The remedy of lime‐induced chlorosis in peanuts by pseudomonas sp. siderophores

Abstract

Strains of siderophore producing Pseudomonas sp. were isolated from the rhizospheres of cotton (Gossypium herbaceum L.) and peanuts (Arachis hypogaea) (strains 1 and 11, respectively). The siderophores were produced in iron deficient culture medium. FeCl₃ was added to the culture media at the end of the growth period in order to produce an iron pigment complex. These solutions were applied to the soil directly or after removal of bacteria and free salts by centrifugation and dialysis. Peanuts grown in 0.5 kg pots on a highly calcareous soil (63% CaCO₃) and exhibiting severe iron chlorosis were used as test plants to the iron‐siderophore or iron‐siderophore‐bacteria activity as soil amendment for iron deficiency. The plants were treated with (1) FeEDDHA&Mdash;10 mg 500 g^‐1 soil; (2) iron pigment complex of the two isolates; and (3) bacterial suspension containing the iron pigment complex. Plants grown on untreated soil were used as a control.

Significant increase of chlorophyll concentration of the treated plants was observed after seven weeks of growth in a growth chamber. Strain 1 was more efficient than strain 11 although both strains produced a similar amount of pigment. In both strains, the bacterial suspension was more effective than the separated iron‐pigment complex. DTPA‐extractable iron was twofold higher in soils treated with the various pigment treatments in comparison to the control and the FeEDDHA treatments. The pots were replanted with peanuts but were not treated with any additional iron amendment. After six weeks of growth, the chlorophyll content of plants grown on the previously pigment‐treated soils was significantly higher than the FeEDDHA treated and control plants. The siderophores producing bacteria may have a potential role in controlling lime‐induced iron deficiency in plants.

Key words:

• Siderophores
• Iron
• Chlorosis
• Peanuts
• Pseudomonas
• Pseudobactin
• Arachis hypogaea