The objectives of this project are consistent with the highest priority research objective as outlined by the National Grape and Wine Initiative (Research Priority 1.1.1, “Using modern analytical and sensory techniques identify and quantify the components of grapes and grape products that impact key sensory quality attributes.”) The specific goals of this project are the following:
- To precisely manipulate the pre-véraison and post-véraison temperature of clusters grown under field conditions to achieve the following:
- Variance in daytime and nighttime temperature separately
- Variance in diurnal temperature amplitude (constant mean temperature)
- To determine the composition of the following compounds in clusters grown under the various temperature treatments:
- Tannins, anthocyanins, flavonols, flavan-3-ol monomers, polysaccharides, pH, sugars, organic acids
In order to more completely understand the influence of temperature on the growth of the berry and the accumulation of solutes, this field experiment is being conducted with clusters that are growing under different temperature environments under otherwise normal growing conditions. Of specific interest in this study is understanding the effect of diurnal temperature variation on berry growth and development (the integrated temperature was the same but the temperature variation was dampened).
To date and for pre-veraison growth, when one compares the data collected during the first year to images of the clusters collected there are some clear relationships. Overall, a reduction in diurnal temperature variation increased berry size and color suggesting that these berries were temporally advanced in development. In contrast to the influence of diurnal temperature variation, there was a relationship between overall temperature and tannin accumulation, with higher temperatures associated with more tannin production.
Additional analyses for pre-veraison experiments are currently in progress in addition to a separate experiment that was conducted during fruit ripening.