Physiological investigation of tolerance of navelina orange budded on different citrus rootstocks to iron chlorosis

In this study, physiological responses of Navelina orange budded on eight different citrus rootstocks were investigated to iron stress under high pH conditions. The experiment was evaluated in a climate-controlled plant growth chamber under 26oC-20oC day-night temperature, 16 hours of photoperiodism and 60% humidity. Navelina oranges grafted on Tuzcu 31-31 sour orange, Gou Tou sour orange, Volkameriana, Antalya Cleopatra mandarin, Carrizo citrange, Troyer citrange, C-35 citrange and Poncirus trifoliate were grown for two months and irrigated with a modified nutrient solution. At the end of this period, 10 µM FeEDTA+3 mM NaHCO3 and 2g/l CaCO3 (pH=7.8) were added to the nutrient solution to mimic an iron chlorosis environment and control plants were irrigated with a nutrient solution containing 100 µM FeEDTA (pH=6) for five months. At the end of the experiment, plant height, leaf number, plant fresh weight, iron chlorosis color scale and leaf total and active Fe concentrations parameters were determined. Chlorophyll concentration was estimated using a portable SPAD-502 meter and chlorophyll fluorescence was measured with a portable fluorometer. Also leaf gas exchange parameters (photosynthetic rate, stomal conductivity, leaf transpiration rate, leaf water use efficiency) were measured using a LCA-4 photosynthesis measurement instrument. With iron stress, plant height, leaf number, plant fresh weight, total and active Fe, leaf gas exchange parameters, chlorophyll fluorescence yield and SPAD values of Navelina seedlings were reduced relative to control plants and tolerance to iron deficiency differed among the rootstocks.As a result, Navelina seedlings budded on Tuzcu 31-31 and Gou Tou sour oranges were found very tolerant; the ones budded on Volkameriana and Antalya Celopatra were mid-tolerant; seedlings budded on Carrizo citrange less tolerant; seedlings budded on Troyer citrange as susceptible and Navelina budded on C-35 citrange and Poncirus trifoliate as very susceptible.