| Melon is a kind of popular and highly nutritional fruit. The severe problem for the melon production is post-harvest diseases caused by pathogenic fungi. For the lacking of powerful and harmLess control ways, the biological control emerges as a promising way to solve this problem.In our study, Pseudomonas strain X4 and 2-17 were isolated from the surface of healthy melon. Bioassay results showed that the strains X4 and 2-17 could strongly protect the melon fruits from infection by: Trichothecium roseum, Fusarium spp. and Alternaria alternate, and the inhibition rate is 90.6 %, 84.4%, 67.4 % and 87.5%,78.6%,70.8%, separately. The strains X4 and 2-17 were identified as Pseudomonas fluorescens biovarâ…¢and Pseudomonas putida biovar A according to its 16S rDNA sequence, morphological characterization, culturing pattern, and physiological and biochemical reactions.2,4-diacetylphloroglucinol(2,4-DAPG) produced by Fluorescent pseudomoas has the antibiosis activity on a broad spectrum of organisms. To contol post-harvest disease of melon, the engineering strain X4-G was generated by inserting the gene of 2,4-DAPG into the genome of X4 via Tn5. The biocontol tests were performed and the results showed the engineered strain X4-G is genetically stable and can control post-harvest diseases of melon efficiently.In addition, the fermentation broth of strain, X4-G, and the fungicide Armistar was adsorbed on CaCO3 micropowder to generate the cocktail formulation to test the control effects of fungicide on the amount of bio-control strains during the storage period . Our research will provide some guides on the combination usage of bio-control and fungicides in the control of post-harvest diseases.
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