Acta Agriculturae Zhejiangensis

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2022, 34(7): 0-0.

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Analysis into amino acids and theanine contents of 115 tea germplasms and special germplasm resource screening in Guizhou, China

YANG Chun, QIAO Dahe, GUO Yan, LIANG Sihui, LIN Kaiqin, CHEN Zhengwu

2022, 34(7): 1351-1360. DOI: 10.3969/j.issn.1004-1524.2022.07.01

Abstract ( 444 )

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In order to screen special tea germplasms with high contents of amino acids and theanine, and to ascertain the characteristics of amino acids and theanine in tea germplasms in Guizhou, the total amino acids content and theanine content of one bud and two leaves from spring shoots of 115 tea germplasms were determined by spectrophotometer and high performance liquid chromatography, respectively. It was shown that the contents of total amino acids ranged from 0.95% to 7.96%, with an average of 3.40%, the content of theanine ranged from 0 to 3.80%, with an average of 1.58%, and the theanine proportion ranged from 0 to 67.66%, and the majority was 40%-<60%. In the 115 tea germplasms, 11 were identified as special germplasms with high amino acids content (≥5%), and 3 were identified as special germplasms with high theanine content (≥3%). The contents of total amino acids and theanine varied in tea germplasms collected from different sources. The tea germplasms from Guiding, Liping and Shiqian showed relatively higher contents of total amino acids and theanine, while the contents of total amino acids and theanine in the tea germplasms from Sandu and Pu’an were significantly (P<0.05) lower than the others. Camellia costata collected from Sandu showed primitive biochemical characters without detection of theanine. By cluster analysis, the 115 tea germplasms could be divided into five categories. Among these categories, Shitai14 was separated individually due to its high contents of total amino acids and theanine.

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Analysis of GhSuSy expression by particle bombardment during initiation of cotton fibers

LYU Shufang, ZHANG Hongxiao, XU Huawei, ZHAO Xingli

2022, 34(7): 1361-1368. DOI: 10.3969/j.issn.1004-1524.2022.07.02

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Sucrose synthase mediated the initiation and development of cotton fiber through regulating plant sugar metabolism. In order to further research the transcription mechanism of sucrose synthase in the process of the cotton fiber initial, the 2 000 bp promoter fragment of GhSuSy gene upstream was cloned and recombinant vector with luciferase (LUC) fluorescent reporter gene was constructed. The recombinant vector DNA were transformed into cotton leaves and petals by particle bombardment, respectively, and LUC activity were compared and analyzed under different pressure, different bombarding distance and incubation time.LUC activity in leaves and petals were determined at the initial differentiation stage of cotton fibers and were compared with GhSuSy expression and sucrose synthase activity. The results showed that the conversion efficiency was the highest under vacuum degree of -0.09 MPa, the pressure was set as 6.80 MPa, the distance of carrier film from the blade was 7 cm after two times of bombardment, LUC fluorescence was the strongest after the transformed samples were incubated for 16 h. Compared with LUC in leaf, LUC fluorescence in petal were stronger and activity were higher, especially at 0 and 1 DPA(days post anthesis).From 3 days before flowering (-3 DPA) to 3 days after flowering (3 DPA), the LUC activity in leaves and petals increased first and then decreased, and the LUC activity reached the highest at 0 and 1 DPA, which were consistent with the quantitative analysis of GhSuSy and sucrose synthase activity in leaves, petals and ovules. These results suggested that GhSuSy gene or the sucrose synthase significantly regulated the initiation and differentiation of cotton fibers at 0 and 1 DPA, and showed that gene gun-mediated transient transformation system could be used to analyze the transcriptional regulation of GhSuSy gene promoters.

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Effects of picking flower buds on yield and quality of tea in spring

ZOU Zhenhao, SUN Yeliang, ZHAO Yubao, LI Xin, ZHANG Liping, ZHANG Lan, DONG Chunwang, FU Jianyu, HAN Wenyan, YAN Peng

2022, 34(7): 1369-1376. DOI: 10.3969/j.issn.1004-1524.2022.07.03

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Tea plant is a foliar economic crop mainly harvested for leaves.In production, the vigorous reproductive growth of tea trees will consume a lot of nutrients, affecting the yield and quality of tea. Comparing the effects of branches with and without flower buds and picking flower buds on the yield and quality of spring tea, can provide theoretical basis and guidance for tea garden management.Zhongcha 108 was used as material. The experiment included three treatments: T1 with flower buds and kept, T2 with flower buds and picked up in November 2020, and T3 without flower buds. Each treatment had 100 tea branches with 3 repetitions..In the spring tea period of 2021, samples were taken on 15^th, 18^th, 22^th and 25^th of March, and the yield and quality of tea were analyzed.The results showed that flowering could significantly reduce the yield of tea. Compared with T1, yield of T3 treatment on 15^th, 18^th and 22^th of March increased by 114.3%, 55.1% and 76.5%, respectively.Compared with T1, the number of fresh leaf sprouts increased by 100%, 55%, 31.6%, and 9.9% in each period of T3 treatment, respectively. T2 significantly increased the number of buds for each time. Significant differences on the 100 buds weight of tea were observed on 15^th of March. The 100 buds weight of T1 treatment was the lowest, and the 100 buds weight of T3 treatment was the highest, which was 3.1 g. It was found that the contents of amino acids and tea polyphenols in fresh leaves under T3 without flower buds were significantly higher than those of T1. After removing flower buds, the contents of amino acids and tea polyphenols in fresh leaves of T2 increased in varying degrees compared with T1. P and K content of fresh leaves were different among treatments. On 22^th of March, P content of T1 was lowest with 5.0 mg g^-1, T2 and T3 were both 5.7 mg·g^-1. On 25^th of March, K content of T1, T2 and T3 were 17.0, 19.8 and 20.9 mg·g^-1. In conclusion,the flowering of tea plants caused a decrease in the yield of spring tea, especially in the earlier period.At the same time, it would also reduce the contents of amino acids and tea polyphenols in tea quality components, which would affect the quality of tea leaves. In the early stage of flower bud growth, picking flower buds could effectively improve the yield and quality of spring tea. Therefore, in actual production, it was necessary to explore measures such as reasonable pruning and picking, chemical flower removal, reasonable dense planting and shading to reduce the flowering of tea trees, thereby improving the yield and quality of spring tea.

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Analysis of microbial community difference between sand and rubber bedding in dairy farm by high throughput sequencing technology

LYU Qian, LUO Qiao, LUO Xue, CHEN Jiubing, MA Li, LUO Zhengzhong, YAO Xueping, YU Shumin, SHEN Liuhong, CAO Suizhong

2022, 34(7): 1377-1385. DOI: 10.3969/j.issn.1004-1524.2022.07.04

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In order to explore the characteristics and differences of the microbial flora of the sand bedding and rubber bedding of dairy farms, 6 samples of sand bedding and rubber bedding were collected from two dairy farms in Sichuan Province,and the sequencing and bioinformatics of 16S rRNA gene in V4 area was analyzed by high-throughput sequencing technology. The results showed that a total of 1 443 818 clean reads were obtained from the 12 samples of the bedding material of the two dairy farms. The effective sequences with a similarity of 97% were subjected to operational taxonomic units (OTUs), and a total 2 311 OTUs were produced. At the level of genus classification, the dominant bacteria in the sand bedding were Acinetobacter, Marinobacter, Riemerella, Corynebacterium, Arthrobacter. The dominant bacteria in the rubber bedding were Corynebacterium, Luteimonas, Fusobacterium,Halomonas, and Vibrio. The relative abundance of Acinetobacter and Riemerella in the sand bedding samples was significantly higher than that of the rubber bedding samples (P<0.05), but the relative abundance of Fusobacterium in the rubber bedding samples was significantly higher than that of the sand bedding sample (P<0.05). Chao index, Ace index, Shannon index and Simpson index were not significantly different between the two groups (P>0.05). The results indicated that difference of the microbial flora between sand bedding samples was greater than the rubber bedding samples, whether it was sand or rubber bedding, there were pathogenic bacteria in environmental conditions.

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Treatment of diseased broilers with Shigella bacteriophage ΦDS8 and the effect on their intestinal flora

CHEN Shiyu, XU Meiyu, DENG Zhengyu, WANG Feng, ZHANG Qilin, DENG Xianyu, LIN Lianbing

2022, 34(7): 1386-1395. DOI: 10.3969/j.issn.1004-1524.2022.07.05

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Shigella is a common enteric pathogenic bacterium, and the bacterial disease it causes is one of the zoonotic diseases that endanger public health safety. With the misuse of antibiotics, the problem of Shigella resistance is difficult to control and new approaches are urgently needed to solve it. The use of bacteriophages to kill drug-resistant bacteria has received increasing attention. In this study, the Shigella infection model of broiler chickens was established. The broiler chickens were treated with phage fluid 2 h before and after infection. The broilers fed with Shigella for 2 h all had diarrhea, with the highest Shigella content in feces of 1×10⁷ CFU·g^-1, a large decrease in the content of dominant flora and a rise in the proportion of harmful flora. After phage therapy, the fecal phage content of broilers increased, Shigella content decreased, the fecal traits and intestinal flora returned to the normal, and the broiler survival rate was 100%. The survival rate of broiler chickens without phage treatment was 60%, and anatomical observation revealed obvious organ lesions. Bacteriophage ΦDS8 has shown promising efficacy in the treatment of Shigella strain infection, and it has good application value and prospect as an alternative product to antibiotics.

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Effect of interaction between translocation-associated membrane protein 1 and σNS protein on replication of duck reovirus

LIU Zhiyi, MI Xiaoyun, HUANG Cong, LI Chuanfeng, CHEN Zongyan

2022, 34(7): 1396-1401. DOI: 10.3969/j.issn.1004-1524.2022.07.06

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Translocation-associated membrane protein 1 (TRAM1) is a host protein which is associated membrane protein 1, found within the endoplasmic reticulum (ER). Studies have shown that TRAM1 can relieve the pressure of endoplasmic reticulum (ER) during stress by increasing its content. Previous studies found that TRAM1 had been changed in duck reovirus infected duck embryo fibroblasts cells. In this study, the interaction between DRV non-structural protein σNS and TRAM1 had been further confirmed experimentally. σNS protein was expressed firstly. Glutathione S-transferase pull-down was utilized to confirm the interaction between TRAM1 and σNS protein extracellular while co-immunoprecipitation (Co-IP) was utilized to confirm the interaction between TRAM1 and σNS protein intracellular. In addition, knockdown of TRAM1 using siRNA and overexpression of TRAM1 gene were conducted to explore its effect on virus replication. The interaction between σNS and TRAM1 has been confirmed. The results showed that TRAM1 overexpression degraded the levels of σNS transcription while TRAM1 silencing enhanced the levels of σNS transcription. In conclusion, our studies could afford help to explore the function of σNS protein on DRV replication. It also provided data to explore the role of interactions between TRAM1 and σNS during DRV infection.

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Single nucleotide polymorphism screening and bioinformatics analysis of TBC1D7 gene in Guanling cattle

LIU Pengcheng, ZHANG Ji, QIU Ganyuan, GONG Yu, LI Xuesong, LI Wei, ZHANG Yiyu, LIU Ruoyu

2022, 34(7): 1402-1411. DOI: 10.3969/j.issn.1004-1524.2022.07.07

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In order to explore effects of single nucleotide polymorphism(SNPs)of TBC1 domain family,member 7(TBC1D7)gene on cattle growth traits, the Guizhou Guanling cattle was selected as experimental objects to construct DNA pools. After PCR amplification, direct sequencing method was used to detect SNPs of TBC1D7 gene in Guanling cattle. The results showed that the coding region of TBC1D7 gene of Guanling cattle was 882 bp in length, encoding 293 amino acids. An unstable soluble protein was formed. There was no transmembrane region and no signal peptide in the protein encoded by TBC1D7 gene, which is a non-secretory protein. There were six potential N-glycosylation sites in the protein, and the secondary structure was mainly composed of α-helix and random coil. Four synonymous mutation sites were found in the coding sequence (CDS) region of TBC1D7 gene in Guanling cattle, namely, c.402T>C, c.414A>G, c.609C>T and c.648T>C. All the four SNPs resulted in changes in mRNA secondary structure, free energy and gene frequency of TBC1D7 gene in Guanling cattle. In this study, four SNPs loci of TBC1D7 gene in Guanling cattle were screened. The results showed that the polymorphism of TBC1D7 gene in Guanling cattle was abundant, which provided a theoretical basis for further research on the correlation between the variation of TBC1D7 gene and the growth and development traits of Guanling cattle.

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Antibacterial effect of thymol against fish-derived drug-resistant Aeromonas veronii in vitro and its mechanism

WU Yuru, LIANG Tianyu, LIANG Chao, TAN Yuanyuan, LIU Yuan, PAN Xingyu, HUANG Xiaoli, CHEN Defang, GENG Yi, OUYANG Ping

2022, 34(7): 1412-1422. DOI: 10.3969/j.issn.1004-1524.2022.07.08

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In order to investigate the antibacterial effect and mechanism of thymol against fish-derived drug-resistant Aeromonas veroniae, a strain of A. veronii was isolated from diseased Pelteobagrus fulvidraco. Drug sensitivity test showed that this strain was resistant to florfenicol, ciprofloxacin and enrofloxacin. The antibacterial activity of thymol against drug-resistant A. veronii was studied by determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and growth curve, and the mechanism was explored by measuring its influence on membrane permeability, soluble protein, lactate dehydrogenase activity, DNA and cell ultrastructural changes. The results showed that thymol had inhibitory effect on A. veronii with MIC of 256 μg·mL^-1 and MBC of 512 μg·mL^-1, respectively. After treatment with 512 μg·mL^-1 thymol for 1 h, the electrical conductivity in strain solution was significantly (P<0.01) increased, and the DNA content in strain solution was increased to (115.6±0.5) mg·L^-1. After treatment with 512 μg·mL^-1 thymol, the soluble protein of this strain decreased, the activity of lactate dehydrogenase significantly (P<0.01) decreased by (32.8±0.7)%, (46.2±0.3)%, (46.1±1.6)%, (60.0±1.0)% at 2, 4, 6, 8 h, respectively, the fluorescence intensity and density of DAPI (4',6-diamidino-2-phenylindole) staining were also decreased, and the surface of this strain seemed to dissolve and collapse, shrink and deform, cell wall and membrane separated, with cytoplasm loss and internal cavitation under electron microscope. All these results suggested that thymol had strong antibacterial activity against A. veronii. The increase of membrane permeability with thymol treatment would cause the loss of intracellular substances, and result in bacterial death. Therefore, thymol could be used as a candidate for the treatment of antibiotics-resistant A. veronii infection.

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Influence of substrate cultivation and soil cultivation on sucrose and citric acid accumulation of Yuexin strawberry

YANG Xiaofang, LI Yunduan, SUN Yunfan, LI Shaojia, MIAO Lixiang, ZHANG Yuchao, JIANG Guihua

2022, 34(7): 1423-1430. DOI: 10.3969/j.issn.1004-1524.2022.07.09

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In order to study the difference of strawberry fruit quality formation under substrate cultivation and soil cultivation, and explore its influence law, the contents of sucrose and citric acid and the expression of related genes in different development stages of strawberry were measured. The results showed that contents of sucrose and citric acid in soil culture were higher than those in substrate culture. The difference of sucrose accumulation was mainly reflected in the tip of strawberry fruit, and the difference of citric acid accumulation was in the tip and base of strawberry fruit. FaSPS2 gene was the key gene for the difference of sucrose accumulation between soil culture and substrate culture, which was positively correlated with sucrose accumulation. The expression of FaACO1 and FaACO3 genes were negatively correlated with the accumulation of citric acid. The expression of FaACO1 and FaACO3 in matrix culture were significantly higher than those in soil culture, resulting in the citric acid content of mature strawberry fruit in matrix culture was lower than that in soil culture. Therefore, FaSPS2, FaACO1 and FaACO3 genes played important role in the accumulation of sucrose and citric acid content of Yuexin strawberry. Soil cultivation might be more conducive to the accumulation of sucrose and citric acid content of Yuexin strawberry than substrate cultivation.

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Optimizing tissue culture media for Rubus chingii Hu multiplication: effects of plant growth regulators and mineral elements

WANG Xiuyuan, ZOU Yiqiao, LIU Lingling, CHEN Zhen, JIANG Jingyong

2022, 34(7): 1431-1438. DOI: 10.3969/j.issn.1004-1524.2022.07.10

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Rubus chingii Hu is a typical dual-function medicine and edible food with prominent nutraceutical, health and economic values. In order to accelerate propagation of R. chingii with high quality, the stems of line 14 with higher contents of medicinal ingredients were used as explants. The effects of combinations and concentrations of plant growth regulators and mineral elements on multiplication and growth of R. chingii plantlets were investigated in this paper, and optimized media was obtained. The results showed that when the concentration of naphthylacetic acid (NAA) was 0.1 mg·L^-1, the effect of 5.0-30.0 mg·L^-1 kinetin (KT) on growth and multiplication of seedlings was equivalent with 0.5-3.0 mg·L^-1 6-benzylamine adenine (6-BA). Therefore, the action concentration of KT was 10 times that of 6-BA. 0.5-3.0 mg·L^-1 6-BA could caused vitrification of tissue culture plantlets and the supplement of 0.1-1.0 mg·L^-1 KT to the media alleviated the vitrification. The multiplication coefficient reached a maximum level of 10.33 under the combination of the two cytokinin, 0.5 mg·L^-1 6-BA and 1.0 mg·L^-1 KT, and the seedlings grew well. Optimization of mineral elements contents in media improved the growth of seedlings. All together, the best media for R. chingii multiplication were: modified MS medium (2-fold concentrations of Ca、Cu and Mn with 1/4 Mg and 1/2 Zn) added with 6-BA 0.5 mg·L^-1, KT 1.0 mg·L^-1 and NAA 0.1 mg·L^-1. Thus, the tissue culture seedlings multiplied and grew well without vitrification.

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Codon usage bias and its influencing factors in the whole genome of three truffles

HAN Lihong, TIAN Xuelian, LIU Chao, FU Xiaolin, WANG Yuanxian

2022, 34(7): 1439-1448. DOI: 10.3969/j.issn.1004-1524.2022.07.11

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Truffle is a rare wild macrofungi for both medicine and food, it has high value in nutrition and health care. Codon bias analysis can provide a theoretical basis for genetic evolution and resource development of truffles. Based on the genomic data of Tuber melanosporum, T. magnatum and T. borchii, CodonW 1.4 2, Mega X software, and EMBOSS online website were used to systematically analyze the codon usage bias and influencing factors of the genomes of three truffles. The results showed that the codon usage patterns of the three truffles were highly similar, with a tendency to use the guanine or cytosine ending codons, and the effective number of codons showed high values. Among them, the similarity of codon usage between T. melanosporum and T. borchii was the highest. The guanine or cytosine (G/C) base related parameters of T. magnatum were higher than other two species. Among the optimal codons of the three truffles, the G/C ending codons accounted for 81.8%, 78.9% and 61.9% respectively. 24 high-frequency codons and 14 optimal codons were common in the three truffles. All of them prefer the guanine or cytosine or thymineas ending codons, but the preference was not strong as a whole. The results of Parity Rule 2 plot, ENC-plot, neutrality plot and correspondence analysis showed that the formation of codon bias of the three truffles were mainly affected by multiple factors such as selection pressure. Among them, T. melanosporum was mainly affected by translational selection pressure, and T. magnatum was mainly affected by other factors other than translational selection, and T. borchii was relatively less affected by selection pressure. The results showed that the codon use patterns of the three truffles were similar, and the codon usage bias was weak with low expression potential. The codon bias was mainly affected by multiple factors. The results provided a theoretical basis for species evolution and genetic breeding of truffles.

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Identification and main biological characteristics of pathogen of Clematis leaf blight in Yunnan

YANG Ling, SHA Nanjing, PAN Pengju, WU Bozhi

2022, 34(7): 1449-1456. DOI: 10.3969/j.issn.1004-1524.2022.07.12

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In order to identify the pathogen of Clematis leaf blight in Yunnan Province, the typical diseased leaves were collected from the diseased plants. The pathogen was isolated and purified by tissue separation method, and identified by morphological characteristics combined with sequence analysis of ribosomal internal transcribed spacer (ITS) and large subunit (LSU), and verified by Koch postulates. The main biological characteristics of the pathogen were determined with different media, temperature, light, pH, carbon and nitrogen sources. The results showed that the pathogen of Clematis leaf blight was Spencermartinia sp., according to Koch postulates, all the leaves inoculated with the pathogen were infected. Potato dextrose agar (PDA) and potato saccharose agar(PSA) were the suitable media, the optimum temperature for growth was 25 ℃, the growth was not affected under different light treatments, the optimum pH for growth was 6.5-7.5, the best carbon source was glucose and sucrose, and the best nitrogen source was sodium nitrate.

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Rapid molecular detection of Diaporthe citri, the pathogen of citrus melanose

ZENG Yating, XIONG Tao, LI Hongye

2022, 34(7): 1457-1465. DOI: 10.3969/j.issn.1004-1524.2022.07.13

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Citrus melanose is a worldwide fungal disease which seriously harms citrus production. Rapid detection of Diaporthe citri, the pathogen of citrus melanose, is of great practical significance for early diagnosis and scientific prevention and control of citrus melanose. In this study, a specific primer pair for D.citri was designed based on β-tubulin gene sequence, and a rapid molecular detection system was established based on conventional PCR and SYBR Green I Real-time PCR(qRT-PCR) to detect and verify the mycelia and typical infected leaves of D.citri. The results showed that in conventional PCR, the primers could obtain a 244 bp specific amplification fragment from D.citri, and the detection sensitivity was up to 0.78 ng·μL^-1. In qRT-PCR, the primers could only obtained a unique product absorpation peak from D.citri, and the detection sensitivity was up to 0.35 ng·μL^-1.The typical infected leaves were detected by PCR detection system. The results showed that the positive detection rate of conventional PCR was 30%, and that of qRT-PCR was 60%, indicating that qRT-PCR was more sensitive than conventional PCR. Therefore, the specific primers designed in this study and the established conventional and qRT-PCR detection method have the advantages of fast speed, strong specificity and high sensitivity, which can be used for molecular identification of D. citri and also have reference value for disease diagnosis.

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Effects of environmental conditions on biofilm formation of Bacillus altitudinis LZP02

HUANG Donghui, ZHONG Peng, WANG Jianli, HU Yunlong, WANG Zhigang

2022, 34(7): 1466-1473. DOI: 10.3969/j.issn.1004-1524.2022.07.14

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Bacillus altitudinis LZP02 is a rice rhizosphere growth-promoting bacterium, which can colonize rice rhizosphere to form biofilm. In order to study the formation of B. altitudinis LZP02 biofilm under different culture conditions, the formation of B. altitudinis LZP02 biofilm was observed by 96-well microplate method, and it was quantified by crystal violet staining. The results showed that B. altitudinis LZP02 formed a stable biofilm structure on surface of the culture medium and had good biofilm formation ability.The optimum temperature of B. altitudinis LZP02 for biofilm formation was 30 ℃, but only a few biofilms were formed at 25 ℃, which indicated that low temperature reduced the biofilm formation ability of B. altitudinis LZP02.Biofilm could be formed at pH 4-10, and the ability of biofilm formation was strongest at pH 7.0. Ca²⁺ had no obvious effect on the formation of B. altitudinis LZP02 biofilm. Fe²⁺, Fe³⁺, Mg²⁺, K⁺, Na⁺, Zn²⁺ and Cu²⁺ inhibited the formation of B. altitudinis LZP02 biofilm, while Mn²⁺ promoted the formation of B. altitudinis LZP02 biofilm.The research results provided an important reference for the further development and utilization of B. altitudinis LZP02, and also provided a realistic basis for further exploring the biofilm formation mechanism of B. altitudinis LZP02.

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Investigation and analysis of continuous cropping obstacle and soil environment in large-scale vegetable bases in Zhejiang Province, China

YAO Yanlai, ZHU Weijing, DING Jian, HONG Leidong, HONG Chunlai, WANG Weiping, ZHU Fengxiang, HE Weike, HONG Haiqing

2022, 34(7): 1474-1484. DOI: 10.3969/j.issn.1004-1524.2022.07.15

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Vegetable industry is one of the 10 leading agricultural industries in Zhejiang Province. However, in recent years, soil quality degradation and continuous cropping obstacles in large-scale vegetable bases have become important limiting factors for the green and sustainable development of vegetable industry in Zhejiang. In order to investigate the continuous cropping obstacles and the soil environment of large-scale vegetable bases in Zhejiang Province, 65 large-scale vegetable bases in 24 counties (cities, districts) were surveyed. A total of 101 soil samples were collected,and the physiochemical properties were analyzed, and the quantity of pathogens of two typical soil-borne diseases in some samples was also determined. The results showed that the planting years of large-scale vegetable bases in Zhejiang Province were relatively long. More than 46.2% of large-scale bases have been planted for more than 10 years. Continuous cropping was common.The average incidence of soil-borne diseases reached 17.82%,the average yield reduction reached 22.12%, and some bases even failed to harvest in some years. The soil degradation of some large-scale vegetable bases was serious. The proportion of soil samples with pH≤5.0 reached 33.7%, and the proportion of soil samples with electrical conductivity>1 000 μS·cm^-1 reached 42.6%. Available nutrients were accumulated in soil. The average soil available P and available K contents reached 184.30 mg·kg^-1 and 387.20 mg·kg^-1, respectively. Correlation analysis showed that there was a significant (P<0.05) correlation between the quantity of Fusarium oxysporum and the content of soil available nitrogen and available phosphorus. Soil acidification, secondary salinization and accumulation of soil available nutrients and pathogens have become the important reasons for the soil quality degradation and the frequent occurrence of continuous cropping obstacles of large-scale vegetable bases. The investigation results could provide basis for the effective control of continuous cropping obstacles of large-scale vegetable bases in Zhejiang Province.

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Effects of different materials on leaching characteristics of salinity in coastal saline-alkali soil

ZHOU Wenzhi, LI Suyan, SUN Xiangyang, LI Xiaochong, ZHA Guichao, WEI Ningxian

2022, 34(7): 1485-1492. DOI: 10.3969/j.issn.1004-1524.2022.07.16

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In the present study, the effect of addition of wood vinegar (diluted 400 time, 200 mL), fly ash (soil volume fraction of 10%) and garden waste compost (soil mass fraction of 4%) on leaching characteristics of salinity in coastal saline-alkali soil were examined via soil column experiment. The changes of electrical conductivity (EC), pH and water-soluble ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO^2-₄、CO^2-₃、HCO^-₃) in the leaching solution and soil after leaching were determined. It was shown that, compared with CK, addition of wood vinegar, fly ash and garden waste compost could increase the leaching of water-soluble ions and reduce the time consumption by 6, 12, 2 d, respectively, when the EC of leaching solution was reduced to 2 mS·cm^-1 and below. With addition of fly ash, the soil pH and EC in soil were significantly (P<0.05) decreased after leaching. However, with addition of wood vinegar or garden waste compost, the soil pH was significantly (P<0.05) decreased, yet soil EC was significantly (P<0.05) increased after leaching. Therefore, under the experiment conditions, addition of fly ash showed the best promotion effect on salinity leaching.

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Effects of soil conditioners on Cd translocation and accumulation and yield of rice in central Guizhou Province, China

LOU Fei, FU Tianling, DAI Liangyu, ZHOU Kai, LIN Dasong, HE Tengbing

2022, 34(7): 1493-1501. DOI: 10.3969/j.issn.1004-1524.2022.07.17

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A plot experiment was carried out to assess the applicability of soil conditioners on Cd-polluted acid paddy fields in central Guizhou Province, China. The effects of soil conditioners on soil pH, contents of total Cd and available Cd, Cd contents in different parts of rice and rice yield were analyzed. It was shown that application of lime or 11 conditioners significantly (P<0.05) increased soil pH by 0.25-1.02 unit compared with the control (CK), and significantly (P<0.05) reduced soil available Cd content by 8.90%-22.14%. Application of 11 soil conditioners could decrease Cd content and Cd enrichment coefficient in different parts of rice, as Cd content in brown rice was significantly (P<0.05) decreased by 19.09%-82.45%, and the Cd enrichment coefficient in root, stem, leaf and brown rice was significantly (P<0.05) decreased by 16.62%-69.90%, 18.40%-94.18%, 25.82%-78.02%, 18.02%-85.46%, respectively. In addition, application of lime and 11 soil conditioners could significantly (P<0.05) inhibit the translocation of Cd from leaf to rachis, and from rice husk to brown rice. The economic cost of application of soil conditioners was higher than that of lime. Among the 11 soil conditioners, Tebeigai showed the lowest application cost of 7 200 yuan·hm^-2. Given the Cd reduction effect and economic cost, the soil conditioner Tebeigai was the best choice under experiment conditions, and could be recommended for further application in central Guizhou.

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Optimization of process conditions and volatile flavor components analysis of bayberry pulp fermented by lactic acid bacteria

PAN Xujie, LIU Ruiling, DENG Shanggui, WU Weijie, CHEN Hangjun, GAO Haiyan

2022, 34(7): 1502-1512. DOI: 10.3969/j.issn.1004-1524.2022.07.18

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In order to optimize the fermentation conditions of bayberry pulp by lactic acid bacteria, and analyze the impact of fermentation on its flavor, the response surface test was based on the single-factor to optimize the process conditions,the content of eight organic acids in bayberry pulp was determined by high performance liquid chromatography(HPLC), and the volatile flavor components of bayberry pulp were analyzed by headspace solid phase microextraction-gas chromatography-tandem mass spectrometry(SPME-GC-MS)combined with relative odor activity value (ROAV). The results showed that the optimized conditions of the bayberry pulp process were: 1.0% of lactic acid bacteria, 10.5% of sucrose, 10.3 h of fermentation time, and 1.0% of color retention agent (1∶1 of citric acid and sodium erythorbate), 0.4% of thickener (1∶1 of pectin and carrageenan).Compared with the unfermented bayberry pulp, lactic acid bacteria fermentation increased the content of oxalic acid, tartaric acid, lactic acid and citric acid in the pulp. The analysis results of volatile substances showed that through the fermentation of lactic acid bacteria, the characteristic flavor components such as (E)-2-heptenal and lupule were added, making the taste of pulp more mellow than the unfermented pulp, and improving the flavor quality of bayberry pulp.

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Residue dynamics and risk assessment of several pesticides commonly used for the control of Apolygus lucorum in grapes

SUN Shuyuan, HOU Lina, YANG Guiling, DU Yuting, ZHAO Yun

2022, 34(7): 1513-1518. DOI: 10.3969/j.issn.1004-1524.2022.07.19

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To clarify the residues and dietary risks of several pesticides commonly used for the control of Apolygus lucorum in grapes, studies were carried out on three common pesticides: emamectinbenzoate, thiamethoxam and acetamiprid. The results showed that the degradation of these three pesticides in grape were in accordance with the first-order kinetic equation, and could degrade to below the maximum residue level (MRL) value after 14 days. Three kinds of pesticide residues in degradation of 14 days dietary risk assessment results showed that the three kinds of pesticide risk of chronic and acute risk and total dietary risk was less than 100%, which indicated that according to the recommended use method, the dietary risk of these three test pesticides was low after 14 days, and could be recommended for control Apolygus lucorum and the recommended security clearances was 14 days.

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Establishment of on-site rapid dual-mode fluorescence RPA detection method for bacterialfruit of blotch

WANG Chenwei, WANG Xiaofu, WEI Wei, CHEN Xiaoyun, SHEN Jie, XU Junfeng, CAI Jian

2022, 34(7): 1519-1528. DOI: 10.3969/j.issn.1004-1524.2022.07.20

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Bacterial fruit of blotch (BFB) is a quarantine disease in China, which spreads very rapidly and no commercial resistant varieties have been found at present. In order to establish rapid fluorescent recombinase polymerase amplification (RPA) detection method of BFB, the best combination of RPA primers and probe were designed and screened out according to the specific sequence of BFB, then RPA results was analyzed using two modes and compared with quantitative real-time PCR(qRT-PCR). One was real time RPA (RT-RPA), and the other was end point RPA (EP-RPA). The results showed that the established dual-mode fluorescence RPA method for detection of BFB had strong specificity, and its sensitivity for detection of pathogens was equivalent to that of qRT-PCR. The results of RT-RPA, EP-RPA and qRT-PCR were identical. The average detection time of EP-RPA, RT-RPA and qRT-PCR were about 20, 5 and 44 min,respectively. The detection speed of RPA was much faster, and the detection process did not rely on large instruments, which was convenient and fast. As a result, it was suitable for on-site detection. The establishment of this constant temperature rapid detection method provided a new technical support for the on-site detection of plant diseases.

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Effect of malonic acid treatment on postharvest storage quality of cowpea

GUO Xuesong, TIAN Libo, SHANG Sang

2022, 34(7): 1529-1536. DOI: 10.3969/j.issn.1004-1524.2022.07.21

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The physiological and biochemical indexes of cowpea treated with malonic acid concentration of 100, 200, 300 and 400 mg·L^-1 were studied during storage at (8±2) ℃ with fresh cowpea as experimental material. The results showed that after 12 days of storage, the rust spot index of cowpea treated with malonic acid was significantly lower than that of the control, the effect of cowpea treated with 200, 300 mg·L^-1 malonic acid were the best; the weight loss rate of cowpea treated with malonic acid was always lower than that of the control and 300 mg·L^-1 malonic acid treatment was significantly lower than that of the control; on the 9th day of storage, the soluble protein content of pods and beans treated with malonic acid was always higher than that of the control. On the 12th day of storage, the soluble protein content of pods treated with 300 mg·L^-1 malonic acid was the highest, 68.49% higher than that of the control and the soluble protein content was 6.42% higher than that of the control; the contents of chlorophyll and vitamin C of cowpea decreased during storage, in 300 mg·L^-1 malonic acid treatment group were always higher than those in the control group. Soluble sugar content of cowpea pods and beans decreased rapidly during storage, the soluble sugar content of pods treated with 200 and 300 mg·L^-1 malonic acid was always higher than that of the control. The cellulose content in cowpea showed an increasing trend, and the cellulose content in cowpea treated with 300 mg· L^-1 malonic acid was significantly lower than that in the control group. The activity of polyphenol oxidase (PPO) in cowpea increased, but the PPO activity in malonic acid treatment was always lower than that in the control during storage. The peroxidase (POD) activity of all treatments reached the peak on the 6th day and then decreased. The changes of POD activity were stable in 300 and 400 mg·L^-1 malonic acid treatment during storage. Different concentrations of malonic acid could inhibit the increase of cowpea rust index, delay the increase of weight loss rate, cellulose content, PPO activity and the decrease of chlorophyll, soluble sugar and soluble protein contents, and maintain a high level of POD activity to eliminate free radicals, so as to maintain the quality of cowpea after harvest, further improve the postharvest fresh-keeping effect of cowpea. The results showed that 300 mg·L^-1 malonic acid had the best effect on the preservation of cowpea.

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Study on driving effects of agricultural science and technology investments on agricultural economic growth:based on the data of 60 counties in Zhejiang Province, China

KE Fuyan, XU Zhiyuan, YANG Liangshan

2022, 34(7): 1537-1544. DOI: 10.3969/j.issn.1004-1524.2022.07.22

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Taking the data of 60 counties in Zhejiang Province from 2015 to 2019, this paper empirically analyzed the effects of agricultural science and technology investments on agricultural economic growth by using panel data model. The results showed that by controlling other input variables, on the whole, financial investment in agricultural science and technology was positively correlated with agricultural economic growth, and its positive effect in underdeveloped south-west counties was significantly higher than that in developed north-east counties. The input of agricultural scientific and technological personnel only showed a positive effect on north-east counties, but not on south-west counties. The effects of other control variables on agricultural economic growth also showed some differences, in which the total power of agricultural machinery did not show a positive effect. Therefore, in the “double strong” action of strengthening agriculture through science and technology and machinery in the coming period, Zhejiang should continue to increase financial investment in agricultural science and technology and tilt to the south-west counties of Zhejiang, and actively optimize the allocation of agricultural science and technology personnel. In the south-west counties of Zhejiang Province, we should focus on optimizing the allocation of agricultural science and technology personnel to adapt to agricultural production. In the north-east counties of Zhejiang Province, we should focus on strengthening the introduction and training of agricultural science and technology personnel to build a strong agricultural science and technology team, Furthermore, the renewal of old agricultural machinery and equipment, as well as the development and promotion of new practical agricultural machinery and equipment should also be accelerated.

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Will aging make farmers flow agricultural land smoothly?

CHENG Weisong, ZHENG Suwen, GAO Huajie, BAI Yunli, YE Chunhui

2022, 34(7): 1545-1557. DOI: 10.3969/j.issn.1004-1524.2022.07.23

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Aiming at the phenomenon of outflow of agricultural land by old farmers, the data cited from the China Rural Development Survey were used in the present study.Based on theoretical derivation, panel fixed effects regression and propensity score matching methods were employed to analyze the impact of the aging of agricultural labor force on the circulation of agricultural land. It was shown that the estimated coefficients increased after the sample missing problem was alleviated. For farming households with full pensions and a smaller household agricultural income per labor (below the average level in village) or lower percentage of household agricultural income (<0.25), the outflow of agricultural land under the influence of aging was greater. When villagers were covered by the new rural cooperative medical insurance or a nursing home in the village, the outflow of agricultural land from old farmers tended to increase. When the villages provided public goods that could improve agricultural efficiency, such as irrigation facilities or mechanized farmland services, there would be a further outflow of agricultural land from farming households with a smaller household agricultural income per labor or lower percentage of household agricultural income. Accordingly, countermeasures were proposed to increase social security for old farmers in rural areas and to actively invest in public goods that could improve agricultural productivity.

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Rural finance and rural vitalization: mechanism analysis and efficiency evaluation

XIA Long

2022, 34(7): 1558-1570. DOI: 10.3969/j.issn.1004-1524.2022.07.24

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In the present study, the theoretical mechanism of rural finance on rural vitalization was first outlined according to the general requirements (“thriving businesses, pleasant living environments, social etiquette and civility,effective governance and prosperity”) of rural vitalization. Then, the composite indexes of rural finance and rural vitalization were constructed, and the impact of rural finance on rural vitalization was empirically studied based on the panel data from 2011 to 2018. It was shown that the development of rural finance and rural vitalization was improved in the study period, but the overall development level was low with regional differences. As revealed by the results of panel stochastic frontier production function, rural finance could promote the realization of rural vitalization, yet the technical efficiency was not high, and the spatial distribution pattern was consistent with that of financial poverty relief. Based on these findings, suggestions were put forward, such as establishing effective link mechanism between poverty alleviation and rural vitalization, taking full advantage of financing institution, exploring new modes, etc.

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