Intra-seasonal fluctuation of bud fruitfulness in 'Chardonnay' and 'Shiraz' in two wine regions

B.P. Holzapfel, B. Orchard, L. Quirk, J. Smith
The number of buds retained on the vine after pruning has considerable impact on canopy development and vine yield in the following season. The aims of this study were to provide information on bud fruitfulness assessments, and to better understand factors that can contribute to yield variation between seasons. Over three years, a survey was undertaken to assess bud fruitfulness in 34 ‘Shiraz’ and ‘Chardonnay’ vineyards in southern New South Wales. Half of the vineyards sampled were located in the Riverina grape growing regions and the other half in the region of South-West slopes, consisting of several smaller grape growing locations. The average fruitfulness was determined on the buds of nodes 1 to 3 of dormant canes collected in winter in each vineyard and primary bud necrosis (PNB) was assessed to estimate initial fruitfulness. The fruitfulness was higher in the Riverina than SW slopes, and within both regions, ‘Chardonnay’ was more fruitful than ‘Shiraz’. However, a key difference between the two regions and cultivars was that there was a much higher incidence of PBN with ‘Shiraz’, particularly in the SW slopes. There did not appear to be a clear trend for vines with low carbohydrate reserve status to have a greater incidence of PBN, but reserve levels at pruning do not necessarily reflect carbohydrate availability during the time of bud development. The weather conditions across the two regions were reasonably similar, but one difference was the limited water availability in the SW slopes. At the regional level average fruitfulness was reasonably stable across seasons, and for Riverina ‘Chardonnay’, bud fruitfulness was also stable at the individual vineyard level. However, for ‘Shiraz’ in both regions, and ‘Chardonnay’ in the SW slopes regions, fruitfulness could vary significantly from season to season in individual vineyards.
Holzapfel, B.P., Orchard, B., Quirk, L. and Smith, J. (2018). Intra-seasonal fluctuation of bud fruitfulness in 'Chardonnay' and 'Shiraz' in two wine regions. Acta Hortic. 1229, 249-256
DOI: 10.17660/ActaHortic.2018.1229.38
grapevines, fruitfulness, yield variation, primary bud necrosis, carbohydrate reserves

Acta Horticulturae