PERTURBATION OF MAIZE RHIZOSPHERE MICROFLORA FOLLOWING SEED BACTERIZATION WITH BURKHOLDERIA-CEPACIA MCI-7

Introduction of a large quantity of exogenous microorganisms may disru pt a local ecosystem and affect the natural microflora. In this work w e investigated the effects of the introduction of a plant growth promo ting strain of Burkholderia cepacia into the rhizosphere of maize on b oth indigenous B. cepacia populations and microbial community structur e of total culturable bacteria using the concept of r/K strategy. More over we studied the distribution of bacterial populations in the root system at various soil depths. Seed bacterization was used as applicat ion method. Root colonization of the introduced strain occurred mainly on roots close to the plant stem, whereas indigenous B. cepacia was r ecovered at higher amounts from the lower parts of root systems of mat ure plants. As far as total culturable bacteria are concerned, an almo st uniform distribution in the root system of mature plants was observ ed. The release of the exogenous bacterial strain affected mainly the microbial populations of young growing plants rather than mature plant s. Indeed it caused only short-term perturbations in the microbial com munity of maize rhizosphere. Colonization of maize roots by indigenous B. cepacia was not significantly affected by the presence of the exog enous strain.