Within-vineyard variation in the ‘pepper’ compound rotundone is spatially structured and related to variation in the land underlying the vineyard

Abstract

Background and Aims Previous studies have highlighted the importance of vineyard variability and the benefits that may accrue through targeting management in response to it. In this study, we were interested to see whether the concentration of rotundone in Shiraz (Vitis vinifera L.) grapes was spatially structured and related to other aspects of vineyard variability so as to inform the possible selective harvesting of grapes destined for wines of ‘peppery’ character. Methods and Results Immediately prior to harvest of a 6.1-ha block in the Grampians region of Victoria, a region known for producing wines of ‘peppery’ character, fruit was sampled from 177 ‘target vines’ and analysed for its rotundone concentration. The resulting data were mapped and overlain with other map layers describing variation in soils, topography and vine vigour. Berry rotundone concentration was found to be markedly spatially variable. The results further suggest that within-vineyard variation in berry rotundone concentration is associated with variation in soil properties and topography, with the influence of the latter on ambient temperature implicated as a likely key driver of rotundone variation. Conclusions Consistent with previous analyses of variability in indices of fruit quality, variation in berry rotundone concentration was found to be spatially structured; that is, its variation was not random. As with these previous studies, variation in berry rotundone concentration was associated with variation in the land underlying the vineyard. Significance of the Study To our knowledge, this is the first study of within-vineyard spatial variability in a grape-derived flavour compound. It highlights the potential opportunity, with further understanding of rotundone biosynthesis, to use selective harvesting and/or viticultural manipulation as a means of influencing wine style – in this case the ‘pepperiness’ of Shiraz.