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Brenner L. Freeman, Janet C. Stocks, Dennis L. Eggett, and Tory L. Parker

cultivar, across the season, and between storage treatments. Materials and Methods Raspberry collection. Six cultivars of Rubus idaeus L. raspberries (‘Autumn Bliss’, ‘Caroline’, ‘Jaclyn’, ‘Joan J’, ‘Polana’, and ‘Polka’) grown on a 20 acre farm in Utah

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V.M. Gingas and B.D. Stokes

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Brent L. Black, Tiffany Maughan, Christina Nolasco, and Blake Christensen

Winter injury to raspberry floricanes commonly limits productivity in cold climates. Primocane-fruiting raspberries avoid winter injury by fruiting on first year canes, but fruit production in the high-elevation valleys of the Intermountain West is later than needed for local markets, and may be limited by early fall freezes. High tunnels were used for early spring heat to advance primocane growth and the fruiting season of two primocane-fruiting red raspberry cultivars. Tunnels were covered with plastic in March and April. Then, they were covered with shade cloth during fruit ripening. Tunnel-covered plots were compared with field plantings for primocane growth rate, fruiting season, yield, and fruit quality over two seasons. High tunnels increased cane growth rate, with the harvest season advanced by 18 to 26 days depending on season and cultivar, but they did not consistently affect the total season yield or fruit size. Low-cost two-season tunnels used in conjunction with early-season primocane-fruiting raspberries may provide a viable method for small acreage producers in harsh climates to reliably supply high-value seasonal raspberry markets.

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Creighton L. Gupton

Anthocyanin-deficient dewberries in Mississippi were evaluated for possible use as a source of marker genes for blackberries. Ratios of normal to anthocyanin-deficient plants from test crosses suggested single-locus control of stem color, with anthocyanin deficiency a recessive trait. Its simple inheritance and easy identification in seedlings provide potential for anthocyanin deficiency (t) to be used as a marker gene in blackberry genetic studies.

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Hugh A. Daubeny

The indigenous North American red raspberry, Rubis strigosus has been neglected in breeding programs. Only four cultivars, `Cuthbert', `Latham', `Herbert' and `Ranere' provide most of the germplasm contained in present-day cultivars; no more than six individual wild genotypes of the species are represented by the four cultivars. In recent years, the B.C. breeding program has screened seedling populations of hitherto unexploited genotypes of the species from various locations in North America. Useful traits identified in selections from the populations include levels of resistance to 1) the North American aphid vector, Amphorophora agathonica, of the raspberry mosaic virus complex, 2) to several cane diseases and 3) to root rot caused by Phytophthora fragariae var rubi, as well as desirable fruit traits, such as bright, non-darkening red color and easy release. Selections with cultivar potential have now been identified in the second and third backcross generations from the species.

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Regina L. Reickenberg and Marvin P. Pritts

The dynamics of nutrient uptake from foliar applied 15N-urea and Rb (a K analog) were quantified in red raspberries. Both N and Rb in an aqueous solution were absorbed rapidly into the leaf and transported throughout the plant. In the greenhouse, about half of the urea and a third of the Rb were absorbed within 32 hours of application. The addition of a surfactant to the foliar solution reduced uptake, while solution pH, time of application and leaf age had little effect. The lower leaf surface exhibited a faster rate of absorption than the upper surface, but the difference was not large. In the field, some foliar N appeared to have been washed off leaves and taken up by the root system; however, none of the foliar applications affected plant growth. We conclude that significant uptake of foliar applied N and K occurs in raspberry, but the absolute amount delivered through a single foliar application is small. The percentage of total plant nutrient supplied through a foliar application is reduced to < 5% over time as the plant grows, so multiple applications would be required to maintain levels significantly higher than would exist through root uptake alone.

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Jean-Pierre Privé, J.A. Sullivan, and J.T.A. Proctor

Leaf removal, cane girdling, and 14C translocation patterns were used to study source-sink relationships of primocane-fruiting (PF) red raspberries. Although the leaves in the reproductive zone were most important for vegetative and reproductive development, compensatory effects between the cane leaves were evident. When 14C translocation was studied in the reproductive portion of the cane, the lateral closest to the 14C-treated leaf was the major sink for carbohydrate from that leaf, independent of leaf position or reproductive development. Thereafter, partitioning to leaves and/or flowers or fruits above the 14C-treated leaf was related to leaf phyllotaxy 75% of the time.

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Stephen F. Klauer, J. Scott Cameron, and Chuhe Chen

With the advent of new rotary-head mechanical harvesters, it is now possible to machine-harvest a wider raspberry canopy. In Spring 1996, a trial was established in a grower's field in Lynden, Wash., comparing raspberries trained to two top wires with a 70-cm spread (split trellis) to the conventional single top wire system. Within the split trellis, increases in leaf number per cane (97%), and leaf area per cane (55%) were not reflected in a concomitant increase in total leaf dry weight per cane (35%). Leaf dry weight per fruit weight was 11% less within the split trellis. These data suggest that the canopy is more efficient with this type of trellis. Increases in estimated yield per cane (49%) and projected yield per acre (50%) associated with the split trellis were due to increases in berry number per cane (47%). Fruit number per meter of lateral was 35% greater within the split trellis. Greatest enhancements to yield components were in the upper parts of the canopy where canes were tied over. Since there were no differences in lateral numbers or lateral lengths between the two systems, this increased productivity was due to increased floral expression, enhanced fruit set, increases through Spring bud initiation or any combination thereof. In both trellis systems, the longest laterals occurred on the middle third of the cane and decreased in length progressively towards the tip of the cane. Primocane lengths were shorter (20%) and diameters were smaller (10%) and more uniform in the split trellis system.

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Mahmoud A. Hassan and Harry Jan Swartz

An efficient protocol for plantlet regeneration using petioles and internodes of two blackberry cultivars has been developed for use in genetic transformation. Maximum shoot regeneration was induced on MS medium supplemented with 5 μM Thidiazuron (TDZ) and 0.5 μM IBA. Preconditioning the source shoots on 0.5 μM TDZ containing MS medium did increase the number of regenerated shoots/explant, but did not affect the regeneration percentage. The antibiotic, kanamycin, significantly reduced the growth and regeneration of explants at 10 mg/L or higher. In contrast, cefatoxime at 100-500 mg/L increased explant growth and percentage regeneration.

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Herbert D. Stiles

Static-V trellis increases raspberry yield, but fruiting shoots grow toward its center making harvest difficult. Shading causes early leaf abscission and it favors fungus diseases inside the V. Static training of floricanes and primocanes to opposite sides of a V trellis prevents neither harvest difficulty, nor primocane injury during harvest. In 1988-89 harvest difficulties were reduced by bloom-time shifting of floricanes on a V-trellis. Over 90% of fruiting shoots were oriented to the trellis ' exterior, but primocane shading and early leaf abscission continued. The 'bent fence' trellis was designed and tested in 1989. It shifts floricanes from horizontal orientation to an upright position on one side of a V-shaped trellis, thus retaining outward display of fruiting shoots and achieving unobstructed display of primocanes on the opposite side. Harvest efficiency, disease reduction, accurate deposition of pesticides, avoidance of solar injury (sun scald), and adaptation of mechanical pest control procedures are potentiated by this system. It also reduces impediments to studies of carbohydrate partitioning, photosynthetic efficiency, yield efficiency, and intraplant competition.