Possibility of Using Chlorosis Degree and Active Iron (Fe2+) to Assess the Tolerance of Some Citrus Rootstocks to Calcareous Soils

In this research, responses of some citrus rootstocks to active and equivalent calcium carbonate in the soils of eastern Mazandaran were evaluated by a factorial experiment in randomized complete block design. The results showed that Swingle citrumello and Sour orange, common rootstock of the region, had maximum and minimum dry weight. Also, average rootstocks chlorosis degree in these soils showed that Swingle citromello had the highest chlorosis degree and C-35, Carizo citrange, Gou tou, Troyer citrange, Smooth flat sevile, and Sour orange ranked after Citromello, respectively. According to the results, with increasing soil equivalent and active calcium carbonate, the average leaf active Fe of different rootstocks decreased. On average, the percentage of total iron in the form of active iron in the leaves was much higher than roots. In contrast, the average of total iron concentration in roots was several times more than that of leaves. Besides, by increasing calcium carbonate, the percent of leaf total iron in active form decreased, but unlike the leaves, the percentage of active iron in roots increased. Also, increase in soil active calcium carbonate did not have any effect on leaf active iron level of Sour orange and Smooth flat sevile. In contrast, leaf active Fe in Swingle citromello, Carrizo citrange, Troyer citrang, C-35, and Guo tou decreased. Therefore, according to leaf chlorosis degree index and trend of reducing leaf active Fe level per unit of active calcium carbonate, Sour orange, and Smooth flat sevile were the most tolerant, while Swingle citromello was the most sensitive rootstock to soil carbonate calcium, followed by Gou tou, Carizo citrange, Troyer citrange and C-35, respectively.