Abstract

RODRIGUEZ, A; BENITEZ PICCINI, E  and  MUNOZ, A. Tolerancia a las heladas por superenfriamiento en cultivares de nogal (Juglans regia) y almendro (Prunus amygdalus). RIA. Rev. investig. agropecu. [online]. 2018, vol.44, n.1, pp.101-110. ISSN 1669-2314.

Walnuts and almond grown in irrigation valley of Patagonia. The freezing damage is one of the most important environmental stresses that affect productivity. The periods of frost risk is from autumn to late spring (April to October). Plants can avoid freezing damage by preventing extracellular ice formation below the equilibrium freezing temperature (supercooling). The objectives were to: 1) evaluate changes in the degree of hardening before and during winter in walnuts stem segments of one-year-old (cv Chandler y Franquette); 2) determine the threshold for supercooling of almond blossom (cv Guara, Ferragnes y Farraduel). To study were compared thermal analysis and the evaluation of tissue health after controlled freezing, based on tissue browning. Our observations and results indicate that the degree of walnut frost tolerance depends on the previous climate history. During late summer and autumn the value TNH is -5ºC, reaching the LT50 to -7.7ºC and 100% damage with minimum temperatures of -10°C for more than an hour. In the winter rest TNH is -6.5ºC and reaches 25% damage with minimum temperatures of -15°C. The desaclimatización induced decreases tissue tolerance (TNH -4.6ºC to -5.6ºC) and increases variability in response to low temperatures, with frost -8ºC the degree of damage can be from 10 to 50% and -15ºC of 25 to 100%. Young walnut wood, the concentration of soluble sugars is the main indicator and physiological regulator of frost tolerance. Almond flowers have TNH of -1.7ºC to -2.5°C. Exposure for more than an hour at these temperatures causes the death of 45% of the organs. If the pre-flowering period is fresh, the degree of desaclimation is lower, TNH values decrease -3.8ºC giving it greater tolerance to frost.

Keywords : Deacclimation; Walnut stem; Almond flowers.

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