Verticillium wilt is a disease that can severely affect yields of rape and it has become increasingly widespread. Last year one in five fields suffered from this soil-borne disease. Yet there are no chemical solutions. The only way to reduce its impact is to grow resistant varieties and/or widen the gap between rape crops in the rotation.
Colin Button, Seed Manager for national distributor Hutchinsons, has been conducting Verticillium trials for 5 years. He reports that many plant breeders are now screening for any tolerance to this disease. “It is an indication of how important and widespread this disease is. I am pleased that this screening is being taken seriously, but I do think it should be started much earlier in the breeding programme. Because of the variable nature of the disease, we really need 4 to 5 years screening data, so that when varieties are close to commercialisation, the information is available. Nevertheless trials to date show that there does seem to be true differences between varieties in their disease expression.”
ADAS trials set out to establish differences between varieties using a Verticillium wilt Index, which indicates disease expression in the crop. In these ADAS trials, three Grainseed varieties – Alegria, Alienor and Mambo all gave good Verticillium Indices – much better than many other varieties tested, reports Neil Groom Technical Director for Grainseed.
“For Verticillium Index, the lower the score, the better. Out of the 30 varieties tested, Alegria had the top Verticillium Index at 13.6, Alienor was third with 16.5 and Mambo 7th with 21.1. To put into perspective, the variety regarded as the standard resistant variety Catana had a Verticillium Index of 16.8 and the variety which is well known for its susceptibility, Castille had an Index of 54.4.”
In another set of independent trials laid down by AICC trials, Mambo was the top yielding variety in the treated plots in the East and the second highest yielding variety in the South. “Mambo was showing just 2% infection in the South and 8% in the East. It does look as though this new variety is demonstrating definite Verticillium resistance, along with Alienor and Alegria.”
“We have extensive anecdotal evidence of Alienor’s and Alegria’s ability to resist Verticillium. Mambo, being a new variety this year, will also find its place as it too is showing good resistance to this damaging disease,.” says Neil.
“All three rape varieties also have exceptional autumn vigour which, without the widespread availability of neonicotinoid seed treatments this autumn, will be absolutely essential. A vigorous variety helps the crop get ahead and grow away from damaging flea beetle attack. It also helps with pigeon grazing. Mambo, Alegria and Alienor all have excellent standing power, too, with the three having 8 ratings for stem stiffness and Mambo and Alegria having a 9 for resistance to lodging, with Alienor having an 8.”
Importantly all three have multigene resistance to Phoma stem canker. “Mambo is one of the highest rated oilseed rapes for Phoma stem canker, with a 7.8. Alienor and Alegria both have a high 7 rating. These excellent ratings can reduce pressure on early autumn fungicide sprays and could save growers some money. Rape growers are thinking more about varietal resistances in rape, just like they do in cereals. A rape variety with strong disease resistance should be grown, in the same way a wheat variety with strong disease resistance is chosen,” advises Mr Groom.
Neil concludes by saying the only practical solution to reduce Verticillium is to grow the right variety and Grainseed can offer growers a choice in Mambo, Alienor and Alegria. “These varieties also fit the exacting requirements of todays’ rape growers, who may be considering growing rape with lower inputs. These conventional varieties are vigorous, low biomass, have strong standing power and effective multigene disease resistance across the board - the complete package for todays’ rape grower.”
