Thermotolerance of Dormant and Actively Growing Cabernet Sauvignon Is Improved by Heat Shock

¹ Irrigated Agriculture Research and Extension Center, Washington State University, Prosser, WA 99350.

Actively growing Cabernet Sauvignon plants grown at 25°C were given a four-hour heat shock at 40°C, followed by a four-hour incubation period at 25°C. The heat shocked plants, when compared to non-heat shocked plants, had less leaf damage, tissue water loss, and electrolyte leakage after exposure to 50°C. Dormant Cabernet Sauvignon cuttings were removed from 3°C cold storage and heat shocked for 30 minutes at either 45°C or room temperature (23°C). This was followed by a four-hour incubation period at room temperature. A group of non-heat shocked control cuttings were held continuously at 3°C. Thermotolerance was tested by placing the cuttings in water baths at 54°C, 56°C, 58°C, or 60°C for 30 minutes. Primary, secondary and tertiary bud survival, time required for buds to begin growth, and root vigor were evaluated for each treatment. Bud survival was high in all treatments at 54°C and 56°C, while at 60°C there was 100% bud mortality in all treatments. At 58°C, however, cuttings that were heat shocked at room temperature were significantly (p < 0.01) more thermotolerant than the control cuttings, and those that were heat shocked at 45°C were significantly (p = 0.01) more heat tolerant than those heat shocked at room temperature. These results show that both dormant and actively growing grape tissues respond to heat shock treatment by increasing their thermotolerance. To our knowledge, this is the first time that heat shock responses have been shown to occur in dormant woody plant tissue. Heat shock treatment could lead to more effective pathogen elimination by allowing grape propagation material to be treated at higher temperatures than are currently possible.

Key words: cuttings, thermotolerance, Cabernet Sauvignon vines

Submitted on May 20, 1994