| Green mould caused by Penicillium digitatum is the most serious postharvest disease of citrus fruit.At present,chemical fungicides are the main way to control green mould,but they are easy to induce drug resistance of pathogenic bacteria and have adverse effects on human health and environment.Cumin aldehyde,a component of plant essential oil,has been proved to have a good inhibitory effect on a variety of food pathogenic bacteria and can be used as a substitute of chemical fungicides.In this paper,the bacteriostatic effect and concentration of cumin aldehyde on sensitive strain(Pds01)and resistant strain(Pdw03)of P.digitatum were studied in vitro and in vivo;the integrity of cell wall and cell membrane as well as the change of intracellular active oxygen content were measured;the relationship between total lipid and MDA content and active oxygen was quantitatively analyzed;the changes of mitochondrial membrane potential and energy metabolism were analyzed The relationship between reactive oxygen species.The main results are as follows:1.Study on the antimicrobial activity of cuminol against sensitive strain(Pds01)and resistant strain(Pdw03)of P.digitatumIn vitro,cumin aldehyde had a good inhibitory effect on Penicillium digitatum.The minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MFC)for sensitive and resistant strains were 0.30 and 0.60 μL/m L,respectively.In vivo experiments,when the susceptible strain infecting 5d,the incidence rate of control group was 100±0%,and the incidence rate of 5× and 10×MFC cumin treatment group were 80±0% and 65±5% respectively.Storage 7d,the control fruit was rotten,the lesion diameter was 72.67±2.52 mm,and 10× MFC treatment group had a diameter of 48.33±7.64 mm.The incidence rate of resistant strains citrus green mold was 6d at 100±0%.The incidence rate of 5× and 10× MFC cumin treatment group was 82±8% and 63±3% respectively.When stored at 8d,the control group was rotten and the lesion diameter was 64±3.61 mm.The diameter of the disease spot in 10× MFC was only 32.10±1.05 mm.The above results showed that10× MFC cumin aldehyde could effectively reduce the incidence rate of susceptible and resistant strains of green mold and control the occurrence of diseases.Scanning electron microscopy(SEM)showed that the surface morphology of sensitive and resistant mycelium of Penicillium digitatum was seriously flattened,twisted andfolded.2.Study on the antibacterial mechanism of cumin aldehyde against sensitive strain(Pds01)and resistant strain(Pdw03)of P.digitatumAfter the sensitive and resistant strains were treated with 1/2 MIC cumin aldehyde,the cell wall was not affected;the cell membrane was damaged,the sensitive strains occurred in 60 min,and the resistant strains were damaged in 30 min;the increase of ROS content in cells occurred in 30 min,but the fluorescence multiple of ROS was 1.46 ± 0.10,which was higher than that of sensitive strains 1.13 ± 0.04,indicating that the accumulation ratio of ROS in resistant strains induced by cumin aldehyde was 1.46 ± 0.10 Sensitive strains are faster.The content of total lipid decreased gradually with time,the content of MDA increased gradually,and the damage of cell membrane decreased significantly after the addition of ROS scavenger Cys and inhibitor DPI,which showed that the fluorescence intensity,total lipid content and MDA content of PI staining experiment were basically similar to those of the control,and no obvious damage was found by SEM.The changes of mitochondrial membrane potential of sensitive and resistant strains were measured after adding Cys and DPI.At 120 min,1/2 MIC of sensitive strain was measured The red-green fluorescence ratio of CU treatment group was0.650 ± 0.052,significantly lower than that of Cys treatment group(0.782 ± 0.040)and DPI treatment group(0.904 ± 0.053);the mitochondrial membrane potential of antagonistic strains,the fluorescence ratio of Cys and DPI treatment group were 1.025± 0.040 and 1.235 ± 0.017,respectively,higher than that of 1/2 MIC CU treatment group(0.909 ± 0.028).It was found that the change of energy content was consistent with that of mitochondrial membrane potential.The results showed that the main site of ROS production induced by cumin aldehyde was in mitochondria and was related to energy metabolism and respiratory metabolism.In conclusion,this study shows that cumin aldehyde has a good inhibitory effect on Postharvest chloromycetes of citrus,and its mechanism is mainly related to cell membrane damage,intracellular energy metabolism imbalance,mitochondrial dysfunction and a large number of intracellular ROS.This study can provide a theoretical basis for the application of plant essential oil in Postharvest preservation of citrus. |
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