Postharvest Parasite Isolation?identification And The Antifungal Activity Of E-2-hexenal

We got some pathogenic fungus from rotten tomatoes, which were separated, purified, and then identified through the morphological characterization and r DNA-ITS method. The main components of the volatile substances in different age tomato leaves were analysised according to the GC-MS technology, and the key enzyme activities of lipoxygenase(LOX), phenylalanina ammonia-lyse(PAL) in the biosynthesis of volatile compounds of tomato leafs were measured. According to the GC-MS analysis, E-2-hexenal was one of the main ingredient in the volatile compounds which were used as an antibacterial study to tomato parasitic fungus, and the possible mechanism of inhibition was explored through a series of experiments. Finally, the inhibitory effect of E-2-hexenal on the bacterial infection during tomtato storage and the influence of the quality of tomato were studied. The specific results were summarized as follows:(1) The study on identification and biochemical characteristics of Penicillium cyclopium on rotten tomatoes surfaceOne pathogenic strains were isolated and purifed from the surface of riping and rotten tomato fruits: Penicillium cyclopium. Morphological characterization and physiological and biochemical characteristics were analysised by means of scanning electron microscopy(SEM). Finally, their r DNA were extracted; the primers were designed according to the conserved sequence ITS and their PCR amplifications were performed. The resulting products were sequenced by the shenggong Company in shanghai. Genetics analysis and sequence alignment were performed by searching NCBI databases, which were learned that they were Penicillium cyclopium. The pathogenic stran was used as research material, It was learned that the optimum growth temperature of mycelium growth was 25? according to the physiological and biochemical characteristics. When the p H value was 5.0, the growth potential of the colonies was the most vigorous. The lethal temperature for the spore was 70?.(2) The analysis of volatile components in different periods of tomato leaves and the determination of key enzyme activities in their synthetic pathwayUsing headspace solid-phase microextraction, the volatile organic compounds(VOCs) of ?A57? tomato were collected, and through the GC and GC-MS technology the volatile components were analysised. The results were shown that the main volatile components in the leaves of tomato, the content of aldehydes were the most, accounted for 47.41%. The content of terpenoid compounds was also higher, which its proportion was 46.51%. However, other components are very few, including alkane, ketones and alcohols, etc. The leaves of different periods including two leaf stage, ten leaf stage and flowering period, different varieties including A57, Christ and Zhongshu 5 were collected, which were used as measuring the enzyme activities of LOX and PAL.(3) The antimicrobial activity of E-2- hexenal against Penicillium cyclopiumUsing GC-MS technology analysis, we found that E-2- hexenal was the highest content among all volatile ingredients. The preliminary results of antibacterial experiment were shown that E-2-hexenal had obvious antibacterial effect. The MIC(Minimum Inhibitory Concentration) of E-2- hexenal on mycelial growth was 160 ?l / L, The MFC(Minimum Fugicide Concentration) of E-2- hexenal on mycelial growth is 320?l /L. Great changes on the morphology of hyphae and spores were observed with scanning electron microscopy. The results of nucleic acid leakage were shown that intracellular solubles existed massive release at MFC, while the OD value of control group had almost no change. The results of determination of conductivity and p H value in fungal culture solution with E-2-hexenal treatment were shown that conductivity variance occurred from the beginning 85.3 ?s/cm to 120 min of 115.1 ?s /cm with MIC concentrations of E-2- hexenal treatment, while the conductivity of the solution MFC concentrations increased from the beginning 99.1?s/cm to 120 min of 128.4?s/cm with MFC concentrations of E-2- hexenal treatment. The p H of fungal culture solution were 6.74 and 6.41 with MIC or MFC concentration of E-2-hexenal treatment, respectively, which were significantly lower than that of the control group(7.13). The contents of K+ were determinated which showed a clear upward trend with the extension of E-2- hexenal treatment time by atomic absorption spectrophotometer. The K+ concentration of the control group was 2.40mg/L at 120 min, the K+ concentration with MIC concentration treatment was 2.56mg/L, while under the MFC concentration of E-2- hexenal treatment, the measured concentration of K+ was 2.76mg/L. Compared with the control group, when the treatment time was 120 min, the lipid content reduced 26.9mg/g at MIC concentration, and at MFC concentration, which reduced by 43.8mg/g.(4) Effect of E-2- hexenal on the antibacterial activity against Penicillium cyclopium in tomato fruitsOnly undamaged and uniform size, shape tomato fruits were used as experimental material, which their varieties were "Zhongshu 5". to study the inhibitory effect of E-2- hexenal agaist Penicillium cyclopium. The infection rates of tomato fruits were counted after 5d infection. In general, the antibacterial effect of E-2- hexenal was more obvious with the inhibitory concentration increasing, 1280?l/L of E-2- hexenal significantly inhibited the incidence of tomato. The experiment results of the effect of E-2-hexenal on the quality of tomato were shown that TSS and TA content dropped slower compared with the control group with 320?l/L of E-2-hexenal during. TSS content difference varied greatly at 5d, after 9d storage, the content of TSS was 3.2% or 3.1%, respectively, which changed little. TA content of the control group tomatoesdecreased from the initial 0.517 to 0.382% during 9d storage, while the TA content decreased to 0.392% with 320?g/m L E-2-hexenal treatment(P <0.05). Soluble sugar content in the treatment group also increased slower, the experiment results were shown that the soluble sugar content was 4.01% with 320?l/L of E-2-hexenal treatment, while that of the control group was 4.25% after 9d storage.