Cheryl R. Hampson

Sensory evaluation as a selection tool in apple breeding

Several conventional sensory methods were adapted to provide aprocedure that is suitable for screening apple (Malus × domestica) breeding selections for dessert quality. Trained judges were presented with randomized coded samples (apple slices) and asked to rate them on 0 to 9 bipolar hedonic (liking) scales for texture and flavour, and 0 to 9 unipolar intensity scales for skin toughness, crispness, hardness, juiciness, aroma, sweetness and sourness. Appearance liking was rated on coded samples of five whole apples, using the 0 to 9 hedonic scale. A minimum panel size of eleven judges was generally sufficient to obtain statistical discrimination of one point on the 0 to 9 scales. Panel mean scores for breeding selections relative to standards have been consistent from panel to panel and year to year. A subset of selections and cultivars was rated for appearance and taste by consumers in blind taste tests. In-house panel findings were comparable to consumer ratings for taste and appearance liking, with a few exceptions in appearance. Panel mean scores for texture and flavour liking were regressed on texture and flavour components. Crispness accounted for about 90% of the variation in texture liking. Juiciness, aroma, sweetness and sourness were all important to flavour liking, but their relative importance changed from year to year and in total accounted for only about 60% of variation in flavour liking. Perceived sweetness and sourness were better predictors of liking than analytical measurements of soluble solids and titratable acidity. Formal sensory evaluation can be used successfully for screening breeding selections, and may provide more reliable data than the opinions of only one or two people.

Identification of new self-incompatibility alleles in sweet cherry (Prunus avium L.) and clarification of incompatibility groups by PCR and sequencing analysis

Abstract Correct assignment of sweet cherry cultivars to cross-compatibility groups is important for the efficient production of cherry fruit. Despite considerable confusion in the literature, these groups continue to be an effective tool for predicting pollination effectiveness for breeders and growers. PCR fragments generated from cherry S-RNase sequences coincided with specific S-allele phenotypes. Twenty five genomic DNA fragments, representing the six most common alleles, were cloned and sequenced. In addition, fragments were characterized from four new S-alleles. These genomic and cDNA sequences were invariant among cultivars with the same S-allele. Using the sequence data, PCR and restriction enzyme-based methodology was developed for rapid analysis of S-genotypes. Analysis and description of fragmentation patterns for S-allele determination are discussed. The method was utilized to characterize the S-allele composition of 70 sweet cherry cultivars obtained from collections in North America, including many of the named releases from the Canadian breeding programs at Agriculture and Agri-Food Canada in Summerland, B.C., and Vineland, Ontario. A number of differences between published S-allele assignments and PCR data were discovered and a new listing of cultivar S-allele assignments is presented.

QTL analysis of soft scald in two apple populations

The apple (Malus×domestica Borkh.) is one of the world’s most widely grown and valuable fruit crops. With demand for apples year round, storability has emerged as an important consideration for apple breeding programs. Soft scald is a cold storage-related disorder that results in sunken, darkened tissue on the fruit surface. Apple breeders are keen to generate new cultivars that do not suffer from soft scald and can thus be marketed year round. Traditional breeding approaches are protracted and labor intensive, and therefore marker-assisted selection (MAS) is a valuable tool for breeders. To advance MAS for storage disorders in apple, we used genotyping-by-sequencing (GBS) to generate high-density genetic maps in two F1 apple populations, which were then used for quantitative trait locus (QTL) mapping of soft scald. In total, 900 million DNA sequence reads were generated, but after several data filtering steps, only 2% of reads were ultimately used to create two genetic maps that included 1918 and 2818 single-nucleotide polymorphisms. Two QTL associated with soft scald were identified in one of the bi-parental populations originating from parent 11W-12-11, an advanced breeding line. This study demonstrates the utility of next-generation DNA sequencing technologies for QTL mapping in F1 populations, and provides a basis for the advancement of MAS to improve storability of apples.

Shelf-life and sensory assessments reveal the effects of storage treatments with 1-methylcyclopropene on new and established apples

Stanich, K., Cliff, M. A., Hampson, C. R. and Toivonen, P. M. A. 2014. Shelf-life and sensory assessments reveal the effects of storage treatments with 1-methylcyclopropene on new and established apples. Can. J. Plant Sci. 94: 1427-1439. This research used shelf-life and sensory assessments to explore the influence of 1-methylcyclopropene (1-MCP) on four apples (Aurora, Fuji, Nicola™, Salish™). Maturity (internal ethylene concentration, starch clearing index), quality (soluble solids, titratable acidity, firmness) and sensory determinations were conducted on fruit that had undergone air (AIR) or controlled atmosphere (CA) storage treatments with and without 1-MCP. Trained panelists evaluated apples, along with industry standards (Gala, McIntosh and either Fuji or Ambrosia), for eight attributes (crispness, hardness, juiciness, skin toughness, sweetness, tartness, sweet-tart balance and flavour). Data were analyzed using analysis of variance and principal component analyses (PCA) to compare the treatment and cultivar responses. Cultivars responded very differently to CA and 1-MCP. Fruit from AIR with 1-MCP were very similar to CA fruit without 1-MCP; further improvements were not observed when 1-MCP was applied to CA fruit. PCA bi-plots of the shelf-life and sensory assessments revealed that treated Salish™ fruits were more similar to one another than to cultivars from other treatments. This work successfully documented the unique changes associated with the use of 1-MCP on new and established apple cultivars. It will assist industry in applying appropriate storage practices for new and established apple cultivars.

SPA493 (Salish™) apple

Hampson, C. R., MacDonald, R. A., McKenzie, D.-L. and Walters, W. 2013. SPA493 (Salish™) apple. Can. J. Plant Sci. 93: 979-982. ‘SPA493’ (Salish™) is a new bi-coloured dessert apple from the Agriculture and Agri-Food Canada breeding program at Summerland, BC, Canada. The fruit is crisp and juicy, with balanced flavour and medium to long storage potential. The fruit reaches harvest maturity in early October in Summerland. ‘SPA493’ trees are moderately vigorous, productive, and not subject to biennial bearing or pre-harvest drop.

Use of planting depth and budding height to modify vigour control of Ottawa 3 apple rootstock

The dwarfing apple rootstock Ottawa 3 (O.3) produces trees slightly too large for high density plantings on fertile soils, but it is more cold hardy and better anchored than Malling 9. Our objective was to reduce the vigour of trees on O.3 by budding scions higher or planting the trees more shallowly. Summerland McIntosh was budded at 15 cm onto O.3 and planted such that 6 to 14 cm of the rootstock shank was above ground. Planting depth did not affect tree size, yield or yield efficiency. Increasing budding height from 5 to 25 cm increased vigour control, yield efficiency and the production of root suckers on O.3. Higher budding may be an effective way to reduce the vigour of trees on O.3 in areas where the greater root suckering is not a fireblight hazard. Key words: Malus domestica Borkh., dwarfing rootstock

‘SPC136’ (Suite Note™) sweet cherry

Hampson, C., MacDonald, R., McKenzie, D.-L., Herbert, L. and Pagliocchini, C. 2014. ‘SPC136’ (Suite Note™) sweet cherry. Can. J. Plant Sci. 94: 1555-1558. ‘SPC136’ (Suite Note™) is a new early-season sweet cherry being released for commercial production by the Agriculture and Agri-Food Canada sweet cherry breeding program at Summerland, BC, Canada. Harvest timing in Summerland (Jul. 09) is similar to that of ‘Bing’ or ‘Van’ but fruit size is much larger (over 12 g). Fruit firmness, soluble solids content and susceptibility to rain splitting resemble those of other cultivars of similar harvest timing, but stem detachment force is higher. The trees are not self-fertile and bloom late in the cherry blossom season.