Plant and Soil 249: 9–18, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 9 Genetic basis of Cd tolerance and hyperaccumulation in Arabidopsis halleri V. Bert 1 , P. Meerts 2 , P. Saumitou-Laprade 3 , P. Salis 1 , W. Gruber 2 & N. Verbruggen 1,4 1 Laboratoire de Physiologie et de G´ en´ etique Mol´ eculaire des Plantes, Universit´ e Libre de Bruxelles, Campus Plaine, CP 242, Boulevard du Triomphe, B-1050 Bruxelles, Belgium. 2 Laboratoire de G´ en´ etique et d’Ecologie V´ eg´ etales, Universit´ e Libre de Bruxelles, Chauss´ ee de Wavre 1850, B-1160 Bruxelles, Belgium. 3 Laboratoire de G´ en´ etique et Evolution des Populations V´ eg´ etales, Universit´ e de Lille I, UPRESA-CNRS 8016, FR-CNRS 1818, bâtiment SN2, F-59655 Villeneuve d’Ascq cedex, France. 4 Corresponding author ∗ Received 3 October 2001. Accepted in revised form 5 March 2002 Key words: Arabidopsis halleri, Arabidopsis lyrata ssp. petraea, cadmium, hyperaccumulation, metal tolerance, zinc Abstract The genetic basis of Cd tolerance and hyperaccumulation was investigated in Arabidopsis halleri. The study was conducted in hydroponic culture with a backcross progeny, derived from a cross between A. halleri and a non- tolerant and non-accumulating related species Arabidopsis lyrata ssp. petraea, as well as with the parents of the backcross. The backcross progeny segregates for both cadmium (Cd) tolerance and accumulation. The results support that (i) Cd tolerance may be governed by more than one major gene, (ii) Cd tolerance and Cd accumulation are independent characters, (iii) Cd and Zn tolerances co-segregate suggesting that they are under pleiotropic genetic control, at least to a certain degree, (iv) the same result was obtained for Cd and Zn accumulation. Introduction Cadmium (Cd) is a widespread heavy metal, released into the environment by heating systems, metallurgic industries, waste incinerators, urban traffic, cement factories and as a contaminant of phosphate fertilizers (Sanita di Toppi and Gabbrielli, 1999). Cd is one of the four metals that have been mentioned to be a world-wide concern in terms of their importance in environmental quality and health (Sanita di Toppi and Gabbrielli, 1999). Its presence in the atmosphere, soil and water, can cause serious problems to all organ- isms, and heavy metal bioaccumulation in the food chain can be highly dangerous (Sanita di Toppi and Gabbrielli, 1999). For a few years, remediation of metal-contaminated soils became a world preoccupation. Hyperaccumu- lator plants could represent a resource for phytore- mediation of metal polluted soils, as they are able to ∗ FAX No: +32/2 650 54 21. E-mail: nverbru@ulb.ac.be extract metals from the soils and to concentrate them in their upper parts (Brooks, 1998). However, very little knowledge is available about this technology. Most of the hyperaccumulators are restricted to metal- enriched soils and also have the character of metal tolerance (Brooks, 1998). However, some hyperac- cumulators, notably Arabidopsis halleri and Thlaspi caerulescens, have populations on normal soils, which are metal tolerant, too (e.g. Bert et al., 2000; Meerts and Van Isacker, 1997). For these species, several au- thors have shown that accumulation and tolerance are uncorrelated or inversely correlated characters (Bert et al., 2000; Escarré et al., 2000; Meerts and Van Isacker, 1997). Moreover, it is well established that a large variation exists within species for metal tolerance and accumulation in hyperaccumulators (Assunção et al., 2001). For a number of metals, including zinc, copper and arsenic, genetic analysis has shown that tolerance is controlled by a small number (one or two) of major genes, with additional modifiers determining the level of tolerance displayed (Schat et al., 1993; Smith and