Regional differences in performance of Canadian-bred apple cultivars and implications for breeding

To evaluate their commercial potential in several major production regions of Canada, 10 Canadian breeding selections and two standard cultivars of apple (Malus × domestica Borkh.) were planted at four locations: one in British Columbia, two in Ontario and one in Nova Scotia. Subsidiary objectives of the trial were to determine whether wider testing of promising apple selections was warranted, and to accumulate information to help guide breeders in selecting apples for widespread adaptation. At each site the planting was arranged in a randomized complete block design with eight replicates. Individual trees were the unit of replication. Data were collected for 7 yr (5 cropping years). The measures of orchard performance recorded were: tree survival, trunk-cross sectional area, final tree height and canopy spread, precocity, times of bloom and harvest, yield, yield efficiency, and average fruit size. The effects of location, genotype and genotype × location interaction were statistically significant for all response variables. The two standard cultivars, Royal Gala and Summerland McIntosh, were intermediate to high in precocity, tree vigour, yield and fruit size. No single cultivar was superior in these characteristics at all locations. Among the test selections, S23-06-153 and 8S-27-43 had the most consistently good performance with regard to tree survival, tree vigour, yield, yield efficiency, pre-harvest fruit drop and fruit size. 8S6923 (Aurora Golden Gala™) and Silken also performed well, except that fruit size was smaller in eastern Canada. Many of the selections took fewer days to reach maturity in Nova Scotia and Ontario than they did in British Columbia. The results obtained suggest that regional testing is highly desirable for characteristics such as tree survival, yield, pre-harvest drop and climatic suitability (e.g. dates of bloom and harvest), all of which profoundly affect the commercial desirability of the cultivar. If the present results can be generalized, breeding and selection of new genotypes at one location are probably adequate for tree vigour, relative order of bloom and harvest, and precocity, despite the genotype × environment interaction demonstated. For these characteristics, the modest changes in rank among cultivars from location to location do not have great practical or economic consequences. Selection at one location may also be effective for fruit size and percentage of over colour, if the breeder takes location effects into account (smaller fruit in Ontario and Nova Scotia, less colour on early-harvest apples in British Columbia). Key words: Fruit breeding, cultivar testing