A NEW disease rating for verticillium wilt in oilseed rape, is ‘one step closer’, AHDB has said after new research highlighted infection level differences.

This key finding means that its ratings as part of AHDB's Recommended List (RL) trials system is on the way – good news for growers, who indicated recently that disease resistance is an important features of the RL.

However, the disease has yet to reach Scotland, with infection centred in the East of England, though as experience has shown, such pathogens can move north!

The presence of the soil-borne disease caused by verticillium longisporum, was first detected in England in 2007. Since then, significant differences in the occurrence and severity of symptoms between varieties were observed in some trials.

In 2014, AHDB instigated research to improve understanding this disease resistance with researchers at NIAB. Inoculated and naturally infected trials were conducted in three seasons.

These found highly consistent differences between varieties in the level of symptom expression. Although none were completely resistant, several showed consistently low infection levels to be ‘different’. Associated with fewer fungal spores, these varieties could play an important role in reducing the amount of disease returned to the soil, said NIAB.

Based on a mean disease index (0-100 scale), the most resistant variety had a score of 26.2 and the most susceptible variety had a score of 60. This translated to a provisional disease resistance rating of 7.6 and 2.1, respectively (1-9 scale).