Effect of Citrus Rootstocks and Scions on Boron Uptake

In arid and semi arid regions with high boron content in irrigation water, boron toxicity is a considerable problem. Critical levels of boron in irrigation water variy between 1 and 10 mg/l for sensitive and resistant plants, respectively. In southern parts of Iran especially large citrus production region as Jahrom and Giroft cities, high boron content in irrigation water at toxic levels in most of the region has been the restricting factor for citrus yield increase and for citrus trees exposed to intensive deficiency of potassium and micronutrients like iron, zinc and magnesium. In this experiment, the separate effects of citrus rootstocks including Macrophylla (Citrus macrophylla Wester), Volkamer lemon (Citrus volkameriana), Sour orange (citrus aurantium), Sour lime (Citrus aurantifolia Swing) and their combination with ‘Valencia’ orange, ‘Washington navel’ orange, ‘Jahrom local’ orange, red pulp orange (‘Moro’) as scions on boron uptake were studied. The experiment was conducted as factorial arranged in randomized complete block design with 5 replications and 2 trees per plot in Jahrom Agricultural Research Station for 4 years. According to experimental results, the highest level of boron uptake belonged to ‘Volkamer’ lemon and the lowest to ‘Macrophylla’ rootstocks. Although, Sour orange rootstock had the medium level of boron uptake, but the leaf boron concentration of grafted cultivars on it was clearly very high. In comparison with other rootstocks, interaction between ‘Macrophylla’ rootstock and ‘Valencia’ orange, ‘Washington navel’ orange and red pulp orange (Moro), except ‘Jahrom’ local orange as scions, caused a significant decrease to leaf boron concentration.