| Penicillium italicum is one of the important diseases of post-harvest fruits in China,which causes huge economic losses to the citrus industry every year.However,due to the proliferation of chemical fungicides,the drug resistance of P.italicum is caused,and it is potentially harmful to human health.Plant endophytes and soil-derived microorganisms are important sources for discovering new anti-pathogenic agents.In this study,active strains against P.italicum were screened from plant endophytes and soil microorganisms,and the mechanism of action was discussed.The main research results are as follows:1)Isolation,screening and identification of active strains: 36 kinds of fungi were isolated from plants and soil,solid fermentation was carried out to obtain secondary metabolites,and the fermentation products were subjected to the bacteriostatic study of P.italicum by the Oxford cup method,and 4 kinds of fungi were obtained.Among the strains with inhibitory effect on P.italicum,one strain GC-09 was selected for in-depth study.The strain GC-09 was identified as Aspergillus aculeatus through a combination of morphological analysis and r DNA-ITS sequencing.The bacteriostatic effect on P.italicum was determined by Oxford cup and minimum inhibitory concentration method.The results showed that the size of the inhibition zone was21.6±0.23 mm under the condition of 10 mg/m L ethyl acetate extract and the minimum inhibitory concentration value was 0.625 mg/m L.2)Research on the antibacterial mechanism of the fermentation product of Aspergillus aculeatus against P.italicum: Using the mycelial growth rate method,it was found that the Aspergillus aculeatus treatment of P.italicum can make its growth rate slow and mycelial weight greatly reduced;through the virulence regression equation The analysis results show that Aspergillus aculeatus has a certain concentration effect on P.italicum.In the spore germination experiment,using 10 mg/m L Aspergillus aculeatus ethyl acetate extract for 36 h can completely inhibit the spore germination of P.italicum;scanning electron microscopy results show that 1/2,1MIC can cause spores and hyphae to fold and break,There are holes.PI staining results showed that the Aspergillus aculeatus extract treatment of P.italicum can destroy the integrity of the cell membrane;the change of intraspore soluble protein verified the change of cell membrane permeability,while the change of extraspore content and electrical conductivity verified the cell membrane permeability Increase,from these three aspects mutually verify the changes in the permeability of the cell membrane of P.italicum.At the same time,after the fermentation product of Aspergillus aculeatus was treated with P.italicum,the active oxygen content in the cell was significantly increased,indicating that Aspergillus aculeatus can induce the membrane lipid peroxidation response of P.italicum;the citrus green treated by Aspergillus aculeatus The activity of CAT and POD enzymes in mold cells is significantly reduced.3)Study on the fresh-keeping effect of the fermentation product of Aspergillus aculeatus on Gannan navel orange: The ethyl acetate extract phase of the fermentation product of Aspergillus aculeatus strain can delay the occurrence of fruit diseases in Gannan navel orange.It can be stored at low temperature(4±1℃)and room temperature(25±2℃)Under the condition of,the fruit decay rate during storage was significantly lower than that of the control group,and the low-temperature storage effect was more obvious than the room temperature storage effect. |
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