Introduction of the Serratia marcescens chiA gene into an endophytic Pseudomonas fluorescens for the biocontrol of phytopathogenic fungi.

An endophytic strain of Pseudomonas fluorescens was isolated from micropropagated apple plantlets and introduced into beans (Phaseolus vulgaris) via their root tips. It was shown to be present as an endophyte in the roots at a level of 1.2 x 10(5) CFU/g fresh weight. The gene coding for the major chitinase of Serratia marcescens, chiA, was cloned under the control of the tac promoter into the broad-host-range plasmid pKT240 and the integration vector pJFF350. Pseudomonas fluorescens carrying tacchiA either on the plasmid or integrated into the chromosome is an effective biocontrol agent of the phytopathogenic fungus Rhizoctonia solani on bean seedlings under plant growth chamber conditions.