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Jean-Pierre Privé and J. Alan Sullivan

Growth rates for two types of tissue-cultured plant stock for `Heritage', `Ruby', and `Redwing' red raspberry (Rubus idaeus L.) were examined. Actively growing plantlets from the greenhouse (G) were compared to cold-treated (CT) plantlets from cold storage. The greatest differences between these two occurred during the first 6 weeks after planting. At 4 weeks, CT plants for all cultivars had longer canes and internodes, sometimes twice that of G plants. Although `Heritage' had greater total plant dry weights following chilling, `Ruby' and `Redwing' had less. Chilling had no effect on `Heritage' root growth but did reduce root dry weight for `Redwing' and `Ruby'. Relative growth rate (RGR) and leaf area ratio (L-AR) were more effective variables for analyzing growth as they considered differences in initial biomass and cane number and provided a better representation of the data during the initial 6 weeks of growth. All cultivars showed a greater total plant RGR and LAR for the CT plants at 6 weeks. During the first 4 weeks, the G plants were more efficient producers of root dry matter while the CT plants were more efficient producers of cane dry matter. By 6 weeks, the G plants had partitioned a greater percentage of their assimilates into cane growth while the leaves, canes, and roots of the CT plants contributed equally to total RGR. No difference in total or individual component RGR was observed after 6 weeks.

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Adam Dale and Theo J. Blom

The objectives of the study were to determine whether raspberries responded to decreased red to far-red ratio and whether it was more effective at the beginning or end of the dark period. Increased proportions of far-red light increased the internode length when at the beginning of the dark period on the three raspberry cultivars `Lauren',`Reveille', and `Titan'. Cultivars varied in that internode length also increased in ambient daylength compared to short days in `Lauren' and `Reveille', but not in `Titan'. They also responded differently to photoperiod: `Titan' and `Lauren' grew under short days, whereas `Reveille' ceased growth.

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Rebecca L. Darnell, Horacio E. Alvarado, Jeffrey G. Williamson, Bryan Brunner, María Plaza, and Edna Negrón

There is increasing interest in red raspberry (Rubus idaeus) production worldwide due to increased demand for both fresh and processed fruit. Although the United States is the third largest raspberry producer in the world, domestic demand exceeds supply, and the shortage in fresh market raspberries is filled by imported fruit from Canada during July and August, and from Mexico and Chile during November through May. The raspberry harvest season is well defined and the perishability of the fruit limits postharvest storage. Winter production of raspberry in tropical and subtropical climates could extend the harvest season and allow off-season fruit production during periods of high market prices. The objective of the current study was to examine growth and yield of red raspberry cultivars grown in an annual winter production system in Florida and Puerto Rico. Long cane cultivars were purchased from a nursery in the Pacific northwestern U.S. in 2002 (`Heritage' and `Tulameen'), 2003 (`Tulameen' and `Willamette'), and 2004 (`Tulameen' and `Cascade Delight') and planted in raised beds in polyethylene tunnels in December (Florida) or under an open-sided polyethylene structure in January-March (Puerto Rico). In Florida, harvest occurred from ∼mid-March through the end of May, while in Puerto Rico, harvest occurred from the end of March through early June (except in 2002, when canes were planted in March). Yields per cane varied with cultivar, but ranged from ∼80 to 600 g/cane for `Tulameen', 170 to 290 g/cane for `Heritage', 135 to 350 g/cane for `Willamette', and ∼470 g/cane for `Cascade Delight'. Economic analysis suggests that, at this point, returns on this system would be marginal. However, increasing cane number per unit area and increasing pollination efficiency may increase yields, while planting earlier would increase the return per unit. The key to success may hinge on developing a system where multi-year production is feasible in a warm winter climate.

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C.A. Weber, K.E. Maloney, and J.C. Sanford

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David C. Percival, John T.A. Proctor, and J. Alan Sullivan

Field experiments consisting of trickle irrigation (TI), IRT-76 plastic film (PF), and straw mulch were initiated to determine the influence of soil temperature and water status on carbon partitioning during the establishment of Rubus idaeus L. `Heritage' (1993, 1994), `Autumn Bliss' (1994), and `Summit' (1994) micropropagated raspberries. Environmental, vegetative, reproductive, and nutrition data were collected. Photosynthesis (Pn) measurements were recorded under field conditions using a Li-Cor LI-6200 portable photosynthesis system. Neither node number nor shoot: root ratio was influenced by TI, PF, or straw mulch. PF, however, increased root and shoot weight, total flowers produced, total berries harvested, and foliar N and P. Although differences existed among cultivars, field Pn measurements indicated that, regardless of groundcover treatment or cultivar examined, the maximum Pn rate occurred at a root-zone temperature of 25C. Hence, results from this study indicate that conditions in both the air and root zone physical environment regulate carbon assimilation and partitioning.

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David C. Percival, John T. A. Proctor, and J. Alan Sullivan

A study examining the influence of trickle irrigation (TI), IRT-76 plastic film (PF) and straw mulch (SM) on the establishment of Rubus idaeus L. cv. `Heritage' micro-propagated raspberries was initiated at Cambridge, Ontario in 1993. Environmental, nutritional, vegetative and reproductive data were collected. Soil temperature and soil water status were greatly affected by TI, PF and SM. TI lowered soil NO3-N and increased soil NH4-N and Mg. PF increased soil NO3-N and NH4-N. Foliar N decreased by 10% with TI and increased by 8% with PF. Foliar P and Ca increased by 45 and 6% respectively, with TI. Node number was not influenced by TI, PF or SM. PF however, increased cane height, cane diameter, dry weight and leaf area by 14, 17, 77 and 11% respectively, and TI increased cane diameter by 13%. Although TI increased the number of fruiting laterals by 63%, there was no effect of TI, PF or SM on harvested berry number or weight.

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John R. Clark, James N. Moore, Jose Lopez-Medina, Chad Finn, and Penelope Perkins-Veazie

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Horacio E. Alvarado-Raya, Rebecca L. Darnell, and Jeffrey G. Williamson

a key role in reproductive development in many plants, and stored carbohydrates are especially important in supporting flowering and early fruit development in woody perennials. In raspberry, roots and primocanes are the primary sites for

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

`Autumn Bliss', `Heritage' and `Redwing' were grown in a controlled environment setting at three day/night temperature regimes (30/25, 25/20, 20/15C) at either 12 or 16 hour photo periods. Vegetative (height, diameter, node number, leaf area, leaf, cane and root dry weight) and reproductive (precocity, numbers of fruiting laterals, flower number and dry weight) parameters were analyzed. Optimum vegetative growth was obtained when plants were subjected to short photoperiods (12 hrs) and cool (20/15C) or moderate (25/20C) day/night temperatures. Reproductive characteristics were enhanced when grown under long photoperiods (16 hrs) and moderate temperatures. High temperatures (30/25) reduced cane height due to a decrease in internode length with the greatest reduction occurring under long photo periods. Precocity and flowering was enhanced by long photoperiods especially at cool and moderate temperatures. This may have implications for the reproductive potential of these cultivars when grown in north temperate areas where high temperatures are common for most of the summer.

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Fumiomi Takeda

Nine-year-old 'Black Satin' blackberry (Rubus subgenus Rubus) plants were dormant pruned to three floricanes with three, six, nine, or twelve 12-node lateral branches (≈108, 216, 324, or 432 axillary buds per plant) to determine the effect of lateral branch number on budbreak, fruit cluster number, fruit number per cluster, fruit weight, total soluble solids (TSS), and yield. Percent budbreak of primary and secondary axillary buds was reduced as the lateral branch number increased. Pruning did not affect fruit weight (6.4 g) or TSS (9.5%). Yield per lateral branch was reduced as lateral branch number increased. A plant with three floricanes, each with 12 lateral branches, produced 21 kg of fruit. The results indicate that pruning lateral branches to a manageable length may be advantageous for eastern thornless blackberry trained on a divided canopy trellis.