Methyl jasmonate (MeJA) protective effect on photosynthetic performance and its association with antioxidants in two highbush blueberry (Vaccinium corymbosum L.) cultivars with contrasting aluminum (Al) resistance under Al toxicity was determined. Legacy (Al-resistant) and Bluegold (Al-sensitive) cultivars were subjected to control, MeJA, Al, and their combination (Al+MeJA) for 0, 24, and 48 h under greenhouse conditions. Al concentration, oxidative damage (malondialdehyde (MDA) and H2O2 concentrations), antioxidant activity (AA), superoxide dismutase (SOD) and catalase (CAT) activities, total polyphenols (TPP), chlorogenic acid, and in vivo photosynthetic performance were determined. The exposure to Al toxicity increased the Al concentration (up to 15-fold) and oxidative damage (up to 5.5-fold) compared to the control at 48 h, despite the antioxidant responses (SOD and CAT activities) were increased (up to 4-fold), mainly in the Al-sensitive cultivar at 48 h. Concomitantly, the photosynthetic performance was strongly reduced in the Al-sensitive cultivar (1.6-fold), while the Al-resistant cultivar was more stable during the experiment. However, when cultivars were exposed to Al+MeJA, the Al accumulation and oxidative damage strongly decreased (7-fold and 1.6-fold, respectively), increasing AA, SOD and CAT activities, and TPP in both cultivars during the first hours of Al exposure. The MeJA application decreased Al uptake and stimulated antioxidant pathways, which may counteract the toxic Al effects, protecting the photosynthetic apparatus in both cultivars, being more evident in the Al-sensitive cultivar.
