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RL results pose questions over OSR candidates

united_oilseeds

The first year of direct Recommended List (RL) comparisons clearly shows this seasons oilseed rape candidates are failing to outshine the leading Recommended varieties, believes United Oilseeds technical manager, Richard Elsdon.

Gross output results that are now in from 10 of this years 11 East & West Region trial sites show that pure line and hybrid RL leaders are failing to be upstaged by candidate varieties.

Richard_Elsdon
Amongst the pure line varieties, a treated gross output of 105.9% puts DK Cabernet just ahead of its most promising rival, Sesame at 105.8%, with existing Recommendation, Fashion (104.1%) not far behind. And PR46W21 at 110.4% stands well clear of leading hybrid contenders, Rhino (107.4%), Compass (106%) and Palace (105.7%) which are only just above long-standing Excalibur (104.9%).

Its only one year, but the 2010 trials are the first chance weve had to directly compare candidate varieties with established RL leaders, Mr Elsdon points out. And I have to say that the candidates really dont seem to offer anything in the way of a significant improvement. Certainly not the sort of superiority the National List (NL) results might have suggested.

In terms of four year means, no candidate exceeds the existing hybrid performance benchmark either, and only one Sesame with a treated gross output of 110% continues to bear comparison with the current pure line leader, DK Cabernet (107%). We must remember that we are still largely comparing apples with pears. Sesames rating, for instance, is based on just 21 actual trials over three years (the fourth year being statistically estimated) while DK Cabernets comes from 33 trials over four years

This really underlines the need to view the RL data with care, Mr Elsdon stresses. Sesames treated gross output of 117% from two years of limited NL trials made it a real prospect even against DK Cabernets rating on Recommendation of 110%. More demanding RL testing has seen the rating gap between the two shrink markedly. At the same time, the only head-to-head comparisons (this years RL trials) reveal theres little, if anything to choose between the two varieties.

We also know from the latest RL data that Sesame is taller and weaker-strawed than DK Cabernet and has a markedly lower oil content. Add to this the fact that its at least as late to mature and has very similar stem canker and light leaf spot ratings and I cant really see much to get excited about.

The extent to which the output rating of varieties invariably drops as they are tested over a wider range of conditions in both years and sites is something Richard Elsdon urges growers to take into account in evaluating all new prospects.

Given the official trials process, the output rating gap between new and established varieties will almost always diminish as they are increasingly tested head-to-head,
he explains. We all accept that DK Cabernet has been a major advance. But the 9% gross output rating advantage it enjoyed over then pure-line leader, Vision as a candidate, fell to 4% in its year of Recommendation and is now running at 3%.

We need to factor this reality into our decision-making as far as new varieties are concerned and learn to value head-to-head RL comparisons as well as the four year means (which at first Recommendation only involve three years of real data).

Perhaps more than this, though, we must place at least as much emphasis on characters other than yield in our variety evaluations. Oil content, for instance, has very much more inherent year-to-year consistency. And relative standing ability, manageability, harvestability and resistance to key diseases all tend to vary relatively little from year to year, yet are vital considerations in delivering an OSR performance we can rely on.

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