Identification Of Pathogen Of Maize Ear Rot In Liaoning And Jilin Provinces And Control

Maize ear rot appears widely in corn planting areas in China.The pathogens can cause yield reduction destroy the maize crop,Moreover,the fungi can produce toxins,which is harmful for human and animals.Various fungal species are responsible for maize ear rot in China but the dominant reported species are different in different corn planting regions.In terms of prevention of this disease,the problems are few resistant maize varieties and few chemical agents with lower effect.Therefore,we isolated and identified pathogens which caused maize ear rot in Jilin and Liaoning provinces to determine the dominant pathogen,then we screened the cycloalkylsulfonamide compounds which had good activity to inhibit Fusarium.The purpose was discovering new compounds for seed coating formulation to control this disease.The main results were as follows::1.The samples were collected from 8 cities in two provinces and 21 sampling sites in Liaoning and Jilin,6 generas were isolated and identified from 158 fungi.After single spore isolation,strains were identified as Fusarium spp.,Trichoderma spp.,Penicillium spp.,Aspergillus spp.,Bipolaris zeicola and Trichothecium roseum by morphological characterization and molecular identification by species-specific primers.It was first reported that T.roseum caused maize ear rot in China.A total of 4 species of Fusarium were identified,such as Fusarium verticillioides,F.proliferatum,F.graminearum and F.subglutinans,percentage incidence of fungi isolated were 73.15%,10.19%,7.40%and 9.26%respectively.In Liaoning province,the dominant species was F.verticillium,the isolation frequency was 84.73%,the isolation frequency of F.subglutinans and F.proliferatum were6.94%,and the isolation frequency of F.graminearum was 1.39%.The dominant Fusarium pathogen in Jilin Province was F.verticillioides,the isolation frequency was 50%,followed by F.graminearum,the isolation frequency was 27.78%,and the isolation frequency of F.subglutinans and F.proliferatum was 13.89%and 8.33%,respectively.2.4 compounds with good inhibition activity against F.verticillioides were screened from 62 cycloalkylsulfonamide compounds using mycelial growth rate method,which were436,77,WML-1,and M-8,respectively.When the compound concentration was 50μg/m L,the inhibition rate of pathogenic reached over 70%and 436 had the highest inhibition rate（90.48%）which was higher than the control（73.8%）.The virulence analysis of these four compounds showed that the lowest EC₅₀ of compound 436 against F.verticillioides was 11.42μg?mL^-1,and the lowest EC₅₀ of compound 436 against F.proliferatum was 12.51μg?m L^-1,Compound 77 had the lowest EC₅₀ for F.graminearum,which was 12.68μg?m L^-1.Compound436 had the lowest EC₅₀ for F.subglutinan,which was 13.21μg?m L^-1.Four compounds have no effect on mycelium morphology of F.verticillioides,The mechanism of the compounds are and were identified as antimicrobial agents.Compound 77 was obvious inhibition effects on conidia germination,with EC₅₀ values of 74.03μg?m L^-1 at 50μg?m L^-1.But the other had no significant difference in conidia germination.By analyzing the expression of genes involved in the synthesis of fumonisin,the results showed that there was no significant difference in the expression level of FUM1 gene after treatment with the four compounds;However,the expression level of FUM19 gene was decreased by 10%.There was no significant difference in the expression level of FUM21 gene after 77,WML-1 treatment,but the expression level of FUM 21 gene decreased by 10.5%after 436 treatment.3.The ZXX seed coating was prepared by 4 kinds of cycloalkylsulfonamide compounds with 40%phoxim EC,film former and compound fertilizer.By measuring the effect of ZXX seed coating agent on plant height,root length and fresh weight of maize seedling stage,the results showed that the seed coating agent could enhance the growth of corn seedlings without phytotoxicity to corn growth.By comparing the control effect test with 20%kefu,TCF and XDS,the results showed that the control effects of ZXX-1 to ZXX-4 seed coating were54.37%,54.18%,53.32%and 52.79%,respectively.It was significantly higher than the control treatment.The effect of seed coating on corn yield was measured.The results showed that ZXX-2 seed coating had the best yield increase rate,with an increase rate of 25.51%,followed by ZXX-1 seed coating agent,with an increase rate of 24.92%,ZXX-4 and ZXX-3seed coating agent production rate were less than XDS seed coating,but greater than 20%of carbofuran and thiram mix seed coating and TCF Trichoderma preparation.