Traits of fluorescent Pseudomonas spp. involved in suppression of plant root pathogens

Certain members of the fluorescent pseudomonad group have been shown to be potential agents for the biocontrol of plant root diseases. The major problems with the commercialization of these beneficial strains are that few wild-type strains contain all the desired characteristics for this process and the performance of strains in different soil and climatic conditions is not reproducible. Consequently, prior to selection and/or improvement of suitable strains for biocontrol purposes, it is necessary to understand the important traits required for this purpose. The production of fluorescent siderophores (iron-binding compounds) and antibiotic compounds has been recognized as important for the inhibition of plant root pathogens. Efficient root colonization is also a prerequisite for successful biocontrol strains. This review discusses some of the characteristics of fluorescent pseudomonads that have been suggested to be important for biocontrol. The genetic organization and regulation of these processes is also examined. This information is necessary for attempts aimed at the improvement of strains based on deregulating pathways or introducing traits from one strain to another. The release of genetically engineered organisms into the environment is governed by regulations, and this aspect is summarized. The commercialization of fluorescent pseudomonads for the biological control of plant root diseases remains an exciting possibility. The understanding of the relevant characteristics will facilitate this process by enabling the direct selection and/or construction of strains which will perform under a variety of environmental conditions.