ISHS Acta Horticulturae 689: VII International Symposium on Grapevine Physiology and Biotechnology
EFFECTS OF DEFOLIATION ON TEMPERATURE AND WETNESS OF GRAPEVINE BERRIES |
| Authors: | P. Pieri, M. Fermaud |
| Keywords: | Vitis vinifera, Botrytis cinerea, berry maturation, grey bunch rot, microclimate, training system, canopy management, cluster compactness |
| Abstract:
The epidemiology of Botrytis cinerea and other cluster pathogens and the maturation of grapevine berries are strongly influenced by the microclimate around the fruit. Berry temperature also can affect physiological functions involved in fruit maturation and also upon pathogen growth, while berry surface wetness can affect spore germination and therefore pathogen infection. Berry and cluster microclimate can be modified greatly by changes in the training system or management techniques. The aim of this study was to quantify berry microclimate response to modifications in nearby leaf area density following a defoliation operation. Temperature and berry wetness were measured with and without defoliation around the clusters in a Bordeaux area ‘Merlot’ vineyard using the vertical shoot training system. Berries were characterized according to cluster position (east- or west-facing), berry position within the cluster (exposed to direct sunlight, internal or opposed) and defoliation treatment. Results indicated that berry temperature was strongly dependent on direct sunlight pattern and duration. Temperature of exposed berries could be greater than 10°C above ambient temperature, especially for west-facing and defoliated clusters during the afternoon. Berry temperature exhibited a dampened variation for the non-defoliated treatment since direct sunlight on the berries was short-lived and erratic, according to foliage arrangement. Rainy days aside, nocturnal dew led to frequent wetness of the berries. Defoliated clusters were less protected against nocturnal long wave radiation cooling and therefore more favorable to dew formation. West-facing clusters also had longer wetness duration since they were not heated in the early morning by solar radiation. The significant differences observed in thermal and moisture microclimate of the clusters will help establish management techniques optimizing fruit maturation and pathogenic risk. | |
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