Resistance to the Large Raspberry Aphid (Amphorophora agathonica) In Black Raspberry

Aphid resistance has long been recognized as an important tool in breeding red raspberries (Rubus idaeus L.) that escape infection by aphid vectored viruses in Europe and North America. Existing black raspberry (R. occidentalis L.) cultivars do not have resistance to the large raspberry aphid Amphorophora agathonica Hottes and sources of resistance in black raspberry germplasm have not been identified.  Consequently, aphid transmitted viruses are a serious problem and have been implicated in the short life of black raspberry fields in Oregon and elsewhere.  In 2007, approximately 4800 seedlings from 85 wild populations of black raspberries, collected as seed from across the species’ native range, were screened in the greenhouse for resistance to A. agathonica, a major vector of Black raspberry necrosis virus and other viruses in Rubus.  Strong resistance was found in two of these populations, one from Ontario and the other from Maine.  Two selections from each of these populations were crossed with the susceptible cultivars ‘Black Hawk’ and ‘Munger’ and all of the resulting progeny tested showed strong aphid resistance.  Subsequent tests with the closely related non-vectoring aphid A. rubitoxica Knowlton, showed that the population from Maine was resistant to this species while those from the Ontario population were not.  The data suggest that aphid resistance in these two populations is controlled by different genes, and each is inherited as a dominant trait.