Dissecting the hierarchical contributions of terroir factors on the volatile composition of grapevine ‘Cabernet Sauvignon’ and ‘Merlot’ (Vitis vinifera L.)

• Maturity was identified as the key determinant of volatile compound accumulation in grape berries, underscoring the critical nature of harvest timing. • Monoterpenoids, particularly limonene, p-cymene, and nerol oxide, were highly responsive to terroir variations. • (E)-2-Octenal was identified as a marker compound more abundant in ‘Cabernet Sauvignon’, and predominantly influenced by maturity. • Nerol oxide was highlighted as a marker compound more abundant in ‘Merlot’, and mainly influenced by temperature and a range of viticultural factors. Terroir leaves its mark on the accumulation of flavours in grape berries, triggering biochemical reactions and ultimately shaping wine styles. However, the complicated relationship between terroir and grape volatiles remains not fully understood. We investigated volatile profiles of ripened berries in two major grape cultivars (i.e., ‘Cabernet Sauvignon’ and ‘Merlot’) during two consecutive vintages across the Ningxia region in combination with analyzation of the corresponding terroirs. The study revealed that maturity had a broad and significant impact on the accumulation of compounds in grape berries, determining the final aroma profile. In the Ningxia region, (E)-2-Octenal and nerol oxide in grapes can serve as stable marker volatile compounds that distinguish ‘Cabernet Sauvignon’ from ‘Merlot’. Specifically, (E)-2-Octenal is sensitive to ripeness but exhibits a weak response to environmental factors, while nerol oxide shows a significant differential response to terroir factors across cultivars and vintages. Beyond climate and soil, viticultural factors such as water status and trellising also significantly affect the nerol oxide content. Our results provide novel insights into the linkage between terroir factors and grape volatile profiles, and can help growers to better understand and control the production of fruits that maximize their aromatic typicity.