Physiological and Nutritional Responses of Satsuma Mandarin on Gou Tou (Citrus aurantium L. var. Gou Tou) in Calcareous Soils

Due to the sensitivity of Sour orange (common rootstock in the region) to Tristiza disease and the sensitivity of Carizo citrange, Troyer citrange, C-35 and Swingle citromelo to high lime in the soil, investigating the response of the rootstocks that are tolerant or relatively tolerant to this disease and soil lime, seems to be very necessary for the stability of production in the east of Mazandaran. The Gou Tou (Citrus aurantium L. var. Gou Tou) has been reported as one of the rootstocks tolerant to soil lime and Tristiza disease. Therefore, the present study aimed to evaluate the growth trend and tolerance of this rootstock to the calcareous soils of east of Mazandaran. An experiment was conducted for two years in a randomized completely block design in seven soils with calcium carbonate content (2 to 45%). Measurements included vegetative growth trend, dry weight, chlorosis rate, fluorescence index (Fv/Fm), chlorophyll and nutrient concentration in leaves and roots. The results showed that the highest average dry weight of aerial parts was obtained from soils with clay texture and total lime content of 30%. There was a significant difference in the chlorosis rate of the leaves of seedlings on this rootstock in different soils, and this difference was mostly caused by manganese deficiency in the leaves The average Fe concentration in the roots was 19.43 times the average concentration in the leaves, indicating the accumulation and deposition of iron in the roots. In most soils, the amount of manganese available for citrus trees was excessive, but the mean concentration of leaf was less than adequate. The overall mean Mn concentration in the roots was about 6 times higher than its mean concentration in the leaves. From macroelements, magnesium and sulfur had the highest and lowest transfer efficiency and from micro elements, active Fe and total Fe had the highest and lowest transfer efficiency, respectively. According to the results of this research, the chlorosis rate of the seedlings in different soils did differ significantly, which shows this rootstock is relatively tolerant to soil lime. Therefore, Gou Tou can not be a good substitute for orange rootstock in calcareous soils (especially with very high lime).