Differences in response to iron deficiency among some lines of common bean

Five dry bean cultivars (Coco blanc, Striker, ARA14, SVM29-21, and BAT477) were evaluated for their resistance to iron deficiency on the basis of chlorosis symptoms, plant growth, capacity to acidify the external medium and the root-associated Fe3+-reduction activity. Plants were grown in nutrient solution supplied or not with iron, 45 muM Fe(III)EDTA. For all cultivars, plants subjected to iron starvation exhibited Fe-chlorosis. These symptoms were more severe and more precocious in BAT477 and Coco blanc than in the others cultivars. An important acidification of the culture medium was observed between the 4th and the 8th days of iron starvation in Striker, SVM29-21 and, particularly, ARA14 plants. However, all Fe-sufficient plants increased the nutrient solution pH. This capacity of acidification appeared more clearly when protons extrusion was measured in 10 mM KCl + 1 mM CaCl2. The above genotypic differences were maintained: ARA14 showed the higher acidification followed by Coco blanc and BAT477. Iron deficiency led also to an increase of the root-associated Fe(III)-reductase activity in all lines. However, genotypic differences were observed: Striker shows the highest capacity of iron reduction under Fe deficiency condition.