Response of leaf and berry skin compounds to different canopy manipulation techniques in Vitis vinifera L. cv. Riesling investigated with non-destructive methods

Abstract

The adaptation of viticultural management systems is important in order to reply adequately to weather-related changes affecting the vineyards microclimate. Therefore, this study was examined to validate non-destructive methods to determine the response of leaf and berry compounds. Weekly measurements (2013 and 2014) in a field trial comparing different canopy manipulation techniques in two different plots (Vitis vinifera L. cv. Riesling) were performed to investigate the response of leaf and berry compounds (nitrogen, blue-green fluorescence and flavonols) with a handheld polyphenolmeter (Multiplex®3 [Mx3], Force-A, Orsay, France). The instrument excites the plant material with RGB and UV-LED responding in different indices (chlorophyll index (SFR_G), nitrogen balance index (NBI_G), flavonol index (FLAV) and anthocyanin index (ANTH)). During maturation berries were sampled and measured under laboratory conditions, while leaves were measured in the field. After measuring the berries using the Mx3, total soluble solids, total acidity, pH and N-OPA were determined.

The SFR_G index decreased with increasing maturity in leaves and berries and showed differences within the treatments and for canopy exposure (east or west facing canopy). All indices on leaves decreased after véraison and differences amongst the treatments were determined. Canopy defoliation is an important management practice to impact on vine´s microclimate and hence can be considered as a seasonal tool to alter fruit ripening.