Fruit Quality and Vine Vigor of Cabernet Sauvignon Grapevines Under Crop Forcing In a Warm Region to Produce Cool Climate Quality Fruit

An experiment was conducted in a commercial vineyard of Cabernet Sauvignon in the San Joaquin Valley of California to determine the fruit quality and vine vigor when using crop forcing (CF) in warm regions. The objective was to shift fruit ripening to the cooler portion of the growing season to produce fruit of similar composition of cooler regions. CF treatments were conducted three, four, or five weeks post-anthesis (mid- to late-June) in 2010 when primary shoots were hedged to six nodes while all clusters, laterals, and leaves were removed. All CF treatments were effective in inducing new shoots and clusters to shifted fruit ripening from the hot portion (July and early Aug.) to the cooler portion (Oct. through early Nov.) of the growing season. CF applied four to five weeks post-anthesis produced the highest yield of high quality fruit for wine making and was defined as the best time for crop forcing. The length of bloom-to-veraison period was slightly shorter (60 vs. 65 days) but that of veraison-to-harvest period was much longer in CF (60 vs. 40 days), in comparison to those under conventiaonl cultural practices (CK). Degree hours was similar during the bloom-to-veraison period between CF and CK. However, degree hours >25C was much less (50%) while degree hours <25C was much greater (2-folds) in CF than CK. Fruit of forced crop at harvest had similar Brix, smaller berries, lower pH, higher TA, and much higher content of anthocyanins (2-folds) and total phenolics (3-folds). CF vines were less vigorous and had more clusters. Yield for CF vines was comparable to CK with shoot thinning. Pruning weight as an indicator of vine vigor was only 20% less than CK. The research demonstrated that CF through complete removal of shoot tips, clusters, and leaves can be used to shift fruit ripening and to produce better quality fruit and a reasonable yield for Cabernet Sauvignon in warm regions.