Co-segregation analysis of cadmium and zinc accumulation in Thlaspi caerulescens interecotypic crosses

Cadmium (Cd) hyperaccumulation in Thlaspi caerulescens varies among ecotypes. Here we investigated segregation of Cd and zinc (Zn) accumulation in F-2 crosses between high (Ganges) and low (Prayon) Cd-accumulating ecotypes. Accumulation was measured in plants grown in compost treated with 5 and 100 mg kg(-1) Cd and Zn, respectively, and in hydroponics with 50 muM Zn and 10 or 50 muM Cd. Another hydroponic experiment examined the relationship between Cd tolerance and accumulation. Parental phenotype distributions for shoot metal concentrations were distinct for Cd, but not consistent for Zn. Shoot Cd and Zn in F(2)s varied continuously, with significant transgression for Zn in all treatments. Shoot Cd correlated strongly with shoot manganese (Mn), and to a lesser degree with shoot Zn. Shoot Cd concentrations in the Cd nontolerant F(2)s were lower than, or similar to, those in the Cd-tolerant F(2)s. We conclude that Cd and Zn accumulation is governed by multiple genes, and that Cd tolerance and accumulation are independent traits in T. caerulescens. Two uptake systems with distinctive affinities for Cd, Zn and Mn are proposed. (C) New Phytologist (2004).