybrids. But the theory is that there is quite a lot more to come that we’ve not seen yet.”
Earlier, oilseeds development manager Wade Stocker had described how the firm’s European InVigor model, based on ‘heterotic pool breeding’ was built on its success in North America.
Its strategy went well beyond traditional crossing of male plants known to produce good hybrids with a wide range of females and hoping for useful offspring, he said. The idea was to gather together pools of genetically isolated material, based on DNA finger-printing and field characterisation, from many sources for up to 15 years.
“We are trying to build isolated pools that we can work with to create tailor-made hybrids that fit certain conditions. It is the best way of taking advantage of hybrid vigour and heterosis.
“It is a strategy that has been hugely successful in Canada.” There the canola crop, all spring varieties, was 100 per cent hybrid.
However, for growers to exploit hybrids’ true advantages they had to be managed differently to conventional open-pollinated varieties.
“It is when they are grown properly the benefits really shine,” said Mr Stocker.
Some growers’ desire to farm-save seed to save perceived costs continued to act as a ‘drag’ on the uptake of hybrids, Mr Cottey acknowledged. But current farm-saving accounted for less than 10 per cent of sowings.
The RL system, however, was designed for conventional varieties not hybrids, he said. “The Recommended List system must not hold back technology.”
Recently registered in Denmark and in Germany, where it had performed consistently well in difficult conditions, Fencer was also showing promise in its second year of official French trials, said Mr Stocker.
“We’re starting to see a bit a geographical adaptation.”
In the firm’s UK trials at two sites comparing results from its trios of conventional and hybrid varieties at three September sowings, Fencer’s yield held up comparatively well. It lost 1.5t/ha (0.6t/acre) between September 3 and September 30 sowings, while all three conventional varieties lost at least 2.5t/ha (1t/acre), said Mr Cottey.
His hunch that better rooting in the hybrids could be responsible was confirmed by what he acknowledged were unscientific assessments showing Fencer had consistently thicker and more branched roots.
“It is not proven, but for us it is a bit of a sign that maybe there is something about this variety above and below ground that is helping it.”
Fencer, with similar canker resistance (rated 8) but better yield, was a progression on the company’s first RL addition, Harper.
A key workload advantage was that early anti-phoma sprays would not be required until after October. “So you can really focus on putting your first fungicide treatment on a little bit later.” That later spray timing was more appropriate for controlling light leaf spot against which Fencer’s resistance rating was only 5, he said.
Another benefit of being able to spray later was that fungicide treatments were not permitted within two weeks of applications of a key oilseed rape herbicide, Centurion Max (clethodim).
Although not the highest yielding RL variety, Fencer offered consistently high oil content and top phoma resistance. “You could argue that this is a new class of hybrid,” said Mr Cottey.
Poor in-depth rooting could be jeopardising oilseed rape yields, according to ADAS’s principle research scientist Pete Perry.
“Rooting is an important element of filling the seeds,” he said.
Detailing the factors determining oilseed rape output, he referred to recently completed work by colleague Charlotte White.
She had surveyed rooting to a depth of one metre in 40 farm crops from 2004 to 2013, measuring root length density.
“You need at least one centimetre of root per cubic centimetre of soil to extract all the available water in the soil,” said Dr Berry.
The survey showed on average the crops’ root length density was adequate to a depth of about 40cm (16in), but below that there were not enough roots to make use of all the available water.
“That increases the likelihood of crops suffering from drought stress in dry years. So anything we can do to maximise rooting, particularly below 40cm, is really beneficial.”
One problem might be compaction. “In which case, we need to find ways of alleviating deep compaction which isn’t easy.” Another project, on wheat, was investigating blasting air one metre down to open up the soil.
Temperature following seed set had a big impact on oilseed rape output, said Dr Berry.
“Yields were pretty good last year, but they could have been even better. The very warm period in May and June curtailed the grain filling period.”
Most of the oil in the seed was formed during the second half of seed filling, he added. “That is why factors which curtail seed filling, such as high temperature, disease, and even frosts, can have a disproportionately large effect on the oil content.”