Assessing the resistance of commercial oilseed rape cultivars to verticillium stem striping disease in Sweden

Abstract Verticillium longisporum is a soilborne fungal plant pathogen, causing stem striping disease in oilseed rape. Currently, there are no effective fungicides available, so management focuses on plant breeding and crop rotation. Symptoms develop late in the growing season and they are often visible as bronze-colored stripes on the stem. Stem striping disease causes yield losses and premature death of infected plants. The objective of this study was to investigate the level of resistance in 14 autumn-sown hybrid oilseed rape cultivars, widely utilized in Sweden, to stem striping disease. These cultivars were infected with two different V. longisporum strains (S22 and S31) isolated from infested soils in Sweden, while one old spring-sown cultivar was used as a control of the infection. The results showed that none of these cultivars display complete resistance against this disease since considerable reduction in biomass was observed, with the S22 strain being significantly more virulent than S31. The cultivars ‘’Commodore’’, ‘’Credo’’, and ‘’Janosh’’ showed no biomass reduction upon infection with the S31 strain. Further, the cultivars ‘’Commodore’’ and ‘’Credo’’ showed the lowest biomass reduction, upon infection with the S22 strain, indicating a degree of resistance against this pathogen. ‘’LG Armada’’ exhibited significantly more dead leaves as compared to the other cultivars. In addition, root architecture assays revealed differences in morphological traits among the cultivars. A possible correlation was found between plant biomass and root architecture, where cultivars with larger total root lengths experienced less biomass reduction, suggesting that larger root systems result in more resistant cultivars, indicating that root morphology may affect the degree of V. longisporum infection.