Rz2.0 Technology Maintains Yields in Beet

Rz2.0 Variety (left) Rz1.0 Variety (right) Grown in AYPR Infected Soil
Rz2.0 Variety (left) Rz1.0 Variety (right) Grown in AYPR Infected Soil

June 2012

With previously resistant varieties now succumbing to different more widely seen strains of Rhizomania, growers have nothing to lose from making the change to new sugar beet types which include the Rz2 gene.

That’s the view of plant breeder, KWS, which launched Isabella KWS the first variety to include this new, major gene source of resistance to Rhizomania, last year.

The comments come after a season when more soils have tested positive and previously resistant varieties have succumbed to the resistant breaking AYPR strain, including some fields in North Norfolk.

According to KWS UK sugar beet manager, Simon Witheford, Isabella KWS contains both the Rz2 gene from wild beet as well as the existing Holly gene and as a result is the only recommended variety to provide protection against the AYPR strain of the virus.

With a 2012 Recommended List yield that is 101% of controls, growers have been quick to grasp this new technology for use on farm, with the result that Isabella KWS has sold out and taking a significant share of the UK beet area.

“Rz2.0 Double Resistance varieties such as Isabella KWS have already been adopted in countries with issues such as France, Holland and the USA,” says Mr Witheford.

“While the incidences of confirmed AYPR resistant strains remain low across most of England, UK growers adopting the new technology will not compromise its long term performance.

“Unlike the first varieties containing the Holly gene Isabella KWS brings no yield penalties and, through reducing the availability of potentially resistant host plants, growers can effectively reduce the development and multiplication of any resistant strains of rhizomania,” he says.

No Yield Penalty

Researchers also back the view that growers need not wait to see the effects of resistant strains in their crops and that by utilising both the two major genes currently available to give resistance against the virus they will ensure best possible Rhizomania protection.

According to KWS sugar beet breeder Knuth Weissleder, the combination of the two resistance genes, which operate in two distinctly different areas, significantly reduces the virus content of the plants.

"Virologists are unanimous in stressing the fact that the more resistance genes with different mechanisms there are in the plant, the more durable the resistance will be.

“The probability of the pathogen overcoming two mechanisms of resistance is much lower compared to a single resistance gene," he says.

“Growing Rz2.0 Double Resistance varieties also decreases the probability of resistance-breaking strains emerging in these currently unaffected sugar beet production areas,” he adds.

Durable Resistance

According to researchers Garcia-Arenal at the Universidad Politecnica de Madrid and McDonald based at the Institute of Integrative Biology in Zurich the duration of resistance based on data of 25 different host-virus interactions is almost 13 years.

As a result, Simon Witheford believes growers will continue to reap the benefits of Rz2.0 resistance in varieties for some time to come. Rz2.0 types are therefore strongly recommended for farmer’s on-farm risk management for Rhizomania and can be seen as a form of insurance.

"We have had 20 good years of performance out of the Holly gene. The Rz2 gene which we have introduced into Isabella KWS is another major gene, and there's no reason why we shouldn't have a similar period of cover from this resistance source," he says.

“In addition, our breeding team is currently examining the potential of further resistance sources to develop stronger varieties for the future.”