Journal of Plant Physiology 163 (2006) 1094—1100 Genotypic variation of N 2 -fixing common bean (Phaseolus vulgaris L.) in response to iron deficiency Abdelmajid Krouma a,à , Jean-Jacques Drevon b , Chedly Abdelly a a INRST, Laboratoire d’Adaptation des Plantes aux Stress Abiotiques, BP 95, 2050 Hammam-Lif, Tunisia b INRA, Laboratoire Symbiotes des Racines et Science du Sol, 1 Place Viala, 34060 Montpellier Cedex 1, France Received 13 January 2005; accepted 8 August 2005 KEYWORDS Common bean; Fe deficiency; Genotypic variability; Symbiotic nitrogen fixation Summary In calcareous soils, the yield of grain legumes is often limited by the lower availability of iron (Fe), especially when they depend upon symbiosis with root nodule bacteria for their N nutrition. In order to explore the variability of responses of N 2 -fixing common bean to Fe deficiency the common bean white-seeded lines Striker and Coco blanc, and coloured-seeded lines SVM-29-21 and ARA14 were inoculated with Rhizobium tropici (CIAT 899) and cultivated hydroaeroponically with a N-free nutrient solution supplied or not with 45 mM Fe. Differences among lines were observed: Fe-deficiency-induced-chlorosis on young leaves was earlier and more severe in some lines than others. Nodule development and N 2 -fixing capacity was less affected in line ARA14 which preferentially allocated Fe towards nodules. Results suggest that Fe use efficiency for symbiotic nitrogen fixation (FeUE SNF) could be used to screen tolerant bean lines to Fe deficiency in condition of symbiotic nitrogen fixation. & 2005 Elsevier GmbH. All rights reserved. Introduction The iron (Fe) concentration in the earth’s crust varies from 200 ppm to more than 10% (Loue´,1993). However, Fe is almost exclusively present in the soil in its oxidised form [Fe(III)]. The availability of Fe(III) for plant nutrition is quite limited because of its very low solubility, especially at alkaline pH and in the presence of oxygen. In calcareous soils which constitute more than 30% of the planet’s cultivated ARTICLE IN PRESS www.elsevier.de/jplph 0176-1617/$ - see front matter & 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.jplph.2005.08.013 Abbreviations: DAG, Days after germination; FeDC, Iron deficiency chlorosis; FeUE DW, Fe use efficiency for dry weight; FeUE SNF, Fe use efficiency for symbiotic nitrogen fixation; PUE SNF, P use efficiency for symbiotic nitrogen fixation à Corresponding author. Tel.: +21671 430855; fax: +216 71 430 934. E-mail address: krm-abdel@yahoo.fr (A. Krouma).