The effect of leaf removal in Mediterranean and maritime climates are well researched. In this project, researchers wanted to evaluate the effects of leaf removal on volatile compounds in a continental climate, as well as determine which genes are responsible for the variations.
The study was conducted on Cabernet Sauvignon in north China. Four treatments were applied:
- Leaf removal at peppercorn stage
- Leaf removal at veraison (LR-V)
- Leaf moving at veraison (here leaves were tied away to expose the bunch without losing photosynthetic capacity) (LM-V)
- Half – leaf removal at veraison
- Analyses were done on grape berries.
- Cluster exposure resulted in a decrease in norisoprenoid and monoterpene concentrations.
- Where clusters were more exposed, some genes showed lower expression levels.
- Both β-carotene and lutein, the substrates of norisoprenoid biosynthesis, were reduced where sunlight exposure increased.
- Esters associated with fruity aromas were also less.
- Alcohol levels were higher in the LR-V and LM-V treatments which corresponded with upregulated expression of specific genes.
- The LR-V treatment resulted in a significant up-regulation in photosynthesis-related genes in the grape berries. This was not the case with LM-V treatment.
Significance of the study:
The effect of leaf removal on volatile compounds and gene regulation in a dry-hot climate was different to the effects in other climates. This means that canopy management should be done differently in dry-hot climates, in order to improve grape quality. The timing of leaf removal is also critical as it affects the wine style. With climate change on our doorstep, some winegrowing areas may become warmer and drier, which could mean that viticultural practices will need to be adapted in future to suit the climate.
He, L., Xu, X., Wang, Y. et al. Modulation of volatile compound metabolome and transcriptome in grape berries exposed to sunlight under dry-hot climate. BMC Plant Biol 20, 59 (2020). https://doi.org/10.1186/s12870-020-2268-y
Image source: http://en.people.cn/n3/2018/1207/c90000-9526315-4.html