Studies On Fermentation And Application Of Antagonistic Streptomyces SZF2 And SZF7 Against Tobacco Brown Spot Disease

Optimum fermention conditions for SZF2 and SZF7 (Streptomyces spp.) werestudied. According to the results,the best fermention conditions as fellows:SZF2optimum temperature is 30±1℃, SZF7 is 28±1℃. SZF2 pH value is 6.0,SZF7 is 7.0.Both of two antagonistic Streptomyces are in the 5-liquid medium shaked 96 hours,respectively. Meanwhile, the optimum foster way was shaked all day.Preliminary determined the potency of the fermentation extract of SZF2 and SZF7against the pathogen was 600 times. The fermentation extract of SZF2 and SZF7exhibited an inhibitory ability to 5 species of phytopathogenic fungi, this showed that thefermentation extract had a broad antibiotic spectrum. By the experiment of stability of anantifungal substances showed that continuous culturing up to 10 generations, SZF2 andSZF7 had a negative influences on inhibitory activity of their antifungal substancesagainst the pathogen.Mechanism of control Alternaria alternata (Fries) Keissler with the fermentationextract of SZF2 and SZF7, microscopic observation showed that they could interfere thenormal development of hyphae and conidiospores. The increased activities of POD, PPOin tobacco upon the treatment by fermentation extract of SZF2 and SZF7 were detected.This suggested the fermentation extract could trigger the defense reactions of tobaccoplants. The germination of tobacco seeds was promoted by the fermentation extract andits diluent in the indoor environment test.Result from inoculating detached leaves and greenhouse trial showed that thefermentation extract could control the disease (Alternaria alternata (Fries) Keissler).More wide application in field will be further studied.