Abstract
Recent warming has shortened and compressed vintages, and altered oenologically relevant berry traits. Late pruning can decompress harvest and preserve fruit quality, hence the interest in exploring the interactions between late pruning and heating.
We established a factorial experiment that combined two thermal regimes, ambient vs heated with open-top chambers, and three pruning times (winter control, and late pruning at budburst and at 2–3 leaves) in Shiraz vines during three seasons in the Barossa Valley. Late pruning delayed budburst up to 23 days, flowering up to 17 days and veraison up to 16 days. Heating advanced flowering in late pruned vines up to 7 days, with a minor effect in winter pruned controls. It advanced veraison up to 7 days and the advancement was more responsive in seasons with warmer springs.
Pruning weights were unaffected by late pruning, and were increased by heating. Yield was increased in a single season by late pruning and heating, but it remained unchanged for the pool data of three seasons. Late pruning delayed maturity in 4 out of 6 cases; the largest delay was 17 days in unheated vines pruned when 2-3 leaves had emerged. Late pruning maintained anthocyanin to sugar ratio, which decreased with heating in two seasons. There was an interaction between timing of pruning and heating, whereby late pruning enhanced berry tannin-to-sugar ratio in heated but not in unheated control vines. Late pruning delayed the harvest by shifting the onset and rate of ripening, with a higher degree of response in the warmest season in both ambient and heated treatments.
- Received March 2018.
- Revision received June 2018.
- Revision received July 2018.
- Accepted July 2018.
- Published online September 2018
- ©2018 by the American Society for Enology and Viticulture
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