Measuring the impact of Verticillium longisporum on oilseed rape (Brassica napus) yield in field trials in the United Kingdom

Verticillium longisporum causes Verticillium stem striping on oilseed rape, which appears towards the end of the cropping season. Thus far, the impact of V. longisporum infection on oilseed yield remains unclear. In this study, we assessed the impact of Verticillium stem striping on British oilseed rape production. To this end, four cultivars (Incentive, Vision, Harper and Quartz) were grown in field plots with different levels of V. longisporum disease pressure at different locations over two consecutive years. Whereas Incentive and Vision developed relatively few stem striping symptoms, Harper and especially Quartz showed severe symptoms during these field experiments. Furthermore, higher inoculum levels induced more severe symptoms in these cultivars. Significant yield reductions upon V. longisporum infection only occurred in a single field trial on all tested oilseed rape cultivars. These preliminary data suggest that Verticillium stem striping does not consistently impact oilseed rape yield, despite the occurrence of abundant disease symptoms.