| Corn is an important staple grain and feed crop,and it is also widely used in industrial deep processing.In recent years,corn ear rot has become one of the main diseases in Anhui Province due to the change of farming system and the return of straw to the field.The mycotoxin produced by Fusarium spp.,the pathogen of ear rot,can cause pathological changes in human and animal organs and do great harm.In this study,the pathogen of corn ear rot was isolated and identified from 15 summer corn planting areas in Bengbu,Suzhou,Bozhou and Fuyang,Anhui Province in September 2020,and its biological characteristics were studied.The sensitivity of corn ear rot pathogen to several commonly used fungicides in Anhui Province was determined,and the sensitive baseline was established,and the cross-resistance between prothiazole and different fungicides was discussed.The main research results are as follows:1.Isolation and identification of Fusarium verticillioides.The pathogen of corn ear rot was isolated from 51 samples collected.158 strains of Fusarium were obtained by single spore isolation method,and the isolation frequency was 97.5%.Among them,80strains of Fusarium verticillioides were obtained,and the isolation frequency was 50.6%.Fusarium verticillioides is the dominant pathogen.The hyphae are curly,white or grayish purple,and the colors of precipitated pigments are roughly orange-yellow,lavender,dark purple,grayish purple and nearly black.The number of small conidia is large,oval or capsule type,without septum or occasionally 1 septum,the size is 4～12μm×2～4μm,and the large conidia are few,sickle-shaped,slender,thin wall,3～5 septum,34～62μm×3～5μm.The CAL genes of 80 tested strains were analyzed by cluster analysis.The phylogenetic tree showed that the homology of 80 tested strains was 95%with standard strains LS423376.1 Fusarium verticillioides and LS423396.1 Fusarium verticillioides.Combined with the identification of morphology and molecular biology and Koch’s postulates,it could be identified as Fusarium verticillioides.2.Biological characteristics of Fusarium verticillioides.The effects of carbon source,nitrogen source,medium,temperature and p H value on the growth of Fusarium verticillioides were determined.The results showed that Fusarium verticillioides could use many kinds of carbon and nitrogen sources,and its spore production and dry weight of mycelium were significantly different with different carbon and nitrogen sources;the most suitable growth medium was PDA medium;It can grow within 15℃～35℃,and the optimum growth temperature is 28℃;the lethal temperature is 70℃,10min;it can grow within the p H range of 3～10,and the optimum p H range is 7～9.3.Virulence of prothioconazole to Fusarium verticillioides.There were significant differences in sensitivity of 80 tested strains to prothioconazole.EC50is 0～0.5μg/m L,56strains,accounting for 70%;EC50is 0.5～1μg/m L,12 strains,accounting for 15%;EC50is1～8μg/m L,12 strains,accounting for 15%.The EC50 of strain AH-15-1-1 was 7.1315μg/m L,and the EC50 of strain AH-3-2-2 was 0.039μg/m L,and the highest EC50 was 183times of the lowest EC50.4.To establish the sensitive baseline of Fusarium verticillioides ear rot of Corn to prothioconazole.Through the analysis of Kolmogorov Smirnov normality test by DPS software,the results showed that the sensitivity frequency distribution of 63 strains of Fusarium verticillioides to prothioconazole conformed to the normal distribution.Therefore,the average EC50 of the 63 tested strains was 0.2980μg/m L was used as the sensitive baseline of Fusarium verticillioides ear rot of corn in Anhui Province.5.Cross-resistance between prothionazole and different fungicides.There was no correlation between the sensitivity of Fusarium verticillioides to prothionazole and its sensitivity to carbendazim and tebuconazole.The results showed that there was no cross-resistance between prothionazole and carbendazim,prothionazole and tebuconazole,and could be used alternately in production. |
