| Maize stalk rot occurs all over the world,and has become an important disease that endangers corn production in China.The yield of corn is greatly reduced and the loss is serious after being damaged by this disease.In this study,Fusarium graminearum,a plant pathogen causing maize stalk rot,was selected as the research object to identify the resistance of the new maize combination selected by Anhui engineering and technology research center of maize breeding,and to determine the inhibitory activity of chemical fungicides and their combinations on Fusarium graminearum.This study could provide theoretical basis and technical support for the selection of resistant varieties and chemical control of maize stalk rot.1.Without Fusarium graminearum inoculation,the ear weight and grain weight of 76×372 maize combination with resistance level 1 were the highest,but the yield decreased more after inoculation,and the ear weight and grain weight lost 71.2 g and 63.8 g respectively.If large-scale planting had a high risk,and the yield of 2×372,81×372 and 78×372 maize combinations with resistance level 2 was high,it can be seen that the inbred line 372 has a high yield and disease resistance potential,and its excellent genes should be further explored.Under the condition of inoculating pathogen,2×372 and 15H037×1090 had stronger resistance compensation ability,higher ear weight and grain weight than Zhengdan 958.These hybrid combinations had higher resistance and yield to maize stalk rot,and their utilization value can be further determined by ecological identification in different places and years.2.The indoor toxicity of 12 fungicides,including fludioxonil,prochloraz,tebuconazole,carbendazim,hexaconazole,epoxiconazole and chlorothalonil,were determined with Fusarium graminearum as the target.The results of virulence test showed that the inhibition activities of four fungicides were the highest.They were fludioxonil,prochloraz,tebuconazole and carbendazim.The EC50 values were 0.16,0.23,0.40 and 0.85 μg·mL-1.The next were hexaconazole,epoxiconazole,chlorothalonil,pyrazoxystrobin and thiram.The EC50 values were 1.50,1.53,1.71,2.00,4.00 and 5.00 μg·mL-1.The EC50 values of mancozeb and triadimefon were 8.00μg·mL-1,and the virulence of these two fungicides to the pathogens was low.3.Using Horsfall formula method,the inhibitory activity of the mixture of chemical fungicides 5:5 to Fusarium graminearum was first determined.The combined toxicity of thiram and other fungicides 5:5 to Fusarium graminearum was determined by Horsfall formula,and the toxicity ratio of the mixture of pyraclostrobin and hexaconazole,thiram,epoxiconazole,chlorothalonil 5:5,thiram and hexaconazole,mancozeb and epoxiconazole 5:5 were 1.11,1.12,1.18,1.38,1.21 and 1.14,respectively.Then,the above six combinations to further determined by Horsfall formula,the suitable ratio of the mixture of pyraclostrobin and hexaconazole,thiram,epoxiconazole,chlorothalonil 8:2,3:7,8:2 and 4:6,thiram and hexaconazole 5:5,mancozeb and epoxiconazole 7:3 were 1.13,1.19,1.34,1.42,1.23 and 1.28,respectively.Finally,the volume ratio of mancozeb to epoxiconazole was 7:3,the toxicity ratio was the highest and the synergism was obvious.According to the above proportion,the Wadley’s formula method was used to verify synergic activity of the mixture of hexaconazole and pyrazoxystrobin,chlorothalonil and pyrazolyl ester,thiram and pyrazolyl ester,and epoxiconazole and pyrazolyl ester,and the SR was between 0.5 and 1.5,which indicated that the type of the four combinations to Fusarium graminearum was additive.The SR of the mixture of mancozeb and epoxiconazole was 1.62,indicating that the combination was synergism type.It can be concluded that synergic activity the combination of mancozeb and epoxiconazole was verified both by Horsfall formula and Wadley formula.Compared with the single inhibitor,the mixture of mancozeb and fluconazole 7:3 could induce a large number of chlamydospores,the hypha was deformed seriously and the surface was rough,and some hyphae were broken. |
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