عنوان مقاله [English]
Introduction: cold resistance has been studied and evaluated by several methods; visional observation after natural cold injury, establishing of freezing condition by transported micro chamber in native places of trees, cold treatment of detached tree segments in laboratory examination. Most physiological traits correlated with cold resistance have multi gene characteristics and have controversial relationships. Russia researchers evaluated cold injury on 30 cultivars of grapevine. Their results showed that only hybrids that accomplished by crossing between Asian and vinifera had more cold resistance as compared with other cultivars. Up to now some researches have been conducted in Iran. Malakooti evaluated the capability of cold injury in some clones. He concluded that only two clones had cold resistance property when treated with -21 OC in 24 hours by duration of cold. All grapevines that have been cultivated in Iran belong to vinifera species. Therefore there is no absolute cold resistance in the most of them. But some clones and cultivars may be showed more cold tolerance comparison with others since they have been selected and acclimated trough the time. By entrance of cold weather that was overwhelming in all of the country in 2011, there had been suitable condition for this survey. In this regard, this research had been conducted to distinguish and evaluate this characteristic.
Material and methods: this study was conducted to evaluate the effect of cold injury on grapevine cultivars and assessment of tolerance to cold injury in the grapevine cultivars. This research was done in a field evaluation in three part of Hamadan province namely, Razan city, Malayer city and collection cultivars in the Agricultural research center of Hamadan. In three regions we collected and evaluated the canes of eight Cultivars, namely, Red Tompson seedless, White Tompson seedless, Askari, Fakhri, Yaghooti, Mehdikhani, ghazne and dozool. After that the winter passed (early spring), we collected the canes and some corsons. Then the canes were separated in three segments. Buds were observed by microscopic detection and survived buds were counted in different segments of the cane. That is a criterion to evaluate the effect of cold injury on buds in this expectation. As we have limited samples in some regions, therefore the experiment was conducted in non-complete randomized design. Tow-way analysis of variance (ANOVA) of the data was carried out using SAS software (v. 8.02, SAS Institute, Cary, NC) and the means were compared through the Duncan’s Multiple Range Test.
Results and discussions: result of analysis variance showed that cultivars have significantly different in respecting to bud growth. There were the most number of activated buds in the first third zone of canes (basal side of the cane). This activation had been decreased comparison with the apical zone. Means comparison showed that two cultivars (Mehdikhani and Yaghooti) had highest number of survived buds in three segments of cane as compared to other cultivars. These two cultivars are early ripening cultivar. It is estimated that less injury of cold in these cultivars might be correlated with their precocity besides inclining with inherits and genetic specifications. These cultivars were harvested 25 to 30 days sooner than other cultivars, so they have more time for repletion of starch and biomass. Other six cultivars had more injured buds as compared with these two cultivars. There were not significant different between these six cultivars, although ghazne and dozool had less survived buds as compared with four other cultivars in three segment of the cane. In comparison between three regions of Hamadan province, Hamadan itself and Razan city had more cold injury than Malayer.
Conclusions: It was demonstrated that in this research two cultivars of grapevine (Yaghooti & Mehdikhani) had more cold tolerance in three regions compared with other cultivars. But red and white Thompson seedless is more widespread in Hamedan. So it is recommended that we have good monitoring on horticultural techniques for preventing and reducing cold injury in these cultivars. These precautions or tactics can be concluded as establishing of better nutrition program, prevention of early harvesting, prevention of any leaf injury and defoliation, good pruning performance and prevention of sever pruning especially in late season, using of resistant rootstock, using of absorbent light mulches in winter, application of some material for inducing cold resistance.