Evaluation and determination of chilling and freezing resistance in three commercial grape cultivars (Vitis vinifera L.) in north of Khorasan

To study the long-term effect of chilling and freezing on most important grape cultivars in north of Khorasan, two analytical experiments were carried out during 2008. In the first experiment, as Kolahdari and Kaje-Angoor were the most important and qualitative cultivars in the region for processing, fresh consuming and export, effect of natural frost on one- year, two- year and perennial branches of these cultivars in two climate conditions of Mashhad and Bojnord were evaluated. In the second experiment, one-year, two-year and perennial branches of Keshmeshi cultivar in three climate conditions of Golmakan, Qochan and Mashhad were evaluated. Factorial experiments based on completely randomized design with five replicates were used for both experiments. The traits that measured were: anatomical description of branch, re-growth, electrolyte leakage and proline content. Results from the first experiment showed that the main effect and interaction effects of genotypes and age of branches on electrolyte leakage from plant cells were significant (P≤1%). One-year and two-year branches of Kolahdari cultivar and two-year branches of Kaje-Angoor cultivar had the highest electrolyte leakage with 90.8, 89.4 and 85.6 respectively. Results of the second experiment also showed that, the main and interaction effects of branches age and sampling area on electrolyte leakage were significant. The Perennial branches from Mashhad area with mean of 65.6 had the lowest electrolyte leakage. These results also showed that there are no significant difference at all significant levels between sampling areas and branches age and interaction effects of these factors. However the effect of area and branches age on proline content was significant.