Antioxidant responses in apples exposed to sunburn injury

COLAVITA G.M.; ORIOLI G.A; VENTURINO A

San Carlos de Bariloche

Congreso; XXXIX Reunión Anual de la SAIB; 2003

SAIB

We reported previously that fruit development under solar stress was accompanied by an increase in lipid peroxides positively correlated to sunburn damage. In the present study we examined changes in ascorbate (AsA), glutathion (GSH), superoxide dismutase (SOD) and catalase (CAT) in the adaptive development of sun-exposed vs. shaded fruit of apple cultivars ?Braeburn? (BR) and ?Red Delicious? (RD). Reaching maturity, SOD increased sharply in shaded fruits (1527 U/gFW in BR and 436 U/gFW in RD), and was additionally induced by sun exposure, mainly in BR where it peaked to 8X and then decreased. CAT showed different profiles between both cultivars, increasing in RD and decreasing in BR, and was induced by solar radiation, being lower in BR (15 IU/gFW ) vs. RD (36 IU/gFW). AsA content increased early in sun-exposed fruits, being always higher in BR, and declining to harvest (112 to 88 nmole/gFW). GSH content was similar in shaded fruits and the increase by solar exposure was higher in RD (160 nmole/gFW, 2X vs BR). Sun exposure of fruits from early stages would cause an adaptive response related to induction of antioxidant compounds and enzymes in both cultivars. The higher sensitivity of BR fruits may be related to reduction in CAT with high SOD levels, and to a higher solar exposure due to morphological and physiological  characteristics