## 2 Results
### Volatiles Emitted In-Vivo from Four Cold-Hardy Grape Cultivars
#### 2.2.1 Emissions from Whole Grape Cluster  
Forty-four of the total 124 grape VOCs emitted in-vivo were detected by whole grape cluster sampling chambers in Frontenac and Marquette cultivars grown in Iowa and South Dakota, monitored from veraison to harvest. Table 1 presents the VOCs that are characteristic of biogenic emissions from Frontenac and Marquette clusters during the 2012 growing season from Iowa and South Dakota. These volatiles were detected in-vivo from whole grape clusters and determined through interpretation of principal component analysis (PCA) and hierarchical clustering analysis (HCA). A detailed summary of all 124 VOC can be found elsewhere [36]. However, only key representative volatiles from the hierarchical cluster analysis (HCA) are labeled with numbers on PCA biplot figures presented in Results. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Cluster**} & **No. of** & \multirow{2}{*}{**Most Representative Variable 3**} & **Cluster Proportion of** & **Total Proportion** \\  & & & & & **Variation Explained 4 ** & **of Variation** \\  & & & & & **Explained 5** ** \\ \hline  & 1 & 5 & & 0.937 & 0.173 \\  & 3 & 5 & 4-Methyl-3-penten-2-one & 0.745 & 0.138 \\  & 5 & 6 & & 0.512 & 0.114 \\  & 2 & 3 & 3-Methyl-1-butanol & 0.845 & 0.094 \\  & 4 & 4 & 1.4-Butanolide & 0.576 & 0.085 \\  & 6 & 2 & 5-(Hydroxymethyl)-2-Aranchenaldehyde & 0.858 & 0.064 \\  & 7 & 2 & Benzophenone & 0.548 & 0.041 \\ \hline  & 1 & 7 & Toluene & 0.712 & 0.208 \\  & 2 & 5 & & 0.820 & 0.171 \\ SD Frontenac & 5 & 3 & 3-Phenyl-2-propen & 0.810 & 0.101 \\  (0.686) 1 & 3 & 4 & 4-Methyl-3-penten-2-one & 0.592 & 0.099 \\  & 4 & 3 & Acetic acid & 0.502 & 0.063 \\  & 6 & 2 & Benzyl alcohol & 0.536 & 0.045 \\ \hline  & 1 & 10 & 1-Octanol & 0.805 & 0.310 \\  & 2 & 5 & Acetaldehyde & 0.814 & 0.156 \\  & 3 & 3 & Methyl methyl ketone & 0.616 & 0.071 \\  (0.739) 1 & 4 & 3 & 1-Hexadecanol & 0.505 & 0.063 \\  & 5 & 3 & Acetophenone & 0.536 & 0.062 \\  & 6 & 1 & Acetic acid & 1.000 & 0.038 \\  & 7 & 1 & 2-Ethyl-1-hexanol & 1.000 & 0.038 \\ \hline  & 1 & 7 & Acetone & 0.817 & 0.249 \\  & 2 & 4 & 4-Methyl-3-penten-2-one & 0.799 & 0.139 \\  & 6 & 4 & Decane & 0.977 & 0.139 \\ SD Marquette & 3 & 2 & 1-Pentanol & 1.000 & 0.087 \\  & 4 & 3 & 2-Ethyl-1-hexanol & 0.532 & 0.069 \\  & 7 & 2 & 1-Hexadecanol & 0.654 & 0.057 \\  & 5 & 1 & Indene & 1.000 & 0.043 \\ \hline \hline \end{tabular}
\end{table} 
Frontenac  
3-Methyl-1-butanol and heptanal were emitted and detected in 2012 Iowa Frontenac grapes at veraison. At harvest, 1,4-butanolide was detected (Figure A1). Nonanal, benzyl alcohol, and toluene were emitted and detected in 2012 South Dakota Frontenac grapes (Figure 3) at veraison. Only one compound, i.e., acetic acid, was associated with harvest time. Other compounds were detected (e.g., 2-methyl-3-penten-2-one and 3-phenyl-2-propenal) but were not indicated to be the most representative compounds from HCA. Results are also presented in this manner throughout the manuscript. Marquette  
2012 Iowa Marquette did not have a'representative' VOC at veraison, as indicated by HCA, and replicate samples had high variability (i.e., unevenly distributed between 2 quadrants of the PCA biplot). By harvest, 1-hexadecanol and methyl ethyl ketone had developed. Similarly, 2012 South Dakota Marquette VOCs emitted at veraison (Figure 4) did not have'representative' VOC at veraison. At harvest, indene was the representative VOC emitted. Figure 4: Evolution of VOCs emitted from whole clusters of 2012 Marquette grapes grown in South Dakota from veraison to harvest. Key to most representative volatiles from HCA, shown as vectors from the origin and read clockwise: 1 = 1-Hexadecanol, 2 = 2-Ethyl-1-hexanol, 3 = 1-Pentanol, 4 = Acetone, 5 = Indene, 6 = Decane, 7 = 4-Methyl-3-penten-2-one. Figure 3: Evolution of VOCs emitted from whole clusters of 2012 Frontenac grapes grown in South Dakota from veraison to harvest.