To explore the composition and structure of Arthrinium phaeospermum toxins which cause wilt of the tender leaves and twigs of a hybrid bamboo ( Bambusa pervariabilis x Dendrocalamopsis grandis) , the crude toxic proteins were extracted from the bacterium by liquid culture, ammonium sulfate precipitation and polyethylene glycol concentration. One composition (P3) with pathogenic activity was obtained by Sephadex G-100 gel chromatography and Q sepharose fast flow anion exchange resin. The sequencing result of P3 showed that the 7-ammonia-acids sequence at the N-terminal end was H2N-Ala-Gln-Ser-Vai-Pro-Tyr-Gly, which had high homology with the precursor of subtilisin protease from Bacillus subtilis by the homonhyly retrieval in NCBI. The molecular weight of P3 (27 kD) was very close to that of subtilisin protease. The pathogenicity experiment of P3 indicated that it could cause the same typical symptom as that of the pathogen, but the reaction was quicker than that of the pathogen itself. The effectively originative concentration was 5 - 10 μg · mL-1, and the higher the concentration, the stronger the pathogenicity.
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