The Role of Genotype and Water Availability in Storage Carbohydrate Distributions in Grapevines

Student Name: Jennifer Chen

UCD Department: Plant Sciences

UCD Mentor: Dr. Kenneth Shackel and Dr. Mark Matthews

Perennial crop plants like grapevine (Vitis vinifera L.) use stored carbohydrates (CHO) from the previous season to sustain early season growth and flower development.  Water deficits inhibit current season growth and yield of the current season and following season, but the effects on stored CHO are not known.  CHO assays were performed on two grapevine genotypes, Grenache and Syrah, across three different irrigation treatments. Specifically, CHO concentrations in basal nodes and internodes were assayed just after the onset of veraison, the onset of ripening, which has been shown to be the annual low point in storage CHO concentrations in grapevine. A series of hot ethanol baths were used to extract soluble sugars. After extraction, CHO samples were digested into glucose using an alpha-amylase and amyloglucosidase solution. A PGO enzyme o-dianisidine dihydrochloride solution was added to each sample for a color reaction. The plate was read using a spectrometer and optical density numbers were recorded and analyzed with a standard starch calibration curve. In general, Syrah had higher storage CHO concentration than Grenache, which suggested that it was more efficient with water. Across both varieties and all three irrigation treatments, internodes contained higher concentration of storage CHO. CHO distribution in internodes supported the hypothesized relationship: decreased water availability results in decreased concentrations of storage CHOs. These data suggest that water deficit and storage CHO concentrations are positively correlated in perennial crop plants like grapevine (Vitis vinifera L.).  CHO in the nodes did not show the predicted distribution. Syrah vines had lower midday leaf water potential than Grenache vines which can be attributed to their anisohydric tendencies. This information on CHO distribution and genotypic variation in response to water deficits is important for identifying water-efficient grapevines and for water-conservation in agriculture.