Metabolic and physiological changes during cold acclimation in two eucalyptus species divergent for frost tolerance

OBERSCHELP, G.P.J.; MORALES, L.; MONTECCHIARINI, M.L.; HARRAND, L.; PODESTÁ, F.E.; MARGARIT, E.

Santa Fe

Congreso; RAFV 2021 - XXXIII Argentinian meeting of Plant Physiology; 2021

SAFV

Most Eucalyptus species planted for wood and paper in subtropical and temperate regions are highly sensitive to sudden or seasonal frosts. Therefore, selection of genotypes with higher frost tolerance and a quicker acclimation to cold is of major interest. In this work, we studied the basal tolerance and the cold acclimation process in two Eucalyptus species (E. grandis and E. benthamii) by exposing 6-month old seedlings to low temperatures in culture chambers (15/5 °C day/night) for different times (0, 5, 10, 15 and 20 days). Evaluation of lethal temperature 50% (LT50) using leaf disc electrolyte leakage assays pointed to E. benthamii as the species with the highest tolerance in control conditions (LT50 of -1.9 vs. -1.0 ºC). Also, E. benthamii showed a quick rise in tolerance after 5 days of cold treatment (-4.7 ºC), reaching -6 ºC by day 10, while E. grandis needed 15 days to reach its maximum tolerance (-3.6 ºC). Physiological parameters such as leaf area, leaf fresh and dry weight, and plant height were also affected by acclimation in E. benthamii, where a decrease in area, height, and fresh weight was noted. Leaf metabolome analysis evidenced a rapid increase in sugar contents in E. benthamii by day 5, as well as higher accumulation of different protective metabolites during its cold acclimation. Principal component analysis and correlation plots allowed pinpointing metabolites and different parameters related to cold acclimation in both species. Our results showed E. benthamii has key traits to breed frost tolerant Eucalyptus.