Effect of pruning time and hydrogen cyanamide on budburst and subsequent phenology of Vitis vinifera L. variety Cabernet Sauvignon in central Victoria

Authors

  • STEPHEN R. MARTIN,

    Corresponding author
    1. Institute of Sustainable Irrigated Agriculture, Department of Natural Resources and Environment, Victoria, Private Bag 1, Ferguson Road, Tatura Vic. 3616, Australia
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  • GREGORY M. DUNN

    1. Institute of Sustainable Irrigated Agriculture, Department of Natural Resources and Environment, Victoria, Private Bag 1, Ferguson Road, Tatura Vic. 3616, Australia
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facsimile +61 3 5833 5337, e-mail Steve.Martin@nre.vic.gov.au

Abstract

This paper presents a detailed description of effects from two pruning times and an application of hydrogen cyanamide on budburst and subsequent phenology in a population of spur-pruned, 13-year-old Vitis vinifera L. Cabernet Sauvignon vines grown in central Victoria in 1998/99. Later pruning (17 August), compared with earlier pruning (7 July), delayed the onset of budburst by an average of 4.3 days and 60% budburst by an average of 5.3 days. This difference persisted at anthesis (5.0 days), veraison (4.1 days) and at harvest (0.91°Brix). Application of hydrogen cyanamide on 26 August did not advance the timing of budburst but increased the number of shoots that burst. This was due predominantly to more ‘extra’ shoots bursting on old wood and at the base of spurs. In the earlier stages of budburst, ‘primary’ buds on clear nodes of 1 year-old wood (spurs) burst in preference to buds at the base of spurs or on old wood. However, by the end of the 5-week budburst period, the number of ‘extra’ shoots per vine was similar to the number of primary shoots on clear nodes. Primary shoots with more bunches tended to burst earlier. Conceivably, the number of inflorescences (potential reproductive sites) and the number of flowers (potential number of seeds) on a shoot that arises from a dormant latent bud indicate a ‘reproductive potential’ that exerts some control over dormancy release. The frequency of budburst was sensitive to fluctuations in air temperature, but limited by the number of buds available to burst. Temperature-based models designed to predict phenological events might be improved by including parameters that take pruning time and reproductive potential into account.

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