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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Field experiments were conducted on two cultivars of saskatoon to test the effectiveness of ethephon in stimulating uniform fruit ripening without compromising fruit quality. Shrubs of cultivars Northline and Smoky were sprayed to runoff with ethephon (0, 250, 500, and 1000 mg·L-1 for `Northline'; 0, 500, and 1000 mg·L-1 for `Smoky') prior to fruit maturity. Fruit were harvested 4 to 8 days after treatment and sorted into ripeness categories by size, and the fully ripe fruit were evaluated for quality (surface color, firmness, mean fruit weight, soluble solids, and titratable acids). Ethephon significantly increased the percent ripe fruit per shrub (by up to 9.7%) in both cultivars, without a significant effect on fruit quality. At concentrations up to 1000 mg·L-1, ethephon may be an effective ripening agent for saskatoon fruit without reducing fruit quality. Although there were significant differences in yield from year to year for both cultivars because of their biennial-bearing habit, ethephon treatments did not significantly affect total yields.

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Cecil Stushnoff, Richard L. Remmele Jr., and V. Esensee

Aqueous fractions in dormant buds of Amelanchier alnifolia Nutt. `Smoky', may exist either as liquid, ice or glass phases depending on the temperature history and the water content of the tissue. Phase diagrams for these states were constructed from differential scanning calorimetry (DSC) freezing and warming scans. The diagrams show that glass transition temperatures shift to warmer temperatures as cold hardening increases and as the water content is lowered by controlled desiccation. Glass transitions were detected from -60 to -20° C, during slow freezing scans in the DSC, suggesting that survival of this extremely cold hardy tissue is based upon a potential to undergo glass transitions in the dormant state. Endogenous raffinose family oligosaccharides (RFO) increase during cold hardening, and decrease as hardiness diminishes with the onset of growth.

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Fruit growth in saskatoons (Amelanchier alnifolia Nutt.), an emerging horticultural crop across the Canadian prairies, results from development of the mesocarp and the endocarp-locular-ovular structure which includes the developing seeds. Contribution of these tissues to fruit size was assessed using transverse sections of ovaries sampled at six developmental stages among large- and small-fruited cultivars. Mesocarp development was similar among the larger-fruited cultivars (Thiessen, Northline, and Smoky); the number of cells increased rapidly through Stage I [162 to 293 growing degree days (GDDs)] of fruit growth, and cell number increase was minimal during Stages II (293 to 577 GDDs) and III (577 to 747 GDDs). In `Regent' fruit (a small-fruited cultivar), the maximal rate of cell division was delayed until Stage II and the mesocarp contained fewer cells than the larger-fruited cultivars at harvest maturity. Mesocarp cell enlargement was similar among all of the cultivars studied where cell expansion was maximal during Stage I and continued at a slower rate during Stages II and III. The area of the endocarp-locular-ovular structure was greatest for `Thiessen' and `Northline', midrange for `Smoky', and smallest for `Regent'. Data suggest that a minimum number of mesocarp cells early in fruit development is required to attain maximal mesocarp size, and that differences in cultivar fruit size are a function of both the mesocarp and the endocarp-locular-ovular structure.

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Saskatoon fruits, an emerging horticultural crop across the Canadian prairies, vary greatly in size among cultivars. In this study, we compare fruit development patterns among large, medium, and small fruited cultivars of saskatoon, and assess the role of seed number and pedicel diameter on fruit size. Fruit growth patterns of four cultivars (Thiessen, Northline, Regent, and Smoky) were determined from weekly measurements of fruit diameters and fresh and dry flower/fruit weights during two consecutive growing seasons. The developmental patterns of fruit growth determined using the above criteria were similar among cultivars and between years. At maturity, the largest fruits (fresh weight) obtained were from cv. Thiessen, followed by `Northline', `Smoky', and `Regent', in descending order. Pedicel diameters (one week prior to maturity) correlated linearly with increasing fruit diameter and fresh weight. At maturity, seed number per fruit correlated linearly with increasing fruit weight. Thiessen contained significantly more seeds per fruit (4.6) than `Northline' (3.7), `Smoky' (3.2), and `Regent' (3.2).

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Saskatoon fruit are an emerging horticultural crop across the Canadian prairies. As fruit size varies greatly among cultivars, knowledge of fruit growth patterns and factors that affect fruit size can be used to establish breeding trials and develop orchard management strategies that could enhance the production of this crop. In this study, we 1) determined fruit and seed growth patterns among large-, medium-, and small-fruited cultivars of saskatoon using growing degree days to standardize time to crop development and 2) assessed the role of seed number on fruit size. Fruit growth patterns of four cultivars (Thiessen, Northline, Regent, and Smoky) were determined from weekly measurements of fresh and dry fruit mass during two consecutive seasons. These growth patterns exhibited three phases. The largest fruit at maturity were from `Thiessen', followed by `Northline', `Smoky', and `Regent', in descending order. Pedicel cross-sectional areas 1 week before maturity correlated linearly with increasing fresh and dry fruit mass and seed number per fruit. At maturity, seed number per fruit correlated linearly with fresh and dry fruit mass. `Thiessen' contained significantly more seeds per fruit (4.6) than `Northline' (3.7), `Smoky' (3.2), and `Regent' (3.2). The results of this research suggest potential areas for orchard management improvement and future research directions for saskatoon crop improvement.

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Brian Baldwin and Karen K. Tanino

In vitro shoot cultures of saskatoon berry were subjected to a 6 week acclimating treatment (4°C/8h day). Acclimated cultures survived freezing to -27°C. Control cultures (24°C/16h day) killed at -6°C. Addition of ABA (5.0 × 10-5M) to growing medium did not increase hardiness of plants under acclimating conditions, but increased hardiness of control plants from -6°C to -10°C.

With standard BA concentration (1.1 × 10-5M) decreased by half, addition of ABA (5.0 × 10-5M) to growing medium resulted in formation of swollen axillary buds with red bud scales. Plantlets on similar medium to which ABA was not added did not show arrested growth or swollen red buds. Following defoliation, removal of shoot apex and transfer to hormone-free medium, buds on ABA-treated plantlets did not resume growth within 30 days. When ABA-treated plantlets were transferred to media supplemented with BA, dormant-looking buds resumed normal growth. Dormant buds collected from field-grown plants and placed in culture broke dormancy on BA medium and maintained the dormant state on hormone-free and ABA medias.

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Naa Korkoi Ardayfio and Harlene Hatterman-Valenti

. 1991 Variability of fruit quality and plant height in populations of saskatoon berries ( Amelanchier alnifolia Nutt.) Fruit Var. J. 45 162 165 Government of Saskatchewan Agriculture 2004 Costs and returns for a saskatoon berry orchard. 23 Sept. 2015

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Ethephon was applied in two consecutive years to saskatoon (Amelanchier alnifolia Nutt.) shrubs (`Northline' and `Smoky') to determine its effects on synchronizing fruit ripening. Ripeness can be visually assessed by color (green = immature; red = mature, not ripe; purple = mature, fully ripe). Ethephon (applied when fruit were ≈ 70% red) at 250, 500, and 1000 ppm increased the percentage of ripe fruit obtained from `Northline' by 2%, 4%, and 6%, respectively. Due to pronounced seasonal yield differences for `Smoky', ethephon had no effect on the percentage of ripe fruit obtained in 1994. However, in 1995, ethephon (applied at 70% red fruit stage) at 500 and 1000 ppm increased the percentage of ripe fruit obtained from `Smoky' by 4% and 2%, respectively. Fruit quality, evaluated with respect to surface color development, flesh firmness, fruit size, soluble solids concentration, titratable acidity, and the soluble solids: titratable acids ratio, was not significantly affected by ethephon treatments. This work was supported in part by AARI-FFF grant no. 940442.

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Glenn R. Thayer and Preston K. Andrews

Dwarfing rootstocks are essential for developing high-density pear orchards with increased precocity. The graft compatibility of Amelanchier alnifolia, A. x grandiflora, A. canadensis, and A. alnifolia `Thiessen' as a rootstock for `Anjou' pear or as an interstock on `Bartlett' seedling, `Old Home × Farmingdale' and Crataegus rootstocks are being tested. Twenty rootstock and rootstock/interstock combinations were top grafted 27 Jan. 1994. Ten replicates will be planted in pots for each graft combination in March after callusing. Growth of successful graft combinations will be measured every two weeks. Shoot length and diameter and trunk diameter at a designated reference point will be measured. Leaf color will be evaluated periodically using a Minolta colorimeter. At natural leaffall, leaf areas will be measured. Graft compatibility will be evaluated. All data will be analyzed by analysis of variance.

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Deborah Willard and Harlene Hatterman Valenti

Weed control is necessary to ensure success in early stages of juneberry (Amelanchier alnifolia) orchard development; however, juneberry growers have limited chemical weed control options. A field trial was initiated at Prosper, ND, to evaluate the efficacy of physical and chemical weed control methods and their effects on juneberry growth. Woven landscape fabric most effectively eliminated weed emergence, whereas winter rye (Secale cereale) cover crop allowed the most weeds to emerge throughout the study. During both years, a hairy vetch (Vicia villosa) companion crop provided poor early- to midseason weed control, but weed suppression increased over time as hairy vetch grew to cover open areas. However, hairy vetch was very competitive with juneberry, reducing crop height, width, and overall growth. Plants within the herbicide treatments (glyphosate at 0.75 lb/acre plus oryzalin at 2 lb/acre and linuron at 1.7 lb/acre followed by flumioxazin at 1 oz/acre) and the hand-weeded control, which was weeded three times each year, had the greatest growth.