| The novel fungal dehydrogenase inhibitors,Y13149 and Y12196 are developed by Central China normal University.The two fungicides exhibit a strong inhibitory activity against mycelium growth of Fusarium graminearum and will be commerized in China.In order to provide reliable recommendations for application and exploitation of the fungicides,antifugal spectrum,baseline sensitivity and field efficacy against wheat head blight were involed in the current study.The results were followed.(1)The antifungal spectrums of the two SDHIs,Y13149 and Y12196 was determined against the five important agricultural pathogens.The results showed that both Y13149 and Y12196 exhibited the powerful inhibition against mycelial growth of Sclerotinia selerotiorum(EC50=0.1245 ?g/mL for Y13149,and 0.1561?g/mL for Y12196),of F.graminearum(EC50=0.1325 ?g/mL for Y13149,and 0.3024?g/mL for Y12196),and of Riziocotinia solan(EC50?0.0143 ?g/mL for Y13149,and 0.0022?g/mL for Y12196).Both Y13149 and Y12196 also inhibited the conidia germination of F.graminearum with EC50 values of 6.2729 ?g/mL and 6.7771?g/mL,respectively,significantly higher than the EC50 values against mycelial growth of the same pathogen.Howerer,the mycelial inhibition of the two SDHIs against Botryosphaeria berengeriana was low.(2)Baseline sensitivities of the 100 isolates of F.graminearum against the two SDHIs were established,which were isolated from wheat head blight from Henan and Jiangsu Provinces where the two fungicides have never been used before.The EC50 values of F.graminearum against Y13149 ranged from 0.06?135.7402 ?g/mL(mycelial growth inhibiton)and with the mean value of 30.7734±30.9404 ?g/ml.Similarly,the EC50 values of 81 F.graminearum isolates against Y12196 inhibiting mycelial growth was ranged from 0.038?188.5796 ?g/mL with the mean value of 50.8059±47.0244 ?g/mL.The results showed that the sensitivities of F.graminearum isolates tested against Y 13149 or Y12196 differred significantly.(3)Translaminar and xylem-systemic movement for the two SDHIs was determined on the wheat seedlings.?Root-irrigated with Y13149 or Y12196 at the concentration of 1000?g/mL,both of the two fungicides exhibited excellent efficacy against F.graminearum,indicating that both Y13149 and Y12196 could be absorbed by the roots of the wheat plants and showed excellent acropetal translocation.? The two fungicides could be moved distally within the leaves.? Painted on the wheat leaves at the concertraion of 500 ?g/mL,control efficacy of Y13149 and Y12196 were 94.64%and 98.21%respectively,suggesting that the fungicides tested exhibited excellent translaminar activity.(4)Effects of Y13149 and Y12196 on the production of trichothecene mycotoxins in F.graminearum were investigated in laboratory and field by a competitive ELISA kit.Treated with Y13149 or Y12196 at the concentrations of EC50 and EC90,mycotoxins of all treatments decreased significantly in the mycelia in vitro,and the expression of toxin-synthesis-related genes Tri5 and Tri6 was significantly reduced by quantitative PCR.In field,accumulation of grain mycotoxins from Y13149 with two sprayings at the 10 a.i.grams per 667 m2 was significantly lower than that of the blank control group,and accumulation of mycotoxins in the mixture of Y13149 or Y12196 with metconazole or prothioconazole decreased significantly.(5)Due to the significant difference between the sentivities of mycelial growth and spore germination of F.graminearum against Y13149 or Y12196,the mixtures with different mode-of-action fungicides were selected,optimized and evaluated in the field.?In vitro selection.The EC50 values of the dual mixture of Y13149 or Y12196 with metconazole,prothioconazole,phenamacril,fluazinam,tebuconazole or fludioxonil against a Fusarium graminearum strain PH-1 was evaluated by mycelial inhibitive growth.The results showed that the synergism was present the following mixtures,including the mixture of metconazole with Y13149 at the ratios of 1:1,1:3 and 1:5,the mixture of prothioconazole with Y13149 at the ratios of 1:1,1:5,3:1 and 5:1,the mixture of phenamacril with Y13149 at the ratios of 1:1,the mixture of Y13149 with fluazinam at the ratios of 1:1,1:3,1:5,3:1 and 5:1,the mixture of Y13149 with tebuconazole at the ratios of 1:1,1:3,3:1 and 5:1,the mixture of metconazole with Y12196 at the ratios of 1:1 and 1:5,the mixture of prothioconazole with Y12196 at the ratios of 1:1,1:3,1:5,3:1 and 5:1,the mixture of phenamacril with Y12196 at the ratios of 1:1,1:3,1:5,3:1 and 5:1,the mixture of Y12196 with fluazinam at the ratios of 1:1,1:3,1:5,3:1 and 5:1,the mixture of Y12196 with tebuconazole at the ratios of 1:1,1:3,1:5,3:1 and 5:1.The mixure of Y13149 orY12196 with metconazole,prothioconazole,phenamacril,fluazinam,tebuconazole or fludioxonil has powerful inhibition against F.graminearum in vitro,and the optimal mixtures of the above-described were further tested to control wheat head blight in field,enhance the control efficacy and delay developing the resistance against the novel SDHIs.?Control efficacy of the mixtures of Y13149 or Y12196 were evaluated against wheat head blight in field.The results of two sprayings at the flowering stage showed that control efficacy of Y13149(at 10 a.i.grams per 667 m2)and phenamacril(at 25 a.i.grams per 667 m2)was 68.82%and 81.95%respectively,while the mixture of Y13149 with prothioconazole ranged from 60.35%?91.30%.The control efficacy of the mixture of Y13149(15 grams per 667 m2)with prothioconazole(15grams per 667 m2)was insignificantly different from that of phenamacril(at 25 grams per 667 m2).The control efficacy of Y12196(at 10 a.i.grams per 667 m2)was 52.03%,while the mixture of Y12196 with prothioconazole ranged from 82.82%?88.94%,the mixture of Y12196 with tebuconazole ranged from 73.93%?86.09%. |
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