Table of Content

20 August 2018, Volume 27 Issue 8

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Orignal Article

Willingness of households on the Longdong Loess Plateau to grow dual-purpose winter wheat and influencing factors: A case study based on 323 questionnaires from Qingyang city, Gansu Province

ZHANG Wen-e, JIANG Cheng-fang, WANG Long-gang, SHEN Yu-ying

2018, 27(8):  1-10.  DOI: 10.11686/cyxb2017395

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It is important to identify the factors affecting householders’ willingness to cultivate dual-purpose winter wheat to promote the dual-purpose winter wheat model and the sustainable development of agriculture. In this study, we conducted a survey about dual-purpose winter wheat in Qingyang city, Gansu Province, and 323 valid questionnaires were collected from surveyed farmers. A binary logistic regression model was developed to analyze households’ willingness to adopt the dual-purpose winter wheat model and to identify the influencing factors. A relatively high proportion of sampled households (57%) was willing to adopt the dual-purpose winter wheat model. Among the influencing factors, householder age (P<0.05), number of months on the farm (P<0.1), family income (P<0.05), size of winter wheat planting area (P<0.1), knowledge (P<0.05), perception of prospects (P<0.01), and cognitive effects on wheat yield (P<0.01) had significant positive effects on households’ willingness to adopt the dual-purpose winter wheat model. The number of students in the family (P<0.05) and the number of livestock (P<0.1) had significant negative impacts on households’ willingness to adopt the model. In conclusion, we can suggest to policy makers to provide comprehensive information about the comparative benefits of agricultural models, to make information more widely available to farmers, to accelerate the transfer of rural land, and to continue to optimize the dual-purpose winter wheat model.

Quantitative classification and environmental interpretation of plant communities on the Ningxia typical steppe after 1-21 years of restoration

NIE Ming-he, SHEN Yan, RAO Li-xian

2018, 27(8):  11-20.  DOI: 10.11686/cyxb2017404

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Studying the classification and succession of plant communities at different timepoints after restoration is important for the design of successful strategies to restore degraded grasslands. This study was conducted at an abandoned grassland in the typical steppe of south Ningxia. We analyzed the diversity of grassland plant communities at different times after restoration (i.e. 1, 2, 3, 5, 6, 8, 9, 11, 15, 16, 20 and 21 years). We used Two-way Indicator Species Analysis (TWINSPAN) to calculate the number of classification groups, and used Detrended Correspondence Analysis (DCA) and Redundancy Analysis (RDA) for the classification and ordination of grassland plant communities. We also evaluated the relationship between soil factors and succession time in the plant communities. The results showed that: 1) The Shannon-Wiener’s index, Patrick’s index, and above-ground biomass growth fluctuated with increasing years of restoration. 2) The 12 sampled plots with different years of restoration were divided into five types based on the TWINSPAN and DCA matching analysis. 3) The vegetation succession was as follows: Artemisia scoparia+Setaria viridis+Poa pratensis community; Leymus secalinus+Elymus dahuricus community; Stipa bungeana+L. secalinus community; L. secalinus+Vicia sepium community; S. bungeana+L. secalinus+E. dahuricus community. 4) The soil environment of grassland plants changed over time after restoration, with higher total phosphorus (P) and soil organic carbon (SOC) at the early establishment stage, higher soil available P and soil total nitrogen (N) contents at the intermediate succession stage, and higher soil available potassium (P) and SOC at the post-restoration stage. These changes were related to the plants TWINSPAN classification groups at different restoration times. We concluded that the succession sequence of the grassland plant community was optimized, the structure of grassland communities became more stable, and the ecological environment improved with increasing duration of grassland restoration.

Effects of artificial lakes on moisture, electrical conductivity and pH of adjacent soil on degraded grassland

AN Chan, QIAO Jian-xia, SHANG Jian-ying, LI Jin-sheng, ZHAO Tian-ci, TANG Shi-ming, SHAO Xin-qing, HUANG Ding, WANG Kun, LIU Ke-si

2018, 27(8):  21-29.  DOI: 10.11686/cyxb2017371

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As an important component of wetland ecosystems, lakes are able to help protect and buffer these ecosystems. In this study, continuously grazed degraded grassland close to an artificial lake in the Bashang area was selected to determine the response of soil physico-chemical properties to the lake in order to identify a potential theoretical basis for the improvement of degraded grassland. The responses of soil physico-chemical properties to the lake differed with distance from the lake and soil depth. Soil moisture decreased significantly with increasing distance from the lake. Soil moisture in the 0-10 cm layer decreased up to 50% (2014), 48% (2015) and 58% (2016), respectively, at 600 m compared to 10 m distance from the lake. Soil pH increased significantly with increased distance from the lake while soil electrical conductivity (EC) initially increased, to a maximum at 100 m, and then decreased. Soil moisture and pH were significantly correlated with distance from the lake, r=0.72 and r=0.44, respectively. Over the duration of the study soil EC decreased in the topsoil (0-10 cm) but increased significantly in lower soil layers, especially 20-40 cm depth indicating that salt had moved down the soil profile since the lake was established. Soil pH in the top soil showed a significant decreasing trend. In summary, the artificial lake had a positive effect on soil physico-chemical properties of degraded grassland.

Changes in soil properties of coal mine spoils in an alpine coal mining area after short-term restoration

YANG Xin-guang, LI Xi-lai, JIN Li-qun, SUN Hua-fang

2018, 27(8):  30-38.  DOI: 10.11686/cyxb2017350

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Studies on plant-soil interactions are important for restoration ecology, and are of great significance when designing artificial restoration methods because they can indicate the extent to which vegetation restoration affects soil properties. In this study, we focused on Elymus nutans, Poa crymophila, and Puccinellia tenuiflora growing on coal gob piles in an alpine coal mining area, and monitored the variations in soil nitrogen, phosphorus, potassium, organic matter, pH value, vegetation coverage, and correlations between those indicators at different times after restoration. The main results were as follows: Soil total nitrogen did not significantly change over time but soil total phosphorus increased by 17.39% (P<0.05) and soil total potassium decreased by 12.77% (P<0.05) after 4 years of restoration. Soil available nitrogen, soil available phosphorus, and soil available potassium decreased significantly by 49.68% (P<0.05), 66.07% (P<0.05), and 18.67% (P<0.05), respectively, in the first 4 years of restoration. Soil organic matter content increased significantly by 7.92% (P<0.05) and 43.02% (P<0.05) after 2 and 4 years restoration, respectively. The soil pH increased as a result of the slow transition from acidic to neutral soil. Vegetation coverage showed no significant variation after 2 and 4 years of restoration. There were significant correlations among the soil nutrient elements, except for soil total nitrogen. There was a significant negative correlation between plant coverage and soil pH. Based on these results, a key factor for the ecological restoration of coal gob piles is to supply available nutrients in a timely manner to satisfy the requirements for plant growth.

Establishment of Vicia sativa-Secale cereale mixed and intercropping methods for the Lhasa valley area

WANG Fu-qiang, XIANG Jie, GUO Bao-guang, YU Cheng-qun, SHEN Zhen-xi, SHAO Xiao-ming

2018, 27(8):  39-49.  DOI: 10.11686/cyxb2017348

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To establish cultivation methods suitable for the Lhasa Valley, we investigated the success of different mixed and intercropping patterns by measuring the yield and quality of forage from a legume, Vicia sativa (pea), and a grass, Secale cereale (rye). The results showed that the effective branch number and biomass of pea were lower under mixed sowing and intercropping than under monocropping, while the effective tiller number and biomass of rye increased under mixed sowing. Compared with intercropping, mixed sowing resulted in an interspecific relationship that resulted in better interspecific interactions and weaker negative interactions. Pea was at a competitive disadvantage in mixed cropping and intermittent cropping conditions. The relative yield value was less than 1 for rye in mixed cropping, but greater than 1 in intercropping conditions, indicative of its competitive advantage. Due to niche differentiation and interspecific interactions between the two species, the resource utilization rate of forage was improved in mixed and intercropping compared with monocropping, and the mixed and intercropping treatments had obvious yield advantages. The combination of V. sativa and S. cereale with an intercropping ratio of 2:1 resulted in the highest yield of fresh grass yield (5253 g·m^-2). The mixed ratio of 20% pea+80% rye resulted in the highest yield of hay (1572 g·m^-2). The overall yield was larger in the mixed treatments than in the monocropping treatments. The nutritional quality of the mixed forage was better than that of rye alone.

Accumulation and distribution of carbon and nitrogen in various organs of maize under different fertilization regimes

XIE Jun, XU Chun-li, CHEN Xuan-jing, WANG Ke, LI Dan-ping, ZHANG Yue-qiang, SHI Xiao-jun

2018, 27(8):  50-58.  DOI: 10.11686/cyxb2017370

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This aim of this research was to determine how different fertilization regimes affect the content and proportional distribution of carbon, nitrogen, and the carbon/nitrogen ratio (C/N) in maize. The overall aim of our research was to provide baseline data for the design of rational fertilization strategies to improve crop yield in Southwest China. We conducted a long-term fertilization experiment with five different treatments: CK (no fertilization), FP (farmers’ practice), OP (optimal chemical fertilization), OM (organic manure nitrogen replacing 100% chemical N), and MF (organic manure nitrogen replacing 50% chemical N). The biomass of maize was 26.2% higher in the MF treatment than in the FP treatment. Compared with the OM and OP treatments, the MF treatment resulted in significantly higher carbon content by 5.4 and 4.2 g·kg^-1, respectively, in maize bracts, and 7.4 and 21.3 g·kg^-1, respectively, in maize roots. Compared with the other treatments, the MF treatment resulted in higher carbon stocks in maize bracts, roots, corncobs, and grains, and significantly increased nitrogen stock in maize stems and grains. Compared with the FP treatment, the MF treatment resulted in significantly increased carbon stock and nitrogen stock by 29.1% and 16.9%, respectively, on a whole-plant basis. At the same nitrogen application rate, compared with the FP treatment, the MF and OP treatments resulted in significantly increased distribution of assimilated carbon to the maize bracts and grains. Compared with the OP and OM treatments, the MF treatment increased the distribution of assimilated carbon to maize grain by 1.7% and 3.6%, respectively. The MF treatment also resulted in a higher C/N ratio. In conclusion, replacing 50% chemical nitrogen with organic manure nitrogen increased biomass and the absorption and accumulation of nitrogen and carbon in maize. It also increased the proportion of carbon and nitrogen allocated to maize grain, and resulted in a higher C/N ratio, which was important for crop yield formation. Therefore, replacing 50% chemical nitrogen with organic manure nitrogen can increase the nitrogen-use efficiency of maize, and decrease chemical inputs and the loss of chemical fertilizer, thereby lowering the risk of nitrogen leaching into the environment.

Effects of rotation systems on yields and physiological indicators of wheat

LIU Hong-qing, FU Dan-dan, WU Hai-jie, MIAO Fu-hong, SUN Juan, YANG Guo-feng

2018, 27(8):  59-66.  DOI: 10.11686/cyxb2018086

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The aim of this study was to determine the effects of three planting patterns (alfalfa-wheat, AW; soybean-wheat, SW; and corn-wheat, CW) on the yields (grain yield, seed production rate, and biomass of above ground parts) and physiological indicators (SPAD value, leaf area index, net photosynthetic rate, transpiration rate, nitrate reductase activity) of wheat. The yield of wheat was significantly higher in AW than in SW and CW, and not significantly different between SW and CW. The SPAD value and leaf area index of flag leaves were significantly higher in AW than in SW and CW in every important period of wheat growth. The net photosynthetic rate of wheat was higher at the later filling and maturity stages, while the wheat transpiration rate significantly decreased at the booting stage. The activity of nitrate reductase was higher in AW than in SW and CW during the whole growing period of wheat. These results indicate that the AW pattern is suitable for optimal use of nitrogen fertilizer by wheat to improve its yields.

Water use strategy of Caragana microphylla during the transition from drought to rainfall

FU Qing-yun, LIU Xiao-yan, LIU Ting-xi, DUAN Li-min, WANG Guan-li, CAO Wen-mei, HUANG Tian-yu

2018, 27(8):  67-77.  DOI: 10.11686/cyxb2017344

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This study compared the water use strategy in 3, 5 and 9 year old Caragana microphylla communities in the Agula eco-hydrological research area. We compared, soil water, precipitation and xylem water content of C. microphyllas using oxygen stable isotope (δ¹⁸O) technology to examine their water utilization pattern in a period of drought followed by rainfall events (15.6, 33.1 mm) after 15 days. Root density and soil moisture dynamics were measured to help identify response mechanisms. The results show that, in drought, C. microphyllas mainly depended on maintaining internal moisture levels rather than absorbing subsoil water to survive. They may be utilized the condensation water of the surface soil; Within a day of rain, the δ¹⁸O content of xylem water at all ages trended to that present in the rain water. Within three days of rain, the δ¹⁸O of xylem water of 3 and 5 year plants changed remarkably, whereas 9 year plants remained stable. C. microphyllas of all ages mainly utilised soil water at 10 to 60 cm depth in the 5 days after rainfall; 3- and 5-year C. microphylla primarily utilised water from 1/3 point and edge, but the 9 year plants mainly used water from edge. With increasing tree age, the density of shallow roots increased markedly. It is suggested that manual control the distribution density of old C. microphyllas plants would help the hydrological balance in the region.

Effects of phosphorus deficiency on acid phosphatase activity and phosphorus efficiency in a low-phosphorus tolerant Stylosanthes mutant

LIU Pan-dao, HUAN Heng-fu, LIU Yi-ming, LIU Guo-dao, BAI Chang-jun, CHEN Zhi-jian

2018, 27(8):  78-85.  DOI: 10.11686/cyxb2017382

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Low phosphorus (P) availability is a major constraint for pasture yields in acid soils. In a previous study, a low-P tolerant stylo (Stylosanthes) mutant, TPRC2001-84, was created using space flight mutation. However, the underlying mechanisms of TPRC2001-84 tolerance of P deficiency remain largely unknown. In this study, plant biomass, P acquisition efficiency, P utilization efficiency, soluble inorganic phosphate (Pi) concentration, cell wall P content and acid phosphatase (ACP) activity were investigated in hydroponically grown TPRC2001-84 and a non-mutant control (RY2) in normal P (+P, 250 μmol·L^-1 KH₂PO₄) or low P (-P, 5 μmol·L^-1 KH₂PO₄) solutions. Plant dry weight and P acquisition efficiency were significantly decreased (P<0.05) by P deficiency, while P utilization efficiency was increased (P<0.05) by low P in both accessions, compared to the normal P treatment. Plant dry weight and P utilization efficiency of TPRC2001-84 were 1.6 and 1.4 times those of RY2 under P deficiency, respectively. Although cell wall P content in leaves and roots of TPRC2001-84 were about 70% lower than in RY2 with low P treatment, the soluble Pi concentration in leaves and roots of TPRC2001-84 were 36.8% and 42.6% higher than in RY2 under P deficiency, respectively. Similarly, cell wall ACP activity in leaves and roots of TPRC2001-84 were 46.6% and 53.6% higher than in RY2 under P deficiency, respectively. These results suggest that increased cell wall ACP activity in TPRC2001-84 may contribute to cell wall P scavenging and recycling, increasing P utilization efficiency under P deficiency. Taken together, our results provide a theoretical basis and germplasm resource for selecting and breeding stylo varieties with high P efficiency.

Effect of fulvic acid on drought resistance of nursery stocks in a dry valley of the Bailongjiang River, Gansu

GUO Xing, XIE Fei, YAN Qian-qian, CAO Xiu-wen, YANG Fan

2018, 27(8):  86-94.  DOI: 10.11686/cyxb2017368

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To explore the influence of fulvic acid on seedling drought resistance of five shrub species in dry river valley of the Bailong River and to provide scientific evidence and technical notes for ecological remediation of the dry river valley. One year old Sophora davidii, Wikstroemia chamaedaphne, Osteomeles schwerinae, Ziziphus jujuba and Vitex negundo plants grown in potting mix were exposed to four concentrations of fulvic acids to assess the physiological response of plants under drought stress. Fulvic acid improved the soluble sugar, soluble protein and chlorophyll content but delayed the peroxidase activity and inhibited malondialdehyde content of S. davidii, W. chamaedaphne, Z. jujuba, V. negundo; fulvic acid also reduced soluble protein and chlorophyll of O. schwerinae under drought stress. It was concluded that fulvic acid at 200 mg·L^-1 improved drought resistance in Z. jujube>W. chamaedaphne>V. negundo>S. davidii; fulvic acid at 100-400 mg·L^-1 reduced drought resistance of O. schwerinae.

Cloning of salt-stressed responsive gene GmWRKY6 and salt resistance analysis of transgenic Lotus japonicus

KE Dan-xia, PENG Kun-peng, XIA Yuan-jun, ZHU Yu-ying, ZHANG Dan-dan

2018, 27(8):  95-106.  DOI: 10.11686/cyxb2017522

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A GmWRKY6 gene from WRKY transcription factor family members from soybean was cloned from salt stress RNA-Seq data. Sequence analysis showed that the gene contained an open reading frame (ORF) of 1674 bp and 557 encoding amino acids. The GmWRKY6 protein contained a conserved WRKY domain and a C2H2 zinc finger motif, belonged to group IIb WRKY transcription factor. Analysis of gene expression pattern showed that the expression level of GmWRKY6 gene is highest in the root and was induced by salt stress. Plant overexpression vector of the GmWRKY6 gene was constructed and 7 positive T₀ transgenic Lotus japonicus plants were obtained. The salt resistance of T₁ transgenic lines was further analyzed, after exposure to 200 mmol·L^-1 NaCl for 14 days; transgenic lines grew well while the wild type were stunted with dry foliage. Proline and chlorophyll content in transgenic lines were significantly higher than wild plants, while the MDA content and the relative permeability of plasma membrane were significantly lower than that of wild plants. In addition, the sodium ion content in transgenic lines was significantly lower than wild plants under salt stress, while the potassium content was significantly higher than that of wild plants. These results showed that over expression of the soybean GmWRKY6 gene can significantly enhance the salt resistance of L. japonicus.

Physiological aspects of photosynthesis and organic acid accumulation in alkali-resistant transgenic alfalfa containing the GsPPCK1 and GsPPCK3 genes

CAI Hua, XU Hui-hui, SUN Na, SONG Ting-ting, REN Yong-jing, YANG Sheng-qiu

2018, 27(8):  107-117.  DOI: 10.11686/cyxb2017391

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Photosynthesis affects the growth and development of plants including their response to salt and alkali stress. Previous studies have shown that over-expression of GsPPCK1 or GsPPCK3 from Glycine soja in alfalfa resulted in enhanced plant tolerance to alkali stress. Here, physiological and biochemical indexes and gene expression related traits were investigated to explore the physiological mechanism of alkali-resistant transgenic alfalfa from the perspective of photosynthesis and organic acid accumulation. The chlorophyll content of transgenic lines P1-5 and P3-8 were not different from untreated plants after 9 days of alkali exposure, decreasing by 11.27% and 13.30% respectively, while that of non-transgenic lines decreased by 39.11%. The photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s) and intercellular CO₂ concentration (C_i) of transgenic lines P1-5 and P3-8 all decreased after alkali exposure, but the decreased was half that of non-transgenic plants. NADP-malate dehydrogenase, NADP-malic enzyme, phosphoenolpyruvate carboxylase, pyruvate orthophosphate dikinase, ribulose-1,5-bisphosphate carboxylase enzyme activity and organic acid content (malic acid, citric acid, oxaloacetic acid and phosphoenolpyruvate) trended upward after alkali treatment. The photosynthetic enzyme activity and organic acid content of transgenic lines P1-5 and P3-8 were significantly different (P<0.01) from non-transgenic plants. The expression of PEPC (Medtr4g079860.1), NADP-ME (Medtr8g014390.1), NADP-MDH (Medtr1g043040.1), PPDK (Medtr4g118350.1) and Rubisco (Medtr4g021210.1) were induced under alkali stress and subsequently declined, the expression level in transgenic lines was greater than non-transgenic lines. The results indicated that under normal conditions, the overexpression of GsPPCK1 or GsPPCK3 did not improve photosynthesis of transgenic lines, but photosynthesis in transgenic alfalfa was less affected by alkali stress. This process may be related to the activity of PEPC. In addition, a significant increase in organic acid content played an important role in stabilizing intracellular pH.

Microbial characteristics of Oxytropis glabra and corn mixed silage and screening for swainsonine-removing lactic acid bacteria

TAO Ya, LI Feng, SUN Qi-zhong, LIU Qian, GAO Run, XU Chun-cheng

2018, 27(8):  118-129.  DOI: 10.11686/cyxb2017374

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To establish a method to use Oxytropis glabra as a silage crop, the influence of different ratios of O. glabra and corn (Zea mays) on microbial characteristics and the diversity of lactic acid bacteria in silage were investigated. We also screened for swainsonine-removing lactic acid bacterial strains. The proportions of O. glabra:corn in the eight treatments were as follows: 10:0 (T₁), 9:1 (T₂), 8:2 (T₃), 7:3 (T₄), 6:4 (T₅), 5:5 (T₆), 4:6 (T₇) and 0:10 (T₈). The microbial community structure and quantities were analyzed after fermentation of silage for 60 days. Lactic acid bacterial strains were isolated from fresh material and silage, and their removal rates of swainsonine were determined. The main results were as follows: 1) The numbers of lactic acid bacteria in fresh material increased with increasing proportions of corn, but did not differ significantly among the silage materials. The mixing ratio did not affect the numbers of coliform bacteria in the fresh material, and coliform bacteria could not be detected after fermentation. The numbers of aerobic bacteria in fresh and silage material decreased with increasing proportions of corn. The amount of yeasts was not affected by the ratio of O. glabra and corn. When more corn was added, the number of molds increased, but molds were beneath the limits of detection in the silage materials. 2) Four lactic acid bacterial strains were isolated from the fresh material: Lactococcus lactis subsp. Hordniae, Lactococcus lactis subsp. Lactis, and Lactococcus taiwanensis. Nine lactic acid bacterial strains were isolated from silage material, including Lactobacillus plantarum subsp. Plantarum, Lactobacillus brevis, Lactobacillus pentosus, and Lactobacillus amylovorus. As the proportion of corn increased, the diversity of lactic acid bacteria increased in fresh material but decreased in silage. 3) The swainsonine-removing rates of all lactic acid bacterial strains were higher than 85%, and 100% for strains JD6E, JD4D, JD10D, JD2E, and JD1F. After pretreatment of silage with boiling water, the swainsonine-removing rates of strains JD10D and JD2E were 100% and 97.76% respectively, but those of other strains decreased by 31.76%-100%. The swainsonine-removing rates of strains JD6D and JD1E dropped to 2.17% and 0, respectively, after the heat treatment. These results showed that with increasing proportions of corn in the mixture, the quantities and diversity of lactic acid bacteria in fresh material increased and the populations of aerobic bacteria both in raw material and silage decreased, which increased the success rate of ensilage. Some lactic acid bacteria were able to remove swainsonine. Strains JD10D and JD2E had the best ability to bind swainsonine, and strains JD6D and JD1E showed the best swainsonine-degradation ability. These four strains can be used as biological detoxification agents to remove swainsonine from O. glabra silage.

Preliminary study on isolation and identification of seed-borne Cronobacter sakazakii from lucerne (Medicago sativa) and determination of its pathogenicity

ZHANG Zhen-fen, SU Jing, YANG Cheng-de, SHI Shang-li, HUA Li-min, WALAA Mohamaden

2018, 27(8):  130-141.  DOI: 10.11686/cyxb2018139

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Cronobacter sakazakii is an emerging opportunistic Gram-negative pathogen, and it is associated with various neonatal infections such as meningitis, septicemia, bacteremia, and necrotizing enterocolitis. The aims of this work were to explore the contents of seed-borne C. sakazakii in lucerne, to determine its pathogenicity against animals and plants, and to understand its bacterial characteristics. Using the dilution plate method, three suspected C. sakazakii bacterial isolates were isolated from surface-sterilized seeds of six lucerne varieties. The representative bacterial isolate 1gF3 was used to prepare a bacterial suspension (about 10⁹ cfu·mL^-1), which was used in a germination test of alfalfa seeds in Petri dishes under controlled laboratory conditions. In addition, intraperitoneal injection (I/P) into pathogen-free Kunming mice was conducted to understand the animal pathogenicity of 1gF3. The results showed that 1gF3 was not pathogenic to lucerne under laboratory conditions. At 12 h after I/P injection, mice showed suppurative encephalitis, myocardial edema dilatation and local myocardial fiber rupture, partial liver necrosis, acute splenitis, and acute diffuse hemorrhage of the lungs and kidneys. These results indicated that 1gF3 showed significant pathogenicity to mice after I/P injection under laboratory conditions. The suspected C. sakazakii bacterial isolate TM2 was isolated from the blood of injected diseased mice. Using phenotypic and 16S rDNA identification methods, 1gF3 and TM2 were identified as C. sakazakii. The biological characteristics of 1gF3 were verified. The bacterium was in the logarithmic growth phase from 24 to 36 h, followed by a recession. Drought stress aggravated the decline of bacterial linear growth. Strain 1gF3 could grow at a wide range of temperatures (10-41 ℃) and pH (3-11). It grew well without salt, but its growth was inhibited by increased NaCl concentrations. A 12-h light:12-h dark photoperiod favored bacterial growth. This research has provided a theoretical basis and new ideas about bacteria that could be pathogenic to animals and plants and could be hidden in plant or animal materials, thus avoiding animal and plant quarantine measures. It also provides a theoretical basis for the prevention and control of the transport and spread of C. sakazakii.

Orginal Article

The research status quo of rural households in China and abroad: A bibliometric analysis

FU Li, XIE Ying-zhong, MA Hong-bin

2018, 27(8):  142-154.  DOI: 10.11686/cyxb2018025

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This study utilized the literature on rural households in core journals accessed through CNKI and Web of Sciences from 1984 to 2017 using quantitative informetrics to identify any apparent trends and to identify the sphere of influence of existing research of different countries, institutions, journals and individuals. We found that the number of published papers globally is generally on the rise with the United States ranking first; China ranked 19th based on the number of the papers indexed by WOS, however, most of these studies are 15 years earlier than the United States and in recent years have been increasing at a faster rate. In terms of international collaboration, the United States has made the greatest contribution. The most cited domestic institutions are the Inner Mongolia Agricultural University, Grassland Research Institute of the Chinese Academy of Agricultural Sciences, Inner Mongolia University and Lanzhou University. Internationally the most cited institutions are Wageningen University, Netherlands, Federal University of Santa Catarina, Brazil and CIRAD, France. In total, these overseas institutions contributed 45.5% of the paper published by top 10 institutions. The academic journals that stand out are Prataculture & Animal Husbandry, Journal of Xinjiang Animal Husbandry in China and Sociologia Ruralis and Journal of Rural Studies aboard. The general citation number is dominated by Journals such as Scientia Agricultura Sinica, Journal of Domestic Animal Ecology and Acta Prataculturae Sinica, although the total number of these three journals is not in the top-ten. With respect to academic level, studies of basic subjects account for a large proportion of reported research. Studies by Han Guodong from China and Acquavella aboard are most often cited helping their institutions became more influential. Based on current research, we propose that most research in the near future will focus on ecological issues for rural households including the dynamic balance between water-land-forage and livestock, and sustainable development.

Alfalfa species in ancient China

SUN Qi-zhong, LIU Qian, LI Feng, TAO Ya, XU Li-jun

2018, 27(8):  155-174.  DOI: 10.11686/cyxb2017450

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The species of alfalfa that existed in ancient China is unclear, because the color of its flowers was not recorded in any of the ancient texts. At present, there are five theories about the species of alfalfa in ancient China: 1) It was Medicago sativa; 2) it was Medicago hispida; 3) it was both M. sativa and M. hispida; 4) it was Medicago falcata; 5) the species is uncertain. On the basis of a critical evaluation of the alfalfa phytobiology literature and modern research findings, we speculate about the origin of alfalfa species in China. The results showed that alfalfa spread throughout China from Dayuan, consistent with the records of M. sativa introduction. Han E wrote in Sishi Zhuanyao in the Tang dynasty that the origin of the alfalfa species with purple flowers distributed along the yellow river was the same as that of the alfalfa referred to during the Han dynasty. After that, many texts recorded alfalfa with purple flowers and even its ecological and biological characteristics. It can be concluded that the alfalfa species naturalized in the Han dynasty had purple flowers, so it was M. sativa. Mei Yaochen in the Song dynasty and Li Shizhen in the Ming dynasty mentioned alfalfa with yellow flowers, indicating that yellow-flowered alfalfa existed and was utilized in China in the Song and Ming dynasties. According to the records in the Illustrated Catalogue of Plants, three alfalfa species (M. sativa, M. hispida, and M. falcata) were grown in ancient China.

Orignal Article

Ecological significance of plant allelopathy and progress in allelopathy research in grassland ecosystems

PING Xiao-yan, WANG Tie-mei

2018, 27(8):  175-184.  DOI: 10.11686/cyxb2017383

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Plant allelopathy has been proven to affect ecological processes on different temporal and spatial scales (individual, population, community, ecosystem, regional, and global scales). Furthermore, allelopathy has been considered as a novel weapon against invading exotic species, and has become a hot topic in ecology in recent years. Many studies have focused on the separation, identification, release pathways, application potential, and functional mechanisms of allelopathic materials, and much progress has been made. However, the lack of a thorough clarification and summary of specific functional mechanisms of allelopathy has constrained our understanding of its ecological significance. In this paper, we summarize recent research progress and controversies about allelopathy and discuss its effects on ecological processes at different scales. We specifically focus on the grassland ecosystem, and discuss the ecological significance of allelopathy for ecological processes at different scales. We discuss the differences in, and connections between, allelopathy and interspecific competition, and explore the roles of allelopathy in community species composition, community succession, and biological invasion. We also discuss the functional mechanisms of allelopathy, and current research progress and methods used to study allelopathy in grassland ecosystems. Finally, we recommend the following topics for future research on allelopathy: 1) Comparisons among greenhouse, field, and laboratory studies on allelopathy; 2) the effects of allelopathy at regional or global levels; and 3) how allelopathy affects the defensive responses of herbaceous plants and the restoration of degraded grassland.

A review of Astragalus sinicus in paddy fields in south China since 2000s

XIE Zhi-jian, ZHOU Chun-huo, HE Ya-qin, SONG Tao, YU Yang, WU Jia

2018, 27(8):  185-196.  DOI: 10.11686/cyxb2017360

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The middle and lower reaches of the Yangtze River are the main areas for rice production, which is vital for food security in China. The legume Chinese milk vetch (CMV, Astragalus sinicus), which is the main winter cover crop or green manure in paddy fields, is the essence of traditional agriculture and is vital for modern agriculture and the health of the environment. However, the fertilization structure has changed from organic materials to chemicals with the development of industry and agriculture, and this has led to a sharp decrease in the availability of green manure. Old, mixed, and seriously degenerated varieties of CMV and poor cultivation and management of this species are bottlenecks for the re-development and popularization of CMV. It is difficult to cultivate CMV using modern production methods and cultivation techniques that have been developed for rice. Also, the soil environmental conditions are also not suitable for CMV production. In this study, we summarize the breeding and identification of new CMV varieties, screening of compatible rhizobia, cultivation and management techniques, the effects of abiotic stresses on CMV, and the effects of planting CMV on soil ecology, rice growth and development, and the yields and quality of rice grain. Finally, we propose some future prospects for CMV cultivation in China. This paper focuses on the development and promotion of green manure as well as its comprehensive utilization value in the paddy fields of south China.

Effects of different amylose to amylopectin ratios in starter feed on the development of ruminal epithelium in pre-weaned lambs

SUN Da-ming, LI Hong-wei, MAO Sheng-yong, LIU Jun-hua

2018, 27(8):  197-203.  DOI: 10.11686/cyxb2017396

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The objective of this study was to investigate the effects of different amylose to amylopectin ratio in starter feed on the development of the ruminal epithelium in pre-weaned lambs. Twenty-four 10-day-old lambs were divided into three groups, and were fed on iso-starch diets containing cassava starch (CS, n=8), maize starch (MS, n=8), and pea starch (PS, n=8). The lambs were separated from their mothers from 4:00-19:00 every day and placed in individual pens. The lambs received starter feed with different amylose-to-amylopectin ratios (CS, MS, and PS) ad libitum. Lambs were fed with their mothers’ milk for 1 h at fixed times (6:30, 10:30, and 15:30) during this period. All lambs received oat hay and water ad libitum. The lambs were slaughtered at 56 days old. Part of the ruminal tissue sample was used for morphological observations. Another part of the ruminal tissue sample was used to extract RNA to quantify the mRNA levels of various genes. Compared with the MS and PS diets, the CS diet significantly (P<0.001) increased the length and surface of rumen papillae in lambs. The rumen papillae of lambs were significantly wider (P=0.001) in CS and MS group than in the PS group. The thickness of different strata of the rumen epithelium in lambs was measured. The stratum corneum was significantly thicker in the CS and PS groups (P<0.001) than in the MS group. The stratum granulosum was significantly thicker in the CS and MS groups (P<0.001) than in the PS group. The total strata, stratum spinosum, and basale of the rumen epithelium were significantly thicker in the CS group (P<0.001) than in the MS and PS groups. The qRT-PCR results showed that different amylose to amylopectin ratios in the starter feed significantly affected the transcript levels of CDK2 and CDK6 (CS>MS>PS, P<0.001); the transcript levels of cyclin A and CDK4 were significantly higher in the CS group (P<0.05) than in the PS group. The transcript level of cyclin D1 was significantly lower in the CS group (P=0.012) than in the PS group. The transcript level of IGF-1 was significantly higher in the CS group (P<0.001) than in the MS and PS groups. The transcript levels of IGF-1R were significantly higher in the CS and MS groups (P=0.001) than in the PS group. These results indicated that a high amylopectin ratio in starch in starter feed promoted ruminal epithelial growth, which was associated with up-regulated expressions of IGF-1 and cell cycle protein in pre-weaned lambs. The results of this study have important significance for formulating appropriate nutritional strategies for lambs.