Measurement of phenology, growth characteristics and berry composition to identify winegrape varieties adapted to future climate scenarios

Abstract

A limited number of winegrape varieties are grown commercially in Australia. This may restrict the capability of the wine industry to meet challenges associated with predicted climate change scenarios. These challenges include the consistent supply of quality product in a variable and changing environment; the effects of temperature on fruit composition and wine attributes; a compression of the seasonal cycle, leading to an inability to process fruit at optimum maturity and, adapting to limited water supply and drought. The potential to exploit genetic variability to meet these challenges through adoption of alternative varieties is being explored. A systematic approach has been used to phenotype 500 varieties grown in a hot climate in the CSIRO germplasm collection for traits considered to be important for climate change adaptability in 2 seasons with contrasting climatic conditions, i.e. the hot dry 2009-10 season and the cool, very wet 2010-11season. The study aimed to identify varieties with optimal berry composition, colour and flavour when grown under hot conditions; varieties with high water use efficiency based on short seasonality and high fruit to leaf ratios and varieties suited to extend the harvest intake period. The phenotyping included assessment of phenology (ie. budburst, flowering, veraison and harvest date); growth characteristics (shoot fruitfulness, maximum canopy size and yield) and fruit composition (total soluble solids, titratable acidity, pH, organic acids, total anthocyanins and phenolics and yeast assimilable nitrogen). In the hot 2010 season, calculated harvest date at similar maturities (22 oBrix) extended from mid January to late April, indicating significant opportunities to identify varieties to mitigate effects of compressed seasons, with short seasonality to improve water use efficiency and with long seasonality to ripen in cooler conditions. There was a 10-fold difference in LAI (0.5 – 5.5 m2/m2) indicating potential to select varieties with smaller canopies to minimise transpiration and improve water use efficiency. Furthermore, there were large differences in pH (range 3.0  –  4.7), titratable acidity (range 2 – 13 g/L), organic acid composition  (range for  malic acid  0.2  – 7.6 g/L, range for  tartaric acid 0.7 – 8.8 g/L), yeast assimilable nitrogen (YAN, range  98 – 696 mg/L) and in red varieties, anthocyanin levels (range 0.2 – 5.0 mg/g) indicating potential to select varieties with optimal berry composition. For the red varieties, berry anthocyanins and phenolics were relatively stable across the two contrasting seasons (i.e. r of 0.93 for anthocyanins and 0.79 for phenolics, n=180). However, for most variables correlations between the seasons were not significant, indicating instability and differing varietal responses to environmental queues.  In conclusion, the study has shown significant potential to adopt a wider suite of varieties to facilitate adaptation by industry to future climate change scenarios. However, the selection of late ripening varieties to extend the season may produce significant problems in cool, wet seasons.