Siderophores: Their Biochemistry and Possible Role in the Biocontrol of Plant Pathogens

Specific strains of the Pseudomonas fluorescens-Pseudomonas putida group rapidly colonize plant roots of several crops and cause statistically significant yield increases (38). Enhanced plant growth caused by these strains is often accompanied by reductions in root-zone populations of fungi and bacteria. These beneficial strains are also effective biocontrol agents of certain soil­ borne fungal pathogens (38). This article reviews and describes recent work implicating siderophores [microbial iron(III)-transport agents] produced by beneficial fluorescent pseudomonads as partly responsible for enhanced plant growth and biocontrol. Beneficial fluorescent pseudomonads and other micro­ organisms can promote plant growth and induce disease suppressiveness by mechanisms other than siderophore production, namely through competition for carbon (12) or through production of hormones, antibiotics, or bacterio­ cins (14, 18, 19, 24, 47).