| Copper ions have a broad-spectrum antifungal effect.Copper-based pesticides have been widely used in the production areas of many plants and have good effects as an important pre-harvest antifungal agent in the citrus production areas.In this study,treatments were performed with different concentrations of copper sulfate on the inhibition of Penicillium digitatum,the in vitro,in vivo and production area storage experiments were conducted to explore the mechanism of copper sulfate on P.digitatum.And the feasibility of using copper preparations as an antifungal agent was confirmed,in post-harvest storage and preservation of citrus.The main results are as follows:1.Preliminary study on the mechanism of copper sulfate inhibiting P.digitatum in vitro.Copper sulfate could significantly inhibit the physiological growth of P.digitatum,and the minimum inhibitory concentration was 0.55 g/L.When the copper sulfate concentration was 0.4 g/L,the colony growth inhibition rate of P.digitatum was greater than 61.0%,which could reduce the spore germination rate to 5%.After 0.25 g/L copper sulfate treatment,the p H value in the fungal solution was significantly reduced,and the p H of the H2O medium dropped from the initial 6.15 to 4.79,with a drop of 22.1%.Electron microscopy showed that the hyphae of P.digitatum were twisted and shrunk,the spores were twisted and deformed,the cell structure disappeared,and the nucleus,endoplasmic reticulum,mitochondria,and other organelles were indistinguishable.308 strains of P.digitatum mutants were screened using copper sulfate solutions of 0.08 g/L and 5.0 g/L,and 3 strains were found to be copper-sensitive transformants.2.The antibacterial effect of copper sulfate on citrus fruits.When the concentration of the copper sulfate solution was 5.0 g/L,the use of mixed inoculation could significantly inhibit the disease incidence of fruit,reduce the incidence rate by more than 20%,and the inhibition rate of lesion diameter was greater than 36.7%;the treatment could significantly delay acidification,and p H at the 5th day was 4.07（3.08 for water treatment）.Using the mixed method of adding fungi solution first and then adding copper,when the inoculation concentration was 0.5 g/L,the pathogenicity of P.digitatum could be enhanced,the onset was 1 d earlier than the water treatment,the diameter of the lesion was longer,and the acidification was accelerated.On the 3rd day,the p H had dropped to 3.88,which was significantly lower than other treatments（p H:5.01-5.20）.3.The pilot test effect of copper sulfate in Ganzhou citrus production area.The copper ion concentration used in the storage and preservation experiment in this production area was 1.0 g/L.After storage for 90 d,the stalks of the citrus fruits did not fall off,and the fruit color was uniform.The weight loss rate of the citrus fruits after the copper sulfate solution soaking treatment（3.27%）was higher than that of the water treatment（2.71%）,but lower than the positive control drug treatment（3.54%）.On the 120th day,compared with 8.35%of the total decay rate of the water treatment,the copper ion treatment reduced the decay rate to 5.51%,but it was higher than the 1.58%of the positive control.In terms of storage quality,on the 30th day,the total soluble solid content of copper treatment was the highest,which was 10.90%;the titratable acid content was slightly higher than that of the water treatment and was significantly higher than the positive control.Compared with the other two treatments,after the copper sulfate treatment,the content of the two substances was the lowest on the 90th day.In summary,the inhibitory effect of copper sulfate on P.digitatum lays a theoretical basis for the study of citrus green mold in postharvest citrus;the development of copper preparations provides a new method for the prevention and control of postharvest citrus green mold. |
