Zinc efficiency of wheat cultivars in a calcareous soil with low zinc status

Due to calcareous soil conditions, zinc deficiency is a yield limiting factor for wheat production in Iran. One solution for this problem is the cultivation of Zn-efficient wheat varieties. Ten wheat cultivars (nine bread wheat and one durum wheat) with different tolerance to Zn deficiency were studied in a greenhouse experiment. Plants were treated with Zn (10 mg Zn Kg-1 soil as ZnSO4.7H2O) and without it. Based on the results of pot experiment, two wheat cultivars with different Zn efficiency were selected to assess the ability of phytosiderophore release from their roots. Visual Zn deficiency symptoms, such as light colored necrotic patches and reduction in plant height appeared more severe in Alvand, Mahdavi (bread wheat) and Yavares (durum wheat) cultivars. Under Zn deficiency, shoot dry matter decreased in most cultivars. Zn efficiency of wheat cultivars ranged from 80.4% to 106.2%. Based on shoot dry weight, Pishtaz and Darab were the most Zn-efficient and Alvand and Mahdavi were the most Zn-inefficient wheat cultivars. Zn supply markedly increased the Zn concentration and content of shoots of all cultivars. Cultivars differed in Zn uptake under Zn-deficient and Zn-sufficient conditions. On average, Zn-efficient cultivars had more Zn uptake efficiency compared to Zn-inefficient cultivars. Our results strongly suggested that sensitivity to Zn deficiency varied widely among wheat cultivars. Different susceptibility of cultivars did not correspond well with the Zn concentration of the shoot. In contrast, the total amount of Zn of shoot was better related to the sensitivity of wheat cultivars to Zn deficiency. Under Zn deficiency, different ability of genotypes to release phytosiderophore from roots was observed. Pishtaz exuded more phytosiderophore than Alvand. Higher Zn uptake in Zn-efficient wheat genotypes may be attributed to higher release rates of Zn-mobilizing phytosiderophores from roots.