Biocontrol Of Watermelon Wilt Disease By Actinomycetes CT205and Primary Study Of Its Antagonistic Compounds

Watermelon fusarium wilt, one of the fungal soil-borned diseases of watermelon, caused by Fusarium oxysporum, is a very serious fungal disease. Since the conventional control methods have some drawbacks, biological control method is becoming a high effective way. In this paper the biocontrol effects of actinomycetes CT205against watermelon fusarium wilt and characteristics of its antagonistic compounds were studied. The main results are as following:(1) Strain GYO1, a fungal strain caused watermelon fusaarium wilt, was obtained by F. oxysporum selective medium from fusarium disease watermelon plant. Baesd on the morphological characteristics and infecting experiment to healthy watermelon, strain GYO1was identified as F.oxysporum. Actinomyces strain CT205showed stable antagonistic activity against to F. oxysporum GYO1. Pot experiment results for three times showed that application of strain CT205could control watermelon wilt disease incidenc on a certain degree. Treatment with disinfection methods first, then application of strain CT205with organic fertilizer would improve the biocontrol efficacy to watermelon wilt disease.(2) By microscopic observation, the strain CT205showed more branches on aerial mycelium and loose spiral sporothrix on the top mycelium. Strain CT205showed strong resistance to ampicillin and amoxicillin.100ug/mL ampicillin and50p,g/mL amoxicillin in Gause medium have no effect on the growth of strain CT205.(3) Crude extract from the fermentation broth of strain CT205had a significant inhibitory effect on F. oxysporum and Saccharomyces cerevisiae. The crude extract from strain CT205showed stability to high temperature because it did not lose its antagonistic activity after treated at100℃for15min. The crude was stable after treatmented at pH4,6.5,10. It was also very stable to UV in30min.(4) The crude product from fermentation broth showed UV absorption peak at220nm. After separated with layer chromatography, the active substance was measured by mass spectrometry, its molecular weight was speculated to be337.