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水稻尾孢霉(Cercospora oryzae)是水稻条叶枯病的致病菌。24个菌株用抑制稻种胚根生长生物测定法进行产毒筛选。大部分菌株培养滤液对胚根生长有抑制作用。6个菌株:I-16,I-26,I-28,I-38,I-42和I-49选为进一步试验的菌株。添加10％稻叶汁马铃薯蔗糖培养液适于菌株的生长和产毒。生长适宜的温度和pH范围分别是25°-30℃和pH 6—7,光线和通气可促进菌株生长,但温度、光线和通气对培养滤液的毒性无影响,pH6—7的培养滤液毒性最强。接种后3周的培养滤液表现强毒性。多数菌株生长高峰出现在第4周。对水稻尾孢霉毒素进行了初步鉴定。结果表明菌株都能产生红色色素和黄色物质,红色色素经薄层色谱,可见光谱分析和颜色反应证明与尾孢霉毒素相同。培养滤液和尾孢霉毒素提取物能抑制稻种和4种作物种子胚根生长,并能在损伤稻叶上引起褪绿和枯死。这一作用与稻秧的品种抗性和秧龄无关。
Cercospora oryzae is a pathogen of rice leaf blight. Twenty-four isolates were screened by bioassay using rice seed radicle growth inhibition assay. Most strains of culture filtrate on the radicle growth inhibition. Six strains: I-16, I-26, I-28, I-38, I-42 and I-49 were selected for further testing. Add 10% rice leaf juice potato sucrose broth suitable for the growth of strains and toxin production. The suitable temperature and pH range of growth were 25 ° -30 ℃ and pH 6-7, respectively. Light and ventilation could promote the growth of the strain, but the temperature, light and aeration had no effect on the toxicity of culture filtrate. The culture filtrate pH6-7 was the most toxic Strong. Three weeks after inoculation, the culture filtrate showed strong toxicity. The majority of strains peaked at week 4. Cotyledosis of rice cotyledons was initially identified. The results showed that the strains can produce red pigment and yellow substance, red pigment by TLC, visible spectrum analysis and color reaction proved to be the same as ciclosporidin. Culturing the filtrate and cercosporin extract inhibited the radicle growth of seed and four crop seeds and caused chlorosis and blight on the damaged rice leaves. This effect has nothing to do with the variety resistance and seedling age of rice seedlings.