Incidence of aphid-transmitted viruses in raspberry and raspberry aphids in Norway and experiments on aphid transmission of black raspberry necrosis virus.

Raspberry ( L.) is susceptible to aphid-borne viruses. We studied the incidence of four of them - black raspberry necrosis virus (BRNV), raspberry leaf mottle virus (RLMV), raspberry vein chlorosis virus (RVCV), and Rubus yellow net virus (RYNV) - in raspberry plants and aphids in and around Norwegian raspberry crops for three years (2019, 2021, and 2022). Most of the samples were from symptomatic plants. Applying RT-PCR, 274 leaf samples and 107 aphid samples were analyzed. All four viruses were found, but BRNV dominated: it was detected in 93% of the 178 leaf samples with virus and was the only virus that occurred more frequently as a single infection than in co-infections with the other viruses. The old cv. Veten had the highest virus incidence (97%) among the sampled plants, followed by uncultivated raspberry in the boundary vegetation (82%). All aphids identified were and BRNV and/or RLMV was detected in 27% of the aphid samples. Notably, BRNV was detected in 30% of samples, a species not known as a BRNV vector. In subsequent transmission experiments we found that although can acquire BRNV within one hour, it did not transmit the virus to healthy raspberry plants. In contrast, , a known BRNV vector, was able to acquire the virus within one minute and transmit it within one hour of inoculation. Our study will improve the identification and management of BRNV.