The Inhibitory Mechanism Of Boscalid Against Sclerotinia Sclerotiorum Of Sunflower And Its Field Holdup Period Were Determined

Sunflower sclerotinia rot is one of the diseases that harm sunflower growth seriously caused by Sclerotinia sclerotiorum.At present,it is the principal method to prevent the disease by chemical control.However,due to the unitary fungicides are reused for a long time,there are some reports gradually increased,which about the resistance to drugs of the preventive medicine of the Sclerotinia sclerotiorum which used in production.Therefore,it is urgent to select the new fungicides which have the new mechanism of action,in order to prevent and cure the sunflower sclerotinia rot.Thus,in this study,the indoor measurement method has been used by us in order to study the biotoxicity and physiological toxicity and some other fields of the boscalid to the Sclerotinia sclerotiorum under ionic conditions,in addition,we have used the field trial,in order to measure the duration and the control efficiency of preventing and curing the Sclerotinia sclerotiorum by boscalid,and the residual dynamics of boscalid in sunflower discs,meanwhile,the research results are as follows:1.Using the method of indoor measurement,in order to measure the effect of boscalid on the biological toxicity of Sclerotinia sclerotiorum under ionic conditions.The results show that boscalid has an inhibiting effect on the growth rate,sclerotium yield,dry weight of the sclerotia and packed mycelial volume of Sclerotinia sclerotiorum and it enhanced with the increase of dinicromide concentration..The inhibition rates were 91.69%,84.62%,61.07% and 55.47% with the dosage was 16.667?g/m L,and it can lead to abnormal mycelial morphological and protoplasm shrinkage of the Sclerotinia sclerotiorum;In addition,the boscalid can lead to obviously inhibitory effect on the germination of the ascospore and the elongation of the germinal tube of Sclerotinia sclerotiorum,but it has no obvious effect on the morphology of the ascospore.2.Spraying 50% boscalid water dispersible granule(WG)respectively on the sclerotium which cultured in laboratory and field,and observing the germination of the sclerotium,meanwhile,the results show that it has an impact on sclerotium's germination rate,the quantity of the formation of apothecium,and apothecial livability,in which using boscalid in different drug concentration or different spray date.In addition,the germination rate of sclerotia is higher than that of boscalid before sclerotia's germination if boscalid is sprayed after sclerotia'sgermination;Moreover,when the dosage of the 50% boscalid WG is the 750g/hm2,the inhibitory effect on the sclerotia germination is the best.3.Under ionic considerations,we detect the effect on the physiology and biochemistry toxicity and pathogenic factor after handling Sclerotinia sclerotiorum with EC50 and EC95.Thus,the results show that boscalid could destroy the cell membrane permeability of Sclerotinia sclerotiorum and inhibit the respiration of Sclerotinia sclerotiorum of sunflowers,in addition,the relative permeability of sunflower's Sclerotinia sclerotiorum is significantly increased after handing,and the relative permeability of EC95 group is higher than that of EC50 group;Furthermore,Succinate dehydrogenase activity is obviously inhibited,and the enzyme activity of EC50 group and EC95 group decreased by 38.83% and 58.08% respectively.Moreover,the oxalic acid biosynthesis of sunflower's Sclerotinia sclerotiorum is significantly reduced after handling by boscalid,meanwhile,compared with the reference substance,the content of oxalic acid in the experimental group with boscalid concentration of EC50 is always higher than that in the experimental group with boscalid concentration of EC95.In addition,boscalid can inhibit the protease activity of Sclerotinia sclerotiorum.The inhibition effect of EC95 group on protease activity is greater than that of EC50 group,which is 40.68% and 22.03% lower than that of reference substance respectively;besides,boscalid can inhibit amylase activity of Sclerotinia sclerotiorum,and at the 3rd day of culture,EC50 and EC95 groups decreased by 26.23% and32.79% compared with the reference substance.After handling by boscalid,the variation trend of the activity of degrading enzyme of sunflower's Sclerotinia sclerotiorum cytoderm is identical to the reference substance,but the enzymatic activity of the cell wall-degrading enzyme is always lower than the reference substance,and the enzymatic activity at the concentrate of EC95 is lower than that at the concentrate of EC50.Furthermore,the inhibitory effect of boscalid on PG and PGTE produced by Sclerotinia sclerotiorum is stronger than that on PMG and PMTE.The treatment of Sclerotinia sclerotiorum with pyridamidine EC95 had the best inhibitory effect on its biochemical,biochemical and pathogenic factors.4.After using 50% boscalid WG in the field trial,The control efficiency and residual dynamic detection were detected.The results show that the duration of 50% boscalid WG in sunflower plants is 14 days.The average control effect of 750g/hm2 WG was 89.68% and the increase of production was 34.58%,when the dosage of the 50% boscalid WG is the 750g/hm2 that had the best control effect on Sunflower Sclerotinia sclerotiorum and increased the yield of sunflower.The disease control effect in the field decreased,and the residue of 50% boscalid WG in the flower tray decreased at 14 d and it gradually permeates into the grains and then into the sponge tissue from the columnar flowers.