Check On Tolerance Levels Before You Buy Into BCN

That’s the view of KWS sugar beet manager, Simon Witheford, who says that responses will vary according to season, severity of BCN infestations and the variety’s level of tolerance.

For this reason, the Cambs-based breeder is backing a new BBRO research project into the pest, which aims to properly identify its significance in UK conditions and the performance of tolerant varieties.

“While there are now three varieties on the 2011 UK Recommended List, these varieties have not been widely compared in conditions where the pest causes damage.  The new BBRO work will help plug this gap in our knowledge,” he says.

“Indeed, until we have this supplementary data, it could be argued that a direct comparison of yields on the Recommended List is meaningless because they are not tested under BCN infested conditions which is where they should be grown.  So, any selection based on the RL alone is dangerous.”

While accepting that other varietal comparisons are needed, Mr Witheford points out that its own field trials evidence from last year – verified by British Sugar and Brooms Barn – is that Annouschka KWS is a step up from its 2010 UK RL BCN introduction, Fiorenza KWS.

“We’ve seen performances in heavy BCN infestations from last year that confirms that Annouschka KWS is highly capable of beating its 4.2% higher yield over Fiorenza KWS as indicated on the UK RL in highly infested soils.  This helps back British Sugar’s step to switch orders to the new variety for this season’s crop.

“Annouschka KWS has also been the most widely tested beet cyst nematode tolerant variety across UK soils,” he points out.   “In all levels of infestation it has been out-standing and in this respect is a step up from other varieties – some of which will only be of use in helping overcome low level infestations of the pest.

“And with over 1000ha of the variety being planted this spring on commercial farms where the pest is becoming increasingly problematic, this will confirm its strong commercial potential on farm.”

Mr Witheford points out that Annouschka KWS has been derived from the most successful BCN breeding programme using technology widely accepted as the best available in Europe, which offers some of the highest levels of tolerance to the pest possible and this should provide further assurance for UK producers. 

KWS has been working on developing varieties for around 20 years introducing a high degree of tolerance to beet cyst nematode from wild beet species.  As a result, the company is the market leader in BCN technology supplying an increasing number of tolerant varieties for problem regions across Italy, Spain, France, Benelux, Scandinavia and Germany. 

He points out that in Scandinavia, varieties are classed as being either BCN tolerant or within a new category described as ‘Nematode Escape’, which means they have a low or light tolerance to the pest.  This trait has not been specifically bred into the varieties but one that has been observed and measured in the field – a kind of low level ‘Field Tolerance’, says Mr Witheford. 

“Our new rhizo-resistor, Rosalinda KWS, which tops the 2011 Recommended List for yield has shown good performance under low levels of BCN infestation in Scandinavia and the UK.   However, we don’t advocate growers use this variety on at risk fields as lightly tolerant types do nothing to reduce BCN populations, leaving following beet crops still at risk

 “Annouschka KWS is a different beast and can cope in low and high levels of infestation because of its high in-bred tolerance.  Indeed, Scandinavian trials have shown Annouschka KWS types will out-yield varieties with ‘Field Tolerance’ under both low and high infestations.   

Mr Witheford points out that while no-one is entirely certain how the tolerance mechanism works, it seems as if the nematodes can’t find a way of fully penetrating the roots of the plant.  It is thought that as the nematode starts to enter the cell, the plant reacts by producing a substance that repels it, minimising any further damage.  

Cysts are still found on tolerant beet, but the degree of nematode multiplication – decreases in soils where varieties with high levels of tolerance are grown.  This depends upon the season and the initial population. Infestations can be kept under control even in tight rotations, but only through using highly tolerant types such as Annouschka KWS. 

“Growers need to test soils and check for evidence of the pest themselves.  At the same time they should take the chance to visit breeder trials – and check on neighbouring farmer crops - so as to gain confidence in the likely performance before they opt to try any variety across a significant area next spring,” says Mr Witheford.