Comparison of methods for determining budburst date in grapevine

Anne Pellegrino,Deidre Blackmore,Rob Walker,Peter Clingeleffer

doi:10.20870/oeno-one.2022.56.1.4751

Abstract

Methods for determining budburst date in grapevine are poorly documented. Budburst date defined from cumulative shoots burst (or arising) and cumulative buds burst (expressed as % of total) were compared using different cultivars, pruning systems and irrigation treatments and assessed at the plant, bearer and individual bud level. The study was conducted at three sites within an Australian vineyard over two years on mechanical pruned Chardonnay and Cabernet-Sauvignon; mechanical, spur and minimally pruned Shiraz; and control, regulated and prolonged deficit irrigated Cabernet-Sauvignon. Budburst defined as ‘50 % of total shoots burst’ was more reliable than ‘50 % of buds burst’ for determining budburst date when final % budburst was low, as observed under lighter (mechanical or minimal) pruning for Shiraz. Differences in final % budburst between pruning systems and deficit irrigation treatments were related mainly to the distribution (%) of bearers according to size (based on node or bud numbers) and their specific budburst percentage at each node position. The timing of budburst based on ‘50 % of total shoots burst’ was dependent on a unique set of parameters for each cultivar, regardless of pruning treatments and irrigation levels. The new knowledge gained in this study about the impact of pruning system and irrigation treatment on % budburst and timing may be useful for adapting phenological models to Australian vineyards.

Highlights

In the southern hemisphere, budburst in grapevine occurs from late August through to October, though mostly during September, with substantial variations in timing depending on variety, region and season (Coombe, 1988; Clingeleffer et al, 2013)
This study has shown that variations in final % budburst between the cultivars or between the pruning systems and irrigation treatments were associated with contrasting distributions of spurs with different numbers of nodes between pruning systems, and different cumulated budburst at a given bearer size between cultivars
The date of budburst was similar between the pruning systems for Shiraz, and was independent of bud number and final % budburst

Summary

Introduction

Budburst in grapevine occurs from late August through to October, though mostly during September, with substantial variations in timing depending on variety, region and season (Coombe, 1988; Clingeleffer et al, 2013). The first visible stage of budburst is ‘budswell’ This is followed by ‘woolly bud’, when the scales begin to separate as the bud swells sufficiently to reveal brown woolly hairs. The ‘green tip’ stage follows, when the bud swells further showing the tip of the young shoot. E-L stage 4 (‘green tip’) was chosen as the major stage for characterisation of budburst for a single bud. This was in agreement with Baggiolini (1952) and Huglin (1958), but in contrast with Pouget (1963), who selected the woolly-bud stage (E-L stage 3) as the most appropriate indicator for budburst

Methods

Results

Discussion

Conclusion