Studies On Mechanism, Mode Of Action Of D-pinitol Against Sphaerotheca Fulijinea And Its Mixture With Other Pestcides

The mode of action of fungicide on plant pathogens is classified asinduction, prevention and control effect, according to the control effect isdifferent as different spraying time. D-Pinitol, as a phytochemical sourcefungicide developed by our lab, has a control function to SphaerothecaFuliginea. D-Pinitol and its formulation with different concentrations aresprayed on the seedlings by the method of which used in the field test atdifferent time and then to investigate the control effects. The mode of actionof D-Pinitol and its formulation against S. Fuliginea is tested. Data displaythat D-Pinitol’s control effects of treatment, prevention and induction areseparately100%,33.52%and16.48%, and that the treatment3days afterinfection has the highest control effect which is64.25%better than that of thetreatment1day or4days after infection. Data also present that three modesof action, mentioned in front, of D-Pinitol formulation against S. Fuligineaare separately100%,-12.21%and-12.21%, and that the treatment3daysafter infection has the highest control effect which is93.07%better than thatof the treatment1day or4days after infection. The result shows that theD-pinitol treatment3days after infection has the best control effect.According to the experiments of the concentration gradient, D-Pinitol2000ppm has the best control effect as well as the D-Pinitol formulation in600-fold dilution. And the control effect of D-Pinitol formulation is betterthan that of D-Pinitol, for both of the control effects are respectively93.07%and81.51%at the7thday after inoculation. The present results indicate that D-Pinitol and its formulation have control effect against S.Fuliginea, moreover the D-Pinitol formulation further reduces the degree ofdisease as well as reducing D-Pinitol concentration for1L D-Pinitolformulation contain300mg D-Pinitol while1L D-Pinitol contain2000mg.So the result provides the feasibility basis for D-Pinitol development.Besides, the mode of action of D-Pinitol and its formulation on S. Fuligineaprovides clues to its action mechanism in-depth study.Powdery mildew （S.fuliginea） infection in cucumber was significantlyreduced by foliar application of D-pinitol three days after inoculation. Theeffects of fungicidal activity on leaves applied with D-pinitol were observedunder UV light. Compared to the control, foliar application of D-pinitol notonly dropped the density of conidia but also shortened the conidial strings.Moreover surfaces of cleistothecia of S. fuliginea were rough, even theconidia were shriveled. These results might demonstrate that the controleffect of D-pinitol on the powdery mildew might due to some effect directlyor indirectly on the conidia, or on conidial strings. The initial response tofoliar application of D-pinitol was abrupt increase of Gallic acid （GA） in theleaves of cucumber plants. One day before and after foliar application ofD-pinitol, GA contents were separately1.764μg mL^-1,2.064μg mL^-1. Andthe GA content maintained a higher level several days after D-pinitoltreatment. Activities of antioxidant enzymes such as PAL, PPO and SODwere also stimulated by foliar application of D-pinitol. Through this study, itmaybe estimate that the control effect of D-pinitol on cucumber powderymildew is due to its stimulation in the increase of GA content and antioxidantenzymes’（PAL, PPO and SOD） activity.As single pesticide use can easily lead to a pest resistance to pesticide.This project studies the control effect of D-Pinitol formulation mixturewith other pesticides. Data showed that the control effect of Amici,D-Pinitol formulation, mixture of D-Pinitol formulation andphenazino-1-carboxylic acid, mixture of D-Pinitol formulation and Phenazine-1-formamide, mixture of D-Pinitol formulation and N, N-diethyl phenazine-1-formamide are separately36.94%,47.75%,54.05%,56.76%and48.64%. The result shows that the control effects of D-Pinitolformulation mixture with other three pesticides are better than that ofD-Pinitol formulation, even much better than Amici. Compared withAmici, as chemistry fungicide widely used in the market present, whichcan easily lead to a fungal resistance, D-Pinitol formulation mixtureswith other three pesticides possess efficient, low toxicity and lowresiduary without those lack, and also reduce the cost of D-Pinitol.Consequently, this study provides theoretical basis for market outlook ofD-Pinitol.