Significant changes to the HGCA Recommended List for winter oilseed rape see 2009/10 with separate lists for two regions – the east and west, and the north. Also included for the first time are semi-dwarf varieties.
Explaining the reasoning behind the separate lists RL manager Jim McVittie pointed out that only about 10% of the UK crop was grown in the north – roughly beyond Scotch Corner.
“To do well in that region you’ve got to have light leaf spot resistance,” says Dr McVittie. “Stem canker resistance is immaterial.”
In most of the east and west region, effectively south of Scotch Corner, stem canker is the most important disease with light leaf spot much less of a problem.
“What we’ve been finding in the past few years is that the performance of varieties in terms of yield has been diverging in the two regions.
“So we’re now selecting varieties separately for each region and producing shorter, more focussed lists for each.”
Incorporating semi-dwarf varieties – hybrids with just one dwarfing gene – have also been tested for several years, notes Dr McVittie.
“We’ve been struggling as to how we can best fit them into the RL system. They may not be much shorter than normal varieties, but they branch much closer to the ground. They’re like a bush not a tree.”
As such they are unsuited to swathing which can make trial comparisons in some cases impractical. Also some of their benefits are not yield related, for example removing the need for high clearance contract sprayers and the ability to combine bigger areas more quickly.
“So it’s difficult to evaluate the total value of the benefits of these types.
“So what we’ve done is brought in a specific category for semi-dwarfs. If a semi-dwarf reaches the same gross output and other characteristics as a normal variety then it will get full recommendation.
“But if it doesn’t then the best semi-dwarf is guaranteed a place on the list.”
The revised system relating to semi-dwarfs is like that for six-row barleys where the best newcomer does not necessarily have to outperform the six-row hybrids to be listed, explains Dr McVittie.
Specialist oil varieties, such as HOL types, have also been examined with a view to specific listing, he notes. However, they tend to be grown on contract and the various oil make-ups have a significant impact on returns.
“But growers are interested in these varieties and we can provide data on their yield, agronomy and disease resistance. Initially we will not be making recommendations on these types, but we have two of these sorts in trials for 2009 harvest and we’ll produce a descriptive list.”
The listings arrangements regarding hybrids versus conventional open-pollinated varieties has also come under renewed scrutiny.
“In some years hybrids seem to do well and in others open-pollinated ones do well. The committee debated this in June and didn’t want to get into a position where it recommended only open-pollinators or hybrids.
“So what it decided to do was to set separate targets for recommendation. So a new hybrid will have to beat the best current hybrid to get recommended, and a new conventional will have to beat the best currently recommended conventional one to get listed.
“But the best hybrid might not beat the best conventional, or vice-versa, depending on how the season is going.”
The outcome is that both types will be mixed together on the lists. Unlike wheats they are all destined for the same market, he points out.