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    16 July 2022, Volume 55 Issue 14
    CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS
    Cloning of the Soybean Single Zinc Finger Protein Gene GmSZFP and Its Functional Analysis in SMV-Host Interactions
    ZHAO DingLing,WANG MengXuan,SUN TianJie,SU WeiHua,ZHAO ZhiHua,XIAO FuMing,ZHAO QingSong,YAN Long,ZHANG Jie,WANG DongMei
    Scientia Agricultura Sinica. 2022, 55(14):  2685-2695.  doi:10.3864/j.issn.0578-1752.2022.14.001
    Abstract ( 352 )   HTML ( 235 )   PDF (1259KB) ( 152 )   Save
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    【Objective】The molecular mechanism underlying the resistance to soybean mosaic virus (SMV) infection in soybean is of great importance as soybean mosaic caused by SMV has become one of the major soybean disease worldwide. We have previously performed transcriptome analysis of SMV-inoculated soybean after inhibition of H2O2 production and have identified a differentially expressed C2H2-type single zinc finger protein gene, Glyma.18G003600.1, named GmSZFP. In this study, we use virus induced gene silencing (VIGS) technique to investigate the function of GmSZFP in soybean-SMV interaction, providing a foundation for further investigation of the molecular mechanism of GmSZFP in soybean-SMV interaction. 【Method】Soybean cultivar Jidou 7 and SMV strains SC-8 (susceptive) and N3 (resistance) were used as the materials in this study. Bioinformatic analysis was conducted to predict the protein domains of GmSZFP; its transcription factor activity was measured by transcriptional activation assay in yeast; the expression characteristics of GmSZFP at the transcriptional level in soybean-SMV interaction were verified by real-time quantitative PCR (qPCR); and the function of GmSZFP in soybean-SMV interaction was investigated by VIGS technique. 【Result】The CDS region of GmSZFP gene was cloned; amino acid sequence analysis and transcriptional activation assay in yeast revealed that GmSZFP is a C2H2-type zinc finger protein transcription factor with transcriptional activation activity; qPCR results showed that GmSZFP was strongly induced by SMV inoculation, and the expression pattern was different between the compatible and the incompatible combinations. The expression of GmSZFP was elevated after SMV inoculation, and then decreased in the incompatible combination, and the expression level of GmSZFP was significantly lower in the compatible combination than that in the former. Moreover, the expression level of GmSZFP was found to be reduced to the level that is similar to the level in the compatible combination that was pre-inoculated with imidazole, indicating that GmSZFP responds to SMV infestation at the transcriptional level and is regulated by H2O2; After silencing GmSZFP, we found that callose at the SMV inoculation site was greatly reduced compared to the control, and the expression of callose synthase genes GmGSL7c and GmGSL12b was reduced compared to the control, and the expression of callose hydrolase gene BG was elevated compared to the control; In addition, after GmSZFP was silenced, the virus spread outward to a distance of 2 mm at 72 h and to a distance of 3 mm at 96 h from the central source after SMV was inoculated in a small area, while the expression of SMV capsid protein (CP) gene was not detectable outside the inoculation site in control leaves; 10 d after SMV inoculation, the upper leaves (of the SMV inoculated leaves) in the GmSZFP-silenced plants showed mosaic, greening and curling symptoms, and CP gene was expressed, indicating that silencing of GmSZFP enabled SMV to transport in an unrestricted manner. 【Conclusion】GmSZFP is a canonical C2H2-type mono-zinc finger protein, and the GmSZFP gene plays a positive regulatory role in soybean resistance to SMV infection.

    Effect of Salicylic Acid Priming on Salt Tolerance of Kenaf Seedlings
    HU YaLi,NIE JingZhi,WU Xia,PAN Jiao,CAO Shan,YUE Jiao,LUO DengJie,WANG CaiJin,LI ZengQiang,ZHANG Hui,WU QiJing,CHEN Peng
    Scientia Agricultura Sinica. 2022, 55(14):  2696-2708.  doi:10.3864/j.issn.0578-1752.2022.14.002
    Abstract ( 279 )   HTML ( 241 )   PDF (2754KB) ( 139 )   Save
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    【Objective】To study the growth and physiological response of salicylic acid (SA) priming in kenaf under salt stress, and further reveal the induction pattern of SA priming on the stress-related genes in kenaf, thus provide a theoretical basis for salt tolerance study in kenaf. 【Method】Two different salt-tolerant kenaf cultivars (resistant and sensitive cultivars codenamed CP018 and CP047, respectively) were used as materials. The seeds were tested by SA priming and then subjected to hydroponics experiments to analyze the effect of SA priming on kenaf seed germination and the agronomic and physiological aspects of seedling under 150 mmol·L-1 NaCl stress, and the expression patterns of SA priming stress-related genes were analyzed by qRT-PCR. 【Result】The germination rate, germination potential and germination index of the salt-resistant cultivar CP018 were significantly improved after 0.2 mmol·L-1 SA priming, by 34.78%, 31.30% and 58.07%, respectively; the salt-susceptible cultivar CP047 also showed some improvement, by 7.50%, 10.56% and 6.23%, respectively, but did not reached the significant level. Under salt stress conditions, plant height inhibition was significantly reduced by 4.07% (CP018) and 3.91% (CP047) in the 2 cultivars by SA priming (S1) compared with un-priming (N1), and dry weight inhibition was significantly reduced by 15.50% (CP018) and 15.68% (CP047), in the 2 cultivars, respectively; fresh weight inhibition was significantly reduced by 4.46% in CP047, but not in CP018. Analysis of the root systems showed that root length inhibition was significantly reduced by 10.74% (CP018) and 10.77% (CP047) in the two cultivars, respectively, root surface area inhibition decreased by 5.09% (CP018) and 2.95% (CP047) in the two cultivars, reaching a significant level only in the salt-resistant cultivar CP018, while root activity inhibition was significantly reduced by 46.21% in the salt-susceptible cultivar CP047 and 6.56% in the salt-resistant cultivar CP018, reaching a significant level only in the salt-susceptible cultivar CP047. A grey correlation analysis of the indicators revealed that root activity was the most relevant factor influencing plants dry weight. SA priming reduced the MDA content and increased the POD and SOD enzyme activities of kenaf leaves under salt stress. Expression analysis of 12 stress-related genes showed that ACCD, APX2, SOS1, ARR2, PAL, CHIT and TIFY11 genes expression levels were significantly up-regulated after SA priming, while ERF9, ERS1, ERF.C3 and MYC2 and XTH22 expression patterns differed between the two cultivars, with XTH22 being significantly up-regulated in salt sensitive cultivar CP047 but not in the salt resistant cultivar CP018, ERS1 and MYC2 were significantly up-regulated in the salt resistant cultivar CP018 but significantly down regulated in the salt sensitive cultivar CP047, while the trend of ERF9 was opposite in the two cultivars. 【Conclusion】SA priming at a suitable concentration could significantly alleviate the growth of kenaf under salt stress, and differed in the degree and patterns of effects on different kenaf germplasm resources. SA may regulate kenaf plant response to abiotic stresses by affecting physiological processes such as antioxidant enzyme systems and mediating the expression of specific genes.

    TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY·AGRICULTURE INFORMATION TECHNOLOGY
    Straw Mulching from Autumn Fallow and Reducing Nitrogen Application Improved Grain Yield, Water and Nitrogen Use Efficiencies of Winter Wheat by Optimizing Root Distribution
    GAO RenCai, CHEN SongHe, MA HongLiang, MO Piao, LIU WeiWei, XIAO Yun, ZHANG Xue, FAN GaoQiong
    Scientia Agricultura Sinica. 2022, 55(14):  2709-2725.  doi:10.3864/j.issn.0578-1752.2022.14.003
    Abstract ( 293 )   HTML ( 238 )   PDF (786KB) ( 168 )   Save
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    【Objective】Frequent drought in winter and spring as well as excessive application of nitrogen limited wheat yield and sustainable development in rainfed farming areas of dryland in southwest China. The objective of this study was to clarify the effects of straw mulching from autumn fallow and reducing nitrogen application on root distribution, wheat yield, water and nitrogen utilization of dryland winter wheat, so as to provide a basis for optimizing wheat tillage system and green, high quality and efficient production of winter wheat in dryland of Sichuan province. 【Method】 The experiment was carried out at Renshou experiment station of Sichuan Agricultural University in Sichuan province from 2016 to 2018. The spilt plot design was employed with main plot of maize straw mulching (mulching from autumn fallow to wheat harvesting: SM) and no mulching (NM), and sub-plot of different nitrogen application rates (N0: 0; reducing nitrogen rate (RN): 120 kg N·hm-2, and conventional nitrogen rate (CN): 180 kg N·hm-2). Soil moisture, root length, root distribution, wheat yield, water consumption (ET), water and nitrogen use efficiencies were investigated. 【Result】Compared with NM, SM significantly increased the soil water content in 0-10 cm and 10-20 cm layers from sowing to booting stage and the soil water storage in 0-100 cm layer at sowing and jointing, and the soil water retention effect of straw mulching lasted until booting and anthesis stage. SM also promoted the wheat root growth at jointing and anthesis stage with higher root diameter and significantly higher root length density in 0-10 cm layer. The mean values of total ET, WUE (water use efficiency), nitrogen accumulation amount of wheat plant, nitrogen accumulation rate from sowing to jointing, nitrogen accumulation rate from jointing to anthesis, nitrogen use efficiency for grain production (NUEg), agronomic efficiency of nitrogen fertilizer (AEN), nitrogen fertilizer partial factor productivity (NPFP) and wheat yield under SM increased by 11.4%, 71.8%, 73.1%, 119.0%, 100.0%, 3.6%, 264.7%, 78.2% than that under NM, respectively, and the recovery efficiency of nitrogen fertilizer (REN) under SM increased by 44.4 percentage points compared with NM. The wheat yield under SM increased by 92.9% because of the significantly increased average spike number (31.8%) and grains per spike (44.4%). The effect of straw mulching was greater than that of nitrogen application. Compared with CN, RN did not significantly decrease the wheat root length density, ET, WUE and wheat yield. Combining with SM, RN significantly improved the NUEg, physiological efficiency of nitrogen (PEN), AEN, NPFP, and REN. 【Conclusion】Straw mulching from autumn fallow improved soil water content and storage and optimized root distribution in 0-10 cm layer with higher root length density and root diameter, thus to increase the nitrogen absorption and utilization, wheat yield, and the utilization of water and fertilizer. Straw mulching combined with 120 kg N·hm-2 was a high yield cultivation mode with reducing nitrogen application and high water and nitrogen use efficiency for dryland winter wheat in Sichuan province, China.

    Effects of Tillage Depth and Shading on Root Growth and Nutrient Utilization of Rapeseed
    BAI Fei, BAI GuiPing, WANG ChunYun, LI Zhen, GONG DePing, HUANG Wei, CHENG YuGui, WANG Bo, WANG Jing, XU ZhengHua, KUAI Jie, ZHOU GuangSheng
    Scientia Agricultura Sinica. 2022, 55(14):  2726-2739.  doi:10.3864/j.issn.0578-1752.2022.14.004
    Abstract ( 291 )   HTML ( 44 )   PDF (1898KB) ( 128 )   Save
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    【Objective】The rapeseed (Brassica napus L.) production district in the Yangtze River valley lacks sufficient radiation due to abundant rainfall during its growing season. In addition, the application of dense planting technology intensifies the competition for radiation among individuals. Insufficient radiation and poor soil texture have become main factors for restricting high yield of rapeseed in this area. In order to provide the theoretical support for stable yield and increased income, the effects of tillage depth on root growth and nutrient utilization of shaded rapeseed were studied. 【Method】 The experiment designed by the split-split plot method in three replications was conducted in the tested site of Huazhong Agricultural University in Wuhan, Hubei province, from 2019 to 2021. The experiment consisted of three factors arranged in a split-split plot design with 2 varieties: Xiangzayou 518 (XZY518) and Zheyou 50 (ZY50) in main plots, two levels of tillage depth: 5 cm (T5) and 20 cm (T20) in sub plots, and two levels of shading rate: 0% shading (S0) and 30% shading (S1) in sub-sub plots. The effects of different tillage depths on physical and chemical properties of soil, the antioxidant enzyme activity, nutrient absorption of the root and the dry matter accumulation of root and shoot were evaluated. 【Result】Deep tillage promoted the accumulation of organic matter, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium in each layer of soil, with the largest increase (by 7.5%-42.3%) in 10-20 cm soil. Shading decreased the soil electrical conductivity, root surface area (decrease by 13.3%-36.6%), the utilization efficiency of nitrogen (decrease by 3.0%-28.4%) and root dry weight, while it increased the main root length, root to shoot ratio, lateral root proportion, and the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in roots. The increasing tillage depth in shading condition alleviated the reduction of soil water content, promoted taproot elongation, increased the activities of antioxidant enzymes (POD and SOD) and the root surface area, root to shoot ratio, lateral root ratio finally improved the utilization efficiency of nitrogen, and the accumulation of dry matter. The analysis of variance showed that the interaction between tillage depth and shading on root morphology, dry matter accumulation, antioxidant enzyme activity and nutrient utilization reached a significant or extremely significant difference. Compared with normal light, the root surface area were decreased by 24.9%-36.6% and 13.3%-19.2%, the utilization efficiency of nitrogen were decreased by 10.0%-28.4% and 3.0%-23.9% after shading under the shallow tillage and deep tillage, respectively. 【Conclusion】Under the weak light stress, the deep tillage increased soil nutrients and main root elongation, the ratio of lateral root and root surface area, the activity of antioxidant enzymes in the root, dry matter accumulation, and enhanced the nutrient absorption capacity and nitrogen use efficiency, also delayed the aging of the root system. As a result, all these factors promoted rapeseed growth.

    PLANT PROTECTION
    Function of SlβCA3 in Plant Defense Against Pseudomonas syringae pv. tomato DC3000
    FANG HanMo,HU ZhangJian,MA QiaoMei,DING ShuTing,WANG Ping,WANG AnRan,SHI Kai
    Scientia Agricultura Sinica. 2022, 55(14):  2740-2751.  doi:10.3864/j.issn.0578-1752.2022.14.005
    Abstract ( 301 )   HTML ( 44 )   PDF (2944KB) ( 104 )   Save
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    【Background】With global climate change, the increase of atmospheric CO2 concentration is predicted to exert an influence on plant diseases, which seriously affects agricultural production. Plant β-carbonic anhydrases (βCAs) are important components in plant CO2 sensing and concentration systems and are involved in the immunity of Arabidopsis and tobacco. However, little is known about the functions of βCAs in the regulation of disease resistance in tomato (Solanum lycopersicum). 【Objective】The objective of this study is to explore the role and mechanism of tomato SlβCA3 in disease resistance, so as to provide scientific basis for resistance regulation of tomato in agricultural production. 【Method】Based on the similarity to the amino acid sequences of AtβCAs, four SlβCAs were identified in the Sol genomics network database. Wild-type (WT) tomato ‘Ailsa Craig’ (AC) was used to inoculate Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) in the study. Then qRT-PCR was used to determine the transcript abundance of SlβCAs in leaves to screen the Pst DC3000-induced gene SlβCA3. Furthermore, SlβCA3 stable over-expression lines (OE-SlβCA3) were generated by Agrobacterium tumefaciens-mediated genetic transformation technology as the background of AC. OE-SlβCA3 plants were inoculated with Pst DC3000 to investigate the role of SlβCA3 in disease defense. For exploring the intrinsic mechanism of SlβCA3 regulating plant disease resistance, the transcriptome changes of WT and OE-SlβCA3 plants between inoculation with Pst DC3000 and control conditions were compared, and KEGG (Kyoto encyclopedia of genes and genomes) database was used to analyze functions of the differentially expressed genes. It is speculated that sugar metabolism pathways are involved in SlβCA3-mediated plant immunity. To verify and further analyze the conclusion, the expression of genes related to the sugar metabolism and signaling, as well as the contents of glucose, fructose and sucrose in WT and OE-SlβCA3 plants were determined. 【Result】OE-SlβCA3 plants enhanced the resistance to Pst DC3000, and showed less disease-associated cell death and a lower number of bacteria compared to the WT controls. RNA-Seq results showed that OE-SlβCA3 did not greatly change the overall transcript profile in the absence of the pathogen. In total, 2 100 Pst DC3000-induced transcripts were differentially changed in abundance. Of these, 63.3% were more abundant following Pst DC3000 inoculation in the OE-SlβCA3 plants. KEGG analysis showed that Pst DC3000-induced genes, which are dependent on SlβCA3-overexpression, were enriched in the pathways related to sugar metabolism, including starch and sucrose metabolism, protein processing in the endoplasmic reticulum (glycosylation), amino sugar and nucleotide sugar metabolism, ribosomal biosynthesis in eukaryotes and photosynthesis. Sugar metabolism is closely related to sugar signaling. Further studies found that the expression of genes related to sugar metabolism and signal transduction pathways, as well as the contents of glucose, fructose and sucrose, were higher in the leaves of OE-SlβCA3 plants than those of WT after inoculation with Pst DC3000. 【Conclusion】Overexpression of SlβCA3 in tomato enhances the resistance of plants to Pst DC3000, which may be related to the role of sugar metabolism and signaling in plant immunity.

    Molecular Characteristics and Pathogenicity Analysis of Youcai Mosaic Virus Guangdong Isolate Infecting Radish
    LI ZhengGang,TANG YaFei,SHE XiaoMan,YU Lin,LAN GuoBing,HE ZiFu
    Scientia Agricultura Sinica. 2022, 55(14):  2752-2761.  doi:10.3864/j.issn.0578-1752.2022.14.006
    Abstract ( 261 )   HTML ( 34 )   PDF (4274KB) ( 130 )   Save
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    【Objective】Viral disease is one of the major factors threatening the production safety and radish farming industry. The objective of this study is to identify the viruses that infect radish in Guangdong Province, and to analyze the molecular characteristics and pathogenicity of youcai mosaic virus (YoMV), so as to provide theoretical basis for the prevention of viral disease in radish. 【Method】Three symptomatic and one asymptomatic samples were collected from a radish-planting base in Guangdong and were subjected to total RNA extraction. Small RNA sequencing and assembly (sRSA) was used to identify the virus species, followed by RT-PCR verification with specific primer pairs designed according to the sRSA results. To construct the infectious cDNA clones of YoMV-GD isolate, two primer pairs were designed, and the PCR products were introduced into pCB301 vector by seamless cloning and assembly. Then the full-length genomic sequences of YoMV-GD and other YoMV isolates were used to construct phylogenetic tree by MEGA7 software. Agrobacterium containing pCB301-YoMV-GD was infiltrated into Nicotiana benthamiana and Nicotiana tabacum to verify the infectivity of YoMV-GD infectious cDNA clones. Subsequently, the pathogenicity of YoMV-GD was tested in radish and Chinese flowering cabbage by agroinfiltration. 【Result】sRSA result showed that the viruses that infecting radish in Guangdong include Raphanus sativus cryptic virus 3 (RsCV3), Raphanus sativus chrysovirus 1 (RasCV1), turnip mosaic virus (TuMV), and YoMV. Sanger sequencing reveals that YoMV-GD isolate contains 6 304 nt and encodes four proteins, replication-associated protein, replicase, movement protein, and coat protein. YoMV-GD shares the highest similarity (99.18%) with YoMV British isolate (GenBank accession number: AY318866). Phylogenetic analysis shows that YoMV-GD has a closer relationship with isolates from British, Germany, Shanghai, and Chongqing. In addition, the YoMV-GD infectious cDNA clones could successfully infect N. benthamiana and N. tabacum, causing crinkle, mosaic, and necrosis symptoms in the upper leaves. Moreover, though YoMV-GD isolate could systemically infect radish and Chinese flowering cabbage, the symptoms were very weak. 【Conclusion】Viruses infecting radish in Guangdong include RsCV3, RasCV1, TuMV, and YoMV, and mixed infection is the main type. There was no clear regional difference among YoMV isolates. YoMV-GD is highly pathogenic in tobacco, but weak in radish and Chinese flowering cabbage.

    SOIL & FERTILIZER·WATER-SAVING IRRIGATION·AGROECOLOGY & ENVIRONMENT
    Yield of Wheat and Maize and Utilization Efficiency of Nitrogen, Phosphorus and Potassium in Xinjiang
    TANG MingYao,SHEN ChongYang,CHEN ShuHuang,TANG GuangMu,LI QingJun,YAN CuiXia,GENG QingLong,FU GuoHai
    Scientia Agricultura Sinica. 2022, 55(14):  2762-2774.  doi:10.3864/j.issn.0578-1752.2022.14.007
    Abstract ( 554 )   HTML ( 53 )   PDF (1189KB) ( 198 )   Save
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    【Objective】The objectives of the present paper were to understand current status of fertilizer utilization efficiency of wheat and maize in Xinjiang, to optimize their nutrient management, and to improve fertilizer utilization efficiency, so as to provide basic data and technique support for the food security of Xinjiang and as well as all the country. 【Method】72 field trials (40 for wheat and 32 for maize) were carried out in main grain growing areas of Xinjiang from 2018 to 2020. Four different treatments of fertilizer application were designed, including nitrogen, phosphorus and potassium (NPK), no nitrogen (PK), no phosphorus (NK), and no potassium (NP). Each experiment was conducted in triplicate. Then, the nutrient uptake of main grain crops, the response of nitrogen, phosphorus, and potassium fertilizers, the agronomic efficiency, the utilization rate and other parameters were examined under the current conditions of fertilization for agricultural production in Xinjiang. 【Result】(1) The average application amounts of N, P and K fertilizers for wheat in Xinjiang were 233.1 kg N·hm-2, 128.0 kg P2O5·hm-2 and 75.5 kg K2O·hm-2, respectively; the average application amounts of N, P and K fertilizers for maize were 254.9 kg N·hm-2, 148.0 kg P2O5·hm-2 and 67.8 kg K2O·hm-2, respectively. (2) The wheat yield of per unit area was 7 505 kg·hm-2 under NPK treatment, and the yield responses of N, P and K fertilizers were 2 206 kg·hm-2 (500-3 795 kg·hm-2), 2016 kg·hm-2 (288-4 230 kg·hm-2), and 1 362 kg·hm-2 (105-2 910 kg·hm-2), respectively. The average rates of yield increase for N, P and K fertilizers were 45.0%, 39.7% and 23.0%, respectively. The yield per unit area of maize under NPK treatment was 13 715 kg·hm-2, and the yield responses of N, P and K fertilizers were 4 657 kg·hm-2 (1 559-6 900 kg·hm-2), 1 942 kg·hm-2 (473-4 699 kg·hm-2), and 1 297 kg·hm-2 (113-5 440 kg·hm-2), respectively. The average rates of yield increase for N, P and K fertilizers were 52.2%, 21.2%, and 15.5%, respectively. (3) The uptakes of N and K by wheat and maize were relatively large, whereas the uptake of phosphorus was relatively small. The application of chemical fertilizers could significantly promote the uptake of nitrogen, phosphorus and potassium by plants, and increase the accumulation of nitrogen, phosphorus and potassium in soil. For NPK treatment, it required 2.7 kg (1.7-4.0 kg) of nitrogen (N), 0.8 kg (0.4-1.3 kg) of phosphorus (P2O5), and 2.1 kg (1.2-3.9 kg) of potassium (K2O) to form 100 kg of grains for wheat; for maize using the NPK treatment, it required 2.1 kg (1.5-2.9 kg) of nitrogen (N), 0.8 kg (0.4-1.2 kg) phosphorus (P2O5), and 2.1 kg (0.7-3.4 kg) of potassium (K2O) to form 100 kg of grains. (4) The agronomic efficiency of nitrogen fertilizer for maize was higher than that of wheat. There were no significant differences in the agronomic efficiencies of phosphorus and potassium fertilizers. The agronomic efficiencies of N, P and K fertilizers for wheat were 9.6, 15.9 and 18.7 kg·kg-1, respectively. Therefore, the agronomic efficiencies of P and K fertilizers were significantly higher than that of nitrogen fertilizer. The agronomic efficiencies of nitrogen, phosphorus, and potassium fertilizers for maize were 18.7, 13.4 and 18.1 kg·kg-1, respectively, N and K fertilizers were significantly higher than P fertilizer. (5) The utilization rates of N, P and K fertilizers for wheat were 41.4%, 21.8% and 45.2%, respectively. The utilization rates of N, P and K fertilizers for maize were 46.9%, 20.5% and 49.6%, respectively. The N and K utilization efficiency for wheat and maize were significantly higher than that of P. 【Conclusion】To date, the yield of wheat and maize in Xinjiang was high, the utilization efficiency of nitrogen, phosphorus and potassium was at a high level, and the utilization efficiency of nitrogen and potassium was significantly higher than that of phosphorus. In Xinjiang, wheat and maize yield was most sensitive to nitrogen deficiency. The phosphorus deficiency had lower influence on the wheat and maize yield, and the potassium deficiency had the lowest reduction. The amount of nitrogen application applied to wheat and maize in Xinjiang was reasonable. In contrast, the amount of potassium application was seriously insufficient. The excessive application of phosphate in wheat existed. In the future, it was necessary to increase the input of potassium fertilizer for wheat and maize and to reduce the input of phosphorus fertilizer for wheat.

    Effects of Feedstock, Pyrolyzing Temperature and Biochar Components on the Growth of Chinese Cabbage
    ZHONG JiaLin,XU ZiYan,ZHANG YiYun,LI Jie,LIU XiaoYu,LI LianQing,PAN GenXing
    Scientia Agricultura Sinica. 2022, 55(14):  2775-2785.  doi:10.3864/j.issn.0578-1752.2022.14.008
    Abstract ( 197 )   HTML ( 34 )   PDF (516KB) ( 83 )   Save
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    【Objective】 The objectives of this study were to investigate the effects of biochar feedstocks, pyrolyzing temperatures and biochar components on plant growth and to uncover the mechanism that how biochar increased crop yields. 【Method】 Six biochars were made from sawdust and maize stalk at pyrolyzing temperature of 350, 450, and 550℃. Each biochar was then separated into two parts through hot water extraction method, including the water soluble biochar extract and the washed biochar residue. A pot trial was conducted to investigate the effects of untreated biochar (BC), biochar extract (BE) and washed biochar residue (WB) application on the growth of non-heading Chinese cabbage (Brassica campestris ssp. chinesis). 【Result】 The aboveground biomass of Chinese cabbage under the addition of maize stalk biochars and their components was 16.1 g/pot on average, which was significantly higher than the values under sawdust biochars and their components (13.0 g/pot) amendment and the control (13.5 g/pot). Similarly, the root morphology index of root length, surface area, root volume and number of root tips under the addition of maize stalk biochars and their components improved greatly compared with sawdust biochar and the control. The aboveground biomass under the addition of washed biochar residues was 16.5 g/pot on average, which were 26.9% and 17.9% higher than the values under the addition of untreated biochar and the biochar extracts, respectively. The root length, surface area, root volume and number of root tips under washed biochar residues addition increased by 64.1%, 51.1%, 38.3% and 80.0%, respectively compared with biochar extracts addition. The biochars under different pyrolyzing temperature had no significant effect on the aboveground biomass and root growth of Chinese cabbage. Compared with the untreated biochar, the washed biochar residue addition increased the concentration of nitrogen (N) in aboveground biomass by 25.9%, while the concentration of phosphorus (P) and potassium (K) decreased by 39.7% and 14.1%, respectively. Soil pH, the concentration of soil organic carbon, total N, available P and K under the addition of maize stalk biochar and their components increased by 0.1 unit, 20.3%, 19.1%, 29.1% and 189.2% respectively compared with wood biochar addition. Compared with the untreated biochar, the washed biochar residue addition decreased soil organic carbon, total N, available P and K by 14.6%, 6.6%, 41.3% and 55.1%, respectively, while soil pH increased by 0.13 unit. Soil organic carbon, total N and available P under the addition of biochar extracts decreased by 49.8%, 18.9% and 24.2%, respectively, while soil pH and available K content was not affect. Correlation analysis showed that the aboveground biomass was positively related to root length, surface area, root volume, the number of root tips and soil pH value; while it was negatively correlated to the P concentration in the aboveground of Chinese cabbage. 【Conclusion】The feedstock and biochar component were the two main factors that regulating the response of plant growth to biochar amendment. The biochar from maize stalk was more suitable for soil amendment compared with wood biochar in terms of crop yield increase, and more crop yield could be obtained when maize stalk biochar was amended after hot water extracting. The water-soluble components presented in biochar played a key role in crop yield increase via promoting root growth. The promotion effect was closely related to biochar feedstock, pyrolyzing temperature and the chemical composition in biochar extracts.

    The Characteristics of Ammonia Volatilization of Humic Acid-Urea Complex Combined with Urea from Different Fertilized Soils
    JING JianYuan,YUAN Liang,ZHANG ShuiQin,LI YanTing,ZHAO BingQiang
    Scientia Agricultura Sinica. 2022, 55(14):  2786-2796.  doi:10.3864/j.issn.0578-1752.2022.14.009
    Abstract ( 229 )   HTML ( 39 )   PDF (601KB) ( 83 )   Save
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    【Objective】 The application of humic acid enhanced urea (HAU) can effectively reduce ammonia volatilization, and the humic acid in HAU, named UHA, plays a great role in this process. However, due to the reaction between humic acid and urea, the effect of UHA combined with urea on soil ammonia volatilization may be different from that of conventional humic acid (HA). Therefore, the relevant research will help to further reveal the mechanism of HAU reducing ammonia volatilization from soil. 【Method】In this study, UHA was extracted by absolute ethanol from HAU. Through indoor constant temperature soil incubation, the effects of HA or UHA combined with urea on soil ammonia volatilization from long-term unfertilized soil or fertilized soil were studied. The dosage of HA or UHA was 0.5% and 5% of the amount of urea, code named 0.5HA+U, 5HA+U, 0.5UHA+U, and 5UHA+U, respectively. At the same time, the treatments with urea (U) and without humic acid and urea (CK) were conducted. Soil ammonia fluxes and volatilization, soil urea-N, nitrate, and ammonium content, and soil urease activity were measured simultaneously. 【Result】(1) The ammonia volatilization from long-term fertilized soil for nitrogen fertilization treatments was higher than that from long-term unfertilized soil, which might be related to the decrease of soil pH, the weakening of soil nitrification process and the accumulation of ammonium nitrogen from urea hydrolysis caused by long-term fertilization. (2) Both HA and UHA combined with urea could effectively reduce soil ammonia volatilization, compared with U treatment, but the extent of the reduction depended on whether the soil was fertilized for a long time and the amounts of HA or UHA: urea combined with HA could significantly reduce soil ammonia volatilization for long-term unfertilized soil (P<0.05), and the ammonia volatilization of 0.5HA+U and 5HA+U was 4.4% and 22.9% lower than that under U treatment, respectively. However, the soil ammonia volatilization decreased by only 4.1%-7.5% under the treatment of HA combined with urea, which was not significantly different from that under the treatment of U, when the soil was long-term fertilization. However, urea combined with 0.5%UHA could significantly reduce soil ammonia volatilization (P<0.05) for long-term unfertilized and fertilized soil by 26.5% and 12.9%, respectively. (3) Urea combined with HA or UHA could effectively inhibit urease activity and promote soil nitrification process, respectively, thereby reduced soil ammonia volatilization. 【Conclusion】In summary, compared with HA, UHA combined with urea showed better performance on inhibiting ammonia volatilization under soil incubation, and the effect was independent of whether the soil was fertilized for a long time.

    HORTICULTURE
    Genetic Variation of Alcohol Acyltransferase Encoding Gene in Grape
    JI XiaoHao,LIU FengZhi,WANG BaoLiang,LIU PeiPei,WANG HaiBo
    Scientia Agricultura Sinica. 2022, 55(14):  2797-2811.  doi:10.3864/j.issn.0578-1752.2022.14.010
    Abstract ( 233 )   HTML ( 41 )   PDF (3039KB) ( 72 )   Save
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    【Objective】The purpose of this study was to develop molecular markers suitable for the identification of grape aroma phenotypes, so as to provide a theoretical basis for grape molecular assisted breeding. 【Method】 The aroma components and content of 45 grape varieties were determined by solid-phase microextraction combined with gas-phase mass spectrometry, and the structural variation and SNP variation of VvAAT gene were analyzed by Sanger sequencing and amplicon sequencing, respectively. 【Result】A total of 65 aroma components were found in 45 grape varieties, which could be divided into four types: esters, alcohols, terpenes and aldehydes. Among them, the content of esters showed significant variety differences, and 20 grape varieties such as Kyoho were rich in volatile esters, but little volatile esters was detected in other 25 grape varieties such as 87-1. A total of 5 structural variants have been found in the VvAAT gene. Types I, II, IV and V could not be translated correctly due to premature termination codons or fragment insertion mutations. Only type III could be translated aright. According to the results of the phylogenetic tree analysis of their amino acid sequences, Type III could be divided into two types: III.1 and III.2. Combining the aroma data, it could be inferred that III.1 was functional, while the rest were non-functional. Amplicon sequencing and bioinformatics analysis revealed 8 SNP sites (T32C, A69T, G436C, A1247G, A1818T, G1929T, A1959G, and C1975G) located in the exon region of the VvAAT gene, all of which caused mutations in the coding amino acids. It could accurately distinguish between ester-rich varieties and ester-poor varieties, with an accuracy rate of 97.8%. 【Conclusion】VvAAT gene locus had abundant genetic variation, including gene structure variation and SNP variation; 8 SNP loci located in the coding region of VvAAT gene could accurately determine the phenotype of volatile esters, which could be applied to grape molecular assisted breeding.

    Map-Based Cloning and Molecular Marker Development of Watermelon Fruit Shape Gene
    DUAN YaRu,GAO MeiLing,GUO Yu,LIANG XiaoXue,LIU XiuJie,XU HongGuo,LIU JiXiu,GAO Yue,LUAN Feishi
    Scientia Agricultura Sinica. 2022, 55(14):  2812-2824.  doi:10.3864/j.issn.0578-1752.2022.14.011
    Abstract ( 282 )   HTML ( 37 )   PDF (3557KB) ( 202 )   Save
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    【Objective】 Based on the result of fruit shape gene preliminary mapping by genotyping-by-sequencing (GBS) high-density genetic map, the fine mapping of the fruit shape gene was conducted by using map-based cloning method, and the functional molecular markers were developed in watermelon. The present study could facilitate comprehensive study on the function of fruit shape gene and molecular marker-assisted selection breeding. 【Method】GWAS (Genome-wide association study) analysis was performed on 114 watermelon inbred lines by using whole-genome re-sequencing data and their fruit shape index phenotypes. The candidate regions of fruit shape gene ClFSI were confirmed by combing the results of GWAS with fruit shape gene preliminary mapping. The F2 segregating population were derived from a cross between two inbred lines K2 (oval, FSI=1.54±0.13) and L1 (round, FSI=1.11±0.07), which were purified from commercial small watermelon varieties. Fine-mapping of the fruit shape gene ClFSI was conducted by developing molecular markers. Candidate gene was identified by gene annotation of the candidate region in watermelon reference genome ‘97103’ v1 and validated by using real-time quantitative PCR (qRT-PCR). 【Result】 The 1 152 F2 plants were used for fine mapping and the ClFSI gene was finally mapped into 63 kb region on chromosome 3 between FMFSI-1 and FMFSI-2, containing a total of 5 annotated genes. The Cla011257 gene belonged to the SUN gene family that has been reported to control the fruit shape. There were two SNPs identified in the genomic region of third exon of ClFSI gene in the watermelon oval line K2. One SNP was a mutation from G to A at Chr3: 26846636 (‘97103’ v1), which resulted in a mutation from asparagine acid (Asn) to aspartic acid (Asp). Another SNP was a mutation from G to A at Chr3: 26846636 (‘97103’ v1), which resulted in another mutation from glutamic acid (Glu) to lysine acid (Lys). The FSICAPS-2 functional molecular marker was developed based on the Chr3: 26847041 SNP site. qRT-PCR expression analysis showed that candidate gene expression level was not significantly difference in K2 (oval) and Charleston Gray (elongated), but both were significantly higher than that in L1 (round). 【Conclusion】In this study, the ClFSI gene was mapped into a 63 kb candidate region on chromosome 3, and Cla011257 was the good candidate gene. Chr3: 26847041 and Chr3: 26846636 mutations were important loci that caused elongation of different degrees in fruit shape. A functional marker FSICAPS-2 was developed, which could identify multiple mutation types of Cla011257 simultaneously.

    FOOD SCIENCE AND ENGINEERING
    Effects of Different Drying Methods on Bioactive Components of Shatianyou (Citrus grandis L. Osbeck) Pomace Powder
    LU Qi,JIA XuChao,DENG Mei,ZHANG RuiFen,DONG LiHong,HUANG Fei,CHI JianWei,LIU Lei,ZHANG MingWei
    Scientia Agricultura Sinica. 2022, 55(14):  2825-2836.  doi:10.3864/j.issn.0578-1752.2022.14.012
    Abstract ( 195 )   HTML ( 27 )   PDF (1346KB) ( 58 )   Save
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    【Objective】The composition, contents, physicochemical and functional properties of both dietary fiber (DF) and flavonoids of Shatianyou (Citrus grandis L. Osbeck) pomace powder prepared by hot air drying (HAD) and freeze drying (FD) were compared, so as to provide the theoretical basis for the utilization of Shatianyou by-products in the process of functional food. 【Method】Shatianyou pomace powder was prepared by HAD and FD from pomace residues of Shatianyou after the juice was squeezed. The contents of soluble DF (SDF) and insoluble DF (IDF) of Shatianyou pomace powder were determined. The microstructure of the pomace powder was observed by scanning electron microscope and their water retention capacity (WRC), oil adsorption capacity (OAC) and water swelling capacity (WSC) were measured, respectively. The total phenolic and flavonoid contents of Shatianyou pomace powder were measured by Folin-Ciocalteu colorimetric method and Sodium borohydride/chloroquinone assay, respectively. The flavonoids composition of the pomace powder was analyzed by HPLC, and their antioxidant activities were determined by oxygen radical absorbance capacity (ORAC), ABTS radical scavenging capacity and ferric reducing antioxidant power (FRAP) methods. 【Result】The Shatianyou pomace powder prepared by HAD showed higher total DF (46.10 g/100 g DW) content than those obtained by FD (P<0.05); both kinds of pomace powder had balanced ratios of IDF/SDF (1.5 and 1.6, respectively); the WRC (7.55±0.43 g∙g-1 DW) and OAC (1.94±0.08 g∙g-1 DW) of pomace powder obtained by HAD were slightly higher than those obtained by FD, but the later one showed a higher WSC (12.25 mL∙g-1 DW, P<0.05). Phenolics and flavonoids in Shatianyou pomace powder mainly existed in free form, accounting for more than 95% of their total phenolics. The pomace powder obtained by HAD showed significant higher total phenolic contents (5.54 mg GAE∙g-1 DW) than those obtained by FD (P<0.05), but their total flavonoid contents were similar (13.11 and 11.45 mg CE∙g-1 DW, respectively). Naringin and melitidin were the main flavonoids in Shatianyou pomace powder, accounting for more than 70% of their total flavonoids. These were obviously different from those of other citrus fruits, in which naringin was the main flavonoid. Shatianyou pomace powder obtained by HAD, with the ORAC, ABTS and FRAP values of 141.28, 4.63 and 20.98 μmol TE∙g-1 DW, respectively, showed stronger antioxidant activity than those prepared by FD. 【Conclusion】Shatianyou pomace powder was rich in DF and flavonoids, which showed higher hydration properties and antioxidant activities than those of other fruit by-products. Thus, Shatianyou pomace powder was a good source of DF and flavonoid, and could be used in the development of functional food.

    ANIMAL SCIENCE·VETERINARY SCIENCE
    Dynamic Changes of Yolk Microbiota in Yellow-Feathered Broiler and Its Role on Early Colonization of Intestinal Microbiota During the Embryonic Stage
    DING Peng,TONG YueYue,LIU HuiChao,YIN Xin,LIU JiangJun,HE Xi,SONG ZeHe,ZHANG HaiHan
    Scientia Agricultura Sinica. 2022, 55(14):  2837-2849.  doi:10.3864/j.issn.0578-1752.2022.14.013
    Abstract ( 230 )   HTML ( 30 )   PDF (5834KB) ( 81 )   Save
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    【Objective】 The purpose of this experiment was to study the dynamic changes and functions of the yolk microbiota during the hatching of yellow-feathered broiler fertilized eggs, and the influence of yolk microbiota on the early intestinal colonization of embryos. 【Method】 One hundred fertilized eggs of 35-week-old yellow-feathered broilers were selected and placed in automatic incubators for incubation. Before hatching, the incubator was cleaned and disinfected, and the internal ventilation system and humidity control system were checked for normal operation. The incubation temperature was controlled at (37.5±1) ℃ and the humidity at (60±10)%. Six breeder eggs were randomly selected on days 7, 11, 15 and 19 of incubation to collect the yolk samples by stripped the eggshell and allantoic membrane in a sterile operation table, exposed the embryo to the yolk sac and then pierced it through a sterile syringe. Samples were rapidly snap frozen in liquid nitrogen after collection and subsequently transferred to a -80 ℃ refrigerator for storage pended test. The yolk microorganisms were subjected to DNA extraction, and 16s rDNA sequencing and sequence analysis were performed. 【Result】 1) A total of 4 305 OTUs were annotated in the yolk of fertilized eggs, and a total of 18 Phyla, 34 Classes, 53 Orders, 89 Families and 126 Genera were found in the yolk and intestine at different incubation time points. The phylum level mainly included Proteobactreia, Firmicutes, Bacteroidetes, Verrucomicrobia, etc. The genus level is dominated by Pelomonas, Ralstonia, Aquabacterium, Faecalibacterium, etc; 2) Significant differences in the Chao1 index (P = 0.027) and Shannan index (P = 0.043) were observed in the Alpha diversity of yolk microbiota at different incubating stages. The yolk microbiota tended to stabilize with incubation time, while the relative abundance of Akkermansia in the yolk increased continuously to 0.53%, 0.84%, 1.43% and 3.10% at E07, E11, E15 and E19, respectively. At the genus level, the yolk microbiota mainly included Pelomonas, Ralstonia, Aquabacterium and so on; 3) The functions of yolk microbiota in yellow-feathered broiler breeding eggs mainly include carbohydrates metabolism, amino acids metabolism, lipids metabolism, cofactors and vitamins metabolism; 4) Both the yolk microbiota and intestinal microbiota of fertilized eggs were dominated by Proteobacteria, Firmicutes, Bacteroidetes, and Verrucomicrobia at the phylum level, and Pelomonas, Ralstonia, Aquabacterium and Akkermansia at the genus level. 【Conclusion】There are abundant microbial populations in the yolk of yellow-feathered broiler fertilized eggs, which play an important role in the absorption and metabolism of yolk nutrients and the early microbial colonization of embryo intestine.

    Effect and Mechanism of Caffeic Acid Phenethyl Ester Alleviates Oxidative Stress in Liquid Preservation of Boar Semen Via the AMPK/FOXO3a Signaling Pathway
    LAN Qun,XIE YingYu,CAO JiaCheng,XUE LiE,CHEN DeJun,RAO YongYong,LIN RuiYi,FANG ShaoMing,XIAO TianFang
    Scientia Agricultura Sinica. 2022, 55(14):  2850-2861.  doi:10.3864/j.issn.0578-1752.2022.14.014
    Abstract ( 182 )   HTML ( 27 )   PDF (1051KB) ( 63 )   Save
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    【Objective】The aim of this study was to explore the effect and mechanism of caffeic acid phenethyl ester (CAPE) relieves oxidative stress in boar semen through AMPK / FOXO3a signaling pathway. 【Method】 Eight adult (1-2 years) and healthy Landrace boars were selected to collect fresh semen, and the qualified samples were pooled for determination. Firstly, CAPE was added to basic diluent at the concentration of 0, 0.02, 0.04, 0.06, 0.08 and 0.10 g·L-1 at room temperature, respectively. To transferred the mixed specimens into electronic thermostat refrigerator for room temperature storage, semen samples were equilibrated at room temperature. The sperm kinematic parameters, including total motility and progressive motility, were determined by Computer-Aided Sperm Analysis (CASA) within 1-5 days, the best concentration of CAPE (0.06 g·L-1) was then selected. Secondly, the oxidative stress models were established by the ensure concentration of CAPE (0.06 g·L-1) and 400 μmol·L-1 hydrogen peroxide. At 1st, 3rd and 5th day, the total motility and progressive motility were measured by CASA, the plasma membrane integrity and acrosome integrity were evaluated by fluorescence probe technique, and the activities of catalase (CAT) and superoxide dismutase (SOD) were detected by antioxidant kit. After five days preservation, the mRNA expression of AMPK/FOXO3a signaling pathway related to genes, like AMPK, FOXO3a, SOD1, SOD2, CAT and apoptosis gene BAX, were determined by Real-time quantitative PCR (qPCR) technique, and the AMPK and p-AMPK protein expression were measured by western blot (WB). 【Result】(1) In the concentration screening experiment, 0.06 g·L-1 CAPE significantly improved the total motility on the 3rd day and maintained until the 5th day (P<0.05). Moreover, the progressive motility of sperm on the 1st day was significantly higher than other treatments (P<0.05). (2) In the oxidative stress experiment, the plasma membrane integrity, acrosome integrity, total motility, progressive motility, SOD and CAT activities of sperm in H2O2 group were significantly lower than blank group and CAPE+H2O2 group (P<0.05); however, there were no significant differences in total motility, acrosome integrity, CAT and SOD activities between the blank group and CAPE+H2O2 (P>0.05). Compared with CAPE+H2O2 group, the mRNA expression level of AMPK, FOXO3a, SOD1, SOD2, CAT in H2O2 group were significantly decreased (P<0.05), the expression level of BAX was significantly increased (P<0.05), while there was no significant difference in AMPK, SOD1, CAT and BAX between control group and CAPE+H2O2 group (P>0.05). In the expression level of proteins, AMPK, p-AMPK and p-AMPK/AMPK ratio were significantly higher in CAPE+H2O2 group in compared with H202 group (P<0.05). 【Conclusion】 The supplementation of 0.06 g·L-1 CAPE to basic diluent at room temperature could induce the transcription of downstream antioxidant molecules of AMPK/FOXO3a signaling pathway by promoting phosphorylation of AMPK expression, then alleviate the effect of H2O2 mediated oxidation which affected semen quality, and prolong its storage time. However, the in-depth molecular mechanism of CAPE protecting sperm fight with oxidative damage is still worth for further investigation.

    Colistin Promotes mcr-1-positive IncI2 Plasmid Conjugation Between Escherichia coli
    WANG XueYang,JIANG JunYao,YANG Lu,SHAO DongYan,WU CongMing,SHEN JianZhong,SHEN YingBo,WANG Yang
    Scientia Agricultura Sinica. 2022, 55(14):  2862-2874.  doi:10.3864/j.issn.0578-1752.2022.14.015
    Abstract ( 282 )   HTML ( 29 )   PDF (1683KB) ( 61 )   Save
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    【Background】 Colistin is a last line antibiotic for the treatment of clinical infections caused by multi-drug resistant Gram-negative bacteria, and it has also been extensively used in animal industry as a feed additive and therapeutic drug. In 2015, Chinese researchers discovered the plasmid-mediated colistin resistance gene mcr-1, indicating that this last defense line is at risk of being breached. However, the effects of bactericidal concentration and sub-inhibitory concentration of colistin on the transmission of mcr-1-positive plasmid is still unknown. 【Objective】 This study used the most prevalent mcr-1-positive plasmid IncI2 as an object to explore the influence on the conjugative transfer frequency under different colistin concentrations. 【Method】 The conjugation experiment under different colistin concentrations (0.02-4 μg·mL-1) was carried out by the broth method. Real time quantitative PCR and the constructed formula were used to calculate the conjugative transfer frequency at different timepoints (1-24 h) and also different colistin concentrations. The cell membrane permeability and ROS production of donor and recipient bacteria under different colistin concentrations were detected by using PI dye and reactive oxygen species (ROS) detection kit, respectively. Colistin negative group and the three treatment groups (0.02, 1, and 4 μg·mL-1) were subjected to RNA sequencing as control, low, medium and high concentration groups, respectively, and the gene differential expression was analyzed by Deseq2 software. All statistical analysis were conducted by Prism v8.2.0 software. 【Result】 A formula was established to calculate the conjugative frequency in this study, and it was found that the bactericidal concentration (4 μg·mL-1) of colistin significantly increased the conjugative transfer frequency of mcr-1-positive IncI2 plasmid by 3-10 times at different timepoints, whilst no significant difference on other concentrations. Transcriptome results showed that when compared with control group, the expression of genes related to type IV secretion system (T4SS) in IncI2 plasmid, including virB1, virB2, virB5 and traC, were significantly increased in all colistin concentrations groups. In addition, the expressional level of type I fimbrium biosynthesis genes were significantly increased in all colistin groups. PI staining results showed that 2 and 4μg·mL-1 colistin could elevate the cell membrane permeability in donor and recipient bacteria, and the coincidently transcriptome results showed that the expressional levels of membrane-related genes, including ompAX, bamDE, lolB, yiaD, csgEF, were significantly up-regulated. However, ROS production and expressional level of related genes were not significantly increased after colistin treatment. 【Conclusion】 This study revealed that colistin promoted the conjugative transfer frequency of mcr-1-positive IncI2 plasmid between E. coli by increasing the activity of bacterial T4SS, cell membrane permeability and pilus formation, suggesting the bactericidal concentration of colistin could increase the plasmid transmission in all survived mcr-1-positive E. coli. Therefore, the therapeutic use of colistin in animals might maintain the existence and transmission of mcr-1-positive plasmids. In addition, since colistin has been approved for clinical use in human medicine, this phenomenon could lead to the failure on colistin treatment for mcr-1-positive pathogens.