The Purification And Bioassay Activity Of Toxin Producted By Fusarium Heterosporum

Fusarium heterosporum and its toxin was a potential biological control agent against Alternanthera philoxeroides. The purification, bioassay activity, stability of toxin was investigated in this paper.1. The biological activity of the toxin was assayed with leaf disc method, needle point method and jackknife wound method. The results indicated that the correction disease index (CDI) of A. philoxeroides was65.29-77.75by leaf disc method,44.97-65.12by needle point method,61.07-74.81by jackknife wound method respectively at72h after treatment with the toxin concentration of2.0-5.Og/L from the wheat-grain culture. Similarly, the CDI was76.58-85.81by leaf disc method,70.68-81.96by jackknife wound method repectively at72h after treatment from liquid culture. The results showed that leaf disc method and jackknife wound method were suitable for the determination of the biological activity of the toxin.And for the fraction of the toxin, jackknife wound method was better.2. The crude toxin of F. heterosporum was obtained from fungi-free filtrate by the method of organic solvent extraction and active carbon adsorption, and its activities were detected by leaf disc method. The results indicated that the biological activity of crude toxin harvested by both method of n-butanol extraction and active carbon absorption was the highest. The CDI of leaf disc exposed in crude toxin reached to76.69and74.11, respectively. The relative activity index was85.55%and82.66%compared with fungi-free filtrate, respectively. The lowest relative activity index of crude toxin was the method of petroleum extraction. The results showed that the biological activity fraction of toxin was polar compound(s).3. The crude toxin was purified by silica gel column chromatography, and its activity was bioassayed by jackknife wound methods. The results showed that the CDI of leaf exposed in the fraction1-2-2concentration of2.0g/L was85.55. The functional groups of fraction1-2-2were analysised and identified. The results indicated that the fraction was not phenols, esters, alkaloids, carbohydrates and amino-compounds. The UV-vis spectrum showed the maximum absorption peak was at220nm; The two main compounds were detected through high performance liquid chromatography(HPLC). They were with a retention time of2.740and4.800min, respectively.4. The concentration variation of glucose and protein were measured by spectrophotometry, and the production dynamics of crude toxin was determined by leaf disc method. The results showed that the lower utilization ratio of glucose, high consumption of protein and low biological activity of fungi-free after incubation15days. The utilization ratio of glucose presented a tendency of straight climb, the concentration of protein were significantly increased in broth And the biological activity of fungi-free were significantly enhanced after incubation20-30days5. The stability of crude toxin produced by F. heterosporum was assayed with bioassay methods. The results showed that the disease index of leaf disc treated by crude toxin was no significant difference in between0℃and120℃. The correction disease index of leaf disc exposed in crude toxin stored360d was77.45, it was no significant difference compared with stored5d (78.21). For Id and30d of continuous illumination at25℃, the correction disease index of leaf disc was78.08and76.17respectively, and it was no significant difference. The bioactivity of crude toxin was not significant difference range from the solution pH3.0to pH11.0. The results indicated that the active component of the crude toxin was stable.