Field experiments were carried out to study the grain yield, shoot concentrations of zinc (Zn), boron (B) and phosphorus (P), and tolerance to Zn deficiency of 21 bread wheat (Triticum aestivum) and four durum wheat (Triticum durum) cultivars grown in a B-toxic and Zn-deficient calcareous soil in Central Anatolia with (+Zn = 23 kg Zn ha(-1)) and without Zn fertilization in 1993-1994 and 1994-1995 cropping seasons. Tolerance to Zn deficiency (Zn efficiency ratio) was measured by considering the ratio of grain yield under Zn deficiency to that with Zn fertilization. Zinc fertilization significantly increased grain yield of all cultivars in both years. On average, increases in grain yield of 25 wheat cultivars by Zn fertilization were 37% in the first and 40% in the second year. When results of the 2 cropping seasons were averaged, Zn efficiency ratios or the cultivars ranged from 40% to 84%, with an average of 62%. Despite large genotypic variation in Zn efficiency, shoot Zn concentrations under Zn-deficient conditions did not differ among Zn-efficient and Zn-inefficient cultivars. There were large differences in B concentration in shoots of cultivars under both Zn deficiency and Zn fertilization. However, on average for 25 wheat cultivars, Zn fertilization did not influence B concentration. In contrast to B, Zn fertilization consistently decreased shoot concentration of P in all cultivars. The results presented show that wheat cultivars growing in Zn-deficient and B-toxic soil conditions vary considerably in their grain yield, and these differences were not related to the shoot concentrations of Zn and B. Nevertheless, For many cultivars there was a close relationship between tolerance to Zn deficiency and tolerance to B toxicity. This relationship was discussed in terms of high Zn efficiency-enhanced tissue tolerance to B toxicity.