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  • Author or Editor: John Clark x
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In 2004, two surveys were conducted to assess the presence of four viruses in marketable blackberry nursery stock. The U.S. survey consisted of dormant nursery stock received from 11 nurseries in the southern, southeastern, midwestern, northeastern, and Pacific northwestern regions of the U.S. The second survey was focused only on Arkansas licensed propagating nurseries with samples collected during the growing season. Samples were tested using reverse transcription–polymerase chain reaction or enzyme-linked immunosorbent assay for the presence of Blackberry yellow vein associated virus (BYVaV), Raspberry bushy dwarf virus (RBDV), Tomato ringspot virus (ToRSV), and Tobacco ringspot virus (TRSV). Of the total samples in the U.S. survey, there were 9% that tested positive for virus infection. Ninety percent of the positives were infected with BYVaV. Forty percent of these were detected in `Triple Crown', 40% in `Chickasaw', and 20% in `Apache'. The remaining 9% of the total positive virus samples were infected with TRSV and 100% of these were in `Triple Crown'. No viruses were found on any samples of `Chester Thornless'. In the Arkansas survey, 11% of the total samples tested positive for virus. Of these, 50% were infected with BYVaV.

The percent infected with BYVaV was distributed evenly among `Apache', `Chickasaw', and `Kiowa'. The other 50% of the infected samples were positive for TRSV (67% `Apache', 33% `Chickasaw'). There was one mixed infection of BYVaV and TRSV detected in `Apache'. These findings indicate that BYVaV is the most prevalent virus found in nursery stock and that the occurrence of BYVaV is not restricted to a single region or cultivar.

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Abstract

Literature on blackberry leaf analysis technique is limited. In red raspberry (Rubus idaeus L.), the concentration of all elements investigated was significantly influenced by sampling date (3). The least seasonal variation of elemental concentration of red raspberry leaves occurred in those located between nodes 5 and 12 from the primocane terminal (2). The objective of this study was to determine the effect of leaf part, (blade vs. petiole), and date of sampling on the foliar element concentration of three blackberry cultivars (Rubus spp.).

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Abstract

Soil samples for a nematode assay were taken in 1983 within the root zone of highbush blueberry (Vaccinium corymbosum L.) plants in mature experimental and commercial plantings. Xiphinema americanum Cobb and Paratrichodorus christiei Allen were the predominant nematode species found. Nematode populations were not affected by cultivar. Mulched plots had significantly fewer P. christiei while X. americanum populations were similar in mulched and nonmulched plots.

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The impending release of a new blackberry cultivar and a new grape cultivar by the University of Arkansas Agricultural Experiment station will be discussed. The blackberry, tested as A-1536, is an erect, thornless type ripening two weeks before 'Navaho'. It produces very firm, highly flavored fruit similar to 'Navaho'. The grape, tested as A-1335, is a blue-seeded juice grape with good adaptation to areas with high summer temperatures where 'Concord' does not ripen evenly. Fresh fruit and processed juice quality has been rated equal to or better than 'Concord' juice for quality attributes.

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Nitrogen rates (using urea) of 22, 67 and 135 kg/ha were applied to mature mulched and unmulched highbush blueberries over a 5 year period. Soil samples were taken each year at budbreak (prior to fertilization) and post-harvest at the suggested time of foliar sampling (approx. Aug.1) to determine N rate effects within and among years. Data analysis revealed that the most common soil test variables affected by N rate and date of sampling were pH, electrical conductivity (EC) and nitrate. For unmulched plants, a significant reduction in soil pH was found each year between budbreak and Aug. 1 for the 67 and 135 kg/ha rates, but not usually for the 22 kg/ha rate. For mulched plants, pH reduction within N rate among sample dates was usually not significant. Overall soil pH reduction was greatest for the 135 kg/ha rate over the 5 years, and the pH reduction for the 67 kg/ha rate was similar to the 135 kg/ha rate for the unmulched plants. For mulched plants, 22 and 67 kg/ha rates had a similar trend of only a slight pH reduction over the 5 years. EC and nitrate trends were very similar, with the highest levels of each on the unmulched plants.

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Six cultivars of potted rose (Rosa ×hybrida L.) plants were evaluated for shipping stress-induced leaf chlorosis during holding at 8, 16, or 28C for 2, 4, or 6 days. `Meijikatar' showed more leaf chlorosis than the similar `Meirutral' at the higher simulated shipping temperatures and longer durations. Plants of `Meijikatar' were treated before simulated shipping with BA, TZ, or Promalin at 0, 25, 50, or 100 mg cytokinin/liter each, then paper-sleeved and stored in the dark in fiberboard boxes at 16C for 5 days. Plant quality 5 days after removal from storage was better with BA at 50 or 100 than at 0 mg·liter–1. All cytokinin-treated plants showed less leaf chlorosis than controls. Benzyladenine at 50 or 100 mg·liter–1 reduced leaf chlorosis when compared to all TZ treatments. There were no differences among treatments in the number of etiolated shoots per plant. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); trans-zeatin (TZ); gibberellic acid (GA4+7) + BA (Promalin).

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Thermal analysis was used to determine if muscadine grape (Vitis rotundifolia Michx.) buds supercool and to determine the seasonal cold hardiness of several grape cultivars grown in Arkansas. Buds of the muscadine cultivars Carlos and Summit, sampled from vines grown at Clarksville, Ark., produced low-temperature exotherms consistent with the number of buds tested. Apparent hardiness of the buds increased from 5 Nov. 1993 through 7 Jan. 1994. Mean low-temperature exotherms (MLTE) were lowest on 7 Jan. and were –21.5C for `Carlos' and –23.4C for `Summit'. `Mars' buds, sampled at Clarksville, Ark., and Winchester, Va., were included in the study and increased in hardiness during the same period. MLTE for `Mars' from Arkansas were similar to those of the muscadine cultivars on 7 Jan.; however, `Mars' attained lower MLTE temperatures with vines grown in Virginia than with those in Arkansas. Location differences in hardiness of `Mars' are conjectural.

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Southern highbush blueberry, a hybrid of northern highbush (Vaccinium corymbosum) and southern-adapted Vaccinium species, has the potential to meet the need for an early-ripening blueberry in the southern U.S. southern highbush cultivars can ripen up to one month earlier than the earliest rabbiteye (Vaccinium ashei) cultivars currently grown in the southern U.S. However, chilling requirement and cold-hardiness are cultivar-dependent for southern highbush and cultivar testing has been necessary to determine the cultivars best adapted to specific hardiness zones. In a 4-year study at Hope, Ark. (hardiness zone 7b), several southern highbush cultivars were evaluated for productivity, fruit quality and reliability of cropping. Yields were based on 1089 plants/acre (2690 plants/ha) for southern highbush cultivars and 605 plants/acre (1494 plants/ha) for rabbiteye cultivars. `Ozarkblue' and `Legacy' showed the most adaptability at this location, yielding on average 11,013 lb/acre (12,309 kg·ha-1) and 10,328 lb/acre (11,543 kg·ha-1) respectively, compared to 4882 lb/acre (5456 kg·ha-1) for `Premier' (rabbiteye) over 4 years. `Ozarkblue' and `Legacy' also rated well for plant vigor and fruit quality. We would recommend `Ozarkblue' and `Legacy' for commercial planting in southwest Arkansas and believe these cultivars have production potential for other areas of the southern U.S. that have similar hardiness zones and soil type to southwest Arkansas.

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