Effects of exogenous abscisic acid on antioxidant response and quality of apple exposed to high solar radiation stress
Apple (Malus × domestica Borkh.) fruits are frequently exposed to high solar radiation (HSR) oxidative stress, which decreases fruit quality and promotes sunburn injury. Abscisic acid (ABA), a plant hormone, has been reported to enhance antioxidant defenses during the abiotic stress response. The aim of this work was to assess the effects of exogenous ABA on antioxidant metabolism and fruit quality in Red Delicious apple exposed to HSR. Treatment consisted of monthly (December, January, and February) foliar sprays with S-ABA (400 ppm) on five plants, with untreated plants used as control. Oxidative parameters and pigments were analyzed on skin tissues of HSR-exposed and non-exposed sides of the fruits. Regardless of ABA treatment, HSR-exposed tissues showed higher lipid peroxidation (TBARs) than non-exposed ones (average 182.5 and 153.0 nmol g‑1 FW, respectively; p≤0.05). Neither HSR nor ABA affected antioxidant capacity and polyphenols content. In HSR-exposed tissues, ABA decreased chlorophyll and carotenoid contents but increased anthocyanins synthesis. Cyanidin-3-glucoside levels increased from 15.7 mg (cy3-glu) g‑1 FW in control fruits to 28.8 mg (cy3-glu) g‑1 FW in ABA-treated fruits. Consequently, an increment of 7% in red color (h°) and 10% in luminance (L*) and saturation (C*) was detected. ABA treatment did not affect apple skin plasma membrane integrity nor relative water content. No differences were found on maturity indices and sunburn damage between treated and control fruits. These results suggest that ABA can improve fruit quality by increasing anthocyanin levels and fruit color, but does not enhance the antioxidant response nor improves sunburn tolerance on Red Delicious apples.
Colavita, G.M., Guiamet, J.J. and Civello, P.M. (2020). Effects of exogenous abscisic acid on antioxidant response and quality of apple exposed to high solar radiation stress. Acta Hortic. 1289, 27-34
sunburn, anthocyanin, Malus × domestica, fruit color, growth regulator