Symbiotic response of common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) to iron deficiency

In order to assess symbiotic activity (the nodules integrity and the iron use efficiency) in common bean (Phaseolus vulgaris L.) under low iron availability, the growth of plants and nodules, the concentration of leghaemoglobin and malondialdehyde, and activity of nitrogenase, catalase, peroxidase and superoxide dismutase were analysed in two (contrasting) common bean varieties subjected to iron deficiency. Results show that nitrogen fixation and leghaemoglobin accumulation decreased at limiting iron availability while malondialdehyde concentration increased under these conditions. The tolerant variety to iron deficiency, ARA14, was clearly less affected than the sensitive one, Coco blanc. A significant stimulation of peroxidase (POD) activity was observed in ARA14 under iron deficiency. At the same conditions, SOD and CAT activities in ARA14 plants were maintained at high level. It was also found that the iron use efficiency for leghaemoglobin accumulation, SOD, CAT and POD activities were critical for the protection of symbiotic system against oxidative burst and for the maintaining of an optimal functioning of N₂ fixing system.