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P.J. Macdonald and Margie Luffman

A collection of indigenous North American red raspberry (Rubus strigosus Michx.) was evaluated in an unreplicated field planting at the Canadian Clonal Genebank, Trenton, Ont. The accessions originated in British Columbia (B.C.) and the United States. Useful characteristics in the collection have been identified under B.C. conditions; however, field performance in Ontario has not been reported. Cultivars originating from B.C., Manitoba, and Ontario were included in the planting as standards. Overwintering injury ranged from slight to severe. Indigenous accessions were vigorous, with cane height comparable to standards; however, in some cases, primocane production was excessive. Most B.C. accessions flowered and fruited equivalent to, or earlier than, the earliest cultivar (`Boyne'), while R. strigosus from other locations were mid-season to late. Primocane fruiting was typical in B.C., but was not consistent in Ontario. Fruit were small, but had good color and structure. Accessions showed resistance to powdery mildew [Sphaerotheca macularis (Wallr.:Fr.)], but were very susceptible to late yellow rust [Pucciniastrum americanum (Farl.) Arth.].

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Todd A. Kostman, J. Scott Cameron, Chuhe Chen, and Stephen F. Klauer

The effect of mechanical stress from sources such as wind on the physiology of higher plants has been documented in many species. Some of these reported changes, such as decreased photosynthetic activity, are not well-documented and bear closer examination. Mechanical stress has been reported to decrease the productivity of some crop plants. In both field and greenhouse trials, high-speed blown air was used as a thigmic stress for the temporary, nonchemical suppression of primocane growth in red raspberry. Field trials with the cultivar Meeker in 1993–94 have shown that high-speed blown air can be used to adequately control primocane height for mechanical harvest, while increasing yield through greater numbers of fruit per cane. In both field and greenhouse experiments, photosynthetic activity or red raspberry leaves was not affected by 273 km/h of wind applied twice daily, 5 days per week. Anatomical analysis demonstrated changes in the cross-sectional anatomy of mechanically stressed canes. Stressed canes had increased callose deposition and greater numbers of secondary xylem cells.

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David L. Trinka and Marvin P. Pritts

Micropropagated (MP) raspberries (Rubus idaeus L. var. idaeus) are sensitive to moisture and temperature extremes and to certain preemergent herbicides used at transplanting. We examined fertilizer placement and row covers in conjunction with various weed management strategies to identify beneficial practices for newly planted, MP primocane-fruiting `Heritage' raspberries. Uncontrolled weed growth during plant establishment inhibited raspberry cane growth and production into the second and third growing seasons. Handweeding and herbicide treatments successfully controlled weeds, but soil moisture was apparently insufficient for optimum growth of the MP raspberries when these treatments were imposed, even with normal rainfall in early summer and drip irrigation in late summer. Polyethylene and straw mulches during the establishment year provided both weed control and adequate soil moisture, resulting in more cane growth in the first and 2nd year, and higher yields the 2nd year. Primocane density after the third growing season still was influenced by first-year weed management practices. Raspberry plants responded best to straw mulch without row covers as plant growth was better in both years. Canes were thicker, yields were higher, and a larger portion of the total crop was harvested early. Row covers were beneficial only in bare-soil treatments, and method of fertilizer placement had no effect on any measured variable. Mulching newly transplanted MP raspberries is an alternative to herbicide use that also provides physiological benefits to the plant through microclimate modification.

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Gina E. Fernandez and Marvin P. Pritts

A 2-year study was conducted to investigate the influence of the light environment on source-sink relationships in `Titan' red raspberry. Treatments imposed included flower and cane removal in conjunction with partial or whole canopy shading. Raspberry plants were remarkably resistant to a reduction in carbon supply. Yields and primocane production were maintained even when canopies were shaded. Furthermore, if raspberry plants were prevented from producing a full crop in one year, yields the following year tended to be higher than normal. These data, and other studies demonstrating that raspberry roots are strong carbon sinks, suggest that raspberry plants may rely on stored carbohydrate to mature the current crop of fruits when current photosynthate is inadequate. This trait is characteristic of some perennial species adapted to progressively changing environments, but may not be optimal for horticultural situations where growing conditions are relatively constant from year to year. A large root storage capacity and excessive primocane production likely contribute to the relatively low yields that are typical of this species.

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Hannah G. Rempel, Bernadine C. Strik, and Timothy L. Righetti

The effects of 15N-labeled fertilizer applied to mature summer-bearing red raspberry (Rubus idaeus L. `Meeker') plants were measured over 2 years. Four nitrogen (N) treatments were applied: singularly at 0, 40, or 80 kg·ha-1 of N in early spring (budbreak), or split with 40 kg·ha-1 of N (unlabeled) applied at budbreak and 40 kg·ha-1 of N (15N-depleted) applied eight weeks later. Plants were sampled six times per year to determine N and 15N content in the plant components throughout the growing season. Soil also was sampled seven times per year to determine inorganic N concentrations within the four treatments as well as in a bare soil plot. There was a tendency for the unfertilized treatment to have the lowest and for the split-N treatment to have the highest yield in both years. N application had no significant effect on plant dry weight or total N content in either year. Dry weight accumulation was 5.5 t·ha-1 and total N accumulation was 88 to 96 kg·ha-1 for aboveground biomass in the fertilized plots in 2001. Of the total N present, averaged over 2 years, 17% was removed in prunings, 12% was lost through primocane leaf senescence, 13% was removed through fruit harvest, 30% remained in the over-wintering plant, and 28% was considered lost or transported to the roots. Peak fertilizer N-uptake occurred by July for the single N applications and by September for the last application in the split-N treatment. This uptake accounted for 36% to 37% (single applications) and 24% (last half of split application) of the 15N applied. Plants receiving the highest single rate of fertilizer took up more fertilizer N while plants receiving the lower rate took up more N from the soil and from storage tissues. By midharvest, fertilizer N was found primarily in the fruit, fruiting laterals, and primocanes (94%) for all fertilized treatments; however, the majority of the fertilizer N applied in the last half of the split application was located in the primocanes (60%). Stored fertilizer N distribution was similar in all fertilized treatments. By the end of the second year, 5% to 12% of the fertilizer acquired in 2001 remained in the fertilized plants. Soil nitrate concentrations increased after fertilization to 78.5 g·m-3, and declined to an average of 35.6 g·m-3 by fruit harvest. Seasonal soil N decline was partially attributed to plant uptake; however, leaching and immobilization into the organic fraction may also have contributed to the decline.

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P.G. Braun, P.D. Hildebrand, and A.R. Jamieson

Twenty-five cultivars of red raspberry (Rubus idaeus L.) and one purple raspberry (R. occidentalis L. × R. idaeus L.) were evaluated for their resistance to fire blight caused by Erwinia amylovora (Burr.) Winslow et al. Actively growing raspberry cane tips were wound inoculated with three isolates of the pathogen and disease development was assessed over 17 days. Three methods of evaluating resistance were used: area under the disease progress curve (AUDPC), a weighted AUDPC called the area under the disease severity curve (AUDSC), and lesion length. A wide range of resistance levels was observed, but no cultivars were symptomless. Primocane-fruiting cultivars tended to be more resistant than floricane-fruiting ones. Of the three E. amylovora isolates used in this study, one was significantly more virulent than the other two, but no cultivar × isolate interaction was detected.

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Curt R. Rom and Jason McAfee*

`Apache' blackberry planted in 3-m plots spaced at 0.6 m between plants were maintained either with or without waste municipal wood chip mulch and grown for 5 years. Plots received similar weed control, pest management, and irrigation. All plots were annually hedged at 1.35-m height twice during midsummer to encourage branching. Fruit were harvested beginning in the second season after a season of establishment. Annual yield in the mulched plots was 15% greater, average fruit size was 4% larger, and cumulative yield was 9% greater in the mulched plots compared to nonmulched control plots. In two seasons, average berry soluble solids content of fruit from mulched plots was slightly, but not significantly higher. Annual primocane number was 33% greater, floricane number 41% greater, floricane dry weight after harvest was 15% greater, and average plant height before summer pruning was 24% taller in mulched plots compared to nonmulched plots. Mulch significantly reduced weeds within the plots.

Open access

Esther Nelson and Lloyd W. Martin

Abstract

Three treatments of combined N and K (0, 67, or 135 kgha−1 of each element) were applied to ‘Thornless Evergreen’ blackberries [Rubus laciniatus (West.) Willd]. Fruit were harvested in 1981-1984 with a Littau self-propelled harvester; yield, fruit size, soluble solids, and firmness were measured. Fruit pH, acidity, and anthocyanin content were measured in 1983 and 1984. Treatments affected yield, fruit characteristics, and leaf mineral composition; the intermediate treatment level was the most desirable. There was not a consistent relationship of N and K levels of primocane leaves or soil K level with yield, fruit size, soluble solids, or firmness of the fruit regardless of whether the fruit samples were taken the same year as the leaf and soil samples or the year following. We conclude that the currently recommended rates of N and K for ‘Thornless Evergreen’ need refinement.

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Kim S. Lewers*, Eric T. Stafne, John R. Clark, Courtney A. Weber, and Julie Graham

Some raspberry and blackberry breeders are interested in using molecular markers to assist with selection. Simple Sequence Repeat markers (SSRs) have many advantages, and SSRs developed from one species can sometimes be used with related species. Six SSRs derived from the weed R. alceifolius, and 74 SSRs from R. idaeus red raspberry `Glen Moy' were tested on R. idaeus red raspberry selection NY322 from Cornell Univ., R. occidentalis `Jewel' black raspberry, Rubus spp. blackberry `Arapaho', and blackberry selection APF-12 from the Univ. of Arkansas. The two raspberry genotypes are parents of an interspecific mapping population segregating for primocane fruiting and other traits. The two blackberry genotypes are parents of a population segregating for primocane fruiting and thornlessness. Of the six R. alceifolius SSRs, two amplified a product from all genotypes. Of the 74 red raspberry SSRs, 56 (74%) amplified a product from NY322, 39 (53%) amplified a product from `Jewel', and 24 (32%) amplified a product from blackberry. Of the 56 SSRs that amplified a product from NY322, 17 failed to amplify a product from `Jewel' and, therefore, detected polymorphisms between the parents of this mapping population. Twice as many detected polymorphisms of this type between blackberry and red raspberry, since 33 SSRs amplified a product from NY322, but neither of the blackberry genotypes. Differences in PCR product sizes from these genotypes reveal additional polymorphisms. Rubus is among the most diverse genera in the plant kingdom, so it is not surprising that only 19 of the 74 raspberry-derived SSRs amplified a product from all four of the genotypes tested. These SSRs will be useful in interspecific mapping and cultivar development.

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Hans Spalholz, Mary Jo Kelly, and Marvin Pritts

The use of high tunnels is a technology that can be implemented just about anywhere for a modest cost, and can be used to bring crops on earlier or extend them later in the season. Raspberries are a high value crop that, in season, sell for more than $3.00/lb. In the middle of winter, raspberries can sell for more than $10.00/lb. Our goal was to produce raspberries in October and November, after the field season ends from frost and rain, and when the selling price of raspberries doubles. Our project examined primocane-fruiting varieties and methods of managing plants to delay their production beyond the normal late August-September season. The first part of the study was to monitor the growth and productivity of several late varieties that typically fruit too late for the New York climate. One selection (NY01.64) and one cultivar (Josephine) appeared very promising for high tunnel production. The second set of treatments manipulated `Heritage' so that it fruits later than the normal September season. The five treatments were an unmanipulated control, applying straw over plots in late February at the rate of 6 tons/acre after a period of cold weather, mowing canes to the ground in early June shortly after they emerge, pinching primocanes (removing the top 4–6 inches) when they reach a height of about 2½ ft, and pinching when canes were 3½ ft tall. Each of these 4 treatments delayed flowering and shifted production to later in the season. The late pinching treatment appeared to provide the best yield curve under the high tunnel.