| Fifty-eight species of plant materials were extracted with 80% ethanol in ultrasonic cleanout implement, and the rough extracts were tested for their protective and curative effects on downy mildew of cucumber through leaf-tray method and then tested on living seedings. The extracts of Ts-109, Ts-69 and Ts-121 showed strong protective and curative activity. Their protective efficacy were over 80% and curative efficacy were over 70% at dosage of 5mg/mL. Ts-109 and Ts-69 showed better protective and curative efficacy on living seedings than their performances on leaf-tray. Results demonstrated that when their protective efficacy reach 50%, The dosage of Ts-109 and Ts-69extract were 3.95mg/mL and 2.85 mg/mL respectively.The protective activities of Ts-109 extract was tested after being extracted with different methods and with different time length. Results showed that the efficacy was better after extracted with 80% ethanol in ultrasonic cleanout implement for 30 minutes or shaked for 4d, their efficacy were 68% and 66% respectively at 5mg/mL. But the efficacies were lower after extracted with water.The components of Ts-109 was analyzed by HPLC. Result proved that emodin, chrysophanol, rheuu aloe-emodin and physcion were main components of Ts-109. Emodin and rhein had no activity against disease by preliminary tests, chrysophanol and aloe-emodin was proved to be the main active fraction of Ts-109. Extracts of five species of Rhemum were analysed by HPLC and tested for the efficacies against downy mildew. Results indicated that the amounts of main active ingredients varied remarkable. The protective activities of different extracts increased with the increase of total amount of those five active ingredients.Mixtures of Ts-109 with 30 other plant extracts in 1:1 proportion were tested fortheir efficacies. Results showed the Mixtures of Ts-109 with Ts-5, Ts-38, Ts-121 and Ts-139 could increase the efficacy of Ts-109. After mixturing with Ts-5, the efficacy of Ts-109 increased 20% compared to Ts-109 extract alone. The best mixing proportion between Ts-109 and Ts-5 was 3:1. The inhibiting efficacy of the mixture was 68% at a dosage of 2.5mg/mL when extracted with 80% ethanol for 30 minutes in ultrasonic cleanout implement, but the efficacy was only 26% at the same concentration when extracted with water. |
