Study On Etiology And Chemical Control Techniques Of Fusarium Verticillioides Of Maize Ear Rot In Liaoning Province

Ear rot is one of the main diseases in the later growth stage of maize.In recent years,straw returning and variety replacement have aggravated the damage of ear rot in Liaoning Province.There are significant differences in geographical environment,climatic conditions,varieties and cultivation measures in different regions of Liaoning Province.Therefore,identifying the main fungal pathogens and comparing their pathogenicity and toxin production are the basis for the formulation of control strategies.In this paper,the occurrence of ear rot of in Liaoning Province was investigated,Fusarium spp.were isolated and identified,the pathogenicity and toxin content of the Fusarium were detected,and the effective chemicals were selected as an index Fusarium to provide a basis for the prevention and control of corn ear rot.The following research results are obtained in this paper:1.The occurrence of ear rot of varieties in Liaoning Province was investigated.In 2018,the occurrence of ear rot of 203 varieties in 8 regions was investigated,of which186 varieties showed high resistance and 17 varieties showed resistance.In 2019,the occurrence of ear rot of 295 varieties was investigated in 14 regions of Liaoning Province,of which 273 varieties showed high resistance,21 varieties showed resistance and 1 variety showed susceptibility.2.Isolation and identification of Fusarium.In this paper,352 strains of Fusarium spp.were isolated and identified of 360 samples from 14 cities and 32 sites in Liaoning in 2018 and 2019,respectively.In 2018,Fusarium verticillioides,Fusarium graminearum,and Fusarium subglutinans were identified.Among them,the isolation frequency of F.verticillioides was 74.05%,which was the dominant Fusarium spp.The isolation frequency of 24 strains of F.proliferatum was 12.97%,and the other two species were F.graminearum and F.subgutinans.The isolation frequencies were12.43%and 0.55%,respectively.Five species of Fusarium were isolated from 167 strains of Fusarium in 2019.They were F.verticillioides,F.proliferatum,F.graminearum,F.subglutinans and F.andiyazi.The dominant pathogen was F.verticillioides,and its frequency was 83.23%,which was higher（10.22%）than that in 2018,followed by F.proliferatum,F.graminearum and F.subglutinans.The isolation frequency was 7.78%,5.99%and 1.80%,respectively.F.andiyazi was isolated in Liaoning firstly,and the isolation frequency was 1.2%.3.The temperature range of mycelium growth of F.andiyazi was 15-40℃,and the optimum temperature was 25℃.There was no significant difference on mycelium growth under light conidition.Maltose and sodium nitrate were the optimum carbon and nitrogenAbstractsources to promote mycelium growth,and sucrose and yeast were the optimum carbon and nitrogen sources to promote the production of conidia,respectively.4.The difference of pathogenicity and the ability of producing fumonisin FB1 of Fusarium verticillioides were compared.The pathogenicity and FB1 content of 42 strains of Fusarium verticillioides were randomly selected from 14 cities in Liaoning Province.The results showed that the pathogenicity of SY1-3 was weak,and its FB1 content was 14.61μg/g.The FB1 contents of BX5-10 and PJ11-5 with high pathogenicity were 16.68μg/g and 0.247μg/g,respectively.However,the disease index of FS4-3 with the highest FB1 production capacity was 28.40,and the disease index of DL2-6 and YK7-6 with lower FB1 content was 38.27,which was at a higher level.The results further showed that the F.verticillioides with strong pathogenicity was dispensable have strong ability to produce fumonisin FB1,and F.verticillioides with low virulence did not show defects in pathogenicity.Linear regression analysis showed that there was a poor correlation between the level of fumonisin produced by F.verticillioides strains and its pathogenicity.5.Control effect of chemicals on ear rot of F.verticillioides.By using the method of mycelial growth rate,two fungicides with effective inhibition activity against F.verticillioides were screened from 8 fungicides,which were prochloraz and tebuconazole respectively.Toxicity regression analysis showed that the EC₅₀of prochloraz to F.verticillioides was the lowest,0.1384μg·m L^-1,followed by tebuconazole and EC₅₀,0.3047μg·m L^-1.The effective fungicides were screened through the plot test as tebuconazole and prochloraz,and their control effects were 66.67%and 63.49%.The fungicides with the highest yield were tebuconazole and carbendazim.The control efficiency of 20%chlorobenzamide suspension and 40%carbendazim tebuconazole on Liangyu 99 and Danyu405 were 36.27%and 45.04%,and the production increased by 4.32%and 6.67%,respectively.Based on the results of inhibition tests and field control tests,it is recommended to use tebuconazole and prochloraz to control Fusarium ear rot of corn.