Yield is still the main focus for seed breeders aiming to improve East Anglia's oilseed rape crops – despite the challenges of a changing climate, volatile markets and the onslaught from pests and diseases.
Grainseed, based at Eye near the Norfolk-Suffolk border, is working with independent breeder Mike Pickford to develop new lines such as Keeper, a high-yielding conventional variety which has been added to National List trials.
Mr Pickford, who has been breeding oilseed rape since 1973, travelled to Norfolk from his base in Oxfordshire this week to assess his own trials of the crop in a field at Tuttington, near Aylsham.
He said one of Keeper's key characteristics was a good resistance rating against phoma stem canker, one of the East's most common diseases of oilseed rape, with the potential to cause yield losses of as much as one tonne per hectare.
Another problem is pests. Some of the region's farmers have cut back on their oilseed acreage, or even dropped the crop from their rotation altogether, after the EU ban on neonicotinoid seed treatments left young plants vulnerable to attack from cabbage stem flea beetles.
But Mr Pickford said farmers could use practical measures to mitigate these issues, including optimising the drilling date and seed rates - so his focus remained the same as it has been for 45 years.
"My main criteria is yield," he said. "It has got to be yield, yield, yield. That is what the farmer gets paid on.
"For the last couple of years I have been doing a lot of seed component work, selecting lines that have a higher harvest index. We are looking for bigger seeds and more seeds per pod. I have one line which has an overage of up to 40 seeds per pod, compared to 25 - but that is three years down the road.
"There are other characteristics like disease resistance and being able to stand correctly, but ultimately it is yield we want. Its the same with all crops.
"Going back to last autumn, the main reason the crops were hammered by cabbage stem flea beetle was that it didn't rain. The seeds were sown into dustbowl conditions. If there's no moisture in the seed bed, and no rain in the forecast, then you should hold back and leave the seed in the barn. If the moisture is not there, what's the point?"
Neil Groom, technical director for Grainseed, agreed that moisture in the seedbed is the most critical factor to the success of an oilseed rape crop - but he said farmers may need to weigh the balance between waiting for rain, or sowing seeds early to allow the crop to grow away before flea beetles emerge.
"You do need that rain two weeks before drilling, but it is good if you can get your crop drilled early, before August 20, because the flea beetle don't migrate until maybe September 10 so if you can be germinated and through the cotyledon stage (the first leaves) the plant has a better chance."
Mr Pickford added that if a farmer needs to wait for rain to guarantee a moist seedbed, they could mitigate the pest risk by simply increasing the seed rate to produce more plants per square metre - a much easier decision with conventional varieties, as hybrid seeds are more expensive.
Mr Groom said Grainseed's other supplier, French breeder Euralis, has "gone down the hybrid route", but he wanted to retain some conventional varieties, which prompted the partnership with Mr Pickford, who only deals with conventional crops.
"With a conventional variety, you pack it in a four million seed pack, and so if you sow at 80 seeds per square metre that pack does five hectares," said Mr Groom. "Whereas a hybrid variety is packed in a 1.5 million seed bag, and that only does three hectares - and it costs more, but you don't get any more yield. In the UK, all the trials will tell you a good conventional has got the same yield as a good hybrid."
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