Analysis Of Phytotoxin Ingredients Produced By Streptomyces Galilaeus, A New Pathogenic Species Of Potato Common Scab

Potato scab is an economically important disease caused by plant-pathogenic Streptomyces spp. It has taken place in most potato planting areas in China now. The pathogens of potato common scab include a series of plant-pathogenic Streptomyces spp., which bring a lot of difficulties to study the pathogenesis of the disease. To solve the problem, the common pathogenic factor among the pathogens should be analyzed deeply. A new potato common scab typical strain CPS-2 was identified to be Streptomyces galilaeus species during classifying the scab-related strains in our previous researches. The phytotoxins produced by CPS-2 were systematically analyzed in this paper in order to determine the production condition, bioactivity, and the composition of the toxins.The pathogenicity of the fermentation broth had no significant changes by a series of treatments, such as centrifugation, filtration, organic solvent extraction disposal through analyses of production conditions and the active component of the toxin from the strain CPS-2. Toxins could be dissolved in ethyl acetate, methanol, water, and other solvents. The toxin and its bioactivity was relatively stable in vitro when changing temperature and light conditions in storage. Culturing medium and incubation time for the phytotoxins produced by strain CPS-2 were selected. The optimal medium for toxin production was oat bran culture, and the optimal incubation time was 9 days post inoculation. Phytotoxin purified by silica gel thin layer chromatography (TLC) included 6 ingredients,â… (Rf=0.26),â…¡( Rf=0.38),â…¢(Rf=0.47),â…£(Rf=0.59),â…¤(Rf=0.65) ,â…¥(Rf=0.69).The toxin activity was examined by radish seedlings test in this study. Results showed that both of the crude toxin and culture filtrate restrain the radish seedlings growth. The activated ingredients were purified and determined through bioactivity assay. Two toxin ingredientsâ…¡a ndâ…¢w ere obtained and had 89.0% and 67.3% growth inhibition, respectively. The bioactivities of the two toxin ingredients was correlated to the concentration dilution. The toxin ingredientâ…¡could make potato tuber tissue brown and necrosis. Toxins were purified by extracting with ethyl acetate, TLC, high performance liquid chromatography (HPLC) methods. The activities of purified toxins were stable. The molecular weight of toxin ingredientsâ…¡andâ…¢were 437.1810 and 313.1, respectively. Aboving results showed that a new plant pathogenic S. galilaeus strain CPS-2 produced phytotoxins, and at least two toxin ingredients played an important role in the infection process of the pathogen.