Resistance to freezing in three Eucalyptus globulus   Labill subspecies

The resistance to low temperatures was assessed in seedlings of three subspecies of E. globulus (ssp globulus, ssp bicostata and ssp maidenii) of two different provenances. Lethal temperature 50 (LT₅₀) was obtained by measuring the electrolytic conductivity, nucleation and freezing temperatures were obtained by thermal analysis and the total soluble carbohydrates concentration was determined through the phenol-sulphuric method. Results showed that the most resistant provenance corresponded to Bolaro Mountain of ssp maidenii with a LT₅₀ lower than -9°C. The provenance Moogora of ssp globulus, had a LT₅₀ of -8.47ºC, which situates it, as the second most resistant to low temperatures. According to the nucleation and freezing temperatures, the results indicate that all the provenances analyzed evaded the formation of ice, except for Bolaro Mountain of ssp maidenii which was tolerant to freezing. Finally, an inverse correlation (r = -0.89) between the content of total soluble carbohydrates and the LT₅₀ was found, indicating the cryoprotection effect of these in the resistance to low temperatures.