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    20 May 2021, Volume 30 Issue 5
    Risk assessment of grassland fires at the herder scale: The Dongwuzhumuqin Banner as an example
    Li-li HOU, Wa-la DU, Shan YIN, Shan YU
    2021, 30(5):  1-12.  DOI: 10.11686/cyxb2020200
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    With global warming, the frequent occurrence of grassland fires poses a serious threat to the environment in pastoral areas. The behavior of pastoral householders is of great significance for judging the risks of grassland fires. This study represents an analysis of fire risk on the herder micro-scale, with herders from 57 villages in Dongwuzhumuqin Banner as the research object. We calculated the natural disaster index on the basis of a survey of herders and (geographic information system, GIS) analyses. Then, we used principal component analysis, analytic hierarchy processes, and weighted multivariate analysis methods to analyze the grassland fire risk assessment index system at the herder scale. We generated a distribution map of grassland fire risk levels in the Dongwuzhumuqin Banner, and verified the accuracy of the risk assessment zoning map using fire spots. The main results were as follows: 1) The weights of the four first-level grassland fire risk assessment indicators in the Dongwuzhumuqin Banner were as follows: 25.85% dangerous, 28.86% exposed, 19.17% vulnerable, and 26.12% disaster prevention and reduction capacity. 2) The overall risk of grassland fires in the Dongwuzhumuqin Banner showed an increasing trend from west to east. The vast majority (86.07%) of the research area was in medium-risk and high-risk fire areas. 3) The fire spots in the study area were distributed along the border line from 2001 to 2018, and increased in abundance from south to north. The burned area was 2338.25 km2. The frequency of fires on the national border line was concentrated between two and three times. The proportion of fire spots in the middle and high-risk fire areas was 79.99%. Our analyses indicate that the accuracy of these risk zoning research results is relatively high. The results of this study provide a scientific basis for local government to formulate specific disaster prevention and mitigation policies for grassland fires.

    Coupling relationships between vegetation and soil in different vegetation restoration models in the Loess region of Northern Shaanxi Province
    Xue-hua PUYANG, Yue-ling WANG, Zhi-jie ZHAO, Juan HUANG, Yu YANG
    2021, 30(5):  13-24.  DOI: 10.11686/cyxb2020458
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    The coupling coordination relationship between vegetation and soil is an important basis for the efficient implementation and sustainable development of the Grain for Green Project. Based on investigations and analyses of vegetation and soil in six different vegetation restoration models (coniferous forest, hardwood forest, coniferous and broad-leaved mixed forest [theropencedrymion], arbor-shrub forest, shrubwood, and natural grassland) in the Loess region of Northern Shaanxi Province, an evaluation index system of the coupling relationship between vegetation and soil was established. The weight value of each index was determined by an analytic hierarchy process and entropy method, then models for the degree of coupling coordination between vegetation and soil were constructed. It was found that different vegetation restoration models had significantly different effects on soil moisture and nutrient contents. The comprehensive evaluations indicated that the soil environment in theropencedrymion was the best, and that in arbor-shrub forest was the worst. We detected significant differences in vegetation canopy density, biomass, nutrient element contents, and biodiversity indexes among different vegetation restoration models. The comprehensive evaluations showed that the vegetation community in theropencedrymion showed the fastest development, and that in natural grassland showed the slowest development. Soil environmental factors were significantly correlated with vegetation biomass, nutrient elements, and biodiversity. The vegetation-soil coupling coordination index of theropencedrymion, hardwood forest, natural grassland, shrubwood, coniferous forest, and arbor-shrub forest was 0.767, 0.661, 0.655, 0.646, 0.628, and 0.234, respectively. The development of vegetation and soil in theropencedrymion exhibited an intermediate synchronously coordinated type, while that in the arbor-shrub forest exhibited a moderately imbalanced soil-loss type. The vegetation-soil coupling coordination in other vegetation restoration models was at the primary coordination level. The development of vegetation and soil in hardwood forest was of a synchronous type. Vegetation development in natural grassland lagged behind soil development, while soil development lagged behind vegetation development in shrubwood and coniferous forest. Therefore, theropencedrymion should be selected preferentially for vegetation restoration and reconstruction in the Loess region of Northern Shaanxi Province, while arbor-shrub forest should be avoided. The level of vegetation and soil management should be enhanced in the Grain for Green Project.

    Effects of green manure return regimes on soil greenhouse gas emissions
    Xue-liang ZHANG, Yu-ting ZHANG, Rui LIU, Jun XIE, Jian-wei ZHANG, Wen-jing XU, Xiao-jun SHI
    2021, 30(5):  25-33.  DOI: 10.11686/cyxb2020431
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    There is little published data on the impact on subsequent greenhouse gas emissions of different green manure types and return regimes. To address this knowledge gap, a 91-day laboratory incubation experiment was conducted to explore the greenhouse gas emission impacts of green manure types and return regimes. In this study, two green manure species (vetch and ryegrass) with contrasting herbage C∶N ratios were incubated in two different return regimes (surface mulching and burial) to compare soil greenhouse gas emission of the four treatment combinations. Green manure return significantly increased soil CO2 and N2O emissions at all stages of the 91-day incubation period, and soil CO2 and N2O gas emissions also differed significantly between return regimes (surface mulching or burial) and plant species (vetch or ryegrass). The CO2 emissions associated with surface mulching were significantly lower than those following burial. During the incubation period, surface mulching reduced the CO2 emission rate and cumulative total emission by 17.07%-18.55% and 8.15%-9.79%, respectively, and reduced N2O emission rate and cumulative emission by 22.91%-38.35% and 17.97%-34.39%, respectively, compared to burial. For a given return method, green manure species significantly affected CO2 and N2O emissions. The cumulative emissions of CO2 and N2O following leguminous green manure return were 8.87%-10.85% and 21.90%-52.42% higher, respectively, than those of Poaceous green manure. There was a significant positive correlation between greenhouse gas emissions and soil microbial biomass carbon and nitrogen (MBC, MBN) in each treatment. Compared with surface mulching, green manure burial increased MBC by 21.42%-40.52% and MBN by 28.22%-34.23% (P<0.05). To sum up, green manure mulching can reduce greenhouse gas emissions more effectively than ploughing, and is thus conducive to protecting the ecological environment and saving labor costs, but the impact on crop growth and yield needs to be verified by field experiments.

    Weed community structure in fields of Astragalus membranaceus of different ages
    Yan REN, Sha LIU, Fu-song LIU, Dao-qing WANG, Fa-ming WU
    2021, 30(5):  34-41.  DOI: 10.11686/cyxb2020208
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    Weeds are the main biological factors that inhibit the growth, development, yield, and quality of medicinal plants. Astragalus membranaceus is a perennial medicinal plant, and the structure of the weed community structure in fields of this species evolves continuously during its growth. We conducted field surveys and found 66 species of weeds belonging to 24 families and 59 genera in A. membranaceus fields. Members of the Compositae and Leguminosae were the most abundant, with 10 species in each family. The dominant weed species were Agropyron cristatum Setaria viridisCorispermum mongolicum Convolvulus arvensis, and Ixeris polycephala. The weed community structure differed among fields of A. membranaceus plants of different ages. In fields of annual A. membranaceus, the weed community had low values for richness, the Shannon-Wiener index, and the Pielou index (32, 1.71, 0.49), a high value of Simpson’s index (0.372), and large biomass. In a field of 10-year-old A. membranaceus, the weed community had high values of the Shannon-Wiener index (3.14) and Pielou index (0.82), a low value of Simpson’s index (0.068), and the community structure tended to be stable. The weed community structure was similar among fields of similarly aged A. membranaceus plants, especially 3-to 5-year-old plants Sorenson’s index (0.828). With increasing age of A. membranaceus plants, the dominant species in the weed community changed from annual seed plants to perennial small herbs to perennial large herbs/small shrubs, and the main species of community-building plants changed from C. mongolicum to A. cristatum to Achnatherum inebrians and Artemisia frigida. We detected two main modes of weed propagation in A. membranaceus fields: The guerrilla warfare mode of seed propagation exemplified by C. mongolicum; And the base area mode of rhizome propagation exemplified by A. cristatum.

    Boron promotes secretion of extracellular polysaccharides and indole-3-acetic acid by Rhizobium
    Yong-gang CHEN, Wen-juan KANG, Fang WU, Yun A, Shang-li SHI, Cui-mei ZHANG, Zi-li LI
    2021, 30(5):  42-51.  DOI: 10.11686/cyxb2020220
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    The aim of this study was to determine how boron promotes the production of extracellular polysaccharides and indole-3-acetic acid (IAA) by the Rhizobium strain gn5f. A label-free protein quantitative technique was used to analyze the effect of boron on the protein expression of Rhizobium strain gn5f. The results showed that 100 mg?L-1 was the optimum boron concentration for inducing polysaccharide and IAA production by Rhizobium strain gn5f. A comparison between the control (no boron) and the 100 mg?L-1 boron treatment identified 54 differentially expressed proteins; 7 up-regulated proteins and 47 down-regulated proteins. Bioinformatics analysis showed that these differentially expressed proteins were related to energy production and conversion, fatty acid β-oxidation, gluconeogenesis, amino acid metabolism, and various metabolic processes. The proposed mechanism by which boron promotes the production of extracellular polysaccharides and IAA by Rhizobium gn5f is as follows: boron up-regulates NAD-dependent succinate-semialdehyde dehydrogenase, acetyl-coenzyme A synthetase, and succinate-semialdehyde dehydrogenase (NADP+), which promote metabolic pathways related to the tricarboxylic acid cycle such as pyruvate metabolism, γ-aminobutyric acid (GABA) bypass metabolism, and glutamate metabolism. The energy and various carbohydrates (D-galactose and D-glucose residues, D-glucuronic acid) provided by these metabolic pathways promote the synthesis of extracellular polysaccharides. Finally, IAA is synthesized from tryptophan via indole-3-acetamide (IAM) or indole-3-pyruvate under the action of related enzymes, and boron contributes to this process by improving tryptophan synthesis.

    Effects of nitrogen and phosphorus addition on production performance and nutritive value of pasture species in Northern Tibet
    Yan PENG, Jing-yuan SUN, Su-jie MA, Xiang-tao WANG, Lei SUN, Xue-hong WEI
    2021, 30(5):  52-64.  DOI: 10.11686/cyxb2020202
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    The development of snow pastures is an effective means to relieve rangeland degradation and improve grassland productivity. Rational fertilization is a key measure for ensuring the sustainable development of degraded alpine meadows. Therefore, we conducted field experiments and laboratory analyses to evaluate the effects of different fertilization treatments on the main agronomic traits, nutritional value, and total outputs of cultivated pasture species. This study was conducted at Namache, in the North Tibetan Autonomous Region of Naqu Prefecture. We focused on the effects of the nitrogen(N) and phosphorus(P) fertilizers on the production performance and nutritive value of pasture species to for provide a theoretical basis for the establishment of artificial grassland. The experiment had an orthogonal design with three factors (plant variety, fertilization and mixture of plant varieties). The four pasture species were Secal cerealeAvena sativa, Vicia sativa and Vicia tibetica, five fertilization treatments were no fertilizer (CK); 75 kg·ha-1 urea (N);375 kg·ha-1 NH4H2PO4(P); 22500 kg·ha-1 organic manure (OM) and 75 kg·ha-1 urea+375 kg·ha-1 NH4H2PO4+22500 kg·ha-1 organic manure (NPOM). Data for the sown pastures were evaluated by grey associative analysis, membership function analysis, and similar priority ratio analysis, principal component analysis. The four models and their evaluation results were subjected to a weighted analysis. We analyzed 16 main traits: plant height, growth rate, fresh-dry weight ratio, stem-leaf ratio, number of tillers/branches, sowing rate, stem diameter, total vegetation cover, crude protein content, crude fat content, crude fiber content, ash content, water content, non-nitrogenous components content, calcium content, phosphorus content and dry yield on sown pasture to explore the effects of main traits on dry yield. Then, we used simple correlation analysis and partial correlation analysis to determine which traits were most closely related to dry yield. The results showed that: 1) Compared with CK, the N, P, OM and NPOM fertilization treatments significantly affected the production performance and nutritive value of pasture species. In general, N and P addition advanced the phenological development of pasture species by 1 to 12 days. 2) Plant height, sowing rate, stem-leaf ratio, number of tillers/branches, total vegetation cover and yield showed positive partial correlations with dry yield. 3)The highest dry weight of pasture species was under the N and NPOM treatments. The optimal fertilization schemes were NP and NPOM. The top four pasture species/fertilization combinations were ranked, from highest productivity to lowest, S. cereale +V. tibetica (NOPM)>A. sativa (NP)>S. cereale +V. tibetica (NP)>A. sativa+V. sativa (NOPM). Therefore, at an appropriate planting density, these pasture species are suitable for the development of high-yielding artificial grassland in Northern Tibet. The results indicated excellent performance of A.sativa+ V. tibeticaunder NPOM and S. cereale +V. tibetica NP, the multivariate evaluation indicated that their yield was stable and that they are suitable for wide utilization in Tibet.

    Effects of water stress on life history strategy of Salsola nitraria in Zhundong, Xinjiang
    Lei PENG, Li ZHANG, Xiao-long ZHOU, Yan-bo WAN, Qing-dong SHI
    2021, 30(5):  65-74.  DOI: 10.11686/cyxb2020224
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    In arid areas, water is the key factor limiting plant growth. In this study, we determined the effects of water deficit on Salsola nitraria, the dominant species in the arid desert area of Zhundong, Xinjiang. The results of this field experiment will provide a reference for vegetation reconstruction in large open-pit mining areas in this region. The results showed that, at different growth stages, water deficit had a significant impact on biomass allocation in S. nitraria. The root∶shoot ratio increased with increasing severity of water deficit, and the aboveground biomass decreased faster than did the underground biomass. We used a membership function analysis of fuzzy mathematics to analyze the growth status of S. nitraria. The water content of S. nitraria differed significantly among different growth stages, and was highest at the seedling stage, followed by the growth stage, and then the reproductive stage. The water content of S. nitraria decreased with increasing severity of water deficit. The contents of carbon and nitrogen, but not phosphorus, in S. nitraria differed significantly among the seedling, vegetative growth, and reproductive stages. The nitrogen:phosphorus ratio was less than 14 at the seedling and vegetative growth stages but more than 16 at the reproductive stage. The results indicated that there is an energy trade-off favoring below-ground parts over above-ground parts at the seedling stage and vegetative growth stages. At the reproductive stage, the trade-off favors above-ground parts under low stress and below-ground parts under high stress. S. nitraria under drought stress has similar survival strategies at the seedling stage and growth stage. Under low stress, the survival strategy of S. nitraria at the reproductive stage is consistent with that at the seedling and growth stages, while under high stress, its survival strategy is different at the reproductive stage.

    Effect of water stress on proline accumulation and metabolic pathways in Deschampsia caespitosa
    Qiao-yu LUO, Yan-long WANG, Zhi CHEN, Yong-gui MA, Qi-mei REN, Yu-shou MA
    2021, 30(5):  75-83.  DOI: 10.11686/cyxb2020505
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    This research studied the accumulation of proline (Pro) and changes in the substrate, intermediate products and key enzymes in the Pro metabolic pathway in shoot and root tissues of Deschampsia caespitosa under drought and waterlogging stresses. It was found that: 1) Both drought and waterlogging stresses significantly increased the proline content of D. caespitosaP<0.05), and there was little difference between the proline content of the shoot and root under the same water treatment. 2) Under drought and waterlogging stresses, the glutamate content in the shoots and roots of D. caespitosa were significantly (P<0.05) decreased, but the glutamate concentration in the roots was greater than that in the shoots under the same water treatment. Water stress caused a significant decrease in ornithine content in the shoots (P<0.05), but not in roots. At the same time, the activities of Δ1-pyrroline-5-carboxylic acid synthetase, ornithine aminotransferase (δ-OAT) and Δ1-pyrroline-5-carboxylic acid reductase in the shoot and root tissues of D. caespitosa were significantly increased under drought and waterlogging stresses (P<0.05), and the activity of δ-OAT in shoots was stronger than in roots. In addition, the activities of Δ1-pyrroline-5-carboxylic acid dehydrogenase and proline dehydrogenase were significantly reduced (P<0.05). The results showed that the active accumulation of proline was a primary response of D. caespitosa in alleviation of drought and waterlogging stress. The glutamate and ornithine pathways operated synergetically in the shoots, but the glutamic acid pathway was the main pathway in the roots.

    Effects of salt stress on growth and physiological characteristics of Echinochloa frumentacea seedlings
    An-qiao LU, Feng-ju ZHANG, Xing XU, Xue-qin WANG, Shan YAO
    2021, 30(5):  84-93.  DOI: 10.11686/cyxb2020209
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    The aim of this study was to determine the growth and physiological characteristics of Echinochloa frumentacea seedlings under different degrees of salt stress (NaCl and Na2SO4). We determined growth and development indexes (plant height, root length, fresh weight∶dry weight ratio), contents of photosynthetic pigments and osmoregulation substances (proline, soluble sugars), malondialdehyde and activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase) under two types of salt stress. The results showed that the threshold for growth and development of E. frumentacea seedlings was 50 mmol·L-1 NaCl or Na2SO4. The highest chloroplast pigment contents were in the 50 mmol·L-1 NaCl and 75 mmol·L-1 Na2SO4 treatments. The proline content was significantly higher in all the salt treatments than in the control (P<0.05). The thresholds for increases in proline content were 100 mmol·L-1 NaCl and 125 mmol·L-1 Na2SO4. The highest malondialdehyde contents were in the 100 mmol·L-1 salt treatments (NaCl and Na2SO4). The highest soluble sugars content and catalase activity were in the 75 mmol·L-1 NaCl and 100 mmol·L-1 Na2SO4 treatments, respectively. The activity of superoxide dismutase increased as the NaCl and Na2SO4 concentrations increased, and it was significantly higher than that of the control (P<0.05) when the concentration of either salt was greater than or equal to 50 mmol·L-1. Therefore, our results show that NaCl and Na2SO4 can promote E. frumentacea growth at lower concentrations but inhibit its growth at higher concentrations, and the inhibitory effect of NaCl is stronger than that of Na2SO4.

    Co-inoculation with rhizobia and azotobacter affects the growth of Vicia villosa
    Zhi-min WEI, Bin SUN, Cheng FANG, Zi-wen DAI, Man-qiang LIU, Jia-guo JIAO, Feng HU, Hui-xin LI, Li XU
    2021, 30(5):  94-102.  DOI: 10.11686/cyxb2020210
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    The effects of single or combined inoculation of the nitrogen-fixing bacteria Bacillus megaterium N3 (hereafter N3) and Rhizobium leguminosarum Vic5 (hereafter Vic5) on the growth of Vicia villosa and on soil properties were evaluated in this study. The results showed that, compared with the uninoculated control, V. villosa plants inoculated with strain N3 showed significantly increased nodule nitrogenase activity, and those inoculated with strain Vic5 showed significantly increased aboveground biomass, nodule numbers, and the nodule nitrogenase activity. The aboveground biomass, nodule numbers, nodule nitrogenase activity, and root morphological indexes including root length, root surface area, root volume, and root number of V. villosa were significantly higher (72.55%, 121.20%, 47.22%, 21.46%, 50.48%, 53.85%, and 47.42% higher, respectively) in the single Vic5 inoculation treatment than in the single N3 inoculation treatment. Compared with the soil in the control, that in the single N3 inoculation treatment showed significantly higher total phosphorus, available phosphorus, and available potassium contents, and that in the single Vic5 inoculation treatment showed significantly increased ammonium nitrogen and nitrate nitrogen contents. Combined inoculation with both strains significantly increased the contents of soil organic matter and total nitrogen. Single inoculation with strain N3 significantly increased the soil nitrogenase activity, while single inoculation with strain Vic5 significantly increased soil basal respiration, microbial biomass carbon and nitrogen contents, and soil nitrogenase activity. The highest values for soil basal respiration intensity, microbial biomass carbon and nitrogen contents, and soil nitrogenase activity were in the combined inoculation treatment. The soil nitrogenase activity measured by acetylene reduction reached C2H4 53.77 nmol·g-1·h-1. In conclusion, compared with single inoculation, combined inoculation with nitrogen-fixing bacterial strains N3 and Vic5 can promote the growth of V. villosa and improve soil quality. These results provide a foundation for the development of a specific microbial fertilizer for V. villosa.

    QTL mapping and candidate gene analysis of leaf area in maize (Zea mays) under different watering environments
    Xiao-qiang ZHAO, Yuan ZHONG, Wen-qi ZHOU
    2021, 30(5):  103-120.  DOI: 10.11686/cyxb2020295
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    Leaf area (LA) and its distribution influences the efficiency of photosynthesis and transpiration rate, and is also closely related to drought tolerance, planting density, degree of lodging and grain yield in maize (Zea mays). In-depth analysis of the molecular mechanisms controlling LA under different moisture levels at different growth stages is of great significance for the breeding of drought tolerant and high-yielding new maize varieties. In this study, composite interval mapping (CIM) and mixed linear model mapping based on composite interval mapping (MCIM) was carried out across two F2∶3 populations under eight different ‘environments’. Specifically, experiments were set up in Gansu Province between 1508 and 1785 m altitude at Wuwei and Zhangye in 2014 and Gulang and Jingtai in 2015, and each of the four experiments had contrasting fully watered and moisture deficit treatments. Quantitative trait loci (QTLs) for LA (determined by measuring the 10th-12th leaves in late vegetative and three ear-leaves in early reproductive growth stages) were analyzed in single environments and across all environments. The candidate genes in the stable QTLs (sQTLs) were identified and the corresponding gene functions were determined using the reference genome B73 RefGen_v3. A total of seven QTLs were identified by CIM mapping cross vegetative and reproductive growth stages of the two F2∶3 populations in all eight environments, five of these in fully watered treatments, five in moisture deficit treatments and three shared by both fully watered and moisture deficit treatments. These QTLs exhibited dominance (81.0%), partial-dominance (14.3%), and over-dominance (4.7%) effects. Six joint QTLs for LA were found among all environments by joint analysis with MCIM, three from each of the two populations. One QTL was involved in a significant QTL by environment interaction (QTL×E; Bin 2.08-2.09), and one significant epistasis (Bin 1.08-1.10 and Bin 2.08-2.09) was mapped with an additive by additive (AA) effect. Combining CIM and MCIM methods for further analysis, six stable QTLs (sQTLs) were detected in Bin 1.08-1.10, Bin 2.08-2.09, Bin 4.08-4.09, Bin 6.05, Bin 8.03, and Bin 10.03, and 12 candidate genes that regulated leaf development in maize were located in these sQTL intervals. From bioinformatic data, 75 candidate genes related to leaf development were collected and their phylogenetic tree constructed. The phylogenetic tree of these 75 genes comprised three major evolutionary branches, and the 12 candidate genes identified above were distributed on the three branches. These results lay a foundation for systematic understanding of the molecular mechanisms governing LA in different environments at different plant growth stages. These detected sQTLs identify important genomic regions for LA improvement, and the detected candidate genes can provide reference sequences for further gene cloning, functional analysis, and other breeding applications.

    Genome-wide identification of full-length long-terminal repeat retrotransposons and identification of interrupted genes in Cleistogenes songorica
    Yi-meng WANG, Tian-tian MA, Zi-feng OUYANG, Ji-yu ZHANG
    2021, 30(5):  121-133.  DOI: 10.11686/cyxb2020219
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    Long-terminal repeat retrotransposons (LTR-RTs) are mobile genetic factors that are an important component of, and are widely distributed across, the plant genome. The genome of Cleistogenes songorica is 543 M in size. In total, 299079 LTR-RTs have been identified in C. songoria, accounting for 26.54% of the total genome. The aim of this study was to identify full-length LTR-RTs in the C. songorica genome and determine when they arose and which genes they interrupt. Based on the whole genome sequence of C. songorica, 845 potential full-length LTR-RTs were identified, of which 410 belong to the Gypsy superfamily and 435 belong to the Copia superfamily. These sequences were subjected to phylogenetic and insertion time analyses. The results of those analyses indicated that many full-length LTR-RTs have been transposed within the last 4 million years. The range of insertion time was relatively short, and the peak period of LTR-RTs insertion was between 1 and 1.5 million years ago. We identified 183 genes that have been interrupted by full-length LTR-RTs in C. songorica, and 145 of them were annotated with Gene Ontology functions. We analyzed the transcript levels of the interrupted genes under different drought stress treatments. Identification of the dynamics of retrotransposons is helpful for understanding the complexities of C. songorica evolution, and lays the foundation for further research and analysis of full-length LTR-RTs in C. songorica.

    Genetic structure and diversity of Yading yak and Larima yak populations
    Hui JI, Jiu-qiang GUAN, Hui WANG, Jian-xu ZHOU, Nong-ga A, Zong-wei HE, Zhen-xiang FAN, Long-kang QIU, Shi-xiao CAO, Tian-wu AN, Qin BAI, Jin-cheng ZHONG, Xiao-lin LUO
    2021, 30(5):  134-145.  DOI: 10.11686/cyxb2020212
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    Yading yak and Larima yak are excellent local yak resources for meat and milk production. The aims of this study were to explore the genetic diversity of Yading yak and Larima yak and the genetic relationships among yak populations. We conducted restriction site associated DNA simplified genome sequencing for Yading yak, Larima yak, and seven other local yak populations (Jiulong yak, Maiwa yak, Jinchuan yak, Changtai yak, Zhongdian yak, Yushu yak, and Leiwuqi yak). Genetic statistics were calculated based on the detected single nucleotide polymorphism information. The observed heterozygosity values of Yading yak and Larima yak populations were 0.2186 and 0.2233, respectively. The genetic diversity of Yading yak was relatively poor. The average genetic differentiation index (Fst value) of Yading yak was 0.0653, which was moderately different from those of other Yak populations. A Structure analysis showed that the pedigree of Yading yak is pure, so it can be classified as an independent genetic resource. The lowest Fst value was that of Larima yak (0.0443). Our analyses suggest that the population genetic structure is more complicated for Larima yak than for other yak populations. Our results indicate that here have been genetic exchanges between Larima yak and Jiulong yak as well as Maiwa yak, and that Larima yak is one of the ancestor groups of Maiwa yak. Further research on Yading yak and Larima yak is warranted, and both populations require protection. The results of this study will be useful for developing strategies to protect and utilize yak genetic resources.

    Effects of peanut vine and alfalfa meal on weight gain performance, internal organ development, and blood indexes of Boer×Macheng crossbred goats
    Xiao-jun SUO, Nian ZHANG, Qian-ping YANG, Hu TAO, Qi XIONG, Xiao-feng LI, Feng ZHANG, Ming-xin CHEN
    2021, 30(5):  146-154.  DOI: 10.11686/cyxb2020217
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    The aim of this study was determine the effects of peanut vine and alfalfa meal on the growth performance, internal organ development, and blood indexes of Boer×Macheng crossbred goats. Thirty healthy castrated Boer (♂)×Macheng black (♀) goats [(21.40±1.15) kg, 4.5-5.0 months of age] were randomly assigned to three groups, with 10 goats per group. Goats in the three groups were fed peanut vine, peanut vine+alfalfa meal, and alfalfa as roughage, respectively. Total mixed rations were used, and the nutritional levels of the diets in each group were basically the same. The experiment consisted of a 10-day pre-trial period and a 60-day trial period. The body weight of goats was measured at the beginning and end of the trial. The animals were slaughtered and blood was collected at the end of the experiment. The main results were as follows: the body weight before slaughter and carcass weight were significantly higher in the peanut vine+alfalfa meal and alfalfa groups than in the peanut vine group (P<0.05); the average daily gain and dressing percentage were significantly higher in the peanut vine+alfalfa meal and alfalfa groups than in the peanut vine group (P<0.01); the feed gain ratio was significantly lower in the peanut vine+alfalfa meal and alfalfa groups than in the peanut vine group (P<0.01). There was no significant difference in dry matter intake among three groups. However, the rumen weight was significantly higher in the peanut vine+alfalfa meal group and the alfalfa group than in the peanut vine group (P<0.05). There was no significant difference in organ weight and proportion of LWBS among the three groups (P>0.05). The blood indexes of goats in each group were in the normal range. The serum albumin and blood glucose concentrations were significantly higher in the peanut vine+alfalfa meal group and alfalfa group than in the peanut vine group (P<0.05). The urea nitrogen concentration was significantly lower in the peanut vine+alfalfa meal group and alfalfa group than in the peanut vine group (P<0.05). The average cost per kilogram of weight gain was lower in the peanut vine+alfalfa meal group than in the peanut vine group and alfalfa group. These results show that the combination of peanut vine+alfalfa meal is better than feeding either component singly.

    Optimization of fermentation technology for production of quinoa straw feed using response surface methodology
    Xiao-fei YU, Xiao-nong GUO, Yan ZHANG, Zi-wei LIU, Xi-wen ZHANG, Ke-xin XU, Zhi-yong Wu
    2021, 30(5):  155-164.  DOI: 10.11686/cyxb2020203
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    Microbial fermentation can improve the nutritional value of straw, including quinoa straw. The aim of this study was to determine the effects of lactic acid bacteria alone and in combination with yeast, compared with the effect of Aspergillus niger, on the quality of fermented quinoa straw feed. The overall aim of this research was to provide a reference for the development and utilization of quinoa straw in feed. In the single fermentation with lactic acid bacteria, the three variable factors were fermentation time, water content, and amount of inoculant added. In the fermentations with lactic acid bacteria and yeast, the three variable factors were fermentation time, water content, and ratio of inoculants to quinoa straw. All experiments were designed using the L9(34) orthogonal principle, and the response surface method was used to analyze the four nutritional indicators crude fiber, crude protein, crude fat, and soluble sugar contents. At the same time, a comparative test of the effect of fermenting quinoa straw with A. niger was conducted. The results showed that: 1) Under the same fermentation conditions, cellulose degradation was greater in the mixed fermentations than in those with lactic acid bacteria alone. 2) The average crude protein content was 2.7% higher in fermented quinoa straw than in unfermented quinoa straw. 3) During the fermentation process, the crude fat content showed little change, ranging from 0.24% to 0.31%. 4) After fermentation, the soluble sugar content of quinoa straw was increased by about 3%; 5) A. niger degraded cellulose and increased the soluble sugar content, but the sensory quality of the feed was poor. Our results confirm that microbial fermentation can improve the quality of quinoa straw feed, and show that the synergistic fermentation with mixed inoculants is better than fermentation with a single strain.

    Effects on fermentation in alfalfa mixed silage of added lactic acid bacteria or organic acid salt combined with urea
    Zhan XIE, Lin MU, Zhi-fei ZHANG, Gui-hua CHEN, Yang LIU, Shuai GAO, Zhong-shan WEI
    2021, 30(5):  165-173.  DOI: 10.11686/cyxb2020372
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    This research investigated the influence of added lactic acid bacteria (LAB) or organic acid salt (OAS) together with urea on mixed alfalfa silage fermentation. The silage raw materials were alfalfa, rice straw and wheat bran in proportions of 8∶1∶1 by mass. The experiment design was a 2×4 factorial, with LAB or OAS as factor A and four rates of urea: 0 (U0), 1.5 (U1), 3.0 (U2) or 4.5 (U3) g·kg-1 FW, as Factor B. After 45 days of fermentation, the fermentation quality, nutritional quality and aerobic stability were analyzed. It was found that the pH, crude protein, neutral detergent fiber, acid detergent fiber and relative feed values of the LA treatment group were significantly better than those of the AS treatment group, and the contents of acetic acid, propionic acid, butyric acid and NH3-N/TN in the LAB treatment group were significantly lower than those in the OAS treatment group (P<0.05). The pH value, and levels of acetic acid, propionic acid, butyric acid and NH3-N/TN in the U3 treatment group were significantly higher than those in the other 3 groups. Neutral detergent fiber, acid detergent fiber and soluble carbohydrate content in the U0 treatment group were higher than those in other 3 groups; and crude protein content in the U0 treatment group was significantly lower than that in the other 3 groups (P<0.05). The optimal formulation for mixed silage fermentation was the addition of LAB to U1 or U2 urea treatments.

    Multi-trait evaluation of yield and nutritive value of 12 Lolium multiflorum varieties or lines in Chengdu Plain
    Yi XIAO, Zhong-fu YANG, Gang NIE, Jia-ting HAN, Yang SHUAI, Xin-quan ZHANG
    2021, 30(5):  174-185.  DOI: 10.11686/cyxb2020447
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    This research evaluated the growth rate (measured as rate of height increase), stem∶leaf ratio, mowing height, fresh yield, hay yield and other production performance indexes of 12 Italian ryegrass varieties (lines) in order to select and breed new lines of Italian ryegrass suitable for cultivation in Chengdu, Southern China. Concurrently, herbage nutritional quality at different mowing stages was measured by near infrared spectroscopy (NIRS). It was found that the tested Italian ryegrass varieties (lines) grew rapidly (2.05 to 2.18 cm?d-1) during March and April. However, the stem∶leaf ratio was comparatively high, ranging from 1.02∶1 to 1.14∶1 for fresh weight and from 0.71∶1 to 1.00∶1 for dry weight. The fresh yield of the tested varieties (lines) ranged from 93444 to 109660 kg·ha-1, and the hay yield from 13191 to 15099 kg·ha-1. Among the tested lines, the average hay yield of the new lines JG1 and DC2 was 15099 and 14846 kg·ha-1, and these values exceeded yield of the control variety Angus No.1 by 14.5% and 12.5%, respectively. The crude protein content of Andes (18.44%) was significantly higher than other varieties (lines) (P<0.05). The acid detergent fiber and neutral detergent fiber contents of the new line JG1 were the lowest at 26.09% and 53.43%, respectively, and the water soluble carbohydrate content of Chuannong No.1 was the highest at 21.67%. Ten indices related to forage yield and quality were utilized to evaluate the tested Italian ryegrass varieties (lines) via grey correlation analysis, which showed that DC2, JG1, CA1 and GB performed excellently in Chengdu Plain and could be further tested for promotion and utilization.

    Screening of phosphite-tolerant alfalfa varieties and identification of phosphite tolerance indicators
    Ji-xiang WANG, Huan-yu GONG, Xiang-jian TU, Zhen-xing GUO, Jia-nan ZHAO, Jian SHEN, Zhen-yi LI, Juan SUN
    2021, 30(5):  186-199.  DOI: 10.11686/cyxb2020453
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    Phosphite, a reduced form of orthophosphate, is characterized by its high solubility, high transport efficiency, and low reactivity in soil. The aim of this study was to screen for phosphite-tolerant alfalfa varieties and provide information for the development of phosphite fertilizers by exploring differences in phosphite tolerance among different varieties of alfalfa at the seedling stage. Thirty-seven alfalfa varieties were cultured in Hoagland’s nutrient solution with orthophosphate (0.5 mmol·L-1 KH2PO4) or phosphate (0.5 mmol·L-1 KH2PO3) as the sole phosphorus resource. We analyzed 12 morphological and physiological characters: Plant height (PH), stem diameter(SD), shoot phosphorus content (SPC), shoot dry weight (DWS), root dry weight (DWR), root∶shoot, total root length (RL), root surface area (RSA), root phosphorus content (RPC), chlorophyll content (Chl), leaf area (LA), and net photosynthetic rate (Pn). Based on the phosphite-tolerance coefficient (PTC) of each individual index, we used principal component analysis, membership function analysis, cluster analysis, and stepwise regression to comprehensively evaluate phosphite tolerance characteristics and establish a mathematical model. The results showed that phosphite stress resulted in increased root total phosphorus content, increased chlorophyll content, and decreased values of other indexes in different varieties. The 12 indicators were divided into five composite indicator groups in a principal component analysis. The 37 alfalfa varieties were classified into four categories in terms of phosphite resistance: highly resistant (two varieties; WL903 and Kehan); Moderately resistant (12 varieties); Low resistance (17 varieties), and sensitive (six varieties). The following regression model was developed for evaluating phosphite tolerance: Y=-0.174+0.102PH+0.189DWR+0.168RL+0.187RSA-0.061PnR2=0.9908). The precision of the regression equation was higher than 93.22% for each alfalfa variety. The results show that the highly phosphite-resistant alfalfa varieties were Kehan and WL903. Under phosphite stress, the tolerance of alfalfa varieties to phosphite can be quickly identified and predicted by measuring PH, DWR, RL, RSA, and Pn.

    Cultivation and utilization of herbage in the pre-Qin Period
    Ya TAO, Qi-zhong SUN, Qian LIU, Feng LI, Li-jun XU, Da LI, Di WANG
    2021, 30(5):  200-210.  DOI: 10.11686/cyxb2020216
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    There were three main ways to earn a living in primitive society; collecting, fishing and hunting, and raising livestock. A major turning point for human civilization was the addition of plant cultivation as a means of earning a living. In primitive society, both animal husbandry and agriculture were invented by humans, and animal husbandry was developed from fishing and hunting. With the development of animal husbandry, the demand for fodder increased, which brought about the cultivation of forage. The need for fodder became more urgent as the amount of livestock increased. When people noticed that forage grasses accumulated in certain places, the idea of planting forage crops was born, and knowledge of planting and cultivation was obtained gradually by observations and trial and error. At first, certain wild grasslands were fenced and some cultivation techniques were used, and then grain fit for human consumption was found. In this way, wheat and millet became cultivated crops for human food and forage species were cultivated for livestock feed. In this study, we searched ancient Chinese texts for references to animal husbandry and plant cultivation. During the Xia, Shang, and Western Zhou Dynasties, animal husbandry was relatively well developed in China, and records of fodder cultivation and ruminant grazing appeared in The Oracle. Horses were important livestock during the Shang and Zhou Dynasties, and were fed with grain and millet. As pointed out by Guo Mo-ruo, in The Oracle Bone Inscriptions, the original Chinese character for the word “Tian” does not refer to a field of wheat and millet, but a field for planting fodder and hunting ruminants. That is, the earliest cultivation was for ranching. Records in The Book of Songs indicate that the conditions for the cultivation and utilization of fodder were already established at the time the book was written. The Book of Songs notes that, “The horse in the stable was fattened by food and grass”. This indicates that horses were fed with grain in ancient China, and is indicative of the long history of forage processing in China. In the Western Zhou Dynasty, fire was introduced as a tool for the ecological management of grassland. The Zhouli recorded “Burning the dead grass on the pasture in early spring”. In the Mozi, which includes records for the Chunqiu and Zhanguo Dynasties, it is noted that “All cattle and sheep were fed with fodder”. In the State of Lu, Chengtian was in charge of animal husbandry. These ancient texts provide evidence for, and information about, animal husbandry and the cultivation of food and fodder crops in ancient China.

    Allelopathic effect of root extracts from Astragalus strictus seedlings on eight wild plants of Tibet
    Sai Hen-na BAO, Xiang-tao WANG, Jun-xi WU, Yan-jun MIAO, Xiang JIA, Yan-ting TIAN
    2021, 30(5):  211-220.  DOI: 10.11686/cyxb2020213
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    We investigated the allelopathic effect of an extract of Astragalus strictus root tissues on the following wild plants of Tibet: Medicago lupulina Elymus nutans Oxytropis microphylla Festuca ovina Stipa purpurea Stipa capillacea Kobresia littledaleiand Eragrostis nigra. An aqueous extract from roots of A. strictus was applied at different concentrations (0.1, 0.05, 0.025, 0.0125 g·mL-1) to seeds of the eight plant species, and its effects on seed germination and seedling growth were determined. We detected significant (P<0.05) allelopathic effects of the extract on the germination rate, germination vigor, germination index, vigor index, root length, seedling height, and dry weight of seedlings and roots. There were some differences in responses among the eight tested wild plants. Notably, the root extract significantly (SE>0) accelerated the seed germination and growth of M. lupulina O. microphylla, and F. ovina; It had inhibitory effects on E. nutans and S. purpurea SE<0); And it had no obvious effect on S. capillacea and E. nigra. We calculated the average plant sensitivity index to analyze the allelopathic effect of the A. strictus root extract on the seed germination and growth of the eight wild plants. The plants were ranked, from most to least sensitive to the allelopathic effects of the A. strictus root extract, as follows: E. nutans>S. purpurea>S. capillacea. The remaining plants were ranked from strongest to weakest growth-promoting effects of root extract of A. strictusas follows: O. microphylla>K. littledalei>E. nigra>F. ovina>M. lupulina.