| Phytophthora capsici is an important plant pathogenic oomycete that can cause epidemics of more than 50 crops such as pepper,tomato and cucumber,and its damage is becoming more serious.At present,chemical control is the main way to control Phytophthora blight.With the long-term use of the drug,the strain developed resistance.Scientists are eommitted to finding new drugs with high efficiency,low toxicity and no pollution.Botanical pesticides have become a research hotspot.In this study,the virulence of Litsea cubeba essential oil to different developmental stages of Phyophthora capsici was determined under in vitro conditions,and its effects on soluble protein,cell membrane permeability,mycelial fresh weight and dry weight of target bacteria were determined.The control effect of the essential oil on pepper blight was tested by the vitro leaf method and the drenching root method.The antibacterial activity of Citral,the main active component of the essential oil of Litsea cubeba,against Phytophthora capsici was studied systematically.With the continuous development of high-throughput technology,the proteomics ruethod is applied to speculate on the biochemical pathway of drug action.The results are as follows:1.The virulence regression equations of the essential oil of Litsea cubeba on the mycelial growth,sporangia formation,sporangia germination and spore germination of Phytophthora capsici were Y=-1.6680+3.0288 X?Y=0.6928+2.9252 X?Y=-0.8810+2.5371 X?Y=-2.2061+1.4273 X.Under the biological microscope,it was observed that the mycelium of Phytophthora capsici was more branched after the treatment of the essential oil of Litsea cubeba.The fresh weight and dry weight inhibition rate of 269.15mg/L of Litsea cubeba essential oil was 75.03%and 77.20%,respectively.As the concentration of essential oil of Litsea cubeba increased,the electrical conductivity also increased.The preventive effect of 2 000 mg/L of Litsea cubeba essential oil on pepper blight was 80%,which was comparable to the control effect of azoxystrobin.2.The EC50 of Citral against Phytophthora capsici was 95.11 mg/L.The EC50 for sporangia formation was 18,76 mg/L.The results indicate that Citral is the main antibacterial active substance of Litsea cubeba essential oil.The morphology of mycelium was observed under scanning electron microscope after Citral treatment of Phylophthora capsici.The mycelial branch increased and the top of the hyphae expanded.3.The intracellular glycerol content maintains intracellular and extracellular osmotic pressure.After treatment with Citral,the intracellular glycerol content was 0.51 and 0.70 mmol/g,respectively.Citral destroys the osmotic pressure of the cells to achieve the purpose of inhibition.4.ROS is associated with programmed death of fungi.The control group showed weak green fluorescence under the fluorescence microscope.The fluorescence brightness of mycelia treated with Citral was significantly higher than that of control group.The inhibition of Citral on Phylophthora capsici may be due to excessive ROS disturbing the normal metabolism of cells.5.After staining with SYTOXTM Green Ready FlowTM Reagent,it was observed that the Control cells had no green fluorescence.After Citral treatment of Phytophlhora capsici,green fluorescence was observed in the hyphae.The Citral may destroy the cell membrane of Phylophthora capsici.And the conductivity method was used to determine the effect of Citral on the cell membrane permeability of Phytophthora capsici.The results showed that with the increase of the concentration of the drug,the time was delayed and the conduetivity increased.It was further shown that the membranous membrane of Phytophthora capsici was damaged after Citral treatment.6.Proteomics and transcriptomics were used to analyze the changes of gene/protein expression of Phylopht.hora capsici with Citral treatment.The combined analysis showed that there were 32 genes/proteins with the same expression trend,among which the proteins in glycolysis and membrane process had significant differences. |
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