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Pedro B. Oliveira, Cristina M. Oliveira, and António A. Monteiro

The aim of this study was to determine the effects of date of summer pruning and cane densities on growth and fruiting characteristics of the raspberry (Rubus idaeus) plant. Three summer-pruning dates (early, middle, and late July) and four cane densities (8, 16, 24, and 32 canes/m row) were imposed to the greenhouse-grown primocane-fruiting raspberry `Autumn Bliss' in 2 consecutive years (1994 and 1995). A higher light microclimate and CO2 assimilation rate were measured within the canopy at the lowest density. Some compensation in CO2 assimilation rates were observed in the upper leaves of the high-density treatments, probably in response to low light. Delayed pruning decreased yield per cane and per row. The highest yields per cane were always observed at the lowest cane density. Densities of 16 and 24 canes/m produced the highest fruit yield. Light conditions appeared to be the most important environmental factor affecting plant productivity. Fruit were a weaker sink than roots; therefore, the role of carbohydrate reserves should be investigated.

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Graham Sanders, Elsa Sanchez, and Kathleen Demchak

The increased demand for organic and sustainably grown produce has resulted in a demand for information on organic and biorational fungicides. The efficacy of these fungicides is often not established, yet they are aggressively advertised. In 2005 the efficacy of six organic and biorational fungicides and two controls were evaluated on field-grown red raspberries (Rubus idaeus `Prelude' and `Nova') for gray mold (Botrytis cinerea) management. Phytotoxicity of the fungicide treatments was evaluated on a weekly basis following each fungicide application. Fruit was harvested by hand, sorted into marketable and unmarketable categories and weighed. Subsamples of fruit were evaluated for postharvest disease development. Data analysis showed `Nova' was more susceptible to phytotoxicity than `Prelude'. The application of Phostrol resulted in the highest phytotoxicity rating when compared to all other fungicide treatments. The water spray control, standard fungicide (Captan/Elevate rotation) control, Endorse, and Lime Sulfur treatments resulted in negligible phytotoxity ratings. Applying Milstop, Milstop + Oxidate, and Oxidate + Vigor Cal Phos resulted in similar intermediate phytotoxicity ratings. Differences in marketable yield were nonexistent for the two cultivars and eight fungicide treatments. The predominant diseases observed in the postharvest evaluations were gray mold, blue mold (Penicillium sp.), and rhizopus soft rot (Rhizopus sp.) and/or mucor mold (Mucor sp.). This evaluation will be repeated in 2006.

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Adam Dale, Angela Sample, and Elizabeth King

Experiments were conducted to determine the chilling temperature and length of time required to break dormancy in red raspberry (Rubus idaeus L.). Five weeks of 7 °C with no light was sufficient to break dormancy in `Autumn Britten', `Nova', `Polana', and `Tulameen', while at least 8 weeks were needed for `Titan'. Comparisons with various chilling unit models allowed a model to be developed that could account for the observed chilling variation. In this model, each chilling hour was weighted as follows: below 5.6 °C = 1; 5.7 to 8.0 °C = 0.5; 8.1 to 11 °C = 0; 11.1 to 13 °C = -0.5; and >13 °C = -1. Plants of `Nova' and `Tulameen' chilled before flower initiation occurred, broke dormancy, and the resulting lateral branches remained vegetative. When the plants were fruited in the greenhouse, we were able to produce a second crop on the fruiting canes when the lateral branches that had fruited were removed. These experiments show that raspberries can be manipulated so that plants chilled in mid-September in the Northern Hemisphere can be induced to fruit by the beginning of January.

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Becky R. Hughes*, Wanda J. Cook, and Candy N.F. Keith

In vitro rooting and subsequent greenhouse survival of `Autumn Britten', `Boyne', `Comet',`Nova' and `Qualicum' raspberry (Rubus idaeus L.) plantlets were compared following four weeks on a rooting medium with and without activated charcoal, and with 0.1, 0.5, 1.0, 2.0 or 3.0 milligrams per litre IBA. The addition of charcoal significantly increased the percentage of plantlets that produced roots in vitro for the hard-to-root cultivars. Percent rooting in vitro was highest with the three lower levels of IBA. Root number was influenced only by the cultivar, while root diameter and length were affected by all the factors investigated. Greenhouse survival was affected by the cultivar, the presence or absence of charcoal and the IBA level in the in vitro rooting medium, with significant interactions. Provided charcoal was present in the rooting medium, the level of IBA didn`t alter survival. The addition of charcoal to the rooting medium improved greenhouse survival of the three hardest-to-root cultivars. Plug plant stem length; internode length and dry weight were increased by the presence of charcoal in the in vitro rooting medium for all but the easiest to establish cultivar. Chemical names used: 3-indolebutyric acid (IBA).

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Bernadine C. Strik and Helen K. Cahn

`Meeker' red raspberry (Rubus idaeus L.) cane densities of 5, 10, or 15 canes/hill in a hill system, with canes topped at 2 m or the entire cane length retained and looped, were compared with a 15- or 30-cm-wide hedgerow with canes topped at 2 m from 1995 to 1997. Cane density among all treatments ranged from 2.2 to 9.9 canes/m2 during the study. Plots were harvested by machine every 2 days. Within the hill system, total yield increased with cane density in all years. Looped treatments produced a higher yield/plot than did topped ones in all years except 1996, when the yield difference was insignificant because looped canes had greater winter injury. Weight per fruit ranged from 5.4% to 9.7% less on looped than on topped canes. Hedgerow systems had a lower yield than hill systems in 1996, but a higher yield in 1997. Losses due to machine harvest were not affected by pruning (cane density or topping) or production system (hill system or hedgerow) and averaged 16.2% of total yield in 1997. Thirty-five percent of the loss due to machine harvest occurred between harvests.

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Charles F. Forney

Volatile compounds are responsible for the aroma and contribute to the flavor of fresh strawberries (Fragari×anannassa), red raspberries (Rubus idaeus), and blueberries (Vaccinium sp.). Strawberry aroma is composed predominately of esters, although alcohols, ketones, and aldehydes are also present in smaller quantities. The aroma of raspberries is composed of a mixture of ketones and terpenes. In highbush blueberry (Vaccinium corymbosum), aroma is dominated by aromatic hydrocarbons, esters, terpenes and long chain alcohols, while in lowbush blueberries (Vaccinium angustifolium), aroma is predominated by esters and alcohols. The composition and concentration of these aroma compounds are affected by cultivar, fruit maturity, and storage conditions. Volatile composition varies significantly both quantitatively and qualitatively among different cultivars of small fruit. As fruit ripen, the concentration of aroma volatiles rapidly increases closely following pigment formation. In storage, volatile concentrations continue to increase but composition depends on temperature and atmosphere composition. Many opportunities exist to improve the aroma volatile composition and the resulting flavor of small fruit reaching the consumer.

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Diana L. Lange

Modified atmosphere packaging (MAP) is a technology that is currently used for most packaged salads and fresh-cut vegetables, and to a lesser extent, fresh-cut fruit such as cantaloupe (Cucumis melo L.), pineapple [Ananas comosus L. (Merr.)], and apple (Malus ×domestica Borkh.). In addition, about 750 million lb (340,200 Mg) of strawberries (Fragaria ×ananassa Duch.), raspberries (Rubus idaeus L.) and sweet cherries (Prunus avium L.) are distributed in MAP annually. The fresh produce packaging industry has developed new films to respond to increased produce consumption and changes in the use of film packaging within different produce marketing segments. The produce film industry sold 60 million lb (27,200 Mg) of film in 1994, and in 2000 it is forecasted to sell 110 million lb (49,900 Mg), an increase of 83%. The distribution of film usage has also changed since 1994 when film consumption patterns were as follows: 20% [12 million lb (5,400 Mg)] retail, 15% [9 million lb (4,100 Mg)] warehouse clubstores, and 65% [39 million lb (17,700 Mg)] food service. In 2000 it is projected that consumption patterns will be as follows: 25% [27.5 million lb (12,500 Mg)] retail, 20% [22 million lb (10,000 Mg)] warehouse clubstores, and 55% [60.5 million lb (27,400 Mg)] food service. These changes represent a 10% shift in film market segment usage patterns away from food service applications to an increase of 5% for each of the retail and warehouse clubstore segments.

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Joseph C. Neal, Marvin P. Pritts, and Andrew F. Senesac

Five greenhouse and two Geld experiments were conducted to evaluate tissue culture-propagated (TC) raspberry (Rubus idaeus cv. Heritage) sensitivity to preemergent herbicides. Plant performance was measured by plant vigor, above-ground fresh weight, root development, and primocane number. Simazine and oryzalin caused significant injury to newly planted TC raspberry plants in greenhouse and field experiments. The severity of injury was generally linear with respect to herbicide rate, but no appreciable differences in injury were observed between the granular and spray applications. Napropamide wettable powder caused some foliar injury, but plants recovered within one growing season and growth was equal or superior to the hand-weeded controls. The granular formulation of napropamide produced similar results, but did not cause the initial foliar burn. Pre-plant dipping of roots into a slurry of activated carbon did not prevent simazine or oryzalin injury, but injury was reduced when herbicide applications were delayed. Simazine applied 4 weeks after planting was not Injurious, and oqzalin applied 2 or 4 weeks after planting caused some foliar injury, hut no reduction in plant fresh weight. Delayed treatments of napropamide increased foliar injury. Herbicide tolerance of tissue-cultured plantlets appeared to be less than that of conventionally propagated plants. Chemical names used: N,N-diethyl-2-(1-napthalenyloxy)propanamide (napropamide), 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin), 6-chloro-N,N'diethyl-1,3,5-triazine-2,4-diamine (simazine).

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Séverine Morel, Richard E. Harrison, Donald D. Muir, and E. Anthony Hunter

Fruit from three red raspberry (Rubus idaeus L.) cultivars—`Glen Clova', `Glen Lyon', and `Glen Moy'—were harvested from four sites on two harvest dates and evaluated fresh or following storage at -20 °C to determine the relative importance of genotype, harvest date, location and freezing effects on 19 sensory attributes using a trained sensory panel. Freezing and cultivar × freezing interaction effects were relatively large while site, harvest date, and other interactions were of minor importance. The cultivar × freezing interaction was caused by differential responses among cultivars for the sensory attributes purple, juicy, sweet, and raspberry aroma with less discrimination among cultivars postfreezing. `Glen Clova' fresh fruit received the highest values for juicy, fruity, sweet, and raspberry aroma; `Glen Moy' fresh fruit received the highest values for purple; `Glen Lyon' fresh fruit received the lowest values for juicy, postfreezing, `Glen Lyon' received the highest values for purple and sweet and all three cultivars were similar for the other attributes. These data suggest that selection for improved postfreezing sensory characteristics should not rely solely on fresh fruit evaluations although further study of a more genetically diverse group of genotypes would be beneficial. The significant cultivar and minimal harvest date and location effects suggest that these fruit sensory analysis methods should be useful in selecting raspberry genotypes with superior fruit quality.

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Pauliina Palonen and Leena Lindén

`Maurin Makea', `Muskoka', ` Ottawa', and `Preussen' red raspberry (Rubus idaeus L.) canes were collected from the field and subjected to different hot water treatments (20, 35, 40, 45, and 50 °C) to determine if endodormancy could be removed by a near lethal stress. Estimation of days for 50% budbreak (DD50) was found useful for describing the state of bud dormancy in the samples. Bud dormancy was broken in `Ottawa' by immersing the canes in 45 °C water for 2 hours, in `Maurin Makea' by treating the canes in 40 °C water, and in `Preussen' by both 40 and 45 °C treatments. The influence of this treatment on dormancy and cold hardiness at different times of the winter was further examined using `Ottawa' raspberry. The treatment removed bud dormancy most effectively in October, when the samples were in deepest dormancy. A slight effect was observed in November, but no effect in January. During ecodormancy in February the treatment delayed budbreak. Hot water treatment reduced cold hardiness of `Ottawa' canes by 8 to 15 °C, and that of buds by 9 to 13 °C during both endo- and ecodormancy. Based on the capacity of buds and canes to reacclimate, recovery from the stress treatment was possible at temperatures ≥4 °C. Loss of cold hardiness was caused by high treatment temperature itself and was not related to breaking of dormancy in samples. This finding suggests that dormancy and cold hardiness are physiologically unconnected in raspberry.