Frost Damage and Carbohydrate Metabolism in Citrus Fruit

M.L. FALCONE FERREYRA, S.M. GARRÁN, C.M. ANDERSON, D.E. VÁZQUEZ, A.A. IGLESIAS, F.E: PODESTÁ.

Bariloche, Río Negro, Argentina

Congreso; XXXIX Reunión Anual de SAIB; 2003

SAIB

PL-P29.FROST DAMAGE AND CARBOHYDRATE METABOLISMIN CITRUS FRUITFalcone Ferreyra, M. Lorena1; Garrán, Sergio M.2; Anderson,Catalina M.2; Vázquez, Daniel E.2, Iglesias, A.A.3 and Podestá,Florencio E.1INTA Est. Exp. Agropecuaria Concordia2, Fac. de Bioquímica yCiencias Biológicas, UN del Litoral3 and Centro de EstudiosFotosintéticos y Bioquímicos1. Suipacha 531. 2000 Rosario.Argentina. E-mail: mfalcone@fbioyf.unr.edu.arFreezing temperatures can cause severe damage and economicloses to the citrus industry by reducing yield and by afecting theexternal and internal parameters of fruit quality. The activitiesand levels of the enzymes involved in the carbohydrate metabolismof fruit from orange trees (Citrus sinensis L., cv. Valencia late)exposed to different temperatures were analized. The aim of thework was to find biological markers to develop an early diagnostictechnique for frozen fruits. The enzymatic activity measurements(in terms of U/mg and U/g FW) showed a significative andmoderate increase in frozen fruits compared to control inpyrophosphate-dependent phosphofructokinase (1.85-fold), Alaamino transferase (1.6-fold), phosphoenolpyruvate carboxylase(1.75-fold) and pyruvate kinase (1.75-fold). A more pronouncedrise was observed in lactic and alcohol dehydrogenase activities(4.4 and 4.7-fold, respectively). In contrast, only NADP-malicenzyme diminished (40%). These results were consistent with theprofile in the immunoreactive proteins levels. Another importantfeature to emphasize was the marked decrease in total solubleprotein in frozen fruits. These studies suggest that freezingtemperatures induce the activation of the glycolytic andfermentative metabolisms.