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Martin Paré and Deborah Buszard

Four soil management treatments were applied from 1991 to 1993 to `Spartan'/M.9 apple trees planted in 1987. Geotextile, straw mulch, composted manure mulch, and grass sod were used to control weed growth in a 1-m-wide band under the trees. The experiment was a randomized complete block design with two blocks and seven trees per treatment; data was taken from the five inner trees in each plot. Trees in straw mulch showed the largest increase in trunk cross-sectional area (+45.6%) over the three years; those in the geotextile showed the second largest (40.7%). Straw mulch also resulted in the largest yield 2 years out of 3. Fruit set and fruit quality were also assessed, and trees in manure mulch and grass sod set the least fruit in each season. Fruit from the grass sod treatment remained harder in storage, and both straw mulch and grass sod have a higher proportion of grade A fruit (57 of total fruit).

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Deborah Buszard and W.W. Schwabe

`Cox's Orange Pippin' apple (Pyrus domestics Berth.) trees, which were previously heavily cropped compared to previously defruited trees, had smaller flowers, lower initial fruit set, and a shorter effective pollination period (EPP) than defruited trees. The morphology of apple flower styles and stigmas was studied using scanning and transmission electron microscopy. Virgin stigmas from previously unstressed trees had fully expanded papillae, but 7 days after pollination the papillae were collapsed and distinct pollen tubes penetrated the stigmatic surface. Virgin stigmas from flowers of previously heavily cropped trees were smaller than those from previously defruited trees. The virgin stigmas of the flowers of heavily cropped trees showed collapsed papillae, and differences were observed in the intercellular material in the subtending transmitting tissue. These differences may explain the poor fruit setting characteristics of apple flowers on trees that have borne a heavy crop in the previous year.

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Shahrokh Khanizadeh and Deborah J. Buszard

Promising 1989 strawberry selections from the Agriculture Canada/McGill Univ. breeding program have been evaluated since 1990 at three different sites in Quebec. `Kent', `Glooscap', `Honeoye', `Bounty', and `Veestar' were used for comparison. Yield, average fruit weight at each harvest, firmness, color, taste, and other fruit characteristics were evaluated. SJ89288-2 had the highest yield with large fruit. SJ89700-1 and SJ89264-6 produced similar yield to `Kent' and `Glooscap', with firm and large fruit. SJ89700-1 had bright red skin color and SJ89264-6 had bright pale red color. Both are suitable from fresh-market and pick-your-own (PYO). SJ8976-1, another selection, had a firm, large, bright pale red fruit. All four selections have good shelf life quality and will be tested at four sites during 1993–95.

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Shahrokh Khanizadeh, Clément Vigneault and Deborah Buszard

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Pauliina Palonen, Danielle Donnelly and Deborah Buszard

Low tissue-water content and increased osmotic concentration of cell sap are associated with frost resistance. Changes in total osmotic concentration of cell sap are due mainly to changes in concentration of sugars. Generally, sugar content increases with hardening and decreases with dehardening. This study examined the effect of elevated sucrose levels (3% to 15%) in the medium on the cold hardiness of `Festival' red raspberry (Rubus idaeus L.) shoots in vitro. To determine whether expected hardening is caused by elevated sucrose levels or by osmotic stress, different levels of mannitol in the media have been tested. After growing raspberry shoots on media with different levels of sucrose and mannitol for 2 weeks, shoot moisture content (percent) was determined. Cold hardiness of the shoots was determined by using differential thermal analysis or artificially freezing the shoots and assessing the survival by regrowth test and visual rating.

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Shahrokh Khanizadeh, Clément Vigneault and Deborah Buszard

Development of strawberry fruit depends on the number of fertilized achenes on the surface. The achenes are distributed on the receptacle surface in a pattern of more or less regular rows, spirally arranged. The number of achenes is determined by 1) counting the number of achenes per square centimeter of surface on ripe berries; 2) weighing the achenes after separation from the receptacle; or 3) counting the number of achenes after pressing the fruit between two layers of glass. The above methods are laborious and time-consuming. We, therefore, described anew semi-automated method (Image Analysis System, IAS) as an alternative to the above procedures. The IAS is capable of grouping the achenes into two or more categories based on their size (sound or aborted), surface area, color, volume, etc. This will facilitate the study of the relationship between achene number and fruit weight in strawberry.

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Shahrokh Khanizadeh, Michel J. Lareau and Deborah Buszard

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Shahrokh Khanizadeh, Deborah Buszard and Constantinos G. Zarkadas

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Shahrokh Khanizadeh, Michel J. Lareau and Deborah Buszard

An experiment was conducted to evaluate the mechanical harvesting and processing suitability of four standard strawberry [Fragaria ×ananassa (Duch.)] cultivars (`Kent', `Glooscap', `Bounty', and `Midway') and the recent introductions `Chambly' and `Oka'. `Kent', `Glooscap', `Oka', and `Chambly' had the highest yields and heaviest fruit. Similar percentages of berries of all cultivars were destroyed by the harvester. `Oka' and `Midway' were not suitable for this type of mechanical harvesting due to their susceptibility to bruising during harvest. Based on total marketable fruit harvested mechanically, `Chambly' was the most and `Oka' was the least adapted cultivars for this particular harvester. `Chambly' and `Glooscap' were easiest to decap, followed by `Bounty', `Oka', and `Midway'. None of the cultivars tested were suited ideally for machine harvesting, and further breeding is required to produce well-adapted cultivars.