Carbohydrate dynamics in Shiraz to determine seasonal allocation to the perennial and annual parts in respect to climatic challenges

Abstract

The dynamic changes of non-structural carbohydrates (NSC) in grapevines during the growing season is driven by phenological events and environmental factors. The perennial NSC reserves have a significant role at the beginning of growing season for canopy establishment and may also contribute to grape maturation. In addition, increasing extreme weather events may elicit utilisation of some of these reserves. This will impact on the seasonal carbohydrate balance; an understanding of the interactions between the various sinks and sources is therefore more critical for the future. The aim of the study was to provide a collection of NSC data from the various parts of grapevines to determine the accumulation and mobilisation patterns during the growing season as well as for simulating organ biomass and NSC distribution. The study was undertaken on own-rooted 10-year-old Shiraz in a vineyard located in the warm Riverina wine region in New South Wales, Australia. Four vines were destructively harvested from dormancy to shortly after leaf fall in monthly intervals. The various sections of the below ground parts were divided into rootstock and roots, while the above ground parts were separated into the different perennial, vegetative and reproductive organs. The various sections were washed, then oven dried at 70o C and the dry weight recorded. A freeze-dried sub-sample was ground prior to the determination of the NSC for each section. There was a considerable NSC accumulation in the annual organs during the growing season, being most pronounced between fruit-set and harvest. In contrast, the NSC in the perennial organs declined to half from dormancy to bloom, with replenishment observed at harvest. The mobilisation in spring was most pronounced in the roots, while the fruit became the most dominant sink after fruit set, being most pronounced during grape maturation. While shoot stems accumulate dominantly the NSC from mid ripening to leaf-fall, with the perennial organs accumulating further NSC in the post-harvest period. The reproducibility of dry matter and carbohydrate reserves dynamics in the various parts of Shiraz vines using APSIM grapevine model will be reported. The study further clarified that the amounts of NSC allocated to the perennial structure and annual parts during the growing season. This will contribute to the optimization of carbohydrate balance of grapevines and to the changes required for carbohydrate allocation due to climate change.