| In recent years,the kiwifruit industry in Guizhou Province has developed into a well-drilling industry and has become an important poverty alleviation industry in Guizhou Province.Kiwi soft rot is an important disease in the storage of kiwi fruit,and its main pathogen is Botryosphaeria dothidea.At present,the prevention and control of kiwifruit soft rot is mainly based on chemical control.Although chemical pesticides can effectively control the occurrence of kiwi soft rot,there are many problems such as drug resistance,resistance,environmental pollution and pesticide residues.Methyl jasmonate?MeJA?as widely used of endogenous regulatory hormone in higher plants,play an extremely important role in plant growth and secondary metabolism.Currently,MeJA has been used to directly inhibit phytopathogenic fungal.Achieving better results,but MeJA has not been related to the antibacterial activity and mechanism of kiwi soft rot fungus B.dothidea,which hinders the development and practical application of MeJA as an inhibitor.In view of this,this study determined the antibacterial effect of MeJA on kiwifruit soft rot B.dothidea,and further studied the effect of MeJA on the morphology,ultrastructure,respiratory metabolism and enzyme activity,cell membrane structure and genetic material of B.dothidea mycelium.The effect of MeJA on the control and fruit quality of kiwifruit soft rot was carried out,which provided a theoretical basis for the application of MeJA on kiwifruit.The main findings are as follows:1.The kiwi fruit was separated by tissue separation method,and the pathogenicity was determined by Koch's law,and a strain with higher pathogenicity was obtained.The strain has 100%homology with B.dothidea by morphological and molecular biological rDNA-ITS sequencing.Therefore,the pathogenic strain of kiwi soft rot obtained by the isolation of this test was determined to be B.dothidea.2.The effects of different concentrations of MeJA on the growth,mycelial growth and spore germination of B.dothidea mycelium were determined by mycelial growth rate method,weighing method and spore germination method.The results showed that MeJA inhibited the growth of virgin rot of B.dothidea with EC50 of0.2327 mmol/L;0.80 mmol/L MeJA inhibited the growth of B.dothidea mycelium by86.51%;The spore germination of B.dothidea has an inhibitory effect,and the inhibition rate 83.74%when the concentration is 0.80 mmol/L.After scanning electron microscopy and transmission electron microscopy,0.80 mmol/L MeJA treatment of B.dothidea hyphae can cause the cell wall of mycelial cells to dissolve,the nucleus and mitochondria increase and the shape becomes irregular,and the intracellular cavity increases,thus destroying The B.dothidea mycelial cell structure achieves the effect of killing pathogenic B.bacteria.3.Using three kinds of fungal,iodoacetic acid,malonic acid and sodium phosphate,the typical respiratory inhibitors were superimposed with MeJA.The MeJA and respiratory inhibitor superposition rate were used to judge the respiratory pathway of MeJA inhibiting pathogenic fungal,and the respiratory metabolism after MeJA treatment was determined.Enzyme activity.The results showed that MeJA and malonic acid were superimposed,and the superposition rate was the lowest.It was believed that MeJA inhibited the respiratory metabolism of kiwifruit soft rot pathogen through the Krebs cycle;while the superposition rate of MeJA and iodoacetic acid was higher,suggesting that the glycolytic pathway may also be affected by MeJA.Effects;MeJA treatment has an effect on ATP energy consumption and synthesis,metabolic enzymes,succinate dehydrogenase,and malate dehydrogenase during cell metabolism.MeJA inhibits succinate dehydrogenase and malate dehydrogenase activity.Interfering with the tricarboxylic acid cycle,inhibiting the synthesis of ATP,leading to ATP depletion in the mitochondria,and achieving the effect of killing pathogenic bacteria.4.The conductivity and protein and nucleic acid relative leakage of mycelial culture medium were determined by conductivity method and ultraviolet spectrophotometry.The protein and DNA content of B.dothidea was determined by Coomassie brilliant blue method and CTAB method.The MeJA treatment B.dothidea was studied.Effects on mycelial cell membrane function and genetic material.The results showed that MeJA treatment could cause the relative conductivity of hyphal cell membrane,the relative leakage of protein and nucleic acid to increase,and the effect was more obvious with time;and MeJA treatment of B.dothidea mycelial cell wall?-1,3-Portuguese The activity of glycanase was enhanced,and the content of N-acetylglucosamine,the main component of cell wall chitin,was increased.The protein and DNA content of B.dothidea decreased significantly after MeJA treatment,which may directly inhibit or interfere with the synthesis of DNA and protein of pathogenic bacteria.5.In order to clarify the effect of MeJA on field control and fruit quality of kiwi soft rot,MeJA was used in different growth stages of kiwifruit.The results of field experiment showed that the control effect of 0.5 mmol/L MeJA fruit extract on soft rot of kiwifruit was better in the month before harvest,and the control effect reached77.70%;and MeJA treatment could effectively improve the appearance quality of fruits and improve the vitamin C and solubility of fruits.The content of solids and MeJA treatment can increase the fruit firmness,significantly delay the rate of soluble solids and soluble sugar content,and reduce the loss rate of vitamin C,thus improving the storage performance of kiwifruit.This study showed that MeJA treatment can directly inhibit the growth of B.dothidea,destroy the function and structure of mycelial cells,inhibit the synthesis of DNA and protein,and the protective effect of 0.5 mmol/L MeJA on soft rot of kiwifruit in the field reached 77.70%,and can improve The quality of kiwi fruit improves storage performance.The results can provide a theoretical reference for the application of MeJA on kiwifruit. |
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