BIOLOGICAL ACTIVITYOF PSEUDOMONADSANDTHEIR BIODIVERSITYINTHE RHIZOSPHERE REGION OFSOME ECONOMIC PLANTS

Abstract

The enrichment of plant rhizosphere with beneficial bacteria is a strategy that favors the production of more vigorous seedlings, which is essential for the success of vegetable cultivation. The aim of this studywas to select the most active and beneficial strains of fluorescent pseudomonads which have a broad spectrum of ecofriendlyplant-promoting abilities and antagonistic potential against phytopathogenic fungi, thus can be used as safe alternative for the over use of harmful agrochemicals.Soil and rhizosphere samples were collected from the rhizosphere of economic plants, e.g.Artemisia vulgaris, Gazania splendens, Hypericum perforatum,Solidago Canadensis,Stevia rebaudiana,Gossypium arboretum,Zea mays,lycopersicum esculentum, Cucumis sativus, Phaseolus vulgaris, Sesamum indicum, Olea europaeagrown in SEKEM farm, Bilbis, Elsharkyia governorate, Egypt. Sampling resulted in 71 fluorescent pseudomonads, out of which four pseudomonads isolates were selected according to their efficiency to produce IAA, Cyanide, antagonistic effect and high ability to solubilize potassium and phosphorus.These isolates were identified using 16S rRNA gene sequencing technique. The results showed that the isolates were different strains of Pseudomonas otitidis. Growth kinetics and growth curve were determind using King's and nutrient glucose broth media. Application of these isolates as inoculants on tomato plants in greenhouse was performed. The results showed that inoculation of tomato seedling withPseudomonas strains led to suppress soil-borne pathogen and supported tomato plant growth. Key words: Rhizosphere microflora, Fluorescent pseudomonads, PGPR, Biocontrol, Soil-borne pathogens, Tomato.