Acta Agriculturae Zhejiangensis

Construction of single fragment substitution lines of maize 8th chromosome and sreening of resistant maize germplasm to gray leaf spot

YANG Mei, HU Xiaolan, SHEN Tao, TAN Kang, LIU Dailing, QIU Hongbo

2021, 33(3): 383-389. DOI: 10.3969/j.issn.1004-1524.2021.03.01

Abstract ( 1365 )

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In this study, 23 single segment substitution lines of maize 8th chromosome were obtained by successive backcross and marker assisted selection with T32 and J51, the common inbred lines of maize in Guizhou, as donor and acceptor, respectively. Then, method of natural inoculation was used to identify the resistance to maize gray spot, and 65 pairs of SSR markers that located on the 8th chromosome with obvious polymorphic differences between two parents were used for the following detection of substitution lines. The genetic structure of donor fragments of the substitution lines was evaluated by 29 SSR markers on the 8th chromosome. The results showed that 23 chromosome single-segment substitution lines had different donor fragment sites and length of the substitution fragment was 10.40-129.70 cM, the average length was 36.99 cM, total length of the imported fragment was 850.67 cM, and coverage rate of the replacement fragments on 8th chromosomes was 80.80%. Disease-resistant result showed four kinds of phenotypes: resistant, moderately resistant, susceptible and highly susceptible. Among them, the line of H3 and H17 were identified as resistant, with the two years average disease grade of 2.85 and 2.90, respectively. Two resistant lines were screened out in this study, which could be used as follow-up research materials and lay a foundation for resistant maize breeding to gray leaf spot.

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Development of plasmid DNA reference material of genetically modified maize TC1507

QU Zhan, YANG Litao

2021, 33(3): 390-395. DOI: 10.3969/j.issn.1004-1524.2021.03.02

Abstract ( 1213 )

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The reference material has three typical characteristics of characterization value, homogeneity and stability, which was used as the scale of biological measurement. The development of reference materials for genetically modified organisms was one of the key technologies for the implementation of the GMO labeling system in China. In this study, a novel plasmid DNA standard substance pTC1507 specific to the transgene maize TC1507 was produced, and its homogeneity, stability and characterization were evaluated and measured. The results showed that the pTC1507 had good homogeneity between and within bottles. The stability of pTC1507 was reliable, and it could be stably placed at -20 ℃ for 6 months at least. After sequencing, quantitative real-time PCR analysis, and uncertainty evaluation, the characterization value of pTC1507 was 1.01±0.053. The results of homogeneity, stability and characterization evaluation showed that pTC1507 was satisfied with the typical requirements of reference materials and could replace the conventional matrix-based reference materials in the detection of transgenic maize. The developed plasmid reference material showed the advantages of easy producing, simple preparation, and low cost.

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Effects of NaCl and Na₂SO₄ stress on content and distribution of K ⁺ and Na ⁺ of Echinochloa frumentacea seedlings

LU Anqiao, ZHANG Fengju, WANG Xueqin, XU Xing

2021, 33(3): 396-403. DOI: 10.3969/j.issn.1004-1524.2021.03.03

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In order to explore the characteristic of K ⁺ and Na ⁺ absorption and distribution at seedling stage of Echinochloa frumentacea under salt stress. The variety Haizi-1 was used as test material, eight different concentrations (0, 25, 50, 75, 100, 125, 150, 200 mmol·L ^-1) of NaCl and Na₂SO₄ were set to simulate conditions of salt stress in this study. The results showed that with the increase of NaCl and Na₂SO₄ concentration, Na ⁺ content was increased, K ⁺ content was decreased, K ⁺/Na ⁺ ratio were all decreased in leaf, stem sheath and root; Content and distribution of Na ⁺ was root>stem sheath>leaf, Na ⁺ content in leaf and stem sheath were significantly lower than that in root. K ⁺/Na ⁺ ratio in leaf and stem sheath was higher than that in root. Content and distribution of K ⁺ was stem sheath>root>leaf under low salt concentration, and under the medium and high salt concentration, content and distribution of K ⁺ was stem sheath>leaf>root. Transport selectivity coefficient from root to stem sheath of K ⁺ and Na ⁺ (ST1_{K, Na}) and transport selectivity coefficient from stem sheath to leaf of K ⁺ and Na ⁺ (ST2_{K, Na}) under salt stress were significantly higher than those of the control at salt concentration>25 mmol·L ^-1, and ST1_{K, Na} was higher than ST2_{K, Na}. When the salt concentration was≥125 mmol·L ^-1, K ⁺/Na ⁺ ratio became stable in above ground under Na₂SO₄ stress, K ⁺ content in stem sheath and root and ST1_K,Na were higher than those under the same concentration of NaCl stress, and Na ⁺ content in leaf and stem sheath were lower than that under the same concentration of NaCl stress. ST2_{K, Na} showed an upward trend under Na₂SO₄ stress, and increased firstly and then decreased under NaCl stress. In conclusion, it had been shown that under salt stress, root system of E. frumentacea had a strong restriction on sodium ion transport to the above-ground part and had higher selective absorption capacity for K ⁺, and it had more tolerance to Na₂SO₄ stress than NaCl stress under higher concentration of salt stress.

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Optimization of preparation technology and stability evaluation of sarafloxacin/β-cyclodextrin inclusion complex by response surface method

JIANG Xingcan, LI Bing, YANG Min, ZHANG Jiyu

2021, 33(3): 404-412. DOI: 10.3969/j.issn.1004-1524.2021.03.04

Abstract ( 1021 )

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To prepare sarafloxacin/β-cyclodextrin inclusion complex microcapsules, and to solve the problems of low solubility and unstable physicochemical properties of sarafloxacin, the preparation process of sarafloxacin/β-cyclodextrin inclusion complex was optimized by response surface method, and the drug loading and solubility of sarafloxacin/β-cyclodextrin inclusion complex were determined by high performance liquid chromatography(HPLC). The water content and stability of sarafloxacin/β-cyclodextrin inclusion complex were evaluated by drying weight loss test and influencing factors experiment. The results showed that the optimized inclusion process parameters were as follows: molar ratio of sarafloxacin to β-cyclodextrin 1:2, stirring temperature 50 ℃, stirring time 4 h, spray drying temperature 160 ℃, pump speed 6.3 r?min-1. The results of the liquid chromatographic methodology verified showed that the linear relationship of sarafloxacin was good in the range of 9.94~99.40 μg?mL-1. The regression equation was Y=34.66X-15.867, and the correlation coefficient was 0.999 9. The experiments of influencing factors and drying weight loss showed that the physical and chemical properties of the prepared sarafloxacin/β-cyclodextrin inclusion complex were stable, the water content of the inclusion complex was less than 2%, and the fluidity was good. The results showed that the successful preparation of sarafloxacin/β-cyclodextrin inclusion complex significantly improved the physical and chemical properties of the drug and played a positive role in the application and popularization of sarafloxacin.

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Effects of different interstocks on growth and photosynthetic characteristics of Yuanxiaochun citrus

WANG Tie, HUANG Shengjia, YANG Youting, TAN Liping, QIU Xia, DONG Tiantian, LI Sichen, SUN Guochao, XIONG Bo, WANG Jun, WANG Zhihui

2021, 33(3): 413-421. DOI: 10.3969/j.issn.1004-1524.2021.03.05

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In order to study the effect of different interstocks on the growth and photosynthetic characteristics of Yuanxiaochun citrus, Citrus unshiu Marc., Orah and Citrus sinensis Osbeck were used as the interstock material, and Yuanxiaochun as scion. The effects of different interstocks on the survival rate, growth characteristics, photosynthetic pigment content, specific leaf weight(SLW) and photosynthetic characteristics of scion were analyzed. The results showed that the effect of the interstock on the preservation rate of scion was obvious, and it was expressed as Citrus sinensis Osbeck>Orah>Citrus unshiu Marc. The growth of the scion grafted by Citrus sinensis Osbeck as the interstock was relatively strong, and the ratio of the roughness of the new shoot and the roughness of the interstock was the smallest, and the SLW of the leaves changed little with time, and the content in each period was relatively low, and the leaves had higher P_n, G_s and lower L_s. The content of Chl a, Chl b, Car and Chl(a+b) in the leaves grafted by Orah was higher, and the Chl a/b was lower. The treatment by Orah had higher F_o and lower F_v/F_o. Therefore, different stionic combinations have different effects on the growth and photosynthetic characteristics of Yuanxiaochun citrus, and Citrus Sinensis Osbeck as interstock' performance is better.

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Effect of protein hydrolysate-based amino-acid fertilizers on fruit quality of Hongmeiren citrus hybrid

WEN Mingxia, ZHANG Shunchang, WU Shaohui, HU Lipeng, WANG Peng, HUANG Bei

2021, 33(3): 422-428. DOI: 10.3969/j.issn.1004-1524.2021.03.06

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To establish a fertilization model, reduce the use of chemical fertilizers and improve the citrus tree potential, the protein hydrolysate-based amino-acid fertilizers (PHs) were tested by spraying on the leaves of Hongmeiren citrus hybrid during different fruit growth periods. Starting from two thirds citrus flower faded, 800 times of PHs was sprayed every 20 days, the spraying time of other treatments was 20 days later gradually, and each treatment was sprayed three times in the annual growth cycle, to study the effects of PHs on chlorophyll content, fruit color and quality of spring shoot leaves of Hongmeiren. The results showed that the chlorophyll content of the spring shoots of Hongmeiren was significantly increased by 20.6% and 22.6%, respectively, when spraying PHs at the beginning of two thirds citrus flower faded and 60 days after two thirds of citrus flower faded. The values of color L, color a and color b of the citrus peel with PHs were positive, and they were significantly higher than those of the treatment of spraying PHs at the time of two thirds of citrus flower faded, and the fruit was orange-red with better brightness. The fruit edible rate, soluble solids and vitamin C content of the treatments with PHs were higher than those of the control group, while the titratable acid content was lower than that of the control group, and the fruit quality was better. In addition, spraying PHs at the time of two thirds citrus flower faded can increase the brightness of the citrus peel, promote the fruit color, the fruit weight was larger and conducive to increase the yield, the peel was thinner so that the edible rate increased. Therefore, it is recommended to start spraying on the leaves of Hongmeiren at the time of two thirds of citrus flower faded, spraying once every 20 days, and spraying three times continuously was better.

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Heterosis analysis of photosynthetic parameters of pepper seedling responding to low temperature and low light stress

GOU Bingdiao, DUAN Panpan, YANG Nan, ZHAO Shufang, WANG Yongfu, ZHANG Gaoyuan, WEI Bingqiang

2021, 33(3): 429-436. DOI: 10.3969/j.issn.1004-1524.2021.03.07

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In order to screen the photosynthetic parameters for identifying and predicting the heterosis of pepper, using the parents and their F₁ hybrid of pepper as materials, effects of low temperature and low light on net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular carbon dioxide concentration (C_i), transpiration rate (T_r) and chlorophyll content of pepper seedlings were comprehensively analyzed by the method of subordinate function values, grey correlation and correlation analysis. The results showed that the order of photosynthetic parameters to predict the heterosis of pepper from high to low was C_i, G_s, chlorophyll content, T_r and P_n. In addition, superiority from mid-parent heterosis and super-parent heterosis were chosen as the most suitable standards for appraising heterosis of pepper under low temperature and low light stress. The order of low temperature and low light resistance of the three materials was F₁ hybrid>male parent>female parent. This study enriched the heterosis theory of pepper, and provided theoretical basis for selecting photosynthetic parameters to predict the heterosis of pepper.

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Suitability of fresh spring and autumn leaves from different tea cultivars for ultramicro green tea powder production

SUN Da, GONG Shu, CUI Hongchun, GUO Minming, ZHENG Xuxia

2021, 33(3): 437-446. DOI: 10.3969/j.issn.1004-1524.2021.03.08

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In the present study, the particle size parameters, chromatic aberration and component contents of ultramicro green tea powder made from fresh spring and autumn leaves of eight tea cultivars (Maolv, Cuifeng, Longjing No. 43, Yingshuang, Fudingdabaicha, Jiukengzhong, Baiye No. 1, Soubeizhong) were determined and compared. Sensory evaluation was also used to select the suitable tea cultivars and harvest season. It was shown that the particle size of ultramicro green tea powder made from Longjing No. 43 spring tea was the smallest, and the particle size of ultramicro green tea powder made from Cuifeng spring tea was the most uniform. The ultramicro green tea powder made from Cuifeng spring tea and Fudingdabaicha spring tea had the most pure and gorgeous color. The amino acids content of ultramicro green tea powder made from Fudingdabaicha spring tea and Longjing No. 43 spring tea was the highest, while their tea polyphenols and water extract contents were relatively low. The sensory evaluation result showed that, the ultramicro green tea powder made from Soubeizhong spring tea, Yingshuang autumn tea and Fudingdabaicha autumn tea got the highest total score. All in all, the spring tea of Longjing No. 43, Cuifeng, Fudingdabaicha and Soubeizhong were suitable for the production of ultramicro green tea powder, while the autumn tea of Yingshuang and Fudingdabaicha could be used to produce ultramicro green tea powder for drinking.

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Isolation and phylogenetic analysis of Tremella sanguinea and its fungal host

CHEN Suo, HE Beibei, CHEN Qiwu, LI Li

2021, 33(3): 447-453. DOI: 10.3969/j.issn.1004-1524.2021.03.09

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In order to study the taxonomic status of Tremella sanguinea Y.B. Peng and its fungal host, pure cultures, named as XE01 and XE02, were respectively obtained from basidiospores and basidiocarp tissues of Tremella sanguinea cultivated on Tilia sp. logs. The colony and microscopic morphology, as well as the molecular phylogeny based on rDNA-ITS of the two strains were then analyzed. It was found that the colonies of XE01 on PDA medium were white-creamy, smooth and moist; the cells were oval, budding and yeast-like. In the phylogenetic tree based on rDNA-ITS, XE01 was nested within in the clade of the genus Phaeotremella, and showed closer phylogenetic relationship to P. neofoliacea and P. eugeniae according to the genetic distances. The colonies of XE02 on PDA medium were fluffy and white; the hyphae were septate, and rarely branched; spherical spores and clamp connections were present; the inoculated agar medium was reddish brown due to the production of diffusible pigments. In the phylogenetic tree based on rDNA-ITS, XE02 was nested within the clade of the genus Stereum and showed closer phylogenetic relationship to S. rugosum according to the genetic distances. Based on these results, XE01 might be the free-living unicellular yeast state of T. sanguinea, and XE02 might be its fungal host. The results would contribute towards the classification of T. sanguinea and its fungal host, as well as the identification of their germplasm resources.

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Analysis on alkaloids metabolites of two edible roses

QIAN Xiaohui, CHEN Longqing, LI Shuangqin, SHI Rui

2021, 33(3): 454-463. DOI: 10.3969/j.issn.1004-1524.2021.03.10

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Rosa gallica L. cv. Dianhong (ZY) rose and Rosa chinensis Jacq. cv. Crimson Glory (DH) are the main edible rose varieties in Yunnan. In this research, the UPLC-MS/MS method was used to detect the secondary metabolites of these two types of roses. The results showed that a total of 82 metabolites were detected in the two petals, including 55 kinds of amino acids and its derivatives (67.07%), 16 kinds of alkaloids (19.51%), 7 kinds of phenolamine (8.54%), 4 kinds of plumerane (4.88%). Glutathione in ZY was 26.35 times higher than that in DH, which had stronger antioxidant capacity. However, L-asparagine and S-(5'-adenosy)-L-homocysteine were unique substances in DH, which had a significant hypotensive effect. Compared with the DH, 15 metabolites were significantly down-regulated in ZY, which indicated that DH had more nutrition and healthcare functional substances, meanwhile, the unique ingredients of ZY made it have stronger antioxidant capacity.

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Distribution and growth dynamics of Candidatus Liberibacter asiaticus positive Asian citrus psyllid in Zhejiang Province

MENG Youqing, WANG Enguo, CHEN Wujian, LI Yanmin, CHENG Fan, MENG Minxia

2021, 33(3): 464-469. DOI: 10.3969/j.issn.1004-1524.2021.03.11

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Asian citrus psyllid (Diaphorina citri Kuwayama) is the main vector of Candidatus Liberibacter asiaticus(CLas), the pathogen of Huanglongbing (HLB) in China. In order to reveal the distribution characteristics and growth dynamics of CLas in Asian citrus psyllid, and propose suitable time for pest control and disease prevention, 1 662 samples of Asian citrus psyllid and 2 900 samples of HLB were collected from orchards in 24 counties (cities and districts) from 2002 to 2019, according to the distribution characteristics of citrus orchards in Zhejiang Province. The quantity and positive rate of CLas were detected by quantitative PCR. It was shown that there was linear relationship within CLas amount and latitude, longitude, respectively. It was calculated that the north and west boundary for CLas distribution was 29.20°N and 119.80°E in Zhejiang Province. The positive rate of CLas in Zhejiang orchards increased with the elevated HLB incidence rate, and their relationship fitted the Logistic model. The monthly dynamics of CLas in Zhejiang orchards exhibited 3 peaks in April, July and December, respectively, while the annual dynamics fitted conic curves, and reached the peak in 2010. Based on these findings, it was suggested that early spring, summer and autumn were the best time for HLB prevention and control.

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Expression, purification and bioinformatics analysis of Magnaporthe oryzae MGG-01005

ZHAO Xiuping, WANG Shuang, YAN Xingyi, DUAN Qiang, ZHANG Shuai, CHEN Yongsheng, LI Guorui

2021, 33(3): 470-478. DOI: 10.3969/j.issn.1004-1524.2021.03.12

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MGG-01005 is an important gene associated with mycelia growth of Magnaporthe oryzae.In this study, a series of bioinformatics analysis including general physical and chemical properties, structural domains, and functional site prediction were carried out to construct the prokaryotic expression vector PETM13-MGG-01005. IPTG was used to induce the expression of recombinant protein, and the protein was purified by nickel ion affinity chromatography, anion exchange chromatography and molecular sieve chromatography. The results showed that the molecular weight of the protein was about 16 471.49 u, which encoded 153 amino acids. It contained the domain of Tctex-1, had no transmembrane structure and signal peptide, had no functional site, and had the active site of phosphoric acid, and was an unstable hydrophilic protein. The protein could be induced to express by 0.1 mmol·L ^-1 IPTG. The optimal eluent of affinity chromatography was divided into 20 mmol·L ^-1 Tris-HCl, 500 mmol·L ^-1 NaCl, and 80 mmol·L ^-1 imidazole. Anion exchange chromatography showed that the protein was resistant to low salt conditions. The molecular sieve chromatography has the conformation of uniform morphology and good symmetry, and the molecular weight of the protein corresponding to the maximum elution peak is about 35 ku, indicating that the protein exists in the form of dimer. In this study, a large amount of high purity protein was obtained in order to lay a theoretical and practical foundation for further exploration of the function of this protein and subsequent related studies on Magnaporthe oryzae.

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Antibacterial activities and optimization of fermentation conditions of lipopeptides produced by Aureobasidium pullulans PA-2

YUE Denggao, CHENG Liang, GUO Qingyun

2021, 33(3): 479-489. DOI: 10.3969/j.issn.1004-1524.2021.03.13

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The antibacterial activities of lipopeptides from Aureobasidium pullulans PA-2 was explored, and the fermentation conditions were optimized with the output of lipopeptides as the response value, laying a theoretical foundation for the production and application of lipopeptides. The lipopeptides was crudely extracted by acid precipitation method. The crude extract of lipopeptide was qualitatively detected by in-situ acid hydrolysis and ninhydrin colorimetry. Antibacterial activities were measured by the method of agar drilling diffusion. The fermentation conditions were optimized by central composite design (CCD). Finally, the crude extract was identified as cyclic lipopeptide. The lipopeptides had obvious effects on Staphylococcus aureus, Saccharomyces cerevisiae, Escherichia coli, Mycosphaerella cerasella, Pyrenophorateres drechsler and antibacterial circle were 3.65, 1.95, 2.15, 1.35 and 2.18 cm respectively. The optimal fermentation conditions were: inoculation amount 6.8%, rotation speed 216 r·min ^-1, culture temperature 26 ℃, liquid volume 125 mL and initial pH 7.Under this condition, predicting yield of antibacterial lipopeptides by the model was 0.94 g·L ^-1, actually 0.92 g·L ^-1, which was 51% more than that of before(0.61 g·L ^-1). The optimized fermentation conditions increase the yield of the lipopeptide and reduce the fermentation cost, which may be applied to the control of strains with inhibitory effect above

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Effect of Trichoderma polysporum HZ-31 infection on physiological mechanism of Avena fatua L.

ZHU Haixia, MA Yongqiang, XIAN Wenrong

2021, 33(3): 490-496. DOI: 10.3969/j.issn.1004-1524.2021.03.14

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Avena fatua L. as a common weed in the farmland of Qinghai Province, was selected as the target receptor. The effects of Trichoderma polysporum HZ-31 on various physiological indexes of wild oats were determined after potted inoculation, and the physiological mechanism of the interaction between host and pathogen was analyzed. The results showed that there were various effects of Trichoderma polysporum HZ-31 on the defense enzymes of physiological mechanism of Avena fatua L., PAL and POD activity increased to resist the infection of the strain. The other physiological defense indexes including MDA content, CAT activity, PPO activity, SOD activity, soluble protein content and chlorophyll content were destroyed by the infection of the strain. The effect of the inhibited defense enzyme was greater than that of the promoted defense enzyme. The infection of HZ-31 inactivated or inhibited the main enzymes in Avena fatua L., interrupted the corresponding enzymatic reaction, and caused a wide range of metabolic changes in plants, including changes in cell membrane permeability, interference in photosynthesis, protein synthesis, phenol metabolism and other physiological changes.

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Screening of host factors interacting with wheat yellow mosaic virus P2 by yeast two-hybrid system

HAN Xiaolei, GAO Shiqi, ZHANG Fan, YANG Jian, LIU Peng, JIANG Hongming, LI Linzhi

2021, 33(3): 497-505. DOI: 10.3969/j.issn.1004-1524.2021.03.15

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Wheat yellow mosaic virus (WYMV) is classified in the genus Bymovirus, family Potyviridae. The genome is composed of two sense RNA single-stranded RNA1 and RNA2 and encodes 10 proteins, among which P2 plays an important role in virus replication. In order to identify the targets of P2 in host, co-transformation of cDNA library vector and pGBKT7-P2 was constructed, eighteen candidate host targets of P2 were screened out, which were divided into several types based on their functions, including salicylic acid signal pathway factor, E3 ubiquitin ligase, defense response, oxidoreductase activity and photosystem II assembly. Additionally, the interaction of P2 and TaTIFY or Ta14-3-3 was further verified by Y2H system. Based on the results, it could be speculated that P2 may interact with E3 ubiquitin transcription factor, salicylic acid signal transcription factor, or the factors associated with plant photosystem and chloroplasts formation. In conclusion, P2 may participate in multiple signaling pathways during viral infection, and provide an insight into molecular interaction mechanism between WYMV and the host.

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Effects of six kinds of nematicides on soil microbial population, enzymes activities and nutrients in replanted Chinese yam field

FAN Linjuan, LIU Zirong, XU Xueliang, WANG Fenshan, PENG Deliang, YAO Yingjuan

2021, 33(3): 506-515. DOI: 10.3969/j.issn.1004-1524.2021.03.16

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To clarify the effect of nematicides on soil environment, the effects of two kinds of chemical nematicides (avifosthiazate granules and fluopyram) and four kinds of biological nematicides (Verticillium chlamydosporium, Paecilomyces lilacinus, horseradish and tea curd) on soil microbe quantity, enzymes activities and soil nutrients in the replanted Chinese yam field at seedling stage and maturity stage were studied by conventional analysis methods. The results indicated that, compared with the control without nematicides, two kinds of chemical nematicides significantly (P<0.05) increased the number of soil bacteria and fungi at seedling stage, but the number of soil bacteria and fungi all decreased to the same level as control or lower at maturity stage. Among the four kinds of biological nematicides, tea curd significantly (P<0.05) inhibited the ratio of bacteria to fungi (bacteria/fungi), yet significantly (P<0.05) increased the number of fungi at seedling stage, and significantly (P<0.05) increased the number of soil bacteria and bacteria/fungi at maturity stage. All the treatments had no significant effect on soil urease activity. Two kinds of chemical nematicides and V. chlamydosporium, P. lilacinus, horseradish had significant (P<0.05) promoting and inhibiting effects on soil acid phosphatase activity at seedling stage and maturity stage, respectively; while the activity of acid phosphatase was significantly (P<0.05) inhibited by tea curd at maturity stage. The activity of soil sucrase at seedling stage and maturity stage was significantly (P<0.05) inhibited and promoted by the tea curd, respectively, while all the other nematicides showed significant (P<0.05) inhibition effect all the time. The contents of soil ammonium nitrogen, available potassium and available phosphorus were significantly (P<0.05) affected by nematicides. The contents of soil ammonium nitrogen and available potassium had no significant change compared with that of control at seedling stage after application of nematicides. At maturity stage, the contents of ammonium nitrogen and available potassium in other treatments were significantly (P<0.05) higher than those in the control except for the content of ammonium nitrogen with application of tea curd. At seedling stage, the content of soil available phosphorus with application of nematicides was significantly (P<0.05) lower than that of control, but at maturity stage, there was no significant difference in the content of soil available phosphorus. In conclusion, the effects of these nematicides on soil microbial population, soil urease activity and soil nutrients could be gradually recovered with the prolonged time, and showed no potential harm to soil fertility and crop growth, while the effects on soil acid phosphatase activity and sucrase activity might interfere with soil organic phosphorus mineralization and carbon cycle to some extent.

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Effect of biochar on wheat root-associated microbial community structures

XU Minmin, HUANG Ying, LI Bo, XU Yan, ZHANG Shuai, YAO Lingyun, WANG Zheng

2021, 33(3): 516-525. DOI: 10.3969/j.issn.1004-1524.2021.03.17

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In order to study the effect of biochar on the wheat root-associated microbiome, greenhouse experiment was conducted and the microbial communities in wheat endosphere, rhizosphere and bulk soil were sequenced by high throughput sequencing technology. The results showed that the microbial community diversity in endosphere was significantly (P<0.05) lower than that in the rhizosphere and bulk soil. In other words, plant roots could filter and screen some microorganisms to colonize and grow in the roots, among which Proteobacteria and Cyanobacteria were the dominant bacteria. Biochar could influence the structure and composition of wheat root-associated microbial community. In the endosphere, the relative abundance of Verrucomicrobiaceae and Luteolibacter was significantly (P<0.05) increased with biochar addition; while in the rhizosphere, biochar addition significantly (P<0.05) increased the relative abundance of Verrucomicrobia, Firmicutes, Gemmatimonadetes, Bacillales, Alicyclobacillaceae, Luteolibacter, Tumebacillus, Gemmatimonas, Kosakonia, Lysobacter, Pseudoxanthomonas, Blastomonas, Mssilia, Archangium and Enterobacter. The microbial communities in the rhizosphere was more sensitive to biochar, and the addition of biochar significantly (P<0.05) changed the biomarkers in the rhizosphere of wheat.

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Changes of rheological properties and proteins components of egg albumin during storage at room temperature

YANG Xiaopan, LIU Lili, HUANG Zhengdi, LI Yuanyuan, HAO Weiming, ZHANG Mengjun, SHI Shengjuan

2021, 33(3): 526-533. DOI: 10.3969/j.issn.1004-1524.2021.03.18

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In order to explore the effect of storage at room temperature on rheological properties and proteins components of egg albumin, the main proteins contents and rheological properties of egg albumin were measured when the egg was stored at 25 ℃ for 28 d. The results showed that with the prolonged storage time, the content of ovomucin decreased significantly (P<0.05), while the content of S-ovalbumin increased significantly (P<0.05), reaching (92.99±0.81)% at 28 d. Lysozyme content showed a significant (P<0.05) trend of first increasing and then decreasing, yet its activity exhibited decreasing tendency. With the change of proteins contents, the foaming and emulsifying properties of egg albumin significantly (P<0.05) increased first and then decreased, while the foam stability and emulsion stability decreased significantly (P<0.05). The thermal denaturation temperature and enthalpy value of the egg albumin increased gradually during the storage. In the early stage of storage, the apparent viscosity of the egg albumin increased, and the energy storage modulus value (G') was higher than energy consumption modulus value (G″), which showed the elastic properties of the fluid. In the late stage of storage, the apparent viscosity decreased, and the G' was smaller than G″, which showed the characteristics of viscosity. These findings provided a theoretical basis for further research on the thinning of egg albumin.

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Analysis and risk assessment of cyromazine and its metabolites in bayberry

TIAN Pei, ZHAO Huiyu, LIU Zhiwei, WANG Jiao, DI Shanshan, XU Hao, WANG Zhiwei, WANG Xinquan, QI Peipei

2021, 33(3): 534-540. DOI: 10.3969/j.issn.1004-1524.2021.03.19

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Bayberry is an important economic fruit in south China. Its quality and safety are highly concerned because of lacking registered pesticides and direct consumption habit with bare fruit without washing. Drosophila melanogaster is the most important insect which harm bayberry fruit during harvest time. Therefore, it is necessary to evaluate the residual risk of its control agents such as cyromazine, which has been widely used for preventing Drosophila melanogaster on bayberry. Cyromazine and its metabolite melamine were not easy to be analysed becaused of highly solubable property in water. In this study, an analytical method had been developed for analyzing cyromazine and its metabolite melamine using solid phase extraction coupled with high performance liquid phase tandem mass spectrometer (LC-MS/MS) under multi-reaction monitoring mode. The sample was extracted by 1% trichloroacetic acid solution, followed by purification with MCX SPE, and then detected by LC-MS/MS. The results showed that recoveries of cyromazine and melamine were in the range of 88%-110%. The relative standard deviations were less than 10%. The detection limit (LOD) for both cyromazine and melamine methods were 0.01 mg·kg ^-1. The quantitative limits (LOQ) of the methods were all 0.05 mg·kg ^-1, with good linear relationship in the range of 0.01-0.10 mg·L ^-1. The evaluation result of matrix effect showed matrix inhibition impact. Risk assessment results showed that both chronic and acute risk quotients for cyromazine and melamine were less than 1, indicating that their acute and chronic risks were negligible or within the acceptable range according to the monitoring data. In general, there was no risk protentical for bayberry consumers. This method had the advantages of good sensitivity, friendly to people and environment with less solvent usage. It could be applied for future risk monitoring of cyromazine and its metabolite melamine on bayberry.

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Participation behavior of pork seller in traceability system: empirical analysis of 636 sellers in Beijing, Shanghai and Jinan, China

JIN Liwen, LIU Zengjin, LIU Aijun

2021, 33(3): 541-552. DOI: 10.3969/j.issn.1004-1524.2021.03.20

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Based on the survey data of 636 pork sellers in three cities of Beijing, Shanghai and Jinan, a bivariate Probit model was used to analyze the influencing factors of pork sellers' participation behavior in traceability system. It was found that the participation level of pork sellers in wholesale market and wet market was different. Only 28.62% of the pork sellers took part in the traceability system, and the pork sold by them had the “traceability”. So, the participation level needs to be substantially improved. At present, most pork sellers are young and middle-aged people, their education is generally low, and they have a relatively low level of awareness of the importance of pork traceability. The purchasing relationship, the years of sales, the sales profit, the sales format, the degree of attention, the punishment intensity, the monitoring intensity and the age significantly (P<0.1) affected the pork sellers' participation behavior. Therefore, it is proposed to strengthen the publicity of pork traceability system, to give appropriate rewards to pork sellers who standardize the participation behavior in traceability system, and to strengthen supervision of pork sellers by the government departments and market managers.

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Transportation infrastructure, spatial spillover and rural poverty reduction:an empirical study based on panel data

ZHANG Shasha, ZHENG Xungang, ZHANG Bizhong

2021, 33(3): 553-564. DOI: 10.3969/j.issn.1004-1524.2021.03.21

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The construction of transportation infrastructure is an important work for rural poverty reduction. In this paper, the panel data of 30 provincial administrative regions in China (Hong Kong, Macau, Taiwan, Tiebet not included) from 2008 to 2017 were used to construct adjacency matrix and inverse geographical distance matrix. Based on the spatial correlation test, the corresponding spatial econometric model was selected to study the direct effect and spatial spillover effect of transportation infrastructure density on rural poverty reduction. The results showed that, the rural poverty level exhibited a significant (P<0.01) spatial clustering feature on the whole, while the inter-provincial distribution exhibited the characteristics of high-high or low-low agglomeration, and this characteristic gradually increased with time. From a national perspective,the increase of road density and railway density not only significantly (P<0.01) promoted the local rural poverty reduction, but also had a significant (P<0.05) spatial spillover effect on the rural poverty reduction in neighboring areas, and the railway had a better poverty reduction effect in both of the two effects. From a regional perspective, the increase of road density not only significantly (P<0.01) promoted the local rural poverty reduction in the western region, but also had a significant (P<0.01) spatial spillover effect on the rural poverty reduction in neighboring areas in the eastern region. The increase of railway density had a significant (P<0.05) role in promoting rural poverty reduction in the local and neighboring areas in both the eastern and central regions, and the effect on poverty reduction in the central region was better than that in the eastern region in both of the two effects. Therefore, it was suggested that the government in the eastern and central regions should optimize the railway network structure, improve the quality of the road network, and increase the coverage and accessibility of railways in rural areas. In the western region, the government should actively develop road traffic, and at the same time make up for the shortcomings of railways. By promoting local resource development and material export, it would play a role in promoting employment and realizing poverty reduction.

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