Extraction And Assay On The AT-toxin Excreted By Tobacco Brown Spot Pathogen Alternaria Alternata

AT-toxin produced by Alternaria alteniata was a kind of HST and a pathogenic factor of Tobacco Brown Spot disease .In this paper we did some studies about the pathogenicity of two strains(Al and A10) of A.alternata, the relations between toxic metabolite and it's pathogenicity, the culture conditions and extraction of AT-toxin, and the biological assay of toxin. The results showed that in spores germinating solution and liquid culture filter of Aland A10, there were toxic metabolite. This metabolite was pathogenic and specific on hosts, so it was a crucial pathogenic factor of the pathogen. The lighting had no effects on the ability in producing toxin by Aland A10. In four extracting methods of crude toxin, that the extract from method 1 and method 4 had higher biological activity indicated that the efficiency of method 1 and method 4 was higher than method 2 and method 3 .On toxicity assay, the effects of Direct Injection Assay could be directly perceived through the senses; the Seed Root growth Inhibition Assay was not easy to be disturbed and had good repeatability; Electrolyte Linkage Assay was interfered by salt content easily and only fit for assaying the high purity toxin solution; MTT-Colorimetric Assay wns not interfered by salt contents in liquidculture filter, it was a accurate and reliable way to assay thetoxicity of toxin.