Submitted to: Ecology Symposium
Publication Type: Proceedings
Publication Acceptance Date: 9/23/2004
Publication Date: 3/18/2005
Citation: Synkowski, E.C.C., Perner, H., McIntosh, M.S., Chaney, R.L., Angle, J.S., Baker, A.J.M., Reeves, R.D. 2005. Breeding considerations for improving cadmium hyperaccumulation in two French Thlaspi caerulescens J. and C. Presl populations. Proceedings of Fourth International Serpentine Ecology Symposium. p. 295-303. Interpretive Summary: Phytoextraction of soil Cd is a new technology which uses plant species which hyperaccumulate exceptional concentrations of soil Cd into their shoots using simple agricultural fertilizer and production practices. We found strains of Thlaspi caerulescens from southern France which accumulated 10-20 times higher shoot Cd than any other known plant species and which we are attempting to develop into a commercial Cd phytoextraction system. In the present manuscript, we evaluated the genetic variation within families of Thlaspi caerulescens from several locations in order to learn more about their reproduction methods. This understanding is needed in order to plan breeding strategies to generate improved cultivars which have improved biomass and metal accumulation abilities needed for commercial application. The DNA testing conducted showed that in contrast with some early papers about reproduction in Thlaspi caerulescens, in these highly metal tolerant and accumulation genotypes, nearly all were heterozygous, indicating they did not self-fertilize. Thus the inherent structure of the populations are less uniform and will require more effort in breeding. Still, the genetic diversity available for breeding improved genotypes appears adequate to support commercialization. Further, no other plant species suggest for Cd phytoextraction (rice, willow, poplar, Brassica juncea, etc.) yet identified has higher potential for commercial success.
Technical Abstract: 1. The capacity of Thlaspi caerulescens to phytoremediate Cd polluted soils could be improved by breeding selected ecotypes to increase total uptake of Cd. 2. To develop an effective breeding program, it is important to understand the mode of reproduction and the population's genetic structure. Recent research has reported that T. caerulescens populations have highly variable outcrossing rates, while other work suggests T. caerulescens is predominantly self-pollinated. Populations from contaminated sites in southern France, St. Félix de Pallières (S) and Viviez (V), grown in homogeneous soil had extraordinarily high leaf Cd concentrations (up to 1353 ppm) and exhibited significant phenotypic variation for Cd accumulation at the family and population levels. 3. PCR RAPD analyses were used to determine the genetic structure of these two populations, as well as determine the relationship between phenotypic and genotypic variability.