Phenotyping 60 populations of the hyperaccumulator Noccaea caerulescens

Francés. Noccaea caerulescensis a model plant to understand the genetic determinisms of metal hyperaccumulation as well as a potential source of cultivars for Cd phytoextraction. Sixty populations from non-metallicolous (NM), calamine (CAL) and serpentine (SER) ecotypes were phenotyped in order evaluate more extensively the genetically determined traits of the species and their variations, detect the more appropriate parental genotypes for the creation of phytoextraction cultivars, establish more representative relations between planttraits in order to give reliable information for plant breeding and for the understanding of metal homeostasis.The studied populations came from the Western distribution zone of N. caerulescens, i.e. Belgium, Finland, France, Germany, Luxembourg, Italy, Norway, Slovakia, Spain, Sweden and Switzerland. There were also two populations from Slovakia, corresponding to the Eastern part of the distribution zone of the species. Fifteen plants per population were grown until fruit maturity in a greenhouse on a homogeneous soil spiked with Cd, Ni and Zn. Development, growth and ionome variables were measured.NM and SER ecotypes appear close to each other and different from the CAL ecotype. The latter produces more inflorescences and shoot biomass, flowers sooner and reaches maturity later. Three CAL subgroups geographically structured could be distinguished according to their shoot Cd/Zn ratio, fitting to the genetic units distinguished in another. At the species level, the Ni and Zn contents were strongly correlated. Nickel accumulation was also closely associated to that of Mg and secondarily to that of Ca. The NM and SER accumulate similar amounts of Ni and Zn. Biomass production was not correlated to metal contents, suggesting no trade-off between these traits. These results confirm the genetic potential of N. caerulescensfor phytoextraction and suggest new hypothesis about the mechanisms of metal accumulation