Study On The Toxin Production By Black Rot Of Sainfoin

The aim of experimentation was to study the biology characteristic of the Alternaria tenuis Nees., the condition of phytotoxin-producity and the composing component of the toxin, to synthesize chemical substances which had antagonism for the toxin, and by means of the method of using poisons as antidotes to control the disease.In the experiment, the pathogen was isolated from pathogenic and typical spots of sainfoin leaves in the field. The morphologic and pathogenic identification of the pathogen showed that the disease colony was equal diameter growth, the early colorless, gradually became greenish brown and dark brown, regular edge; the mycelia were slender, had branch and speta, the early colorless, gradually became light brown; conidiophores were straight or little curved, brown. The conidia usually growed in theshape of single or short chain, clavate or ovate, 3～7 transverse, 0～4 longitudinal septa, and 0~2 inclined septa. Their beaks were columnar, hazel and septation. In view of the morphology and comparison with other concerned Alternaria species, the pathogens were identified as Alternaria tenuis Nees.The test of biology showed that the growth speed of the pathogen was the fastest on PSK liquid culture medium in six kinds of culture media(PD liquid culture Medium, PD and the juice of sainfoin leaves liquid culture Medium, PS liquid cultrue Medium, Improved Fries liquid culture Medium, Czapek liquid culture Medium and PSK liquid culture medium).The suitable time for mycelium growth was in the range of 11~13d, and mycelial dry weight reached maximum on 13th day. The appropriate temperature for mycelium growth was in the range of 20～30℃, the optimal temperature for mycelium growth was 25℃. It was not suitable for mycelium growth under 15℃or over 35℃. The mycelium growth speed was the fastest under the alternate condition of light and dark,shaking. The mycelium could grow between pH 5 and pH 12. And the mycelial dry weight was the largest on pH 8. The condition of phytotoxin-producity capability was studied in the experiment. The results showed that PSK liquid medium was the best for producing phytotoxin in six kinds of phytotoxin-producity culture media which were tested in the experimentation. The optimal conditions for producing phytotoxin were cultured period 13d, cultured temperature 15℃, PH 6, continual 24h dark and shaking. Sainfoin seed germination was selected to test the toxicity of crude toxin. The result showed that the crude toxin which was cultured had definite toxicity.Alternaria tenuis was cultured on PSK liquid medium under suitable conditions, and culturefiltrates was extracted by ethyl acetate, and concentration, purification. Found by bioassay, the phytotoxin had toxicity. Using gas chromatograph-mass spectrometer determinated toxin components. The results showed that the main substains of Alternaria tenuis of onobrychis viciaefolia was Acetic acid 2,5-dioxo-1-pyrrolidinyl ester, the relative content was 67.02%.