Options for reducing Verticillium wilt in oilseed rape
Dr. Peter Gladders of ADAS reports that research work in conjunction with HGCA is being undertaken to establish varietal resistance to the increasingly important disease in rape, Verticillium wilt. Alienor appears to be one of the more resistant varieties of the 24 that we tested, he says.
He reports that in the 2010 DEFRA survey 25% of rape crops were affected by Verticillium wilt right across England. "The fungus was first identified in 2007 in Kent and Herefordshire, but has now spread throughout UK. In Cambridgeshire and Northamptonshire 30-40% crops were affected and this soil-borne disease has been found in crops as far north as North Yorkshire. Already we are seeing Verticillium in crops this year. The disease favours warm springs and symptoms are seen as long vertical grey stripes from soil level moving up the stem, with black micro-sclerotia on the stem surface. The impact of the disease is premature ripening, leading to significant yield loss."
Dr Gladders suggests that with more Verticillium being seen in oilseed rape crops, growers should consider planting resistant varieties such as Alienor. "In trials done last year Alienor had just 3.3% of plants with this disease, whereas Castille had 22% and Excalibur 24%. The resistance shown by varieties such as Alienor has a strong genetic base and it is a very useful characteristic for any variety to have, as there are no proven chemical treatments to fall back on. Growing varieties with Verticillium wilt resistance, along with rotations of 1 in 4 years, should help to reduce the impact of this damaging disease."
Neil Groom of Grainseed says that this UK data confirms his knowledge of the resistance of Es Alienor in France where disease levels are much higher than in the UK. "This year we are also testing Es Cubic and Es Venus because their data from France is even better than Alienor’s."
Neil points out that Alienor has already been widely adopted by growers because of its very early maturity. "Alienor matures 7-10 days earlier than Castille, which allows much more opportunity for seedbed preparation and stale seedbeds as well as timely entry for following crops."
"It also shows exceptionally rapid autumn establishment and grows away fast in spring. It mirrors the vigour and the growth habit of the hybrid Excalibur, but has been observed to be much more vigorous than many other hybrids. It offers excellent Phoma resistance (7), good for Light Leaf Spot (6) and is low biomass, giving an excellent all round disease package and making Alienor the easiest variety to grow. All these characteristics plus its innate Verticillium wilt resistance makes up a great overall package for farmers."
Of the other two varieties with potentially high Verticillium resistance in French trials, Cubic is also early maturing and produces good high gross output and high oil content, outperforming Castille. It has very high scores for Autumn vigour, similar to hybrid varieties. It has multigene Stem Canker resistance (7) and is a low biomass variety, 144 cms, that is easy to harvest.
"A new variety for this year, Venus offers high yields and gross output (106%). It shows good high Autumn vigour scores and strong multigene Phoma resistance. It is also a good low biomass variety, an obvious replacement for DK Cabernet," says Neil.
