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R. Keith Striegler and Vidal Perez-Munoz

Crop control methods were evaluated for two seasons in a commercial Zinfandel vineyard. The vineyard was trellised using a vertical two wire system and cane pruned. Vines were third-leaf when the experiment began. Treatments included control, cluster thinning, and shoot thinning. Cluster thinning consisted of removal of all clusters except the oasal cluster, while shoot thinning consisted of removal of 50% of shoots on canes. Treatments were imposed two weeks postbloom. Yield was not significantly affected by crop control method. Cluster thinning tended to increase berry weight and cluster weight. Crop control method had little effect on fruit composition. Vine growth, as indicated by dormant pruning weight, was not influenced by treatment in 1990 but showed a significant increase during 1991 for cluster-thinned vines. These results indicate little negative effect of high crop level on young Zinfandel vines when intensive management is practiced. Treatments will be monitored until equalibrium treatment effects are observed.

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P. Manjula Carter, John R. Clark and R. Keith Striegler

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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R. Keith Striegler, Carter P. Clary, David R. Wineman, Gina A. Wagy and Steve Glossner

Natural sun-dried raisins are susceptible to crop loss and quality reduction when rainfall occurs during the 2-3 week drying period. The purpose of this experiment was to determine the effect of rainfall at selected stages of the raisin drying period on raisin quality. Thompson Seedless grapes were harvested and dried in the field using normal commercial practices. Raisins were moved to a humid chamber at the green, brown, turn, and roll stages of the drying period. Then, raisins were misted with 6.4 or 25.4 mm of water to simulate rainfall. Samples remained under humid conditions for approximately 48 hours after which they were returned to the field to complete the drying process. Raisin quality was evaluated by USDA incoming inspection procedures. The amount of rainfall had little effect on raisin quality at the levels in this experiment. However, raisin quality was significantly reduced when rainfall occurred at the green and brown stage of drying. Raisins which received rainfall at the turn and roll stages of drying were of comparable quality as control raisins.

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Eric T. Stafne, B. Dean McCraw, William G. McGlynn and R. Keith Striegler

Rootstocks can offer benefits such as pest resistance, tolerance of certain soil characteristics and tolerance of salts and salinity. The objective of this study was to determine if `Cabernet Franc' grafted onto various rootstocks differed in a number of measured yield and quality variables. The plots consisted of Clone 1 `Cabernet Franc' with four different rootstocks: 1103 Paulsen, 140 Ruggeri, 3309 Couderc, and St. George. Rootstock did not have much effect on the yield or quality of fruit produced by `Cabernet Franc'. Although not significantly different, the overall yield of 3309C appears to be lower than the other rootstocks. With further data, it might be possible to identify annual climate patterns that favor one rootstock over another with respect to certain quality attributes. One particular problem with `Cabernet Franc' in Oklahoma is its tendency to overbear, thus resulting in uneven ripening.

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Eric T. Stafne, Edward W. Hellman, R. Keith Striegler, James A. Wolpert and Jean-Mari Peltier

Industry involvement is a critical aspect of the Specialty Crops Research Initiative (SCRI). Both a mandate for need and funding are necessary from industry to develop a successful SCRI project. The National Grape and Wine Initiative (NGWI), a nationwide coalition representing all segments of the grape (Vitis sp.) industry including raisin, juice, fresh grape and wine interests, identified extension education as a critical need and charged its extension/outreach committee to concentrate on ensuring industry members are aware of and have access to findings from grape and grape products research. To achieve this goal, the committee decided that a comprehensive online information and educational resource would play an important role. In 2009, the eXtension Grape Community of Practice (GCoP) was funded by the SCRI. The NGWI was active in soliciting letters of endorsement and buy-in from the industry for the project. The Missouri Wine and Grape Board (MWGB) also contributed $20,000 per year for three years to help offset the matching requirement. Research-based grape proposals in subsequent rounds of the SCRI in 2010 and 2011 wishing to have the approval of NGWI have been strongly encouraged to include the GCoP as a portion of their extension component. For the 2011 round of SCRI proposals, this led to the GCoP being included in three projects, two of which were funded. Exploration of future avenues for funding will include subcontracts from other grant awards, NGWI, industry sponsorships, and other creative methods.

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Andrew L. Thomas, Jackie L. Harris, Elijah A. Bergmeier and R. Keith Striegler

An evaluation of establishment techniques and rootstocks for ‘Chambourcin’ hybrid grape (Vitis sp.) was conducted 2009–12. Our objective was to evaluate four establishment methods and their interactions with grafted and ungrafted vines in terms of vine morphology and early fruit production under southwest Missouri conditions. The study was established in May 2009, as a factorial experiment comparing four establishment methods (open-trained without protection—two shoots, grow tube protected—two shoots, paperboard carton protected—two shoots, and fan-trained without protection—six shoots) across two vine types (own-rooted and grafted to ‘Couderc 3309’ hybrid grape rootstock). All vines in four of 12 field replications were destructively harvested near the conclusion of the first growing season, with leaf area and total vine dry matter determined. In years 3 and 4, yield, fruit composition, and vegetative growth were determined from the eight remaining replications. The fan training method increased leaf area and total vine dry matter compared with the other methods, but none of the establishment techniques affected fruit yield. Trunks that were tube protected had longer internodes, smaller diameter, and less dry matter, whereas both protection devices reduced glyphosate injury. Vine type (grafted and ungrafted) did not impact total leaf area or dry weight during the establishment year, but grafted vines had increased trunk and root shank dry weights compared with own-rooted vines. Grafted vines produced greater fruit yield in 2012. The fan training method required more labor to execute; although it was successful at increasing leaf area and root dry weight, it increased susceptibility to glyphosate injury and did not promote increased precocity or early fruit yield.

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R. Keith Striegler, Chris B. Lake, Justin R. Morris, Renee T. Threlfall, Gary L. Main and Simon G. Graves

'Sunbelt' is a juice grape cultivar developed by the Univ. of Arkansas. This cultivar produces 'Concord'-type juice and is adapted to warm climatic conditions of the southern United States. Preliminary evaluation showed that 'Sunbelt' has potential to produce high-quality juice under the hot climatic conditions of the San Joaquin Valley. A study was conducted during the 1998 and 1999 growing seasons to further evaluate the adaptation of 'Sunbelt' to the San Joaquin Valley and determine the response of this cultivar to selected pruning methods. Vines were grown for two seasons without use of insecticides, fungicides, or herbicides. Vines were subjected to four pruning treatments: severe hand pruning (60-80 nodes retained/vine); moderate hand pruning (120-160 nodes retained/vine); machine pruning with hand follow-up (160-180 nodes retained/vine); and minimal pruning (200-400 nodes retained/vine). Vines were trained to a Geneva Double Curtain trellis system. Yield, components of yield, and juice quality were significantly impacted by pruning treatment. In both seasons, mechanized systems of pruning (machine and minimal) produced higher yield than hand pruning. Minimal pruning resulted in the highest yield (42 t·ha-1) in 1998, while yield from the machine-pruned vines was highest (29 t·ha-1) in 1999. Minimally pruned vines had the highest clusters/vine and lowest cluster weight among the treatments. The extremely high yields obtained for the minimal pruning treatments produced fruit that was less mature resulting in juice with lower soluble solids than the other treatments in 1998. However, in 1999 the juice from minimally pruned vines had the highest soluble solids. Sensory analysis of juice produced in 1999 showed that the juice from the machine-pruned treatment had the least color intensity. Sensory analysis showed that minimal and severe hand pruning were ranked higher for sweetness than machine and moderate hand pruning. In the second year of the study, the juice from the minimal-pruned and severe hand-pruned treatment were preferred over the moderate hand-pruned treatment or the machine-pruned treatment.

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R. Keith Striegler, Justin R. Morris, Gary L. Main, Chris B. Lake, Simon R. Graves, Renee T. Threlfall and Janice M. Blevins

`Sunbelt' is a juice grape cultivar developed by the Univ. of Arkansas. This cultivar produces `Concord'-type juice and is adapted to climatic conditions of the southern United States. Preliminary evaluation showed that `Sunbelt' has potential to produce high-quality juice under the hot climatic conditions of the San Joaquin Valley. A study was conducted during the 1998 and 1999 seasons to further evaluate the adaptation of `Sunbelt' to San Joaquin Valley conditions and determine the response of this cultivar to selected pruning methods. Vines of uniform vine size and vigor were subjected to four pruning treatments: severe hand-pruning (60 to 80 nodes retained/vine); moderate hand-pruning (120 to 160 nodes retained/vine); machine-pruning (160 to 180 nodes retained/vine); and minimal pruning (200 to 400 nodes retained/vine). Vines were trained to a Geneva Double Curtain trellis system. Yield and components of yield were significantly impacted by pruning treatment. In both seasons, mechanized systems of pruning (machine or minimal) produced higher yield than hand pruning. Minimal pruning resulted in the highest yield in 1998, while yield from machine-pruned vines was highest in 1999. Minimally pruned vines had the highest clusters/vine, lowest cluster weight, and lowest berry weight among the treatments. Fruit composition was also affected by pruning treatment. Minimal pruning produced fruit which was less mature than fruit from the other treatments in 1998. This result was likely due to the high yield obtained. Few differences in fruit composition were observed among treatments in 1999. The effect of pruning method on processed juice quality will be presented. Acceptable juice quality was obtained for most treatments.