Abstract:

Pseudomonas fluorescensFD6 was isolated from the canola rhizosphere in Fujian. To define the inhibit ability of the strain FD6 to Monilinia fructicola，the causal agent of peach brown rot was detected using microscope concave slides method and on detached peach fruits. The pyrrolnitrin biosynthetic gene cluster was cloned using PCR amplification，and a prnA-deletion mutant was generated by homologous recombinant to identify its function. The results showed that strain FD6 could control completely brown rot on peach fruits. The bacterial culture of strain FD6 inhibited the spores of M. fructicola germination significantly by 93.18%，whereas the cultural filtrate of the strain FD6 only showed a lower inhibition to M. fructicola by 69.36%. The bacterium culture showed that high nematicidal activity  to Meloidogyne incognita. The obtained 5 868 bp prn contained four genes prnA，prnB，prnC and prnD analysis indicated that prn of strain FD6 identified with that of P. protegens CHA0 and Pf-5 by 94%. prnA was required for PRN synthesis in P. fluorescens FD6，and involved in the biosynthesis of 2,4-diacetylphloroglucinol and pyoluteorin as well. organized in a single transcript unit. The phylogenetic

Key words: Pseudomonas fluorescens, Monilinia fructicola, pyrrolnitrin, gene clone