Starch accumulation and agronomical performance of Syrah under winter cycle: responses to pruning and ethephon management
In the Brazilian Southeast, 'Syrah' grape harvested during the winter reaches better quality index than those from summer harvest. However, the management of annual double pruning to produce two grapevine growth cycles (vegetative cycle: spring – summer; reproductive cycle: autumn – winter) has increased the vineyard production costs and the vine reserve accumulation can be compromised. This study had two main objectives to improve the winter cultivation: i) to validate single pruning carried out only in summer (February) (experiment 1); to increase the reserve accumulation by ethephon (ethrel) sprayed two months before yield pruning (experiment 2). Both experiments were carried out in south of Minas Gerais State using three years old field-grown 'Syrah' grapevines grafted onto '1103 Paulsen' and trained in a vertical shoot position. The results from experiment 1 showed that grapevines pruned in summer also need to be pruned during the winter after grape harvest to avoid bud infertility during the following autumn-winter season. Single pruning reduced the starch contents in shoots, trunks and roots sampled before yield pruning and the commercial grape harvest was completely unavailable due to unfruitful shoots. On the other hand, the autumn-winter cycle was improved by ethephon sprayed in the previous vegetative growing cycle (summer cycle). During the autumn-winter cycle, sprayed grapevines showed higher starch content in trunks, high vegetative vigor and the yield and grape quality were not negatively affected.
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