A comparison of the phenology, berry ripening and canopy temperatures of four common grapevine cultivars in response to high temperatures

Field measurements of phenology and ripening were undertaken in four cultivars of grapevines; Vitis vinifera 'Pinot Noir', 'Shiraz', 'Riesling' and 'Sauvignon Blanc' growing in the Charles Sturt University Experimental Vineyard. Air and canopy temperatures were followed over the summer. Phenology was tracked to determine times of budbreak and flowering in each cultivar and berry ripening was followed by measuring total soluble solids. Across the growing season, air temperatures exceeded 40°C on 11 days whereas on western sides of the vine, canopy temperatures exceeded 40°C on 12 and 13 days for 'Pinot Noir' and 'Sauvignon Blanc', on 15 days for the 'Shiraz' vines but on only two days for the 'Riesling' vines. There were up to 6 days difference in time of budbreak, with 'Pinot Noir' and 'Shiraz' breaking first on 4-5th of September, 'Riesling' on the 7th of September and 'Sauvignon Blanc' delayed until the 11th of September. By contrast, there were no differences in the flowering times and all cultivars flowered between the 3rd and 5th of November. Similarly, all cultivars reached berry pea size on the same date on the 26th of December. There were marked differences in the ripening process, with both the 'Pinot Noir' and 'Sauvignon Blanc' berries ripening most rapidly at 0.48±0.02 °Brix day-1, 'Shiraz' berries at 0.36±0.01 °Brix day-1 and 'Riesling' berries slowest at 0.30±0.01 °Brix day-1. The conclusion of this study was that cultivar tested in this study differed in their response to seasonal temperatures.