Agronomic performance of ‘Viognier’ grapevines in subtropical conditions and wine aromatic compounds under different bud numbers retained at pruning

Managing bud load is a major concern for vine growers, affecting vine balance and thus, fruit quality. Achieving the right bud number requires consideration of vineyard conditions and desired outcomes, and it is normally controlled through pruning. Subtropical climates often have longer growing seasons, and finding the optimal bud load is even more important, as vines tend to have increased growth. This study evaluated the influence of different bud numbers on the agronomic performance and aromatic composition of ‘Viognier’ grapevines grown under subtropical conditions. The experiments were conducted in a commercial vineyard in the municipality of Campo Largo, Paraná, Brazil, during the 2019/2020 and 2020/2021 growing seasons. Vines were pruned using the Guyot system and evaluated under different bud numbers at pruning: 10, 20, 30, and 40 buds per plant. Agronomic performance, grape technological maturity, and wine volatile compounds using Gas Chromatography and Mass Spectrometry detection (HS-SPME-GC-MS) were assessed. Higher bud numbers (30 and 40 buds per plant) resulted in increased yield, larger leaf area, and balanced Ravaz index values. The morphology of the bunches and technological ripeness were not significantly different between the treatments. However, the highest bud number (40 buds) increased the percentage of blind buds and decreased shoot length. Some volatile compounds, such as citronellol and β-damascenone, were found in higher concentrations in wines from the lowest bud number (10 buds per plant), while hexanol, ethyl octanoate, and ethyl-2-phenylacetate were more prevalent in treatments with higher loads.