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采用子叶喷雾法分别测定了大黄酚(chrysophanol)对黄瓜白粉病菌(Sphaerotheca fuliginea)的保护和治疗生物活性。结果表明,大黄酚能有效降低黄瓜白粉病的病情指数,其保护和治疗作用的EC50分别为0.23μg/mL和25.88μg/mL,对照药剂50%硫磺悬浮剂保护作用的EC50为59.75μg/mL,10%苯咪甲环唑可湿性水分散粒剂治疗作用的EC50为13.55μg/mL。在此基础上,利用2.4μg/mL大黄酚溶液处理黄瓜子叶24h后接种白粉病菌,在不同时段对病组织进行透明染色观察白粉病菌的变化情况。结果发现,大黄酚可有效降低黄瓜白粉病菌分生孢子的萌发率和萌发芽管个数,并能抑制菌丝的生长以及降低新生分生孢子的个数。接菌后24h,清水对照萌发率为66.6%,而大黄酚处理后的孢子不萌发;接菌后48h,对照菌丝的平均长度为414.7μm,大黄酚处理的菌丝平均长度为40.1μm;接菌后144h,对照的新生分生孢子串最多为8个孢子,大部分为6~7个,而大黄酚处理后的新生分生孢子串孢子个数最多为2个,大部分为1个。接菌7d后对照的病情指数为72.2,大黄酚处理组的病情指数仅为2.1,其保护作用防治效果达到97.1%,远高于50%硫磺悬浮剂65.4%的防效。
The protective and therapeutic bioactivity of chrysophanol to Sphaerotheca fuliginea was determined by cotyledon spray method. The results showed that chrysophanol can effectively reduce the disease index of cucumber powdery mildew and the EC50 of protection and curative effect were 0.23μg / mL and 25.88μg / mL, respectively. The EC50 of the control agent 50% sulfur suspension was 59.75μg / mL The EC50 for the therapeutic effect of 10% benzimizole wettable powders was 13.55 μg / mL. On this basis, the powdery mildew was inoculated with 2.4 μg / mL chrysophanol solution for 24 h, and the pathogen tissues were inoculated with powdery mildew at different time points to observe the change of powdery mildew. The results showed that chrysophanol can effectively reduce the conidial germination rate and the number of germinated germinant cucumber powdery mildew pathogen, and can inhibit the growth of mycelium and reduce the number of nascent conidia. After 24 hours of inoculation, the germination rate of fresh water was 66.6%, while the spores did not germinate after chrysophanol treatment. The average length of control hyphae was 414.7μm and the average length of chrysophanol treated hyphae was 40.1μm at 48h after inoculation. At 144 h after inoculation, the number of fresh spore germination strings in the control was 8 spores, mostly 6 to 7, whereas the number of spore conidia spores after chrysophanol treatment was up to 2, mostly 1 . After 7 days of inoculation, the disease index of the control was 72.2. The disease index of chrysophanol treated group was only 2.1, and its protective effect was 97.1%, which was much higher than that of the control with 65% of sulfur suspension concentrate.