Control effects of leaf extracts of Vitis rotundifolia and V.vinifera on grape downy mildew
In order to clarify the control effects of leaf extracts from grapevines with different levels of resistance on grape downy mildew(DM),ethanol extracts of young leaves and adult leaves of two grapevine varieties,DM-immune variety Vitis rotundifolia cv.Noble and DM-sensitive variety V.vinifera cv.Cabernet Sauvignon,were selected as test materials.The leaf was ultrasonically extracted with 95%ethanol after dried and crushed.Effects of leaf extracts with different concentration gradients on germination of spo-rangia and zoospores and their preventive effects on downy mildew in laboratory were determined.The results showed that both leaf extracts significantly inhibited the germination of sporangia and zoospores of Plasmopara viticola.The germination rate of sporangia treated with 10 mg/mL leaf extract was significantly lower than that of control(treated with sterile water and 5%ethanol),and the germination rate of sporangia decreased significantly when the concentration of leaf extract increased from 10 mg/mL to 50 mg/mL.The germination rate of zoospores treated with 10 mg/mL leaf extract was significantly lower than that of control.When the concentrations of extracts of young leaves and adult leaves were 10,25 and 50 mg/mL,the control effect of 10 mg/mL extracts of Cabernet Sauvignon was 95.0%,and that of the other treatments were 100.0%.The leaf extracts of Noble and Cabernet Sauvignon could inhibit the germination rate of sporangia and zoospores of P.viticola,and their control effects on downy mildew in laboratory was significant.
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