PHYSIOLOGICAL INVESTIGATION OF TOLERANCE TO IRON CHLOROSIS OF NAVELINA ORANGE BUDDED ON DIFFERENT CITRUS ROOTSTOCKS

In this study, physiological responses of Navelina orange budded on eight different citrus rootstocks to iron deficiency were investigated under high pH conditions. Navelina scion budded on Tuzcu 31-31 sour orange, Gou Tou sour orange, Volkameriana, Antalya Cleopatra mandarin, Carrizo citrange, Troyer citrange, C-35 citrange and TGK0633 trifoliate orange were grown in a plant growth chamber and irrigated with a modified Hoagland nutrient solution. In order to mimic an Fe deficient environment, 10 µM FeEDTA, 3 mM NaHCO₃ and 2 g L^-1 CaCO₃ (pH=7.8) were added to the nutrient solution. Control plants were irrigated with a nutrient solution containing 100 µM FeEDTA (pH 6) for five months. At the end of the experiment, Fe chlorosis color scale, leaf total and active Fe concentrations, chlorophyll fluorescence, ascorbate peroxidase and catalase activities were determined. In Fe-deprived leaves of Navelina budded on C-35 citrange and TGK0633 trifoliate, total and active Fe concentrations and efficiency of PSII significantly decreased. These plants exhibited more severe Fe chlorosis symptoms than plants budded on the rest of rootstocks. Young Navelina trees budded on Tuzcu 31-31 sour orange and Gou Tou were less affected in terms of all parameters. As a result, Navelina scions budded on Tuzcu 31-31 and Gou Tou sour oranges were the most tolerant; the ones budded on C-35 citrange and TGK0633 were the most susceptible to Fe deficiency.