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  • Author or Editor: Chaim Kempler x
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Resistance to colonization by the raspberry aphid (Amphorophora agathonica Hottes) has been an important objective in North American red raspberry (Rubus idaeus L.) breeding programs since the 1930s because of its effectiveness in controlling the spread of aphid-transmitted viruses in red raspberry. The most widely used source of resistance in North America has been the gene Ag1 from ‘Lloyd George’. The widespread use of Ag1 to control aphids led to the appearance of a resistance-breaking biotype in British Columbia, Canada, in 1990. Our objective was to identify biotypes of A. agathonica present in the commercial red raspberry production region of southwestern British Columbia and northwestern Washington and determine what sources of resistance may still be effective against this pest. We collected 12 aphid isolates and screened them against 15 raspberry cultivars and four selections. Although it has been widely believed that only two biotypes (regular and Ag1-breaking) of A. agathonica were present in the region, we identified six distinct biotypes and characterized them by their ability or inability to colonize a differential set of raspberry cultivars. This has confirmed the loss of previously recognized and unrecognized sources of resistance in some cultivars. The data also support the presence of a seventh biotype that has not yet been observed. In addition, we confirmed resistance from three sources of wild North American red raspberries that hold up to each of these biotypes. Our results will serve as a guide for future efforts to characterize the prevalence of different aphid biotypes in the region and the identification of new sources of resistance for breeding.

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In 1989, 2-year-old A. arguta varieties Geneva, Annaysana, Dumburton Oaks, Fairchild, National Arboretum, 74-7', 74-8, and the self-fertile variety Issai, were planted in Agassiz, B.C., on a well-drained soil site. The plants were grown with a single trunk to 1.8-m with permanent cordons, and fruiting laterals trained on a 2.1-m-wide winged T-bar trellis support. Plant spacing was 2.75 m within the row and 4.8 m between rows. Staminate varieties (Meader and 74-6) were planted at a 1:6 ratio of male: female for pollination. Fruiting canes were renewed every 2 years by winter pruning. All plants began to bear harvestable yields by 1991. A. arguta vine required 622 heat units from bud break to full bloom and the average flowering date was 29 May. Fruit begin to mature during September, depending on the variety. `Geneva', `Annaysana', and `Issai' were the most suitable for commercial production. In 1993, they produced a yield of 26, 38, and 26 kg/vine, with average fruit weight of 7.7, 6.3, and 4.8 g, respectively. `Geneva' was the earliest to mature, followed by `Annaysana' and `'Issai'. A. arguta ripen very unevenly and, at harvest, a certain proportion of the fruit are over-ripe. Fruit are best harvested early when they are firm. Storing the fruit at 1C improved ripening uniformity.

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