Chilling injury and drought resistance of 5 varieties of Olea europaea L. cultivated in Patagonian steppe

ARIAS N; BUCCI SJ; SCHOLZ FG; GOLDSTEIN G

Luxemburgo

Seminario; 9th International Plant cold hardiness Seminar; 2011

Centre de Recherche Public Gabriel Lippmann

Temperature and drought are the most important factors that limit the distribution of many crops. Olive tree (Olea europaea L.) is mainly cultivated in the Mediterranean region where prolonged droughts may occur during the vegetative period. This species has developed physiological mechanisms to tolerate drought and resist low temperatures. During recent years, the increasing demand of olive oil has allowed the expansion of olive cultivars into geographical zones at higher latitudes. Moreover, cold autumns which slow down fruit maturation process, improve the quality of olive oil, and this has led to cultivate olive trees in regions under recurrent danger of frost. We evaluated sensitivity to low temperatures and resistance to drought in 5 varieties of olive: Arbequina, Manzanilla Californiana, Frantoio, Changlot Real y Hojiblanca during 2010-2011summer in Patagonian steppe (45¨¬ 47¡¯S, 67¨¬ 30¡¯W). Summers are characterized by long dry periods and minimum absolute temperatures as low as 2¡ÆC. Two-years old- plants were grown outdoor in 20-dm3 pots (one plant per pot) filled with a mixture of clay and sand soil irrigated bi- weekly. Electrolyte leakage method was used to evaluate cellular damage of mature leaves and determine LT50, that is the temperature corresponding to 50% of the total ion leakage. Osmotic potential at turgor loss point (¥÷TLP), relative water content at TLP (RWCTLP), bulk elasticity modulus (ɛ) and solutes content (Ns) were estimated from pressure-volume curves for 4 leaves per variety. Manzanilla Californiana was the variety that showed highest values of LT50          (-2¡ÆC), RWCTLP (71.92 ¡¾ 7.69%) y ɛ (4.17 ¡¾ 1.7 MPa) while Hojiblanca showed lowest values of LT50 (-5.8¡ÆC), RWCTLP  (52.14 ¡¾ 5.20%) y ɛ (2.03 ¡¾ 0.34 MPa). ¥÷TLP was higher in Manzanilla Californiana than in Hojiblanca (-4.09 ¡¾ 0.71MPa, -4.74 ¡¾ 0.72MPa respectively). Osmotically active solutes were lower in Manzanilla than in Hojiblanca (0.34 ¡¾ 0.012 mosmol.g-1, 0.43 ¡¾ 0.03mosmol.g-1respectively). Arbequina, Frantoio and Changlot Real showed intermediate values for those variables. The temperature at which 50% of the total ion leakage was measured, reflecting 50% loss in cellular intactness was positively correlated with ¥÷TLP (R2=0.85, p<0.05) and osmotically active solutes content (R2=0.86, p<0.05). Results indicate that Hojiblanca could be the most resistant variety to low temperatures and long periods of drought in Patagonian steppes. This variety presented cells that lost the cellular intactness at lowest temperatures. High solutes content found in Hojiblanca could protect membrane against chilling injury. In addition, low ¥÷TLP could allow to this variety decrease minimum leaf water potential to continue extracting water from drier soils without loss turgor. Results suggest that Hojiblanca could maintain the integrity of the plasmatic membrane and continue growing under non-favorable conditions.