Abstract
Rotundone is an attractive wine aroma compound, especially important for cool climate Shiraz. Its presence in wine is mainly from the grape skin, but can also be found in non-grape tissues, such as leaves and stems. Whether rotundone is produced independently within different grapevine tissues or transported amongst non-grape tissues and grape berries remains unclear. The current study investigated the distribution of this compound in different vine tissues during development and studied the most likely mode of rotundone translocation—via phloem—using stable isotope feeding. In addition, local production of rotundone induced by herbivore feeding was assessed. Results showed that rotundone was firstly detected in the petioles and peduncles/rachises within the development of Vitis vinifera L. cv. Shiraz. Different grapevine tissues had a similar pattern of rotundone production at different grape developmental stages. In the individual vine shoots, non-grape tissues contained higher concentrations and amounts of rotundone compared to berries, which showed that non-grape tissues were the larger pool of rotundone within the plant. This study confirmed the local production of rotundone in individual tissues and ruled out the possibility of phloem translocation of rotundone between different tissues. In addition, other terpenes, including one monoterpenoid (geraniol) and six sesquiterpenes (clovene, α-ylangene, β-copaene, α-muurolene, δ-cadinene, and cis/trans-calamenene) were, for the first time, detected in the ethylenediaminetetraacetic acid-facilitated petiole phloem exudates, with their originality unconfirmed. Unlike other herbivore-induced terpenes, herbivorous activity had limited influences on the concentration of rotundone in grapevine leaves.
Highlights
Rotundone has been reported to be the main compound responsible for the “peppery” aroma in Shiraz grapes and wine, and is the first sesquiterpene compound that have been shown to contribute to grape and wine aroma (Siebert et al, 2008; Wood et al, 2008)
The distribution of rotundone was firstly investigated at vineyard-wide scale, and the rotundone concentrations in individual vine tissue were analyzed at different phenological stages (Figure 3)
Large deviation in rotundone concentration were observed in grape and non-grape tissue samples, which was consistent with the previous report of large within-vineyard variations in rotundone concentration (Zhang et al, 2015a)
Summary
Rotundone has been reported to be the main compound responsible for the “peppery” aroma in Shiraz grapes and wine, and is the first sesquiterpene compound that have been shown to contribute to grape and wine aroma (Siebert et al, 2008; Wood et al, 2008). Distribution of Rotundone in Grapevines berries, rotundone is only produced in berry skin (exocarp), and its concentration levels vary amongst different Shiraz clones (Herderich et al, 2012, 2013; Matarese et al, 2013). Previous studies observed higher concentrations of rotundone in the berries produced by high-vigor grapevines, in seasons with high water availability, and in grape bunches located closer to leaves (Scarlett et al, 2014; Herderich et al, 2015; Zhang et al, 2015a,b), which could be related to higher shade and lower temperatures or a potential relocation of rotundone from the vegetative organs to grape berries. Herbivore-induced sesquiterpene production does not happen systemically within the whole plant in response to leaf feeding by herbivores, but only at the wounding leaf site and distal leaf parts (Köllner et al, 2013), which indicates the localized formation of sesquiterpenes
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