Genotypic differences in Zn efficiency of Medicago species

Nineteen annual Medicago genotypes from eight species were grown in Mt. Com pass sand at three levels of soil Zn application (0, 0.1 and 0.9 mg Zn kg(- 1)) to achieve Zn status from deficiency to adequacy. Genotypes differed in growth response: under Zn deficiency, those classified as Zn-efficient had less reduction in shoot growth, a higher root mass, greater concentration of Zn in the shoot and total Zn content per plant, and a stable shoot/root ratio compared with Zn-inefficient genotypes. While seed Zn content did not influence the Zn-efficiency ranking, it did affect yield, and so it plays an important role in yield response and Zn accumulation as Zn supply decrea ses.