Whilst there is little evidence Extase will benefit from heavy duty spray programmes, growers need to be mindful of leaving it too exposed in years with a heavy disease threat, says KWS senior researcher at KWS Nick Bird.
“There are a number of ways a wheat variety can put up its own defences, but septoria is very good at adapting. It’s a tough one to tackle.”
“We’ve narrowed down the specific regions responsible for fighting septoria and found the precise location of Stb6 (Septoria tritici blotch) – a major gene found to confer resistance – but unfortunately this is now only effective against a very small proportion of the UK septoria population.
“Extase has a fair degree of genetic strength built in, as we’ve combined this with a whole host of other genes known to confer resistance and it’s this combination that offers the stability of control and overall resilience.
“Breeding for resistance takes time and if the genetics are abused, the resistance won’t last as long as it needs to.”
“Once we identify a promising source of resistance it still takes 8-10 years to bring it to market so we really want to make sure Extase stays as robust as possible for as long as possible.”
KWS knowledge transfer manager Dr. Kirsty Richards says the strength of Extase’s genetic base should stand it in good stead for the future, but growers should not see it principally as a low input variety.
“Some varietal disease resistance may rely heavily on a single gene, which is equivalent to using a fungicide with one mode of action. Others, including Extase, feature multi-gene resistance, which is more resilient, but both types benefit from chemical protection.
“In a low risk year, there are definitely opportunities for cutting fungicide spend with Extase.
“But whilst it is very tempting for growers to try to grow resistant varieties very cheaply, that’s not sustainable for protecting genetic resistance as all it does is ramp up the selection pressure on that resistance mechanism.
“Genetics and chemistry must be used responsibly in tandem and this is very much the case with Extase - too much emphasis on either one will break the chain.”
Trials carried out by Bayer and KWS looking at integrate varietal disease resistance with existing chemistry have highlighted the complexities of choosing the best strategy to achieve this, says Beyer’s Gareth Bubb
“Varietal resistance is brilliant, but we need to use it sensibly as a risk management tool. There may be opportunity to reduce inputs on more resistant varieties, such as not applying an SDHI at T1, but cost-savings shouldn’t be the driver.
“One main benefit from varietal resistance is to buy more time around key spray timings and help prioritise fields to treat first.”