Zinc tolerance and hyperaccumulation in F1 and F2 offspring from intra and interecotype crosses of Thlaspi caerulescens

The relationship between zinc (Zn) tolerance and hyperaccumulation in Thlaspi caerulescens was investigated from F1 and F2 crosses within and among metallicolous and nonmetallicolous Mediterranean populations. F1 offspring were grown on increasingly Zn-enriched soils to test Zn enrichment effects, and many families of F2 offspring were grown on a Zn-rich soil. Tolerance of F1 offspring depended on stress intensity. Tolerance of interecotype crosses was intermediate between that of the intraecotype crosses. No difference in Zn accumulation appeared among the F1 offspring from the three crosses involving metallicolous parents. Otherwise, none of these offspring exceeded the Zn hyperaccumulation threshold (10,000 mg kg(-1)), unlike the nonmetallicolous ones. The latter also showed the highest mortality. In some F2 families from interecotype crosses, hyperaccumulation values exceeded 15,000 mg kg(-1) in nontolerant offspring, whereas tolerant offspring displayed lower values (c. 10,000 mg kg(-1)). There was no difference between tolerant and nontolerant offspring when they showed low hyperaccumulation. Therefore, the relationship between tolerance and hyperaccumulation in F1 and F2 crosses depended on the hyperaccumulation level of plants.