Plant growth-promoting bacterium Pseudomonas sp. strain GRP 3 influences iron acquisition in mung bean ( Vigna radiata L. Wilzeck)

Abstract

Siderophores produced by Pseudomonas sp. may be used by the bacteria (homologously) or in effecting plant nutrition (heterologously). The problem of iron non-availability particularly in calcareous soils may be overcome by incorporation of siderophore producing strains of fluorescent psuedomonads (FLPs). Siderophore producing bacterium Pseudomonas strain GRP 3 was used in a pot experiment to assess the role of microbial siderophores in the iron nutrition of mung bean ( Vigna radiataL. Wilzeck) using Fe–citrate, Fe–EDTA and Fe(OH) 3 in different concentrations with Hoagland's solution. After 45 days, the plants showed a reduction of chlorotic symptoms and enhanced chlorophyll level in GRP 3 bacterized plants. Bacterization with GRP 3 increased peroxidase activity and lowered catalase activity in roots. In 10 μM Fe–citrate alongwith GRP 3 treatment, chlorophyll a, chlorophyll b and total chlorophyll contents increased significantly by 34, 48 and 39%, respectively, compared to the control. Peroxidase activity in the same treatment was increased by 82% whereas catalase activity decreased by 33%. There was also a significant increase in total and physiologically available iron. A closely similar pattern was observed in chlorophyll content and peroxidase activity in Fe–EDTA and Fe(OH) 3 treated plants; catalase activity was an exception. The data suggests operation of heterologous siderophore uptake system in mung bean in presence of GRP 3. Such siderophore producing system has the potential of improving iron availability to plants and reduce fertilizer usage.