Root hardiness for the apple (Malus domestica Borkh.) rootstocks M.26, MM.106, MM.111, M.7A, and M.7EMLA at - 8 and - 11C and trunk survival for the tender cultivar Gravenstein and the hardy cultivar Wealthy at -25 and -35C were evaluated both destructively (tissue examination) and nondestructively (regrowth measurement the following season). No differences in root survival were detected at -8C by either method; at - 11C, MM.111 rated better than the others, while regrowth was higher on M.26, MM.111, and M.7A than on MM.106 or M.7EMLA. Root survival did not differ for the scions at either temperature, but regrowth was greater for `Gravenstein' than Wealthy' at both temperatures. Trunk tissue survival at -25C was consistently lowest for scions on M.7EMLA, and regrowth was less than on M.26 and MM.111. At -35C there were no significant rootstock effects. For the scions, lateral wood tissue survival at -25C was highest for Wealthy', but the weight of the new growth did not differ. At -35C bark tissue survival and regrowth was greater for Wealthy' than for `Gravenstein'. Evidence is presented in support of the occurrence of reciprocal effects. Correlation between the two methods was highest for root exposure at - 11C and for the assessment of trunk bark.
C.G. Embree and K.B. McRae
P. Allan-Wojtas, K.A. Sanford, K.B. McRae and S. Carbyn
The apple industry worldwide would benefit from an improved and standardized description of fresh-apple textural quality. The description proposed here is unique in that it integrates structural, sensory, and consumer information. To demonstrate its benefits, 24 apple cultivars [Malus ×sylvestris (L.) Mill. var. domestica (Borkh..) Mansf.] were sampled over two harvest seasons and analyzed using microstructural and sensory techniques. Cultivars were selected to cover a range of known sensory textures, and microstructural profiles were compiled in parallel with sensory and instrumental studies. Each cultivar was pre pared for conventional scanning electron microscopy (SEM) observation using standard methods. Representative fruit from each cultivar were photographed at three magnifications to visualize fruit architecture, tissue relationships, and size, shape, and arrangement of cells within layers to compile the microstructural profile. A trained sensory panel evaluated the cultivars for crispness, surface coarseness, sponginess, hardness, juiciness, degree of melting, mealiness, and skin toughness while a consumer panel rated liking. This information was compiled into a texture profile. The microstructural and texture profiles were then combined into a cultivar profile for each sample. Cultivar profiles were collected to form a database; subtle similarities and differences among the 28 market-quality samples were interpreted and noted. With this technique, those structures with similar sensory properties can be identified with some form of microscopy. Clarifying and predicting the parameters that are related to textural quality in new cultivars will streamline the introduction process.
C.G. Embree, K.B. McRae, E.N. Estabrooks and C. Pratt
Vegetative and fruiting characteristics were measured for a spur mutant of `McIntosh' apple (Malus × domestics Borkh.). Nine-year-old `MacSpur' trees in an orchard in New Brunswick, Canada, were grouped according to three degrees of spurriness. Reduced terminal growth, fewer limbs per tree, more flowering spurs per unit length of 2- and 3-year-old wood, less yield, and lower yield efficiency were associated with the highest degree of spurriness. The variability suggests that `MacSpur' may be an unstable periclinal chimera.
K.A. Sanford, P.D. Lidster, K.B. McRae, E.D. Jackson, R.A. Lawrence, R. Stark and R.K. Prange
Postharvest response of wild lowbush blueberry (Vaccinium angustifolium Ait. and V. myrtilloides Michx.) to mechanical damage and storage temperature was studied during 2 years. Fruit weight loss and the incidence of shriveled or split berries were major components that contributed to the loss of marketable yield resulting from mechanical damage and storage temperature. Decay of berries resulted in only 1% to 2% of the total marketable fruit loss. In general, the major quality attributes (firmness, microbial growth, hue, bloom, split, and unblemished berries) deteriorated with increasing damage levels and increasing storage temperature without significant interaction. Temperature had consistent effects in both years on moisture content, soluble solids concentration, titratable acids, weight loss, shriveled and decayed berries, Hunter L values, and anthocyanin leakage, while damage level had inconsistent or no significant effect.
Barbara J. Daniels-Lake, Robert K. Prange, Sonia O. Gaul, Kenneth B. McRae, Roberto de Antueno and David McLachlan
In Fall 2001 in Nova Scotia's Annapolis Valley (Canada), several million kilograms of processing and table-stock potatoes (Solanum tuberosum L.) were affected by a severe “musty” “off” flavor and “off” odor that persisted after cooking. 2,4,6-Trichloroanisole (TCA), a potent musty flavor/odor compound that is not known to be a potato metabolite was detected in samples of three potato lots rejected by consumers. To determine the role and source of TCA in the affected crop, samples of tubers from 30 fields were evaluated, including examination of production inputs and industry estimation of the “off” flavor, expert organoleptic assessment of flavor–odor intensity, and analytical quantitation of the TCA content of affected tubers, followed by a soil challenge to provoke TCA production. Production of “musty” potatoes was associated with unusually hot (>30 °C) soil temperatures during the 2001 growing season, and in some cases with γ-cyclohexane hexachloride (CHC) applied to control soil wireworm (putatively Limonius agonus Say). TCA quantitation and organoleptic assessment were in general agreement. Samples of soils from “idle” fields (no agricultural inputs for at least 8 years) and “production” fields (produced “off”-flavor potatoes in 2001) were subjected to several factors: 1) presence or absence of potato tubers; 2) preheating at 30 °C for 3 days, or no preheating; and followed by 3) no pesticides, or γ-CHC, chlorothalonil, chlorpyrifos, fludioxonil, imidacloprid, or linuron applied singly, or all six pesticides applied together. After incubation for 2 weeks at 22 °C day/14 °C night with a 14-hour photoperiod, solid-phase microextraction/gas chromatographic–mass spectrometric analysis revealed that untreated soils released small quantities of TCA (2.8 mol·kg−1) whereas higher quantities of TCA were present in soils treated with pesticides (3.8–6.6 mol·kg−1). The quantity of TCA released was not significantly affected by the presence or absence of potato tubers, but it was increased by preheating the soil sample, regardless of the other two factors, and by an interaction between pesticides and soil source. The quantity of TCA from both “idle” and “production” soils was highest when γ-CHC was added alone (214% and 284% of checks respectively). TCA production increased in the presence of the other five pesticides applied singly in “production” soils, but not in “idle” soils. Application of the six pesticides together increased TCA in both soils. Such an association of TCA-based “musty” “off” flavor with field soils containing γ-CHC and other pesticides combined with high soil temperature had not been reported previously.