Frost-resistance of the blackberry (Rubus subg. Eubatus Focke) cultivars in the Forest-Steppe zone of Ukraine

Abstract

Purpose. To improve the blackberry assortment based on studying the economic and biological peculiarities of new cultivars and their adaptabivity under the soil and climatic conditions of the Western Forest-Steppe zone of Ukraine for the further variety research and use in breeding programs. Methods. Laboratory, field, analytical and statistical ones. Results. Investigations were carried out to determine the influence of variable temperatures on 25 blackberry cultivars and their frostresistance to artificially created low temperatures (25and -30 °C). The degree of shoot tissue damage of blackberry plants with low temperatures in the field was also analyzed. Conclusions. The analysis of the degree of damage of blackberry plant shoots showed that a shoot apex appeared to be the most susceptible to the influence of low temperatures and the middle part of the shoot was most resistant. On the basis of the results of the laboratory free­zing of the blackberry plant shoots, cultivars were defined to be the most resistant to the both -25 and -30 °C low temperatures (‘Sadove chudo’ and ‘Orkan’). ‘Ouachita’ and ‘Cacanska Bestrna’ cultivars were also resistant to the temperature -25 °C (their total damage score did not exceed 9.0%). It is risky to cultivate ‘Nasoloda’, ‘Black Diamond’, ‘Tornfree’, ‘Loch Tay’, ‘Triple Crown’ and ‘Black Butte Blackberry’ in the areas where the temperature can be lowering to -25 °C without taking additional agrotechnical measures to protect against damage with low temperatures. The most sensitive to the temperature of -30 °C was the ‘Black Butte Blackberry’, ‘Nasoloda’, ‘Black Diamond’, ‘Black Pearl’ and ‘Jumbo’ cultivars (damage of more than 50% shoots was noted). This temperature conditions were critical for ‘Chief Joseph’, ‘Reuben’, ‘Tornfree’, ‘Karaka Black’, ‘Black Magic’, ‘Loch Tay’ and ‘Triple Crown’. The ‘Kiowa’ cultivar was quite resistant to both temperatures. The dependence of the shoots damage degree on the scrub architectonics was determined. The cultivars with creeping shoots are more susceptible to the effect of low temperatures than those that are more upright.