Research On The Inhibitory Mechanism Of Cantharidin Derivatives Against Sclerotinia Sclerotiorum

Sclerotinia sclerotiorum is an important fungus that harms crops and can infect many monocotyledonous and dicotyledonous plants.At present,a variety of chemical fungicides are mainly used to prevent the disease,but the abuse of fungicides leads to the increase of resistance to pathogens,and it will also damage the nutritional value of crops.Fungicide residues will also cause pollution to the environment and destroy the ecosystem,so it is urgent to develop natural biological fungicides.Finding and developing new lead compounds is one of the ways to develop biological fungicides.In the former research,it was found that five kinds of cantharidin derivatives with similar structure had strong antifungal activity on many plant pathogenic fungi.Based on this study,the inhibition effect of five halogenated aromatic amines（7-0,12-0,15-0,18-0,21-0）on mycelial growth and sclerotia formation of Sclerotinia sclerotiorum was determined,control efficiency on detached leaves was determined.The antifungal mechanism of cantharidin derivatives were analyzed by measuring mycelial morphology,mycelial relative conductivity,malondialdehyde content,reduced sugar content,soluble protein content,chitinase activity,DNA content and oxalic acid content.The results provided theoretical basis for the development and utilization of biological fungicide.The results of this study are as follows:1. Five kinds of derivatives had good antifungal activity on S.sclerotiorum.EC₅₀values of 7-0,12-0,15-0,18-0,21-0 were 37.64,8.78,6.45,12.25 and 50.41μg/m L respectively.2. Five kinds of cantharidin derivatives showed significant inhibitory acttivity on the mycelial growth of S.sclerotiorum.Derivative 15-0 had the most significant inhibitory effect.The dry weight of hypha decreased gradually with the increase derivative concentration.3. The higher the concentration of cantharidin derivatives,the better the effect on the inhibition of sclerotia formation,the inhibitory activity of the derivative 15-0 on sclerotia formation was the strongest,the inhibition rate reached 86.52%at 12.5μg/m L.Cantharidin derivatives would delay the time of sclerotia germination,but could not inhibit the final germination.4. On detached leaves of oilseed rape,cantharidin derivatives all exhibited control effect.The control efficacy of derivative 15-0 on vitro was the strongest,derivative 15-0 sprayed at100μg/m L obtained 97.71%curative efficacy and 98.39%protective efficacy.5. After treated with cantharidin derivatives,the surface of mycelia was rough,or dehydrated and shriveled,or deformed and expanded;the cell membrane permeability was increased,the reduced sugar content and soluble protein content were decreased,chitinase activity was increased,the DNA content and oxalic acid content were decreased significantly.