• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Isolation and Identification of Pathogenic Microorganisms Causing Postharvest Spoilage in Hami Melons

    2021-03-31 02:01:30ZHAOXinxinNINGMingZHANGQinCAIWenchaoSHANChunhuiTANGFengxian
    食品科學 2021年6期

    ZHAO Xinxin, NING Ming, ZHANG Qin, CAI Wenchao, SHAN Chunhui, TANG Fengxian

    (Food College, Shihezi University, Shihezi 832003, China)

    Abstract: To investigate the relationship between microorganisms and postharvest spoilage of Hami melons, with traditional cultivation of microorganisms, we studied the dynamic changes of cultivatable microorganisms on Hami melons during storage at different temperatures. It was found that the main pathogenic bacteria causing postharvest spoilage of Hami melons were mycetes, including Fusarium, Alternaria, Penicillium, and Staphylococcus. The dominant pathogens causing spoilage in Hami melons during refrigerated transport and storage were Penicillium and Fusarium. This study indicated that postharvest spoilage in Hami melon was caused by single pathogenic bacteria and interactions among multiple pathogenic bacteria through a complicated mechanism. This study is conducive to a better understanding of the dynamics of microbial community during the storage of Hami melon fruit. Further study should be conducted to monitor characteristics of spoilagerelated species isolated from Hami melons so as to restrict the growth of pathogens and extend the shelf-life of Hami melons,which will provide theoretical foundation for improvements in the existing post-harvest preservation technology.

    Keywords: Hami melon; preservation; pathogenic bacteria; spoilage

    Hami melon (Cucumis melovar.saccharinus) is an elite cultivar of muskmelon that belongs to Cucurbitaceae. More than 100 varieties of Hami melon have been grown in China in the Turpan Basin and the Hami region of Eastern Xinjiang,Jiashi, Pishan, and Megeti of southern Xinjiang, as well as the five rivers and Altay in the northern frontier[1-2]. Hami melons are grown because they are an important economic crops, which are sold to the developed cities and regions in southeast China and exported to Asia, Europe and America[3].Hami melons are popular worldwide and are considered in China to be a national geographic product and the king of melons because of their sweet color, pleasant aroma, and crisp taste. However, the Hami melon is extremely vulnerable to infection and corruption by pathogenic microorganisms after harvest, which gives it a short storage period of around 60-70 days[1].

    The most recent research has shown that the corruption of Hami melons originated because of infection by pathogenic microorganisms, as well as the respiration of Hami melons.Various methods, including independent or combined treatment with chitosan[4-5], chlorine, chlorine dioxide[6-7],ethylene wax[8], natamycin[9], allyl isocyanate,Streptococcus lactis, hot water, X-ray, and benzothiazide[10]have been used to prolong the shelf life of Hami melons to inhibit or delay the growth of pathogenic microorganisms[11-12]. In addition,to reduce the rot rate of Hami melons, exogenous substance can also be used to reduce the melon’s respiratory rate during storage to delay the respiratory peak time[13-15]. Therefore,it is of great significance to isolate and identify the main pathogens of Hami melon after harvest and take effective measures to reduce the storage loss and to prolong the storage period of Hami melon after harvest.

    Many opportunistic and potentially pathogenic bacteria have been reported, includingStaphylococcusspp.,Clostridiumspp., and Enterobacteriaceae[16]. In particular,Salmonellaspp.,Escherichia coli, and isolates of theBacilluscereus-group have been found on the rinds of Hami melons. According to research reports, the main pathogenic microorganisms of Hami melon during postharvest storage areFusarium,Rhizopus,Cadophora,Aspergillus, andPenicillium. When Hami melon is infected byFusarium,white velveteen mycelium will emerge from the fissure,producing orange-red mucilage granules. The infection caused by variousFusariumspecies in the subdivision of Hemiptera isF. oxysporumf. sp.[17].Fusariumare widely found in air and soil. When conditions are suitable, the conidia produced can be reinfected from the mechanical wound of Hami melon. When being infected byRhizopus, the mechanical wound or fissure often has white to gray thick or sparse floss, and a little black mold appears on it, which is the fruiting body of pathogenic bacteria. Finally, water drips from the diseased part of Hami melon, which leads to rapid decay of Hami melon. Soft rot of Hami melon is caused by a variety ofRhizopusin the subgenusConjunctiva, the most important pathogen of which isR. stolonifer[18]. When Hami melon is in contact with the ground or has an injured part,Penicilliumfirst forms a dark yellow necrotic spot in the form of water stain[19], which is sunken downward. With the development of the disease, the diseased tissue gradually begins to soften and rot. The dense green mildew on the surface of the diseased spot usually only infects the over-ripe, mechanically injured or partially necrotic fruits. Of this list, the fungi belonging toFusariumandPenicilliumare most often observed. However,there has been no definitive evidence that corruption is an immediate result of a fungal infection, and the dominant pathogens and their pathogenicities remain unknown.

    The deterioration of a Hami melon is always accompanied by the growth of the Hami melon, which indicates that pathogenic microorganisms are likely the main cause of the deterioration of Hami melon. Since Hami melons are vulnerable to infection and corruption by pathogenic microorganisms, technologies to maintain the freshness of Hami melons have become one of the most important challenges to developing a Hami melon industry in China.Although it has been reported that multiple microorganisms contribute to the deterioration of Hami melons[6], there is little research on the dynamic change of microbial polymorphism during the preservation process of Hami melons. In this study, we aimed to investigate the variation of microbial diversity on the skin of Hami melons at different preservation temperatures, the dynamic changes of culturable microorganisms using traditional microbiological separation technology. This study provides a theoretical basis of the improvement in the postharvest preservation technology of Hami melons.

    1 Materials and Methods

    1.1 Materials and reagents

    1.1.1 Melon preserving

    Jiashi muskmelon, a representative Hami melon from Xinjiang, was collected from Shihezi and used as the sample in this study. The harvested Jiashi muskmelon with a degree of ripeness of eight, a uniform size, and with no pest diseases or mechanical damage. According to the normal preservative method, Hami melons were washed with running tap water to remove adhering soil prior to disinfection of the surface using 70% ethanol. Then, samples were placed at (3 ± 0.5) ℃ and(21 ± 0.5) ℃ in a cold storage warehouse and were removed at 60, 67, and 74 days. The infected fraction was eluted with sterile lint and sterile water and was collected on a sterile plate.

    1.1.2 Medium and reagent

    Peptone, beef extract, NaCl, natamycin, agar, glucose,KH2PO4, MgSO4, C20H2Cl4I4Na2O5, chloramphenicol was purchased from Sinopharm Group Chemical Reagent Co.Ltd.; dNTPs Mix, 5 ×TransStartTM, FastPfuBuffer and FastPfuFly DNA was purchased from Polymerase Bao bioengineering Dalian Co. Ltd..

    1.2 Instruments and equipment

    SW-CJ-10 clean bench was purchased from Suzhou Purification Co. Ltd.; XSS-2 electron microscope was purchased from Olympus (China) Co. Ltd.; DYY-6C electrophoresis apparatus was purchased from Beijing Liuyi Biotechnology Co. Ltd.; PHS-3EpH meter was purchased from Shanghai Yidian Analytical Instrument Co. Ltd.; A300 gradient polymerase chain reaction (PCR) instrument was purchased from Hangzhou Langji Scientific Instrument Co.Ltd.; GIS-630 gel imager was purchased from Hangzhou mio instrument Co. Ltd..

    1.3 Methods

    1.3.1 Isolation and purification of pathogens

    The pathogens were plated separately on nutrient agar(10.0 g/L peptone, 3.0 g/L beef extract, 5.0 g/L NaCl, 0.1 g/L natamycin, 15.0 g/L agar, final pH (7.3 ± 0.2)), then cultured for 1-2 d at 30 ℃, and Rose Bengal medium (5.0 g/L peptone, 10.0 g/L glucose, 1.0 g/L KH2PO4, 0.5 g/L MgSO4,0.03 g/L C20H2Cl4I4Na2O5, 0.1 g/L chloramphenicol, 20.0 g/L agar, final pH (7.2 ± 0.2)), and then cultured for 3-4 d at 28 ℃.Screening was performed by conventional culture techniques using the surface of the cantaloupe rot as a microorganism source. The culture was then streaked on an Agar plate and Rose Bengal agar plate and incubated at 28 ℃ to develop colonies for 1-2 d. The colonies that appeared were picked up independently and transferred to the medium, and the plate cultures were repeated twice. Once a pure culture was obtained, it was named according to the different conditions of the strain separation, and a total of 118 strains were obtained as pure cultures.

    1.3.2 Morphological observations

    Booth’s method was used to identify the morphological characteristics of the isolates[20]. The spore of each fungus was inoculated into Rose Bengal medium and cultured at 28 ℃ for 7 d, and the morphological characteristics of the colonies, microconidia, macroconidia, and sporulated cells were observed.

    The macroscopic colony morphological characteristics of the 13 isolates were observed on nutrient agar after being incubated for 7 d at 30 ℃, and morphological characteristics were assigned to each isolate using Berger’s Bacterial Identification Manual.

    1.3.3 Pathogenicity measurement

    Three Hami melons, each with a mass of approximately 3.5 kg, were divided into one group containing 3 parallels. A bacterial suspension enriched with filter paper was incubated overnight in a shaker and then applied to the surface of the melon, and sterile water was applied to the corresponding position of each melon in the group as a control. Then the melons were covered with plastic wrap and kept at room temperature ((21 ± 0.5) ℃) and cold storage ((3 ± 0.5) ℃).After inoculation for 0, 12, 24 and 36 h, 3 parallel samples were taken from the same set of points.

    1.3.4 Re-isolation of pathogens

    Pathogens were placed on PDA medium. Each Petri dish contained a single isolate of one pathogen. There were six replications for each isolate from each Hami melon,which were arranged in a completely randomized design.A non-inoculated dish was used as a control. The sporulated fungi from each Hami melon were examined after incubation at 25 ℃ for 7 d.

    1.3.5 DNA extraction

    After the isolates were cultured on a potato dextrose agar (PDA) medium for 7 d, the mycelia of each isolate were collected in 2.0 mL centrifuge tubes and ground using a disposable plastic rod to extract genomic DNA.

    Once the bacterial isolates were cultured in a nutrient agar liquid medium for 3 d, the bacterial suspension of each isolate was collected in a 2.0 mL centrifuge tube. After centrifugation, the bacterial cell pellet was collected, and genomic DNA was extracted. Finally, the extracted DNA samples were stored in a refrigerator at -20 ℃.

    DNA was extracted from each specimen according to the modified urea method[21], and the extracted bacterial and eumycete DNA were sequenced by Sangon Biotech Co. Ltd.(Shanghai, China).

    1.3.6 Molecular identification of pathogenic microorganisms

    Bacterial DNA was extracted from the pathogenic isolates for PCR to amplify the 16S rDNA gene using the universal primers 27F (5’-AGAGTTTGATCCTGGCTCAG-3’)and 1492R (5’-GGTTACCTTGTTACGAC TT-3’), and the universal primer for eumycete DNA for amplification PCR, ITS1 (5’-TCCGTAGGTGAACCTGCGG-3’) and ITS4 (5’-TCCTCCGCTTATTGATAT GC-3’). The PCR reaction volume was 25 μL, including 12.5 μL of 2×mix enzyme, 0.5 μL of primer, 1.5 μL of DNA template, and 10 μL of double-distilled water (ddH2O). The eumycete DNA PCR reaction procedure was performed as follows:pre-denaturation was performed at 94 ℃ for 3 min, followed by 35 cycles of denaturation at 95 ℃ for 30 s, annealing at 55 ℃ for 30 s, an extension at 72 ℃ for 30 s, and finally an extension at 72 ℃ for 6 min. The procedure for the bacterial DNA PCR reaction was as follows: pre-denaturation was performed at 95 ℃ for 5 min, followed by 35 cycles of denaturation at 94 ℃ for 45 s, annealing at 55 ℃ for 45 s, and extension at 72 ℃ for 1 min 30 s, and finally an extension at 72 ℃ for 5 min 30 s. The PCR products were separated and purified by performing gel electrophoresis with 1.0% agarose.Of the 107 isolates confirmed as non-repetitive, 69 were identified at the species level.

    1.3.7 Phylogenetic analysis

    MEGA 7.0.21 software was used during the phylogenetic analysis based on 16S rDNA or ITS sequences of the isolated strains. Homogeneous sequences of strains were obtained from the GeneBank database and were then analyzed on the NCBI standard nucleotide BLAST. Sequence analysis enabled the isolates to be identified at the species level based on their percentage identity. The pathogens were then identified based on their similarity to records in the GenBank database by using the online BLAST tool.Neighbor-Joining (NJ) methods of MEGA software were used to construct phylogenetic trees according to sequence construction methods. The bootstraps of all branches were tested in over 1 000 replicates, and the phylogenetic tree was classified by genus[22].

    1.4 Statistical analysis

    The incidences of spoilage were calculated as the mean of the replicates (n= 3). Differences between the 107 isolates within poilage were calculated using the statistical software package SPSS 13.0. Analysis of variance (ANOVA) with Duncan’s multiple range test and Dunnett’s tests method atP< 0.01 were performed. A general linear model was used to perform an interaction analysis of spoilage and isolates.

    2 Results and Analysis

    2.1 Isolation and selection of pathogenic microorganisms causing post-harvest spoilage in Hami melons

    A total of 118 isolates (74 fungi and 44 bacteria) were collected from 60 samples taken from the 121 Mission Farm in Shihezi, Xinjiang over period of 74 d. The results from the BLASTn alignment of the individual isolates identified 14 different genera, comprised of multifarious species within each genus. When comparing the internal transcribed spacer(ITS) rRNA sequences from isolates obtained in our research to the BLASTn, 45 isolates showed > 98% similarity.

    Pure cultures from diseased Hami melons were isolated on Rose Bengal medium and were numbered CCaDW.4,CCaDW.5, CCaDW.9, CCaDO.1, CDW.1, CDW.3, CUY, and CUG+B.3, respectively. Each culture had similar features, and after being cultured for 7 d, the colonies were 40 to 46 mm in diameter.Their hyphae were floccose, and white to pinkish at the back sides (Fig. 1). They produced many microeonidias which was round or oval, and a small number of macroconidia which were sickle-or spindle-shaped, with slightly curved terminal cells. Initially, these fungal isolates were considered to beFusariumspp., according to their morphological characteristics. They were labelled 3 ℃-CaUA.1, 3 ℃-U.2,3 ℃-CaDA.1, 3 ℃-CaDA.2, 3 ℃-CaDAQ, CCaDW.2,3 ℃-DG.2, CCaD.5, 3 ℃-CaD.4, CCaDO.2, 3 ℃-CaUA.2,3 ℃-DJ.2, 3 ℃-CaU.4, CaDAQ.6, and CCaDG. The colony colors varied from light to dark greenish gray, including grayish, pale, pale yellowish and olive green, whereas the colony textures varied from velvety to fasciculate, including weakly floccose. There was a considerable variation in their size, and some isolates exhibited a very thin margin,whereas others displayed a thick margin which comprised up to one third of the colony’s diameter. These fungal isolates were identified asPenicilliumspp., and theAspergilluswas morphologically identified based on the black or yellow colony. The isolates numbered 3 ℃-CaD.1, 3 ℃-CaU.5,3 ℃-DJ.1, and CUG+B were separated into two groups since the appearance of the colonies were slightly different from one another. Two isolates produced compact black colonies with a greyish central region and occasionally produced slightly yellowish colonies and a brighter reverse colony appearance, whereas two others grew hugely on the plate with uniform black to greyish black colonies. The surface of the colony was gray short-fleece aerial hyphae, which were raised in the center with a circle of immersed hyphae at the edge. The isolates numbered CCaDQ.1, CCaDQ.2, CCaDQ.5,CCaDQ.6, CCaDW.1, CCaDW.3, CCaDW.6, CCaDW.10,CCaDY, and CCaDA.1 were identified asCladosporiumspp..Meanwhile, the mycelium of the genusMucordeveloped and branched into a spider web and was white with a black sporangium. According to its morphological characteristics,the isolates numbered CCaDG.3, CCaD.1, CCaD.2, CCaD.8,CCaDW.11, 3 ℃-CaD.5, and CCaDW.5 were identified asMucorspp.. Additionally, according to the Berger’s Bacterial Identification Manual, the bacterial isolates were identified asStaphylococcusspp.,Enterococcusspp.,Stenotrophomouasspp.,Curtobacteriumspp.,Bacillusspp.,Exiquobacteriumspp.,Pantoeaspp.,Acinetobacterspp., andSteuotrophomonasspp. (Fig. 2).

    Fig. 1 Variations in fungal community composition at different stages of storage

    Fig. 2 Changes in the microbial communities of Hami melons during storage

    2.2 Molecular identification

    Phylogenetic analysis of the 16S rRNA sequence data resembled the BLASTn results, which formed 8 distinct clusters includingStaohylococcus,Enterococcus,Stenotrophomouas,Curtobacterium,Bacillus,Exiquobacterium,Pantoea,Acinetobacter,andSteuotrophomonas. Closely-related genera, such asPantoeaandEnterococcusspecies, were not easily differentiated within the 16S rRNA phylogenetic tree and were simply grouped together instead of being defined in groups. Of the 21 isolates sequenced, isolates appeared to belong to the genusStaohylococcus(13, 20, 23, 27, 112, 114, 115 and 119),Pantoea(10, 14 and 29),Curtobacterium(1 and 121),Bacillus(3 and 7),Enterococcus(15 and 24), while the additional four isolates were grouped in the known genus withAcinetobacter,Steuotrophomonas,ExiquobacteriumandStenotrophomouas. In addition, a search of sequences in the NCBI database revealed 3 isolates that were the most homologous toB. amyloliquefaciens(Fig. 3a), with a homology greater than 99%. Isolates 13, 20, 28, 29, 112, 114,115 and 119 were 100% homologous toS. succinus(Fig. 3b),Exiguobacterium indicum(Fig. 3c),P. dispersa(Fig. 3d).

    Fig. 3 Phylogenetic trees of strains 3 (a), 13-20-112-114-115-119 (b),28 (c) and 29 (d)

    Sequencing of the ITS rRNA region was also performed for 24Penicilliumisolates, 11Fusariumisolates, 4Asoergillusisolates, 4Cladospriumisolates, 2Mucorisolates,and 2Gibellulopsisisolates. The PCR amplified 18S rRNA genes from the isolated fungus were sequenced and analyzed using the BLAST program of the NCBI. The BLAST results showed that the 18S rRNA gene sequences of isolates exhibited 98% to 100% similarity to known sequences.

    Fig. 4 Phylogenetic trees of strain 52 (a), 61-71 (b),78-79-96-98 (c) and 105 (d)

    During phylogenetic analyses based on 18S rRNA gene sequences, twenty-four isolates showed a strong similarity toPenicillium; eleven isolates were similar toFusarium; four showed incredible similarity inCladosporium; four isolates were similar toAspergillus; two isolates were similar toMucor; and the additional two isolates were grouped with the known genus ofGibellulopsis. The 18S rRNA gene sequence from isolate 52 showed 99% sequence similarity withF. pseudoanthophilum(Fig. 4a), while isolates 61-71 showed 98% similarity withM. nanus(Fig. 4b), isolates 78-79, 98 showed 100% similarity withP. crustosum(Fig. 4c),and isolate 96 showed 100% similarity withP. polonicum(Fig. 4c), while isolate 105 showed >99.9% sequence identity toC. endophytica(Fig. 4d).

    2.3 Pathogenicity test results

    Fig. 5 Dominant microfloras during the pre-vaccination period

    Reverse inoculations were performed as a quick and reliable method to select pathogenic bacteria for additional screening of Hami melons.Penicillium,Mucor, andAspergilluswere the dominant flora present during the preinoculation period (Fig. 5). Replicated inoculations were similar across all experiments and are presented in Fig. 6.Penicillium,Mucor, andFusariumsubstantially reduced the quality of the Hami melon and putridity symptoms began to be displayed 3 d after inoculation, whereas the melon quality was not affected by the strainsGibellulopsisandCladosporium. After the Hami melons were inoculated,pathogenic bacteria were re-isolated from symptomatic tissue,which was consistent with previously-isolated pathogens, thus fulfilling Koch’s postulates. During the same experiment,the quality of Hami melons was reduced byPenicilliumtwo days after the initial inoculation. Melon quality was not seriously reduced by any other species and isolates tested when compared to the non-inoculated control. Three days after inoculation, isolates ofMucorandFusariumwere shown to reduce melon quality. At the same time, the Hami melon quality of plants inoculated withGibellulopsisandCladosporiumshowed no differences from the non-inoculated control. Reductions in Hami melon quality were observed as sunken areas on the melon surface and undermining.

    Fig. 6 Results of pathogenicity test

    3 Discussion

    According to the research reports of Ozbahce[23]and Suzuki et al.[24], Hami melon can be latently infected by pathogenic bacteria during the whole growth and development process, of which reticulate period is an important period of pathogenic bacteria infection. Gautam et al.[25]investigated the interactions betweenSalmonella entericaPoona, the melon pathogenic bacteriumErwinia tracheiphila, and cantaloupe fruit. The study was conducted by inoculating fruit surfaces with pathogenic bacteria during the natural cracking stage either independently or together, over a 2 cm × 2 cm area of rind that contained a crack. Liu Tao et al.[26]determined that the main pathogenic fungi causing postharvest decay of Hami melon in Xinjiang includeFusarium,Stachybotrys,PenicilliumandGibberella,which are consistent with the results of this study. Chen Cunkun et al.[27]have isolated the pathogenic bacteria with strong infectivity from the main Hami melon varieties in Xinjiang through research. The results show that the main pathogenic bacteria causing decay and deterioration of Hami melon during post-harvest storage includePenicillium,Cladosporium,Aspergillusand so on. Previous studies have demonstrated that the main spoilage microbial species on a variety of Hami melons wasPenicillium. In the present work,we observed thatPenicilliumdominated the microbiota after a storage period of 67 d. The rapid growth ofPenicilliumcould be due to a higher competitivity compared to other pathogenic bacteria under the current storage conditions(3 ℃). Either a strain or a microbial group was collectively responsible for melon spoilage, but not all species or strains are necessarily responsible for the spoilage. Generally,spoilage is attributed to the dominant microbiota, which are usually referred to as specific spoilage organisms (SSO)[28-29].Penicilliumwas frequently discovered to be the dominant reference species, and would likely be considered the SSOs,which was recognized since SSOs may be associated with the spoilage of Hami melons during storage. However, the putridity mechanisms and characteristics should be investigated further.Additionally, the multiformity showed thatCladosporiumsteadily increased after day 67, and significant changes alternately occurred in the predominant microbiota ofCladosporiumandPenicilliumon day 74, whenCladosporiumunderwent a dramatic increase and then became the dominant bacteria (21 ℃). Furthermore,Aspergilluswas isolated on the 60thday and then increased on day 67 and afterwards reached its stationary phase and then declined but still remained at a relatively high level. Previous studies have shown thatAspergillusis frequently isolated from a variety of foods and are frequently the predominant members of microbial communities found in foods[29]. Previous research has also shown thatAspergillusalso have been detected in melons, and although theAspergillusare frequently isolated from melons,they are rarely present in large numbers. The results presented in the current study agree with these results.Aspergillusis considered to possess extensive potential for melon spoilage and is important players in Hami melon storage. In addition to mold, Hami melon spoilage is often associated with bacteria such asStaohylococcus,Enterococcus,Stenotrophomouas,Curtobacterium[30],Bacillus[31],Exiquobacterium,Pantoea[32],andAcinetobacterandSteuotrophomonas. In the present study,Staohylococcuswas present in abundance at all points of storage, but it is not an important member of the microbial community that is typically associated with spoilage[33].

    Hami melon can be latently infected by pathogenic bacteria during the whole growth and development process,which eventually leads to the decay and deterioration of the harvested Hami melon and makes the Hami melon lose its nutritional quality and commercial value. Moreover, there has been a report that the microbial populations of molds and yeasts were significantly higher on the lower surface of the Hami melon that is in direct contact with the soil[34].This research has shown that an uneven distribution of microbial populations exists on the surfaces of field-grown Hami melons, which suggests that direct contact with soil is likely a major source of microbial melon contamination.Field production practices should be undertaken to minimize direct contact of Hami melon with the soil to ensure a safer product for the consumer, and more effective surface cleaning methods should also be explored.

    As early as the early 1960s, some scholars proposed that pathogenic bacteria could produce cell-wall degrading enzymes (cell-wall degrading enzymes, CWDE). Cellwall degrading enzymes play a very important role in the pathogenic process of plant pathogenic bacteria. Studies have found that the activities of various cell-wall degrading enzymes in some diseased plants infected by pathogenic bacteria are much higher than those in healthy tissues.During the development of the same disease, various cell wall degrading enzymes appear in different time modes and play different roles. Plant cell tissues primary wall and secondary wall contain more polysaccharides, which can be degraded by cell wall degrading enzymes produced by pathogenic bacteria. The pathogenic bacteria invade plant cells and spread in host tissues, which is the main cause of plant diseases. In the process of pathogenic bacteria infecting plant tissues, their pathogenic factors can sometimes act on plant tissues alone, and sometimes require synergistic effects among various mechanisms. Isoenzymes are the enzymes that first interact with each other, and the isoenzymes of pectate lyase have mutually reinforcing effects. Pectin esterase and galactopyraldehyde have synergistic effects,and the two enzymes produced by pathogenic bacteria also have synergistic effects. Pathogenic bacteria can secrete many different kinds of cell wall degrading enzymes in the process of invading plant tissues. The cell wall components of plants are components of plant tissues, which are the main barriers to prevent pathogenic bacteria from invading host tissues. The cell wall components of the cell wall degrading enzyme can destroy host plants. A series of experimental results have shown that the cell wall degrading enzymes have a very significant pathogenic effect on plant tissues.Cell wall degrading enzymes play a very important role in the pathogenic process of plants. Cell wall degrading enzymes secreted by plant pathogenic fungi can cause plant tissue infection and damage. The cell wall degrading enzyme produced by plant pathogenic fungi in the process of infecting plant tissues will lead to the destruction of plant tissues. The destruction mechanism to host tissues has been discovered, which makes the important role of cell wall degrading enzyme in the pathogenic process of pathogenic bacteria to plant tissues proved by some domestic researchers through the use of electron microscope technology. However,for a specific disease, the specific mechanism of action on plant tissues during its onset is not very clear. As far as a particular plant disease is concerned, its mechanism of action in the specific pathogenesis of plant tissue is not particularly clear. Exploring the interaction between pathogenic bacteria and plant tissues and studying the pathogenic mechanism of pathogenic factors of pathogenic bacteria have always been an important part of researchers’ efforts. Up to now, although there have been reports on pathogenic bacteria causing other fruits or plants to rot, there are relatively few reports on the specific pathogenesis of cantaloupe rot. With the continuous progress and development of social science and technology,the specific action mechanism of cell wall degrading enzyme should be clear, which not only lays the foundation for studying the molecular mechanism of pathogenic bacteria,but also has great significance for establishing new disease control measures.

    4 Conclusion

    In this study, 74 strains of fungi, which belong toFusarium,Penicillium,CladosporiumandMucor, were preliminarily identified by isolating and purifying pathogenic microorganisms causing the deterioration of Hami melon epidermis during postharvest storage, combining with disease characteristics and microscopic observation. Additionally,according to the Berger’s Bacterial Identification Manual,the bacterial isolates were identified asStaphylococcus,Enterococcus,Stenotrophomouas,Curtobacterium,Bacillus,Exiquobacterium,Pantoea,Acinetobacter, andSteuotrophomonas. In the reverse inoculation verification experiment,Penicillium,Mucor, andFusariumsubstantially reduced the quality of the Hami melon and putridity symptoms began to be displayed 3 d after inoculation,whereas the melon quality was not affected by theGibellulopsisandCladosporiumstrains.

    最近最新中文字幕大全免费视频| 1024香蕉在线观看| www日本在线高清视频| 后天国语完整版免费观看| 久久精品综合一区二区三区| 日韩欧美一区二区三区在线观看| 国产私拍福利视频在线观看| 女人高潮潮喷娇喘18禁视频| 久久久久免费精品人妻一区二区| 精品久久久久久成人av| 最近在线观看免费完整版| 香蕉丝袜av| 亚洲av美国av| 免费看a级黄色片| 夜夜看夜夜爽夜夜摸| 男男h啪啪无遮挡| 国产成人啪精品午夜网站| 国产av又大| 亚洲av第一区精品v没综合| 国产精品一及| 国产精品久久久久久亚洲av鲁大| 亚洲欧美日韩东京热| 91大片在线观看| 精品熟女少妇八av免费久了| 51午夜福利影视在线观看| 国产成年人精品一区二区| 啦啦啦免费观看视频1| 国产一级毛片七仙女欲春2| 欧美日韩国产亚洲二区| 精品久久久久久久久久久久久| 午夜激情福利司机影院| 免费搜索国产男女视频| 一夜夜www| 我要搜黄色片| 日本 av在线| 男女午夜视频在线观看| 国产精品99久久99久久久不卡| 成人欧美大片| 国产精品永久免费网站| 国内精品久久久久久久电影| 中国美女看黄片| 天天添夜夜摸| 深夜精品福利| 一级a爱片免费观看的视频| 12—13女人毛片做爰片一| 麻豆成人av在线观看| 精品高清国产在线一区| 婷婷丁香在线五月| 热99re8久久精品国产| 日本 欧美在线| 麻豆国产97在线/欧美 | 国产精品久久久久久久电影 | 波多野结衣高清作品| 国产在线观看jvid| 欧美又色又爽又黄视频| 久久婷婷成人综合色麻豆| 国产亚洲精品久久久久久毛片| 久久精品91蜜桃| 成人高潮视频无遮挡免费网站| 777久久人妻少妇嫩草av网站| 窝窝影院91人妻| www.熟女人妻精品国产| 国产v大片淫在线免费观看| 欧美人与性动交α欧美精品济南到| 久久亚洲真实| 亚洲九九香蕉| 长腿黑丝高跟| 国产欧美日韩精品亚洲av| 亚洲片人在线观看| 午夜影院日韩av| 一进一出抽搐gif免费好疼| 亚洲av五月六月丁香网| 精品不卡国产一区二区三区| 小说图片视频综合网站| 999精品在线视频| 亚洲专区国产一区二区| 亚洲最大成人中文| 超碰成人久久| 成人18禁高潮啪啪吃奶动态图| 欧美一级a爱片免费观看看 | 在线观看一区二区三区| 亚洲美女黄片视频| 日韩成人在线观看一区二区三区| 日韩精品青青久久久久久| 成人av一区二区三区在线看| 国产视频一区二区在线看| 国产1区2区3区精品| 淫妇啪啪啪对白视频| 99热这里只有是精品50| 国产日本99.免费观看| 黄色片一级片一级黄色片| 亚洲人成电影免费在线| 国产成人影院久久av| 一夜夜www| 性色av乱码一区二区三区2| 在线观看美女被高潮喷水网站 | 999精品在线视频| 午夜激情av网站| 欧美性长视频在线观看| 成人欧美大片| 亚洲在线自拍视频| svipshipincom国产片| 老司机午夜福利在线观看视频| 国产69精品久久久久777片 | 精品久久久久久久末码| 国产精品爽爽va在线观看网站| av有码第一页| 亚洲男人天堂网一区| 黄片小视频在线播放| 亚洲精品美女久久久久99蜜臀| 91麻豆精品激情在线观看国产| 亚洲片人在线观看| 久久天堂一区二区三区四区| 国产亚洲欧美在线一区二区| 欧美黄色片欧美黄色片| 精品乱码久久久久久99久播| 男女做爰动态图高潮gif福利片| 一区福利在线观看| 亚洲国产看品久久| 久久久国产欧美日韩av| 99久久精品热视频| 国产精品免费一区二区三区在线| avwww免费| 中文字幕人成人乱码亚洲影| 每晚都被弄得嗷嗷叫到高潮| av中文乱码字幕在线| 少妇人妻一区二区三区视频| 巨乳人妻的诱惑在线观看| 久久精品aⅴ一区二区三区四区| 91麻豆精品激情在线观看国产| 亚洲熟妇熟女久久| 久久人妻福利社区极品人妻图片| 在线观看美女被高潮喷水网站 | 美女午夜性视频免费| 啦啦啦免费观看视频1| 国产av在哪里看| 欧美日韩瑟瑟在线播放| 欧美日本视频| 岛国在线观看网站| 午夜福利高清视频| 在线观看www视频免费| 成年版毛片免费区| av免费在线观看网站| 一级黄色大片毛片| 小说图片视频综合网站| 国内精品一区二区在线观看| 在线十欧美十亚洲十日本专区| 香蕉久久夜色| 中文字幕高清在线视频| 午夜精品一区二区三区免费看| 日韩欧美国产在线观看| 国产成人av激情在线播放| 黄色a级毛片大全视频| 日日爽夜夜爽网站| 精品久久久久久久人妻蜜臀av| 亚洲一区二区三区不卡视频| 国产精品1区2区在线观看.| 麻豆成人av在线观看| 国产精品1区2区在线观看.| 日本黄色视频三级网站网址| 欧美日韩黄片免| 夜夜看夜夜爽夜夜摸| 校园春色视频在线观看| x7x7x7水蜜桃| 国产成人啪精品午夜网站| 国产片内射在线| 亚洲一区二区三区不卡视频| 欧美日本视频| 亚洲 欧美 日韩 在线 免费| 国产一级毛片七仙女欲春2| 身体一侧抽搐| 国产精品久久久av美女十八| 在线永久观看黄色视频| 搡老岳熟女国产| 国产精品香港三级国产av潘金莲| 国产精品av视频在线免费观看| 国产精品免费一区二区三区在线| 国产成年人精品一区二区| 99精品欧美一区二区三区四区| 麻豆国产97在线/欧美 | 国产一区二区三区在线臀色熟女| 叶爱在线成人免费视频播放| 国产成人精品无人区| 在线观看午夜福利视频| 在线观看日韩欧美| 操出白浆在线播放| 国产69精品久久久久777片 | 中文资源天堂在线| 丁香六月欧美| 亚洲专区国产一区二区| 黑人巨大精品欧美一区二区mp4| av中文乱码字幕在线| 亚洲av日韩精品久久久久久密| 欧美xxxx性猛交bbbb| 欧美最黄视频在线播放免费| 国产黄片美女视频| 久久亚洲精品不卡| 一级毛片我不卡| 亚洲图色成人| 在线a可以看的网站| www.色视频.com| 一级毛片久久久久久久久女| 日本撒尿小便嘘嘘汇集6| 日本一本二区三区精品| 久久久久国产网址| 村上凉子中文字幕在线| 精品久久国产蜜桃| 亚洲国产精品成人综合色| 欧美色视频一区免费| 蜜桃亚洲精品一区二区三区| 国产亚洲av片在线观看秒播厂 | 亚洲av二区三区四区| 18禁黄网站禁片免费观看直播| 嫩草影院精品99| 午夜激情福利司机影院| 一级毛片aaaaaa免费看小| 欧美日韩一区二区视频在线观看视频在线 | 久久久国产成人免费| 国产成人a区在线观看| 两个人的视频大全免费| 黑人高潮一二区| 午夜老司机福利剧场| 麻豆精品久久久久久蜜桃| 国产成人一区二区在线| 亚洲中文字幕日韩| 草草在线视频免费看| 国产黄色小视频在线观看| 性插视频无遮挡在线免费观看| 午夜精品在线福利| 晚上一个人看的免费电影| 成人美女网站在线观看视频| 国产探花在线观看一区二区| 熟妇人妻久久中文字幕3abv| 麻豆久久精品国产亚洲av| 久久99热这里只有精品18| 免费电影在线观看免费观看| 校园人妻丝袜中文字幕| 成人性生交大片免费视频hd| 久久午夜福利片| 一本久久中文字幕| 欧美色欧美亚洲另类二区| 中文在线观看免费www的网站| 亚洲图色成人| 国产av麻豆久久久久久久| 人人妻人人澡人人爽人人夜夜 | 一区福利在线观看| 床上黄色一级片| 免费人成视频x8x8入口观看| 简卡轻食公司| 欧洲精品卡2卡3卡4卡5卡区| 亚洲在线观看片| 国产精品一区二区三区四区免费观看| 亚洲第一区二区三区不卡| 人人妻人人澡欧美一区二区| 丰满人妻一区二区三区视频av| 国产精品爽爽va在线观看网站| 欧美成人一区二区免费高清观看| 久久人人爽人人片av| 尤物成人国产欧美一区二区三区| 欧美高清成人免费视频www| 99久久九九国产精品国产免费| 悠悠久久av| 久久这里只有精品中国| 午夜福利在线观看吧| 亚洲无线观看免费| 寂寞人妻少妇视频99o| 一区二区三区高清视频在线| 亚洲美女视频黄频| 波多野结衣高清作品| 欧美xxxx黑人xx丫x性爽| 性欧美人与动物交配| 最近最新中文字幕大全电影3| av福利片在线观看| 日韩中字成人| 国产一区二区三区在线臀色熟女| 日本欧美国产在线视频| 国产91av在线免费观看| 免费av观看视频| 1000部很黄的大片| 精品一区二区免费观看| 少妇裸体淫交视频免费看高清| 99久国产av精品国产电影| 中文字幕制服av| 日日摸夜夜添夜夜添av毛片| 我的老师免费观看完整版| 国产高清激情床上av| 久久综合国产亚洲精品| 欧美色欧美亚洲另类二区| 精品久久久噜噜| 又粗又爽又猛毛片免费看| 九九热线精品视视频播放| 99在线视频只有这里精品首页| 成人综合一区亚洲| 大型黄色视频在线免费观看| 国产亚洲91精品色在线| 成人性生交大片免费视频hd| 可以在线观看毛片的网站| 日韩av不卡免费在线播放| 99久久精品热视频| 天天躁日日操中文字幕| 亚洲av成人精品一区久久| 1000部很黄的大片| 日本爱情动作片www.在线观看| 精品久久久久久久久久久久久| 国产精品.久久久| 日本熟妇午夜| 看非洲黑人一级黄片| 91久久精品国产一区二区成人| 精品久久久久久久久久久久久| 三级经典国产精品| 国产一区二区三区av在线 | 成人午夜高清在线视频| 成人毛片60女人毛片免费| 69人妻影院| 美女cb高潮喷水在线观看| 国产精品久久久久久久久免| kizo精华| 国产高潮美女av| 欧美日韩精品成人综合77777| 国产精品一及| 国产av不卡久久| 成人午夜高清在线视频| 中文字幕精品亚洲无线码一区| 国产精品麻豆人妻色哟哟久久 | 午夜福利在线在线| 色吧在线观看| 免费大片18禁| 国产人妻一区二区三区在| 亚洲精品乱码久久久v下载方式| 久久久久久久久中文| 成人亚洲欧美一区二区av| 国产精品无大码| 亚洲av一区综合| 能在线免费看毛片的网站| 99热全是精品| 亚洲在线观看片| 国内精品一区二区在线观看| 久久久午夜欧美精品| 亚洲内射少妇av| 久久午夜亚洲精品久久| 国产av一区在线观看免费| 久久久久国产网址| 91午夜精品亚洲一区二区三区| 色综合亚洲欧美另类图片| 欧美激情在线99| 久久精品夜色国产| 丝袜喷水一区| av.在线天堂| 色吧在线观看| 丝袜美腿在线中文| 久久久久性生活片| 一级毛片aaaaaa免费看小| 亚洲第一区二区三区不卡| 一区福利在线观看| 欧美zozozo另类| 国产精品久久久久久久久免| 亚洲欧美成人精品一区二区| 成人毛片a级毛片在线播放| 亚洲精品影视一区二区三区av| 国产精品久久久久久久久免| h日本视频在线播放| 日韩三级伦理在线观看| 精品人妻熟女av久视频| 黄色一级大片看看| 亚洲精品色激情综合| 亚洲成人久久爱视频| 亚洲性久久影院| 久久婷婷人人爽人人干人人爱| 午夜老司机福利剧场| 中文字幕久久专区| 亚洲成人精品中文字幕电影| 女人十人毛片免费观看3o分钟| 久久草成人影院| 欧美人与善性xxx| 国产精品无大码| 日本免费a在线| 婷婷色av中文字幕| 日韩成人伦理影院| 亚洲自拍偷在线| 天美传媒精品一区二区| 成人鲁丝片一二三区免费| 久久久久免费精品人妻一区二区| 午夜福利在线在线| a级毛片a级免费在线| 日韩 亚洲 欧美在线| 美女被艹到高潮喷水动态| 1000部很黄的大片| 久久人人爽人人爽人人片va| 99久久精品国产国产毛片| 观看免费一级毛片| 成人毛片a级毛片在线播放| 亚洲精品粉嫩美女一区| 久久国内精品自在自线图片| 精品久久久久久久人妻蜜臀av| 男女下面进入的视频免费午夜| 亚洲精品久久国产高清桃花| 成人午夜精彩视频在线观看| 国产午夜精品久久久久久一区二区三区| 听说在线观看完整版免费高清| 非洲黑人性xxxx精品又粗又长| 午夜视频国产福利| 日韩精品青青久久久久久| 美女xxoo啪啪120秒动态图| 麻豆精品久久久久久蜜桃| 久久久久免费精品人妻一区二区| 亚洲真实伦在线观看| 激情 狠狠 欧美| 中出人妻视频一区二区| 看免费成人av毛片| 少妇丰满av| 日韩高清综合在线| 人人妻人人看人人澡| 国产精品无大码| 日韩成人av中文字幕在线观看| 夜夜夜夜夜久久久久| 成人永久免费在线观看视频| 久久国产乱子免费精品| av在线播放精品| 国产乱人偷精品视频| 国产精品久久久久久久电影| 九九热线精品视视频播放| 精品无人区乱码1区二区| 国产精品1区2区在线观看.| 欧美性猛交╳xxx乱大交人| 中文字幕人妻熟人妻熟丝袜美| 日本免费一区二区三区高清不卡| 美女xxoo啪啪120秒动态图| 蜜桃亚洲精品一区二区三区| 久久久久国产网址| 日韩欧美一区二区三区在线观看| 男人的好看免费观看在线视频| 亚洲三级黄色毛片| 国产精品久久久久久亚洲av鲁大| 嫩草影院新地址| 99久国产av精品| 网址你懂的国产日韩在线| 亚洲av男天堂| 亚洲国产色片| 天天一区二区日本电影三级| 久久久久久伊人网av| 亚洲av免费高清在线观看| 国产在线男女| 免费看a级黄色片| 精品久久久久久久久av| 久久精品夜色国产| 国产精品99久久久久久久久| 久久久久久久久大av| 久久精品夜色国产| 中国美白少妇内射xxxbb| 村上凉子中文字幕在线| 六月丁香七月| 欧美潮喷喷水| 神马国产精品三级电影在线观看| 又粗又硬又长又爽又黄的视频 | 久久久色成人| kizo精华| 久久精品国产自在天天线| 成人性生交大片免费视频hd| 亚洲精华国产精华液的使用体验 | 午夜精品在线福利| 国产伦一二天堂av在线观看| 中文字幕久久专区| 网址你懂的国产日韩在线| 国产一区亚洲一区在线观看| 成人二区视频| 亚洲中文字幕日韩| 亚洲欧洲日产国产| 国产v大片淫在线免费观看| av福利片在线观看| 床上黄色一级片| 女人被狂操c到高潮| 国产精品久久久久久久电影| 国产视频首页在线观看| 久久人妻av系列| 在线观看一区二区三区| 麻豆国产av国片精品| 白带黄色成豆腐渣| 亚洲精品粉嫩美女一区| 欧美成人免费av一区二区三区| 身体一侧抽搐| 日日干狠狠操夜夜爽| 日韩大尺度精品在线看网址| 久久亚洲精品不卡| 蜜桃久久精品国产亚洲av| 伦理电影大哥的女人| 床上黄色一级片| 老司机福利观看| av在线蜜桃| 亚洲av第一区精品v没综合| 久久人妻av系列| 只有这里有精品99| 国产亚洲av嫩草精品影院| 亚洲色图av天堂| 国国产精品蜜臀av免费| 国产色爽女视频免费观看| av免费观看日本| 国产人妻一区二区三区在| 波野结衣二区三区在线| 精品免费久久久久久久清纯| 啦啦啦观看免费观看视频高清| 亚洲美女视频黄频| 日本撒尿小便嘘嘘汇集6| 成人特级黄色片久久久久久久| 日韩成人av中文字幕在线观看| 国产精品麻豆人妻色哟哟久久 | 在线观看美女被高潮喷水网站| 亚洲图色成人| 国产午夜精品久久久久久一区二区三区| 禁无遮挡网站| 看免费成人av毛片| 听说在线观看完整版免费高清| 成人综合一区亚洲| 国产伦精品一区二区三区视频9| 少妇人妻精品综合一区二区 | av国产免费在线观看| 可以在线观看的亚洲视频| 国产精品1区2区在线观看.| 国产一区二区激情短视频| 尤物成人国产欧美一区二区三区| 国产精品久久久久久亚洲av鲁大| 欧美性猛交╳xxx乱大交人| 亚洲精品乱码久久久v下载方式| 午夜福利高清视频| 久久久久久大精品| 中文字幕制服av| 欧美又色又爽又黄视频| 男人和女人高潮做爰伦理| 欧美最新免费一区二区三区| 免费看美女性在线毛片视频| a级一级毛片免费在线观看| 国产一区亚洲一区在线观看| 欧美另类亚洲清纯唯美| 亚洲精品乱码久久久久久按摩| 一级毛片我不卡| 一个人看视频在线观看www免费| 久久人人爽人人爽人人片va| 九九爱精品视频在线观看| 国产午夜精品久久久久久一区二区三区| 成人av在线播放网站| 国产亚洲精品久久久久久毛片| 91久久精品国产一区二区成人| 久久久久久久久久成人| 久久久久久久午夜电影| 国产成人精品一,二区 | 简卡轻食公司| av.在线天堂| 亚洲高清免费不卡视频| 国产成人freesex在线| 国产一区二区激情短视频| 国产亚洲av片在线观看秒播厂 | 青春草亚洲视频在线观看| 午夜精品一区二区三区免费看| 一区福利在线观看| 性欧美人与动物交配| 91午夜精品亚洲一区二区三区| 免费观看的影片在线观看| 在线a可以看的网站| 男插女下体视频免费在线播放| av.在线天堂| 久久久久网色| 国产乱人视频| 简卡轻食公司| 色哟哟哟哟哟哟| 春色校园在线视频观看| 夫妻性生交免费视频一级片| 成人午夜高清在线视频| 特级一级黄色大片| 国产精品日韩av在线免费观看| 观看免费一级毛片| 日韩欧美一区二区三区在线观看| 午夜福利成人在线免费观看| 成人三级黄色视频| 亚洲一区高清亚洲精品| 国产精品无大码| 如何舔出高潮| 欧美日韩精品成人综合77777| 特大巨黑吊av在线直播| 26uuu在线亚洲综合色| 亚洲欧美精品综合久久99| 国产 一区精品| 欧美丝袜亚洲另类| 12—13女人毛片做爰片一| 亚洲四区av| 久久精品91蜜桃| 在线观看午夜福利视频| 人人妻人人澡人人爽人人夜夜 | 一本一本综合久久| 欧美日韩一区二区视频在线观看视频在线 | 国产v大片淫在线免费观看| eeuss影院久久| 久久人妻av系列| 久久久精品94久久精品| 91狼人影院| 免费看美女性在线毛片视频| 国产精品99久久久久久久久| 日韩成人av中文字幕在线观看| 不卡视频在线观看欧美| a级毛片免费高清观看在线播放| 不卡视频在线观看欧美| 能在线免费看毛片的网站| 亚洲欧美精品自产自拍| 在线免费观看不下载黄p国产| 亚洲精品日韩av片在线观看| 天堂影院成人在线观看| 国产成人福利小说| 免费av观看视频| 女人十人毛片免费观看3o分钟| 中文亚洲av片在线观看爽| 精品一区二区三区视频在线| 亚洲一区二区三区色噜噜| 在线免费十八禁| 日日啪夜夜撸| 日韩一区二区三区影片| 成人三级黄色视频| 一本精品99久久精品77|