Influence of Pre- and Post-Treatment Storage on Rooting of Hot-Water-Treated Cuttings of Cabernet Sauvignon

¹ Department of Horticulture and Landscape Architecture, Washington State Univer- sity-Prosser, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350-0030.

This study examined the practical aspects of pre-, post- and combined pre- and post-treatment storage on root development of hot-water-treated dormant cuttings of Cabernet Sauvignon. Cuttings were either collected in November and stored at 3°C to 4°C until treated (pre-treatment storage) or collected monthly, from November through February, 24 hours prior to treatment. Treatments were made to cuttings removed from storage and cuttings collected the previous day. Hot water treatments consisted of 52°C, 54°C, 56°C, 58°C, or 60°C for 10, 20, or 30 minutes. After treatment, half of the cuttings removed from storage and half of those collected 24 hours earlier were placed in cold storage (3°C - 4°C) until mid-February (pre-/post-treatment storage and post- treatment storage, respectively). The other half of the cuttings from storage and those collected the previous day were transferred to the greenhouse (pre-treatment storage and no storage, respectively) for rooting. Greenhouse samples were evaluated after nine weeks for root development. When analyzed for temperature effect only, cuttings showed good root development up to 56°C. Root development declined slightly with increasing time of treatment at 52°C and 54°C, and to a greater extent at 56°C, 58°C, and 60°C. Cuttings that received either no storage or post treatment storage generally showed the best root development. Heat treating cuttings at temperatures up to 56°C appeared feasible, especially if this was combined with post- treatment storage at 3°C to 4°C. When all treatments were combined, cuttings taken in November showed the best root development. Harvesting cuttings at this time would reduce the risk of winter injury in late December and January under Washington State conditions. If hot water treatment proves to be effective in eliminating crown gall from dormant grape cuttings, this study indicates that post-treatment storage of cuttings is not detrimental, and in fact may promote root development.

Key words: propagation, Agrobacterium, crown gall, rooting, cold injury, thermotolerance, Cabernet

Submitted on September 17, 1996