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  • Author or Editor: Lynn J. Mills x
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The juice grape (Vitis labruscana) cultivar Sunbelt has been reported to ripen more uniformly than the cultivar Concord in warm climates; thus, ‘Sunbelt’ might be useful as either a blending partner with or replacement for ‘Concord’ as global climate change intensifies. We conducted a 4-year field trial to evaluate ‘Sunbelt’ alongside ‘Concord’ in arid southeastern Washington. ‘Concord’ yields were on the average 57% higher than ‘Sunbelt’ yields because ‘Concord’ vines produced more shoots of higher fruitfulness and consequently had more clusters. The 31% larger berries of ‘Sunbelt’ were insufficient to compensate for its lower cluster number. Conversion from hand pruning to minimal (machine) pruning had no consistent influence on yield in either cultivar. Juice soluble solids, titratable acidity (TA), red color intensity, and color hue were significantly higher in ‘Sunbelt’ than ‘Concord’, whereas pH and potassium were often similar. Both cultivars cold acclimated in autumn and deacclimated in spring, but hardiness varied during winter depending on prevailing temperatures. With some exceptions, the two cultivars had similar bud, phloem, and xylem hardiness. When differences were significant, ‘Sunbelt’ was 1 to 4 °C less hardy than ‘Concord’ and also tended to deacclimate more readily in spring. The results from this study indicate that ‘Sunbelt’ shows promise as a blending partner with or an alternative to ‘Concord’ for warm vineyard sites or growing seasons even in regions with cold winters.

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Although the inland Pacific Northwest has a warm climate during the growing season, grapes grown in this region may be exposed to colder than optimal temperatures at several times during the year. In addition to damage from spring and fall frosts, intermittent winters with little to no snow cover and subzero temperatures can cause vine dieback and death. Temperature patterns in the recent past indicate that both fall and midwinter are times when risk of bud damage from cold events is probable, making proper site selection and cultivar choice critical. Water is not used for frost protection in this climate, but wind machines have proven to be useful. In frost-prone sites, annual sucker growth with cane burying is practiced as an insurance strategy. Modifying pruning strategies has not been shown to be advantageous after fall cold events. If rootstocks are used, research has shown greater scion survival with higher graft positions.

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