TOLERANCE TO LOW TEMPERATURE, INDUCED BY SALICYLIC ACID AND HYDROGEN PEROXIDE IN POTATO MICROPLANTS

Abstract

The effects of salicylic acid (SA) and hydrogen peroxide (H2O2) on freezing-tolerance (-6 ± 1 °C) were studied on S. tuberosum microplants of cvs. ‘Alpha’ and ‘Atlantic’. The response to low temperature was previously determined by exposing microplants 3-7 weeksold for 2 or 3 h. Microplants 4 weeks old exposed for 3 h to low temperature were selected as a model for further experiments. ‘Alpha’ cultivar was more tolerant to freezing than ‘Atlantic’. Nodal explants of both cultivars were incubated in H₂O₂ (0, 0.1, 1, 5, 50) mM for 1 h and allowed to grow in MS medium for 4 weeks. Nodal explants were also grown for 4 weeks in MS medium with SA (0, 0.001, 0.01, and 0.1 mM). Plant survival and catalase activity were measured in these treatments. The SA-treatment 0.1 mM enhanced survival by 31 % in ‘Alpha’ and by 78 % in ‘Atlantic’, relative to controls, whereas the H₂O₂ 50 mM treatment induced an increment of 44 % in ‘Alpha’ and 92 % in ‘Atlantic’. Catalase activity was 37 % lower in ‘Alpha’ and 36% in Atlantic in the SA 0.1 mM treatments, while in the H₂O₂- treatment 50 mM the catalase activity increased 17 % in ‘Alpha’ and 28 % in ‘Atlantic’. It is possible that SA and H₂O₂ may have contributed trough different routes to freezing-tolerance signaling. These compounds are potentially useful for inducing freezing tolerance in potato microplants.