Research project shows the uniqueness of clones.
Titled ‘Assessing clonal variability in Chardonnay and Shiraz for future climate change’, this four-year research project was completed last year and the final report now available from the Wine Australia website. The aim of the project was to assess the viticultural performance and wine sensory properties of a common selection of Chardonnay and Shiraz clones grown in a diverse range of climatic regions across Australia.
Sites of mature plantings in Victoria, South Australia and Western Australia were selected. The majority of the sites were not replicated clonal trials, rather being row by row plantings of the different clones. In WA, Chardonnay sites were in Margaret River and Great Southern (Mount Barker) and a Shiraz site also in Margaret River.
Field work commenced in the 2013-14 season, three consecutive seasons of vine performance and wine sensory data were collected from the Shiraz sites while four consecutive years of data was collected from the Chardonnay sites.
Chardonnay clones included in the study were; 76, 78, 95, 96, 277, FVI10V1, FVI10V5, Gingin and Penfold 58. The Shiraz clones included; BVRC12, BVRC30, 1654, SARDI 4, SARDI 7, PT15, PT23, R6WV28, WA Selection and Bests.
The following discussion focuses on the findings from the WA sites concerning viticultural performance and wine sensory attributes.
Chardonnay viticultural performance
In terms of canopy volume, the Gingin clone was comparably lower in the Great Southern than the other four clones. Pruning weights of Gingin were consistently lower in both Great Southern and Margaret River.
In the Great Southern, clones 277 and 96 were consistently higher yielding and perhaps the most stable across the four seasons, while 76 was the lowest yielding of the Bernard clones which aligned with the Margaret River observations. Gingin had the highest number of bunches in both Great Southern and Margaret River. The data suggests the conditions of 2015-16 and 2016-17 favoured the Gingin clone in Margaret River as it out yielded all other clones although the large standard deviation of the data suggests there was a high vine-to-vine variability.
Bunch compaction measurements were restricted to three years, in Margaret River the Gingin clone recorded the lowest bunch compactness in all three years. In the Great Southern, Gingin had the lowest bunch compactness in two of the three years and equal lowest in the other year.
Observations from the two WA sites clearly shows the Gingin clone exhibited different cropping characteristics from the other clones assessed.
In the Great Southern, 96 recorded the highest number of berries per bunch in each of the four seasons and Gingin had the lowest berry weight in three of the four seasons. Clone 277 had the highest or second highest across all seasons.
Clone 96 in Margaret River had the heaviest berry weights in three of the four seasons while Gingin was highly variable (highest in 2013-14, lowest in 2016-17).
Gingin in both regions was picked at consistently higher Baumé, indicating this clone has a tendency to ripen before the Bernard clones. Clone I10V1 in Great Southern also showed a similar trend in ripening before the other clones. In both Margaret River and Great Southern Gingin repeatedly recorded the highest TA and lowest pH, a similar trend was observed in the 76 clone.
Shiraz viticultural performance
No significant difference was found between Shiraz clones in Margaret River in terms of canopy volume, surface area, porosity or leaf area index. The WA selection of Shiraz had the heaviest prunings in each of the three years in Margaret River.
Inconsistency was observed between Shiraz clones for berry weights and berry numbers per bunch. There were no significant differences between the productivity of the four Shiraz clones across the three seasons in Margaret River.
Soluble solids concentrations of the Margaret River Shiraz clones were significantly influenced by yield rather than clone and there appeared to be no relationship to clone considering pH and titratable acidity.
Wine attributes
Within each region there were significant differences in the sensory scores between clones in each year while the number of attributes that were significantly different varied between regions.
Great Southern Chardonnay
In all four years, Gingin scored the highest of the clones for yellow colour while 277 scored lowest in two of the years. Gingin scored highest in stone fruit flavour in three of the years as did I10V1 in 2016 and 2017. As a contrast clone 96 scored low in stone fruit flavour in three of the four years. In 2014 and 2015 clone 76 scored high in box hedge aroma.
Margaret River Chardonnay
There were less consistent scores across the years but still significant differences between the clones within each year. Similar to the Great Southern results, the sensory panel noted Margaret River Gingin to have higher yellow colour than the other clones, ranking highest in 2014 and 2016. However, the other Great Southern results in regard to Gingin weren’t replicated in Margaret River wines. There were high scores for both box hedge and citrus aroma in 2015 and 2017 for Margaret River Gingin.
Margaret River Shiraz
Of the Shiraz clones from Margaret River there were no consistent attributes over the three years however there were a number of consistent observations over two seasons worth noting. In 2014 and 2016 clone PT15 scored high in dark fruit flavour and low in confection aroma compared to the other three clones. The WA selection scored low in green flavour in both 2015 and 2016 while 1654 scored high in green flavour in the 2014 and 2015 seasons. Scoring opacity (colour intensity) BVRC12 was comparably lower than the other clones in 2015 and 2016.
Overall the project found statistically significant differences in sensory attributes of a range of Chardonnay and Shiraz clones however, there were few consistent trends in the differences between clones. The project concludes there is merit in planting a range of clones within vineyards and then using the diversity between the wines to produce specific and unique wines.