Abstract:

【Objective】 Phytotoxins produced by the Streptomyces galilaeus strain CPS-2, a new pathogenic species and caused potato scab in China, was studied in order to determine the production condition, activity, and the composition of the phytotoxin. 【Method】 Appropriate medium and incubation time for the phytotoxins production of strain CPS-2 were screened. Toxins were purified by using ethyl acetate extract, silica gel thin layer chromatography (TLC), high performance liquid chromatography (HPLC) methods. The molecular weights of toxin ingredients were determined by mass spectrometry. The toxin activities were examined through radish seedlings test, potato tuber slices test and immature tubers test after each toxin ingredient purification process. 【Result】 Oat bran culture medium was selected to be the best medium for toxin production, and the optimal incubation time was 9 d. Two toxin ingredientsⅡand Ⅲ were obtained and showed inhibitory effects on radish seedlings growth. The bioactivity of the two toxin ingredients was correlated to the toxin concentration. The toxin ingredientⅡ could make potato tuber tissue brown and necrosis. The molecular weight of toxin ingredients Ⅱ and Ⅲ were 437.1810 and 313.1, respectively. 【Conclusion】 The results showed that the strain CPS-2 of the new plant pathogenic Streptomyces galilaeus could produce phytotoxins. At least two toxin ingredients played an important role in the infection process of the pathogen.

Key words: potato common scab, Streptomyces, phytotoxin, toxin ingredient