Research On Biological Activity And Application Of Controlling Sclerotinia Stem Rot Of Benzothiostrobin

Benzothiostrobin[(E)-2-[2-(5-methoxy-benzothiazol-2-methylthio)phenyl]-3-methoxyacrylate](development code number:Y5247)is a novel Qol fungicide that was developed by Key Laboratory of Pesticide&Chemical Biology of Ministry of Education,Central China Normal University.Different types of Qol fungicide performed different antifungal activity,antifungal spectrum,systemic translocation and the prevention and control effect of diseases,because of its physical and chemical properties.Before the novel fungicides are on the market,it is necessary to study their biological activities against plant pathogens and control effects to important diseases.The study has an important role in the novel fungicides development and application strategy.The toxicity of a new compound benzothiostrobin was studied against 9 species of important agricultural pathogens.The biological characteristics of a novel strobilurin fungicide benzothiostrobin(Experiment code Y5247)were presented.The EC50 values of the chemical inhibiting the mycelial growth of plant pathogen Rhizoctonia solani,Magnaporthe grisea,Sclerotinia sclerotiorum and Botrytis cinerea,on the AEA medium containing 50 ?g/mL salicylhydroxamic acid(SHAM),were 0.004,0.009,0.016 and 0.023 ?g/mL,respectively.While the EC50 values of azoxystrobin were 0.030,0.071,0.407 and 0.206 ?g/mL,respectively.The EC50 values of benzothiostrobin inhibiting spore germination of Colletotrichum capsici and Botrytis cinerea were 0.448 and 0.019?g/mL,respectively.While the EC50 values of azoxystrobin were 0.453 and 0.028 ?g/mL.The protective and curative activities controlling powdery mildew caused by Blumeria graminis were 0.991 and 1.823 ?g/mL,respectively.While the EC50 values of azoxystrobin were 0.858 and 1.657 ?g/mL.Benzothiostrobin has not systemic translocation but penetrative activity on the wheat leaf.Benzothiostrobin appeared its good bio-properties of rain-washing tolerance,adhesion and long persistence against Blumeria graminis on wheat leaf.Efficacy of the chemical controlling wheat powdery mildew got to 72.48%,when the pathogen was inoculated on the 14th day after sprayed with 25 ?g/mL benzothiostrobin.The baseline sensitivity of S.sclerotiorum to benzothiostrobin was determined using 100 strains collected from different geographical regions in Jiangsu Province of China,and the average EC50 value was 0.0218(±0.0111)?g/mL for mycelial growth.The difference of sensitivity was small and baseline sensitivity curves were approximately normally distributed.So these EC50 values of S.sclerotiorum could be used as baseline sensitivity to benzothiostrobin.The analysis of cross-resistance showed that no cross-resistance was detected between benzothiostrobin and carbendazim,iprodione,fludioxonil,or boscalid.In laboratory,we had not obtained resistant mutants derived from wild-type S.sclerotiorum isolates through fungicide training methods.Therefore,a preliminary assessment of benzothiostrobin against S.sclerotiorum has low risk.In this study,we determined the effect of benzothiostrobin on biological activities of S.sclerotiorum and analyzed its impact on physiological and biochemical metabolism.The results indicated that benzothiostrobin had a strong inhibition on mycelia growth of S.sclerotiorum.After benzothiostrobin treatment,hyphae were contorted with off-shoot of top increasing.The number and dry weight of sclerotia decreased with the concentration of benzothiostrobin increasing.Sclerotia numbers of all isolates that treated with 2 ?g/mL benzothiostrobin were significantly fewer than the control.After benzothiostrobin treatment,cell membrane permeability increased markedly,while oxalic acid content significantly decreased.Benzothiostrobin strongly inhibited mycelial respiration within 12 h and the oxygen consumption of the mycelia could not be inhibited after 24 h.On detached rapeseed leaves,the protective and curative activity test of benzothiostrobin suggested that benzothiostrobin had good control efficiency against S.sclerotiorum,and protective activity was better than curative activity.The activity of the dual mixture of benzothiostrobin with fluazinam to S.sclerotiorum was evaluated by inhibiting mycelium growth on AEA medium.A formulated mixture of benzothiostrobin and fluazinam at 1:1 had synergistic activity against S.sclerotiorum,the SR value was 2.7735.In field trials,benzothiostrobin alone or formulated with fluazinam at 1:1 was superior to iprodione in controlling Sclerotinia stem rot of rapeseed;mean control at 150 g a.i.ha-1 was 68%for benzothiostrobin alone and 74%for the benzothiostrobin and fluazinam mixture.