Using real-time PCR to quantify resistance in sugar beets to Beet necrotic yellow vein virus

Beet necrotic yellow vein virus resistance in commercial sugar beet cultivars is largely dependent on the Rz gene and its selection can be inaccurate and time-consuming. It was hypothesized that real-time PCR could quantify differences in viral infection between resistant and susceptible cultivars. Seedlings of seven sugar beet cultivars were inoculated with BNYVV and repotted. Viral infection of leaves and roots was quantified over time with real-time PCR and compared among cultivars. Additionally, resistance of a susceptible and resistant cultivar to a standard isolate of BNYVV and a new, aggressive isolate was compared. Viral infection increased over time and was higher in roots than leaves. During the second week post-inoculation, infection by standard BNYVV was significantly higher in susceptible vs. resistant cultivars; however, infections by the aggressive isolate were not significantly different between a susceptible and resistant cultivar. This study indicates that real-time PCR may be useful in quantifying resistance to BNYVV beyond that based on the Rz gene, and supports the identification of a new, aggressive BNYVV strain.