Influence Factors And Management Of Maize Kernels Contaminated With Fusarium Species And Mycotoxin During Storage

The occurrence of stored grain diseases is the main reason for the decrease of grain quality and the aggravation of grain loss during storage.As one of the most important crops in China,maize is prone to fever,mildew and seed deterioration during storage,and the loss is serious.At this stage,the research focuses on the research of state-owned large and medium-sized grain storage grain storage technology.At present,there is a lack of in-depth study on the occurrence of disease in farmers during storage.In this study,121maize ears collected from 31 regions of 12 provinces in China from 2016 to 2018 were isolated and identified by morphological and molecular biological methods.The results showed that the main contaminant fungi carried by maize kernels were Fusarium verticillioides.In the field experiment,F.verticillioides was inoculated at silking stage of maize,and spraying fungicides for early prevention and control to reduce the base of pathogens during storage.In addition,setting storage conditions to analyse the influences of different factors on kernel fungi.Fumonisin content in different parts of maize grain was analyzed by tissue anatomy and enzyme-linked immunosorbent assay?ELISA?.Fumonisin content was reduced by deep processing after storage,which provided theoretical basis for food security.The main results are as follows:1.121 maize samples from 31 regions of 12 provinces were isolated and identified by morphological and molecular biological methods.A total of 3954 strains belong to six Fusarium species were isolated and identified,including 1904 strains of F.verticillioides,1305 strains of F.oxysporum,400 strains of F.graminearum complex,188 strains of F.equiseti,124 strains of F.proliferatum and 33 strains of F.subglutinans.The isolation frequencies were 52.5%,36.0%,11.0%,5.2%,3.4%and 0.9%,respectively.In addition to F.oxysporum isolated from Gansu?Wuwei,Pingliang,Zhangye,Zhenyuan?and Heilongjiang?Harbin?provinces,F.oxysporum and F.verticillioides were the main pathogens in Shandong?Liaocheng?and Guizhou?Puding?provinces,while F.verticillioides was the main pathogen in other eight provinces.Fumonisin B₁ and B₂ were detected by high performance liquid chromatography with fluorescence detection.A total of 70 samples were contaminated with fumonisins,and the contamination rate was 57.9%.The average contamination level was 2.0657 mg/kg,and the highest contamination level was 10.0627 mg/kg.2.The suspension of F.verticillioides was inoculated into the ear of healthy maize variety Xianyu 335 by filament injection method.The fungicides,BR and insecticides screened by our research group were sprayed separately and in reduced dosage on the third day after inoculation.The results showed that compared with the control group,the average disease index could be reduced by all the medicament treatments.The best control effect was the combination of pyraclostrobin,difenoconazole,prochloraz and BR,reaching51.2%.Absolute quantitative PCR was used to detect the quantity of F.verticillioides in maize kernels.It was found that the quantity of F.verticillioides of the four drug combinations was the lowest.The results of fumonisin test by HPLC-FLD showed that all treatments could reduce the content of FB₁ and FB₂.3.Through the investigation of the maize storage conditions of farmers in 11 regions of 5 provinces in Henan,Shanxi,Sichuan,Hebei and Inner Mongolia,and identification of F.verticillioides from maize kernels with different moisture content.The results showed that isolation frequency of F.verticillioides in maize kernels with higher water content was higher.The best treatment of the combination of pyraclostrobin,difenoconazole,prochloraz and BR,which can reduce the source of fungi and the control were set to store at different initial water content for 90 days at different temperatures.It was found that the control of the source of fungi and initial water content before storage can reduce FBs content in maize kernels.FBs content of maize grains with different initial moisture content increased with temperature during storage period.4.Tissue anatomy,absolute quantitative PCR and enzyme-linked immunosorbent assay?ELISA?were used to detect the fungi content and fumonisin content in the seed coat,fruit stalk,embryo and endosperm of maize kernels.The results showed that the amount of F.verticillioides and the content of fumonisin in fruit stalks were the highest.