Rhizo Switch Advised

According to sugar beet specialist, Martin Lainsbury, the days of a yield penalty from rhizo-resistors are long gone.  “Now, newcomers such as Rosalinda KWS provide a yield that is 2% ahead of anything else, some 5% ahead of controls and it is important to use this to maximise production, wherever you farm.  

“In addition with a 96% establishment score and the best possible disease resistance combination on the RL of 9 for powdery mildew and 7 for rust, agronomically, Rosalinda KWS is one of the strongest varieties available,” he says.

“Growers will find it a useful partner variety to Carissima which was last year’s highest yielding RL variety,” he suggests.  “Again a rhizo-resistor, Carissima has one of the highest sugar contents on the UK RL and a low root weight, and has produced some outstanding yields on farm.”

KWS worldwide product manager for beet, Gunter Diener backs this.  He says that when KWS introduced the first rhizomania resistant types they were 20% lower yielding than non-resistant types.

“Now though our breeding team has focused on building resistance in to all of our highest yielding material from the earliest stages of the breeding process,” he says.  “By changing the breeding strategy from backcrossing to forward breeding, rhizomania resistant types are now the top yield performers,” he says.

As a result, the company’s sales in Belgium, Netherlands and France are now 100% rhizomania resistant varieties and that this will probably be the case within three years in the UK, where all new entries into BBRO/NIAB Recommended List trials are rhizomania resistant types.

Dr Diener points out that most current varieties gain their resistance from one single ‘Holly’-gene (Rz1).  This offers resistance in virtually all cases across the main growing regions of Europe, including the UK.

However, future resistance could come from other genes.  KWS is working on material that utilises a gene from Californian material – the so called Rz2 gene - which is on the same chromosome as Rz1 gene, and reports some advantages from the new material in some areas.

UK growers may see this different source of rhizomania resistance introduced in 2012 in the variety Diana KWS which is currently in UK RL trials.  “It could potentially offer an advantage against any different strains of the disease should these occur,” he suggests. 

At the same time, Dr Diener says that KWS is examining the role of a range of minor genes which add to the resistance Rz1 and 2 package.   “While Rz1 and 2 might improve yields by 20-30% over a non-resistant type grown in heavily infected soils, these minor genes only raise yields by 2-3%. 

“Nonetheless UK growers can be confident that we have a range of resistance mechanisms being introduced into new, high yielding material which will maintain good control of the disease, should resistance issues occur.  Eventually our goal is double-resistance in varieties with both Rz1 and Rz2 as well as the minor genes in combination in the same high yielding varieties,” says Dr Diener.

KWS is also looking to introduce beet cyst nematode (BCN) tolerance into the best, highest yielding rhizomania resistant types.   “We have already secured light or field tolerance to BCN in the highest yielding types, such as Rosalinda KWS, but growers need to be aware that these types will not be fully effective under high pest pressure,” confirms Dr Diener.

Far better to select highly tolerant BCN type such as Annouschka KWS, he says.  “Our experience is that it is simply not worth taking the risk of letting the pest gain a foothold by growing weaker material.  Yields on farm from highly tolerant types – despite their lower yields in non-infested soils - are usually much higher than light tolerant types on farm where the pest is an issue.”