Biopsia transepitelial por cepillado: Oral CDx®

Results showed a clear difference between the high and low vigour plots from all farms concerning soil analysis. The lowest resistance was found on Farm A Chenin blanc and Farm B Pinotage, where the low vigour sites exhibited resistance levels lower than 300 Ohm, which according to Raath (2016) indicates a large amount of salts are present in the soil, which as the resistance lowers have a growing negative impact on the vineyard. The highest Na concentrations were found for Farm B Pinotage, whereas the soil pH of all farms were quite variable, however Farm B Pinotage showed the highest

116 pH for both the low and high vigour plots. The highest ESP was discovered to be on Farm A, where some ESP values were greater than the 15%, making those soils Na alkaline rich (Raath, 2016). The climate variation between Farm A, Farm B and the weather station near the farms showed some differences. Farm A had the highest GDD values, whereas Farm B showed the highest HI and GST. The weather station had the lowest values for all the indices (GDD, GST and HI). Usually the mean February temperature is used as an index as it is the warmest month of the year. However, results showed January mean temperatures were higher than the mean February temperatures during the 2016 vintage.

The vegetative measurements showed high variability between sites and vigour levels. Trunk circumference measurements were different between vigour levels as well as sites. The low vigour plots depicted the smallest trunk circumference. The bush vines on Farm A Chenin blanc had the largest trunk circumference, however the vines also showed the most variability. Both the Chenin blanc and the Pinotage on Farm B displayed the smallest trunk circumference. A positive correlation was found between the soil resistance and trunk circumference, as the soil resistance increases, so did the trunk circumference. Shoot growth on vines from Farm A and B Chenin blanc exhibited differences between vigour levels, whereas the Pinotage showed very little difference between vigour levels. The Pinotage however, had the slowest shoot growth, with the shoots also being the smallest compared to the vines from Farm A and B Chenin blanc. The Chenin blanc on Farm A was topped during the season, so no clear conclusion can be drawn from this plot. Leaf area also showed variability between vigour levels, where the low vigour vines always had the smallest leaf area. The highest total leaf area per shoot was on vines from Farm B Chenin blanc. The high vigour vines on Farm A Chenin blanc had the highest lateral to main leaf area ratios. A positive correlation was also found between soil resistance and total leaf area per shoot.

Leaves and petioles were sampled at bloom and véraison. The analysis of these samples displayed large difference between the stages of sampling, bloom and véraison, but also between sample types, petioles and leaves. The petiole samples usually depicted the highest concentrations of minerals, like Na, K and Mg, however Ca levels were highest in the leaf samples. Sampling done during véraison, showed the highest Na, Cl and Mg concentrations, whereas Ca levels were highest during bloom. K concentrations were quite variable between bloom and véraison. The highest Na levels were in the petioles of the low vigour vines on Farm B Chenin blanc during véraison. The high vigour vines from Farm B Chenin blanc exhibited the highest petiole K concentrations during bloom and véraison. The Ca levels in leaf samples taken during bloom from vines from Farm A and B Chenin blanc were highest in the high vigour vines. Similar Mg levels were found on all farms, samples and vigour levels. Positive correlations were found between the leaf (Na, K, Ca and Mg) and petiole samples (Na, K, Ca and Mg respectively). Cane mineral analysis was done post-harvest. Differences in the concentrations of minerals (Na, K, Ca and Mg) between the vigour levels and the farms were found. The low vigour

117 canes from Farm B Chenin blanc exhibited the highest Na concentrations. The K levels in the canes were highest from vines on Farm A and B Chenin blanc. The highest Ca levels were found in the canes from Farm B Pinotage, whereas the Mg concentrations from the canes of all farms displayed similarities. A positive correlation was found between Na and Mg concentrations in the canes. All farms and vigour levels depicted differences in TSS accumulation and TA. Generally the low vigour TSS accumulation was slower and less than the high vigour plots, except for the Farm B Chenin blanc, where both vigour levels showed very similar berry TSS accumulation. The TA of the high vigour plots on Farm A and B Chenin blanc decreased linearly and showed lower TA values than the Pinotage on Farm B. Yield measurements displayed differences between vigour levels and sites, where for the low vigour plots on Farm A Chenin blanc and Farm B Pinotage had a lower average bunch and berry mass. Farm B showed very little differences between the high and low vigour plots. The grape component mineral analysis exhibited cation and anion concentration differences between the grape skins, homogenate, juice and sediment samples. It was found that Ca, Mg, B, Zn and P were at highest concentrations in the grape skins and homogenised samples, whereas the highest levels of K, Al, Fe, Mn, Ba and Si were found to be in the sediment. The juice samples showed no minerals at high concentrations. This has implications for wines undergoing skin contact. A more detailed look, showed Na and Cl content was highest in the homogenised samples, K was highest in the sediment and Ca and Mg were highest in the grape skins.

The grape juice to wine mineral content interactions, showed that grape juice Na, Cl and Mg concentrations had positive correlations with the Na, Cl and Mg levels in the wine, respectively. No correlations were found between the grape juice K and Ca levels and the K and Ca wine concentrations. However, if the K and Ca correlations were considered separately according to farms, K correlated strongly to all farms separately and Ca grape juice and wine correlations showed strong correlations from Farm A Chenin blanc. The soil to grape juice and wine interactions showed no correlations between minerals found in the different soil depths and the grape juice and wine concentrations, except for K. K levels in the soil at different depths showed moderate to strong correlations with wine K concentrations. Correlations could also been seen between wine K concentrations, pH and the TA of the corresponding wine. As the K levels rose, the pH also increased, whereas as the TA dropped as the K concentrations increased.

The grape juice and wine mineral concentrations were quite variable between sites, years and vigour levels. The Na concentrations in the grape juice was highest from the low vigour plots from Farm B Chenin blanc grape juice. K was highest in grape juice obtained from high vigour plots during the 2016 vintage, whereas Ca concentrations were highest in 2016. Mg levels on the other hand, showed that the grape juice from the low vigour plots during 2016 were the highest. All minerals found in the wines, showed great variability between sites, vigour levels and years. Na and Mg levels were highest

118 in the low vigour plot grape juice. The K concentrations were higher in the high vigour plots, whereas no clear differences between the vigour levels, years and sites were noted between the Ca levels. The highest Cl concentrations in the grape juice and wine were found in the low vigour plots, which corresponds to the Na grape juice and wine concentrations, and the increased soil salinity.

The red wine colour and phenolics of the Pinotage from Farm B, showed variation in vigour and vintage. The differences in years could be attributed to the time of harvest, especially in 2016, where phenolic ripeness had not occurred before the grapes were harvested. Generally the 2015 low vigour sites wines showed higher anthocyanin and phenolic content, as a result of the smaller berries. The wine colour hue was high, which meant the red: brown colour ratio was lower. The colour hue differences may have been due to the high pH content of the Pinotage wines. The VA was also higher in the Pinotage from Farm B. The total acid was highest from wines made from grapes from Farm A Chenin blanc, where the highest malic acid concentration were found in wines made from Farm B Chenin blanc grapes. Glucose concentrations were quite variable and high, which may have been as a result of high sugar levels, incomplete fermentation or an analytical error.

The descriptive analysis showed only significant differences between attributes generated for the Farm A and B Chenin blanc wines made in 2016. The Pinotage wines made from Farm B also showed significant differences between the vigour levels. Significant aroma descriptors for Farm A and B Chenin blanc wines were passion fruit, quince, cooked veg and herbaceous, with significant taste attributes being sweet and sour. Farm B Pinotage made in 2016, only had significant taste descriptors, such as sour, bitter and astringency. It was also concluded the salt content in the wine did not affect the wine’s aroma and taste profile, the differences between the wines were probably site differences, in particular the soil and climate.