Antibacterial Effect Of Honokiol On Kiwi Fruit Soft Rot And Effect On Fruit Quality

Soft rot disease is one of the important factors restricting the development of kiwifruit industry,people lack of understanding of the disease,resulting in inaccurate and unscientific use of drugs,causing pesticide pollution and other problems.In order to identify the pathogenic of"Hongyang"kiwifruit soft rot in Liupanshui City of Guizhou Province and screen a good safety control agent.This experiment through the isolation,identification and pathogenicity test,the pathogen of"Hongyang"kiwifruit soft rot disease was identified,through the determination of different plant extracts of kiwifruit soft rot disease pathogen virulence,obtain the bacteriostatic activity of the advantage of the higher natural products,and through the physiological and biochemical test preliminary clear the antibacterial mechanism of the extract,through field experiments at the same time made clear its control effect and effect on fruit quality,To provide scientific basis for the prevention and control of kiwifruit soft rot disease.The main results are as follows:1.The pathogen of"Hongyang"kiwifruit soft rot in Shuicheng area was identified as Botryosphaeria dothidea.Through sampling,isolation,purification and pathogenicity detection,pathogenic fungi SC-03 were obtained.In PDA medium,the fungi showed white colonies in the early stage,with loose mycelia and long and protrudes in the middle.After 12days,a large number of mycelia showed gray to black.The width of mycelia was 3-5μm,and there were a lot of septum in the middle of mycelia.Through the comparison analysis of homology and development tree,it was found that B.dothidea had 100%homology and was in the same branch.Combined with the morphological characteristics of pathogenic fungus,the fungus that caused the soft rot of"Hongyang"kiwifruit in Shuicheng county was B.dothidea.2.Natural products honokiol with better antibacterial effect were screened.The toxicity of honokiol to kiwifruit soft rot pathogen was higher than that of other plant extracts,and the EC₅₀value was only 31.3107 mg/L.Compared with the EC₅₀value of 30%difenoconazole WG to Kiwifruit soft rot pathogen,there was no significant difference between them.MIC,mode of action and biomass determination results showed that honokiol can not directly kill kiwifruit soft rot fungus,but inhibit the growth of mycelia,reduce the content of dry matter,can make mycelia fine,fracture,deformity,disorderly.3.It is preliminarily confirmed that honokiol can achieve inhibition of fungus effect by destroying cytoplasmic membrane.SEM and TEM observation showed that the kiwifruit soft rot pathogen fungus mycelia were seriously damaged after treatment with honokiol.Mycelia were malformed,withered and ruptured,etc.In the cell structure,cytoplasmic membrane and membrane organelles were seriously damaged,but the cell wall damage was not obvious.CFW staining,chitinase andβ-1,3 glucanase activities showed that the cell wall integrity of kiwifruit soft rot pathogen was not seriously damaged after treatment with honokiol.The results of PI staining and relative conductivity measurement showed that with the increase of honokiol concentration,the damage degree of mycelial membrane of kiwifruit soft rot pathogen increased.4.The rate of kiwifruit soft rot disease was only 8.00%when the concentration of honokiol was 80 mg/L.The rate of kiwifruit soft rot disease was 8.67%when the test concentration of 30%difenoconazole WG was 2000 times.The control effect of the two treatments was 77.98%and 76.15%,respectively,with no significant difference.In addition,honokiol treatment had no significant effect on the appearance index of kiwifruit fruit,improved the quality index of kiwifruit fruit at soft ripening stage,slowed down the changes of hardness,vitamin C,soluble solids and soluble total sugar at storage stage,and extended the storage time,indicating that honokiol is safe for kiwifruit.