Various growth regulators and dormancy-breaking chemicals were applied to cane-pruned grape vines (Vilis vinifera L. cv. 'Palomino') in an attempt to increase bud break, fruitful shoots, and yield. Application of morphactin to young terminal shoots increased subsequent bud break but significantly reduced yield. Similar treatments with 6-benzylaminopurine and 2-chloroethyltrimethylammonium chloride had no effect on bud break or yield. In one year, thiourea (1-5%) applied 5.5 weeks before anticipated bud break increased bud break, fruitful shoots, and yield per bud. Otherwise, thiourea, urea, dinitro-o-cresol, ammonium nitrate, potassium nitrate, calcium nitrate, and calcium ammonium nitrate applied at any time during the winter had no effect on bud break or fruitful shoots. Calcium ammonium nitrate applied in late July or late August increased yield the following season without significantly decreasing berry sugar or increasing berry acid.
INTRODUCTIONThe variability in bud break C'blind bud") along the length of l-year-old 'Palomino' canes has been related to the amount of light received by that cane during the previous growing season (Hopping 1977). It is possible that the problem of blind bud could be overcome by changing the training system of the vine so that potential fruiting canes develop under conditions of maximum light interception (Shaulis & May 1971). However, many growers in New Zealand claim that the gain in production which might occur as a result of a change from the conventional multi-wire trellis to a divided canopy system would not offset the costs involved.The variation in bud break along the length of the cane is typically the consequence of apical dominance where the terminal bud develops at the expense of adjacent lateral buds. Growth regulators such as morphactins (Tognoni et al. 1967; Weaver & Pool 1971;Tjia et al. 1973) and growth retardants (Brooks 1964;McGuire et al. 1965) have been found to stimulate lateral bud development and overcome apical dominance in a wide range of plants Erez et al. (1971) and Balasubrahmanyam et al. (1975) reported that thiourea hastened the termination of dormancy and increased bud break at nodes on the proximal end of the cane.The effectiveness of growth regulators and of dormancy-breaking chemicals in overcoming blind bud in grape vines trained on a conventional trellis was investigated during 3 growing seasons.
METHODS AND RESULTS
Growth regulators (1972-3)A plot of 36 grape vines (Vilis vinifera L. cv. 'Palomino') was selected from a block of cane-pruned (approx. 50 buds/vine) vines growing at a commercial vineyard near Gisborne. The following treatments were assigned to the plot in a randomised complete block design with 3 replicates:" 6-benzylaminopurine (BA; 0, 50, 250, 500 mg/l, 2-chloroethyltrimethylammonium chloride (CCC; 0, 100, 300, 500 mg/l, and methyl-2-chloro-9-340 N.Z. JOURNAL OF EXPERIMENTAL AGRICULTURE, VOL. 5, 1977 hydroxyfluorene-9-carboxylate (morphactin 3456~0, 10, 50, 100 mg/l, Each growth regulator was dissolved in 25 ml ethano...
