Identifying Maize Germplasm With Resistance To Aspergillus Flavus And Resistance-related Pathway

Zea mays.L is an important economic crop in our country.The pathogenic fungus Aspergillus flavus is a major disease in maize production prior to harvest and through storage,and pose serious health hazards to humans for it can secret aflatoxins,which have a strong carcinogenicity.Identifying maize germplasm with resistance to Aspergillus flavus is an effective and efficient method for preventing and controlling aflatoxin contamination ultimately.In this paper,340 high-throughput sequenced maize inbred lines were used for screening resistant varieties,and genome-wide association analysis was performed to analyze the main metabolic pathways associated with maize resistance to aflatoxin.The main results are as follows:1.The influence of different combinations of temperature(20°C,28°C and 37°C)and water activity(0.90,0.95,0.99 aw)on growth and aflatoxin B1(AFB1)production were investigated.The results showed that the optimal condition for A.flavus NRRL 3357 growth and toxicity was at 28 and? 0.99 aw.2.KSA experiment was performed by infected 340 maize inbred lines with A.flavus,6 high resistant lines and 17 highly susceptible lines were obtained,respectively.The concentration of AFB1,detected by HPLC,was 8.319?g/g ~ 13.839?g/g in resistant samples,and 26.101?g/g ~120.566?g/g in susceptible samples.The amount of fungi is more in the susceptible samples by qPCR.3.To investigate the difference of the process of A.flavus infecting the resistant and susceptible materials,kernels were inoculated with GFP labeled conida.The results indicated that the mycelia grew through the pedicel,past the abscission zone(black layer)and into the surrounding tissues(scutellum,endosperm,aleurone layer)in susceptible material,in constrast limited infection in resistant kernels.4.GWAS analysis that the significantly SNP locus of maize resistantce to A.flavus mainly distributed in 1,2,9 chromosomes.Gene Ontology comments and KEGG pathway analysis with access to 11 major metabolic pathways associated with resistance.5.The data of peptidomics were analyzed,63 differentially peptides were obtained,including 36 up-regulated peptides and 24 down-regulated peptides.Finally,21 metabolic pathway related to resistance was obtained by KEGG pathway analysis.6.Combination of the data from GWAS and peptidomics analyses,cyanide amino acid metabolism and phenylpropanoid biosynthesis may be related to maize resistance to A.flavus.In this paper,the suitable conditions for the production of aflatoxin were explored,and effective screening system for maize resistance to A.flavus was established.High resistant inbred lines were identified.The main metabolic pathway of maize resistance to A.flavus was analyzed at the level of gene expression,which laid the foundation for the future mining of resistant genes.Moreover,our research would facilitate uncovering the molecular mechanism of maize resistance to A.flavus,and supply theory for the rational use of resistant inbred lines and create new resistant germplasm.