小麦长蠕孢菌毒素

STUDY ON THE TOXINS OF HELMIN THOSPORIUM SATIVUM

小麦长蠕孢菌(Helminthosporium sativum)在21—25℃的Fries溶液中振荡培养时产生的毒素,易引起与病原菌感染小麦类似的特征性病状。培养滤液的浓缩物,经丙酮沉淀,正丁醇-氯仿萃取,二次硅胶柱层析等程序,将毒素部分纯化,毒素的硅胶TLC层析表明,毒素层离组分至少为6种,在紫外灯下和碘蒸气中观察,显蓝紫色光斑和棕黄色斑,它们的Rf值依次为0.12,0.16,0.25,0.36,0.43,0.54,并具有倍半萜类化合物特有的紫外吸收带,它们的最大吸收值(max)分别为270,285,287,290,287,287nm,与国外报道乙醚提取物的紫外吸收特性相近(sommereyns & Closset,1978)。生物检测结果表明,上述组分均为毒素活性部分,它除能溶于ε为10以上的溶剂外,对热和光稳定,最适pH 4—7,极端pH下,毒素活性被钝化,回调最适pH后,活性仍可恢复,即令高温蒸煮也不丧失活性。毒素对小麦叶组织伤害能力及其活性与温度,毒素浓度和剂量,作用时间的变化呈正相关。

When toxins produced by Helminthosprium sativum in Fries solution at 21—25℃ on shaker functioned on wheat leaf, the symptom was similar to that caused by H.sativum in the field. Partially purified toxin was obtained from condensed cultural solution by precipitation with, extraction with n-butanol and chloroform and passage through silica gel chromatography column twice. The components showed bluish-violet and brownish-yellow spots inspected in UV light and iodine vapour, their RF value were 0.12, 0.16, 0.25, 0.36, 0.43, 0.54 respectively and showed special UV absorption spectrum of sesquiterpene compounds. They exhibited absorption maximum at 279, 285, 287, 290, 287, 287 nm, similar to those of extraction with ethyl ether reported by Sommereyns & Closset (1978). All these components were active parts of the toxin, examined by bioassay and were soluble in some organic solvents with dielectric constant over 10. They were also stable to heat and light. In the range of pH from 4 to 7 they showed the maxima activity and were heat stable up to boiling. The activity was inhibited at high or low pH but would be recovered by adjusting pH to the optimum. The damage activity of toxins to wheat leves was positively correlated to temperature, concentration, dose of toxin and treating time as well.