Pseudomonas fluorescens P5 was isolated in Yunnan Province and proved to be an effective biocontrol agent of various soil-borne plant diseases. The aim of the study was to enhance the biocontrol effect of this strain by introducing a chitinase gene. A 6.5 kb DNA fragment containing the chitinase gene chiB was inserted into pDSK519 vector to construct a new plasmid, pDSK51965. This plasmid was introduced into P. fluorescens P5 and resulted in a new strain named P5-1. Restriction enzyme digestion and chitin plate culture confirmed that P5-1 contained a functional chitinase gene. Compared with wild-type P5 in pot experiments, P5-1 had an increased effect against rice sheath blight and cotton damping-off caused by Rhizoctonia solani. It also increased the effect on suppression of wheat take-all caused by Gaeumannomyces graminis var. tritici.
