辣椒疫毒致病毒素

PHYTOPHTHORA CAPSICI PHYTOTOXIN

辣椒疫霉（PhytophthoracapsiciLeonian）在培养液中振荡培养时可分泌毒素，这种毒素能引起辣椒叶片形成水渍状褐腐斑，类似病原菌侵染后形成的症状。Plich’s和V8C培养液适于P.capsici的生长和产毒；生长适宜温度和pH范围分别为20～30℃与pH6～7，在25～30℃、pH5～8的条件下培养滤液毒性最强；培养15天产毒达到最高值。滤液先后经85％硫酸铰沉淀、DE52、CM32和SephadexG－75柱层析将毒素纯化。经鉴定该纯毒素为39．8kD酸性糖蛋白，并对80℃以上高温或蛋白酶敏感，而β-D-葡萄糖苷酶处理不影响其毒性，蛋白亚基为毒素的活性中心。毒素处理寄主叶片引致病理性坏死，这一作用与辣椒品种抗病性有关。

Phytophthora capsici Leonian secreted toxin when cultured in liquid medium on shaker. The toxin induces brown rot lesions of pepper leave, and the symptoms are similar to those caused by P. capsici in the fields.Pitch's and V, C liquid medium are suitable for P. capsici growth and toxin production. The optimum temperature and pH for growth are 20~30℃ and pH6- 7,respectively. The filtrates at 25~30° and pH5-- 8 have highly toxic activities. The highest toxicity of culture filtrates occurred on the fifteenth day after inoculation. The purified toxin, obtained from culture filtrates by precipitation with 85% saturated ammonium sulphate, was subjected to chromatography on a diethylaminoethyl-cellulose (DE52), carboxymethyl-cellulose(CM32) and Sephadex G-75 column, respectively. The toxin was shown to be a Kind of acidic glycoprotein (pI 4.1, Mr. 39.8kD), and found to be sensitive to temperature upwards of 80℃ and proteinase, and to be stable to β-D -glycosidase. The protein subunit is a center of toxin activities. The results of bioassay show that toxin induces pathogenic lesions of pepper leave, and its response is closely related to resistance to Phytophthora blight of different varieties.