Effects of hot-water treatment, post-hot-water-treatment cooling and cold storage on the viability of dormant grafted grapevines under field conditions

Background and Aims: Hot-water treatment (HWT) is an effective control method for black-foot and Petri disease, in grapevine propagating material. However, plant hydration and cold storage have emerged as critical factors in the production of quality planting material. The effects of HWT protocols on the performance of dormant plants ready to be sold to producers under field conditions were investigated. Methods and Results: The effects of HWT at 53 degrees C for 30 min, cooling (post-HWT cooling or no post-HWT cooling) and cold storage (0, 1, 2 and 4 weeks) on sprouting, and shoot length and weight in dormant grafted plants (Tempranillo cultivar grafted onto 110 Richter rootstock) were evaluated. Eight bundles of ten cuttings were treated for each factor combination, and eight additional bundles of ten untreated cuttings were prepared as controls (no HWT). Dormant grafted plants were immediately planted in two field sites in March 2010. The number of plants that emerged from dormancy was counted in July 2010. In January 2011, shoot length and fresh weight were evaluated. Although significant, the percentages of plants emerging from dormancy among treatments were relatively small. A significant reduction was observed in shoot length and weight for all treatments compared with the control, particularly in all variables for non-hydrated hot-water-treated cuttings kept in cold storage for 4 weeks immediately after HWT. Conclusions: The findings obtained in this study indicate that long-term cold storage could be detrimental to planting material, especially when plants have not been previously hydrated following HWT. Significance of the Study: This study represents the first approach for evaluation of different HWT protocols under field conditions. It improves the knowledge of the different steps used in the HWT process and provides valuable information about the most reliable protocol that can be used successfully in a commercial situation.