Evaluation of Resistance of Oilseed Rape Genotypes to Turnip Yellows Virus.

Turnip yellows virus (TuYV), is one of the most important pathogens of oilseed rape, which has caused enormous yield losses in all growing regions of the world in recent years. Therefore, there is a need for resistant varieties for sustainable crop protection. We have investigated the resistance of known varieties and newly developed advanced-breeding lines of oilseed rape to TuYV in greenhouse and field trials. We have analysed the TuYV titre of individual genotypes inoculated with the virus using viruliferous aphids Myzus persicae . The genotypes 'DK Temptation' and 'Rescator' had the lowest and highest virus titres, respectively, and were used as resistant and susceptible models for comparative analyses with other genotypes. In the greenhouse, the best results were obtained with the genotypes 'OP-8143 DH' (2.94 × 10 5 copies), OP-BN-72 (3.29 × 10 5 copies), 'Navajo' (3.58 × 10 5 copies) and 'SG-C 21215' (4.09 × 10 5 copies), which reached virus titres about 2 times higher than the minimum virus concentration measured in 'DK Temptation' (1.80 × 10 5 copies). In the field trials, the genotypes 'Navajo' (3.39 × 10 5 copies), 'OP-8148 DH' (4.44 × 10 5 copies), 'SG-C 21215' (6.80 × 10 5 copies) and OP-8480 (7.19 × 10 5 copies) had the lowest virus titres and reached about 3 times the virus titre of DK Temptation (2.54 × 10 5 copies). Both trials showed that at least two commercial varieties (e.g., DK Temptation, Navajo) and three advanced breeding lines (e.g., OP-8143 DH, OP-BN-72, SG-C 21215) had low titres of the virus after TuYV infection. This indicates a high level of resistance to TuYV in 'Navajo' or the newly developed breeding lines and the basis of resistance is probably different from R54 (as in 'DK Temptation'). Furthermore, the greenhouse trials together with RT -qPCR-based virus titre analysis could be a cost-effective and efficient method to assess the level of resistance of a given genotype to TuYV infection compared to the field trials. However, further research is needed to identify the underlying mechanisms causing this difference in susceptibility.