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Rengong Meng and Chad Finn

Nuclear DNA flow cytometry was used to differentiate ploidy level and determine nuclear DNA content in Rubus. Nuclei suspensions were prepared from leaf discs of young leaves following published protocols with modifications. DNA was stained with propidium iodide. Measurement of fluorescence of 40 genotypes, whose published ploidy ranged from diploid to dodecaploid, indicated that fluorescence increased with an increase in chromosome number. Ploidy level accounted for 99% of the variation in fluorescence intensity (r 2 = 0.99) and variation among ploidy levels was much higher than within ploidy levels. This protocol was used successfully for genotypes representing eight different Rubus subgenera. Rubus ursinus Cham. and Schldl., a native blackberry species in the Pacific Northwest, which has been reported to have 6x, 8x, 9x, 10x, 11x, and 12x forms, was extensively tested. Genotypes of R. ursinus were predominantly 12x, but 6x, 7x, 8x, 9x, 11x, and 13x forms were found as well. Attempts to confirm the 13x estimates with manual counts were unsuccessful. Ploidy level of 103 genotypes in the USDA-ARS breeding program was determined by flow cytometry. Flow cytometry confirmed that genotypes from crosses among 7x and 4x parents had chromosome numbers that must be the result of nonreduced gametes. This technique was effective in differentiating chromosome numbers differing by 1x, but was not able to differentiate aneuploids. Nuclear DNA contents of 21 diploid Rubus species from five subgenera were determined by flow cytometry. Idaeobatus, Chamaebatus, and Anaplobatus were significantly lower in DNA content than those of Rubus and Cylactis. In the Rubus subgenus, R. hispidus and R. canadensis had the lowest DNA content and R. sanctus had the highest DNA content, 0.59 and 0.75 pg, respectively. Idaeobatus had greater variation in DNA content among diploid species than the Rubus subgenus, with the highest being from R. ellipticus (0.69 pg) and lowest from R. illecebrosus (0.47 pg).

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David Mettler and Harlene Hatterman-Valenti

Research on blackberry production systems and cultivar selection is needed to expand the industry into colder hardiness zones in the United States ( Takeda et al., 2013 ). This would provide growers with the necessary techniques to provide high

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Sydney Lykins, Katlynn Scammon, Brian T. Lawrence, and Juan Carlos Melgar

Blackberry ( Rubus subgenus Rubus Watson) production has greatly increased since 2005 in North America, Central America, Australia, and Europe as a result of newly developed floricane-fruiting and primocane-fruiting cultivars from both university

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Syuan-You Lin and Shinsuke Agehara

Blackberry ( Rubus L. subgenus Rubus Watson) is a deciduous berry crop grown primarily in temperate regions. In recent years, the global blackberry industry has grown significantly, driven by increased consumer demand, year-round product

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P. Perkins-Veazie, C. Finn, and E. Baldwin

Oregon produces most of the processing blackberries in the United States. `Marion' blackberry (Rubus hybrid) is a trailing, thorny plant type with fruit highly prized for its unique flavor and superior processing quality. Blackberries developed in other parts of the United States grow well in Oregon but differ in flavor from `Marion' fruit. `Marion' blackberry plants are thorny and highly susceptible to freeze injury; growers desire a thornless, higher yielding, and more winter tolerant plant with similar fruit flavor and quality. This experiment was done to identify volatiles unique to `Marion' that may be incorporated into new germplasm. Forty-two volatile peaks were identified in blackberries using headspace gas chromatography and known standards. Ethylacetate and trans-2-hexenol were present in very low amounts and nerilidol was present in an unusually high amount in fresh `Marion' homogenates relative to other blackberry cultivars. Nerilidol is a volatile commonly associated with raspberry flavor and may come from the raspberry germplasm in the breeding background of `Marion'. It appears that the flavor of `Marion' fruit results from proportional differences in several volatile compounds rather than the presence of volatiles unique to this cultivar.

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Fumiomi Takeda and David Handley

A combination of simple cultural practices, a modified rotatable crossarm (RCA) trellis system, and covering plants with insulation material in winter overcame the lack of cold hardiness in trailing blackberries that have been established at Kearneysville, W.Va. After tying canes to trellis wires and rotating the cross-arms to below horizontal, tied canes were close to the ground, allowing them to be covered with protective materials, such as floating rowcover and polyethylene plastic during winter. Covers were removed in early spring and the canes remained in the horizontal orientation until bloom, which promoted flowering laterals to grow upright. After bloom, the cross-arm was rotated beyond vertical to position the fruit on one side of the row and improve harvest efficiency. In Jan. and Feb. 2005, the daily minimum temperatures under the FRC+PE covers were about 3 °C higher than in the open. The covers also provided protection against the wind. Tissue damage in protected trailing blackberries was significantly less than for unprotected plants. `Siskiyou' plants in covered plots produced 3 to 5 times more fruit than plants in the open. Harvesting of `Siskiyou' fruit occurred during the red raspberry harvest season or 2 to 3 weeks earlier than for eastern blackberries. Our findings suggest that trailing blackberries can grow satisfactorily and produce fruit if the adverse effect of low temperatures and winds is mitigated with our trellis system and winter protection method. If practical cultural techniques for improving their winter survival become available, there is a potential for early-season high-quality blackberry production in the mid-Atlantic coast region.

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John R. Clark

Eastern U.S. blackberries (Rubus subgenus Rubus) have advanced in recent years in production and quality of cultivar choices. Mainly a pick-your-own and local sales item of the early 1990s and before, the increased presence of blackberries in retail grocery stores in the last 10 years has broadened the market for this small fruit. Cultivars that can be shipped and have extended shelf life have been the cornerstone of this expansion. Also, off-season production in Mexico has provided fruit for retail marketing during most months of the year. Further advances in production, marketing, and consumption can be achieved with the continuation of improved cultivar development and expansion of production technology.

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Emily K. Dixon, Bernadine C. Strik, and David R. Bryla

Organic blackberry ( Rubus L. subgenus Rubus , Watson) production is becoming an important niche market in Oregon, where almost 50% of the U.S. hectarage (organic or conventional) is located [ U.S. Department of Agriculture (USDA), 2014 ]. Oregon

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A.L. Busby, D.G. Himelrick, and D.J. Eakes.

Two cultivars of blackberry (Rubus sp.) were propagated in July under intermittent mist by rooting 2-node softwood stem cuttings. Differences in root development among cultivars were evident with the thornless erect cultivar, `Navaho', producing a better root system than the thorny erect cultivar, `Cheyenne'. Treatment of `Navaho' with 3000 and 8000 ppm indolebutyric acid (IBA) in water and treatment of `Cheyenne' with 8000 ppm IBA in water and 3000 ppm IBA in talc improved rooting.

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P. M. Perkins-Veazie, J. K. Collins, and J. R. Clark

Blackberry fruit are considered highly perishable, having an average shelflife of 2 to 3 days. Fruit of erect blackberry cultivars were stored at 2C for 7 days to determine shelflife and quality changes. Weight loss was 1.8 and 3.4% after 3 and 7 days storage, regardless of cultivar or color stage. Soluble solids concentration (SSC), titratable acidity (TA), anthocyanin content, and skin firmness did not change during storage, but differed between ripeness stages and cultivars. Mottled (50% black) fruit were low in SSC and high in TA compared to shiny or dull black fruit. All dull black fruit were rated softer and lower in overall appearance after storage compared to shiny black fruit. `Choctaw' fruit were less firm and rated softer and of marginal appearance after 7 days storage while `Navaho' fruit remained firm and highly acceptable. Ethylene production ranged from 0.4 (`Navaho') to 2.8 nl/g-h (`Choctaw'). Results indicate that erect blackberry fruit harvested at the shiny black stage are of acceptable quality and have excellent shelflife potential.