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ISHS Acta Horticulturae 1133: XI International Rubus and Ribes Symposium

Breeding raspberries for aphid resistance in British Columbia: progress and challenges

Authors:   M. Dossett, C. Kempler
Keywords:   Amphorophora agathonica, Raspberry mosaic virus, Rubus idaeus, Rubus strigosus
DOI:   10.17660/ActaHortic.2016.1133.17
The raspberry aphid, Amphorophora agathonica Hottes, is the principal vector for four viruses in the Raspberry mosaic virus complex which contributes to field decline and crumbly fruit symptoms in red raspberries (Rubus idaeus L.) in the Pacific Northwest. Breeding for aphid resistance has been a major emphasis in raspberry breeding in British Columbia since the 1960s. The most widely used resistance gene in the breeding program, Ag1, broke down in 1990. The appearance of additional resistance-breaking aphid biotypes since then has resulted in the need to identify new sources of resistance and develop approaches for maintaining their durability. We surveyed aphids from commercial fields in the Fraser Valley of British Columbia and identified seven biotypes of A. agathonica as determined by a differential set of cultivars and selections. Every cultivar released by the program to date is susceptible to one or more biotypes, though biotypes A and B, which are only capable of colonizing plants with no identified resistance (A) or with resistance from 'Newburgh' (B), appear to be the most common. A single aphid isolate capable of aggressively colonizing strawberry (Fragaria ×ananassa Duch.) in addition to raspberry was also identified, opening up the possibility of virus exchange between these species. Several sources of resistance in wild raspberry germplasm have been identified and current efforts are aimed at identifying markers for unbroken resistance sources to aid in effectively pyramiding resistance genes to slow the breakdown of resistance. Existing sources of resistance and the current status of knowledge on each will be presented as well as instances of apparent genetic drift of aphid colonies in the greenhouse.

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