Abstract
Making raisins (dried grapes) is a laborious process and grape growers around the world are increasingly interested in adopting mechanized methods, especially dry-on-vine (DOV). The DOV method entails severing canes bearing mature fruit, causing them to DOV, after which they may be harvested by machine. The overhead arbor is an important DOV raisin trellis system, but basic agronomic performance of raisin varieties on that system are scant. Therefore, a three-year experiment was conducted to compare the performance of several raisin grape varieties (Vitis vinifera L.), on an overhead arbor trellis, for production of DOV raisins. Grapevine variety, ‘DOVine’, ‘Fiesta’, ‘Selma Pete’, or ‘Thompson Seedless’, was the main-plot factor, and number of canes, six or eight, was the sub-plot. ‘Fiesta’ produced the highest yields, averaging about 12.24 Mg/ha raisins. However, ‘Fiesta’ generally had the lowest soluble solids and among the lowest raisin grades. The later ripening of ‘Fiesta’ fruit delayed harvest pruning to initiate fruit drying compared to the other varieties. Therefore, its raisins did not dry sufficiently to meet industry standards. ‘Selma Pete’, ‘DOVine’, and ‘Thompson Seedless’ had similar yields, generally about 20% less than ‘Fiesta’, but ‘Selma Pete’ produced fruit that were the largest in size, with the highest soluble solids, and that produced raisins of the highest grades, compared to the other varieties. Vines pruned to eight canes produced higher yields without sacrificing raisin quality. In conclusion, ‘Fiesta’ was notable for its high productivity, and ‘Selma Pete’ for its earliness and high quality, and both varieties had sufficient capacity to carry eight 15-node canes.
Highlights
In other countries, such as Argentina, raisin grapes are traditionally dried in yards, a process that is even more laborious and costly than drying in the vineyard, as yard drying requires similar tasks as tray-drying in a vineyard, and requires transporting fresh fruit from the vineyard to the yard [3]
DOV raisin yield and quality of Thompson-type raisin grapes on the overhead arbor have not been published in the scientific literature, but such data would be useful for comparative purposes as other possible raisin production systems are considered in California [1], and as other raisin producing countries consider adopting
The number of clusters per vine differed in some years, as expected (Table 2)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Simpson developed a high-density overhead arbor vineyard in 1991 with head-trained and cane-pruned ‘Fiesta’ grapevines, whereas Pitts’ system uses vines that are more widely spaced and trained to quadrilateral cordons [12] In both systems, the vine’s canopies are separated into fruiting and renewal sections by pruning the vines and tying their canes in such a way that trellis wires spanning the spaces between adjacent rows support either fruiting canes or renewal shoots (Figure 1). DOV raisin yield and quality of Thompson-type raisin grapes on the overhead arbor have not been published in the scientific literature, but such data would be useful for comparative purposes as other possible raisin production systems are considered in California [1], and as other raisin producing countries consider adopting. Figure and before budbreak to illustrate the arrangement of canes (right of center) and spurs (left of center) and before budbreak to illustrate the arrangement of canes (right of center) and spurs (left of center) on the vine’s quadrilateral cordons
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