Study On Inhibition Of Chinese Medicine Extracts On Actinidia Soft Rot Pathogen And Its Effect On The Preservation Of Fruits

Kiwifruit is one of the main fruits industry in Hunan Province,especially in the west of Hunan Provinc.Kiwifruit is not storage-resistant and has a high incidence of soft rot(20%-50%),at the same time,chemical preservatives are currently used to store kiwifruit.The purpose of this paper is to improve the storability of kiwifruit on the premise of environmental protection,health and high efficiency,so as to improve its economic benefits.Taking Hongyang kiwifruit as the experimental material,the isolation and identification of actinidia soft rot pathogen,the screening of botanical antimicrobial agents,the extraction technology of antibacterial substances,the synergistic inhibition of compound compounds,the identification of antibacterial active substances,the antibacterial mechanism of extracts,the storability of extracts on fruits,and the mechanisms of the storability of extracts on fruits were studied.The main research results are as follows:1.Analysis of pathogenic microorganisms in soft rot Kiwifruit.Ascomycota was the most dominant phylum in soft rot kiwifruit.The relative abundance of Ascomycota was 19.20%,which was much higher than Basidiomycota(6.80%).The dominant pathogens in Ascomycota were Botryosphaeia dothidea and Diaporthe phaseolorum.After the isolation and identification of pathogens,the above two pathogens were obtained and identified.The optimum growth p H value of the two pathogens was 5?7,the optimum growth temperature was 25?30?,and the lethal temperature was 85?90?.The utilization rates of organic nitrogen,glucose,sucrose etc.carbon sources were high.2.Screening of botanical fungicides and extraction technology of antibacterial substances.It was found in 120 kinds of Chinese medicinal materials,Syzygium aromaticu,Cinnamomum cassia,Scutellaria baicalensis,Oil tea meal,Pogostemon cablin,Acorus tatarinowii,Acorus tatarinowii,Rosmarinus officinalis,Coptis chinensis,Caulis impatientis,Litsea cubeba etc.plants were treated,the diameter of the inhibition zone of both pathogenic fungi could reach more than 15 mm.The minimum inhibitory concentration and minimum bactericidal concentration were low,which respectively were about 12.5 mg/m L(crude drug)and 125 mg/m L(crude drug).When the concentration of the extract reached 2 mg/m L,the dry weight of mycelia was less than 0.1 mg,and the incidence rate of fruit was reduced by more than 30%.Under the conditions of solid-liquid ratio of 1:27.5(g/m L),ultrasonic extraction for2.5 h,extraction temperature of 72.5?,and ultrasonic power of 850 W,the extract of Scutellaria baicalensis had strong antibacterial effect.The extract stored at 25?for40 d had little effect on the activity.3.Optimization of compound ratio of extracts and identification of active components.The optimum formulation conditions were as follows:A baicalein 1.375,B clove 1.125,C cinnamon 0.45,D spina gleditsiae 0.5,E patchouli 1.35,F calamus1.25,G Camellia oleifera meal 2.8.Under this technological condition,the theoretical value of inhibiting rate of 0.4 mg/m L compound to bacteria was 43.2%.The IC₅₀ of the compound was 0.489 mg/m L.when the concentration reached 0.8 mg/m L,the antibacterial effect was very good,and the inhibition rate reached more than 85%.Flavonoids are the main components in Scutellaria baicalensis,volatile oils are mainly in Syzygium aromaticu,Acorus tatarinowii and Pogostemon cablin.Saponins are mainly in Oil tea meal and Gleditsia sinensis.The compound contained more flavonoids,saponins and oleic acids,respectively reaching 10.74%,14.40%and19.84%.The relative contents of baicalein,eugenol,cinnamaldehyde,saponin,Pogostemon,Acorus calamus and Camellia saponins respectively were 2.23%,0.60%,4.52%,0.48%,1.75%,5.79%,9.32%in their respective plants.4.Study on the antibacterial mechanism of the extract compound against Botryosphaeria dothidea.The results showed that the metabolites,enzyme activities and DNA content of the pathogen were significantly reduced in the compound treatment group.And the mitochondrial membrane potential was decreased,the level of reactive oxygen species was increased,and the mycelial structure and spore structure were seriously damaged.The number of down regulated genes was much more than that of up-regulated genes.The main metabolic pathways affecting pathogen death include membrane,oxidoreductase activity,immune system,cell growth and death.5.Study on the regulation of the extract compound on Kiwifruit storability.Kiwifruit was treated with compound,The results showed that the good fruit rate of kiwifruit was increased significantly,the water loss rate was decreased,the degradation of small molecular substances and the decomposition of macromolecular substances was slowed down,and the decline of fruit hardness was delayed.The activity of oxygen free radical scavenging enzyme waas increased,the activity of macromolecular catabolic enzyme decreased,and the amount of respiration and ethylene production was decreased.The gene expression of kiwifruit will be affected by pathogen infection or medicament(compound)treatment.The gene was significant difference between the diseased fruit group and the other three groups(principal component 1,66.25%),and that of the good fruit+medicine group was significantly different from the other three groups(principal component 2,16.07%).The main pathways affecting the storability of kiwifruit were carbohydrate metabolic process,polysaccharide metabolic process,starch and sucrose metabolism pathway etc.Through the analysis of gene expression in different storage period,It was found that the experimental results were basically consistent with the change trend of related enzymes.