Table of Content

20 December 2024, Volume 33 Issue 12

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Evaluation of vegetation-soil synergistic coupling in winter rangeland of the Qilian Mountains under different winter grazing management systems

Ze-hang YU, Yang YU, Quan CAO, Yu-zhen LIU, Bin FENG, Xiao-fang ZHANG, Quan-min DONG

2024, 33(12):  1-12.  DOI: 10.11686/cyxb2024050

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The degree of synergistic coupling of the vegetation-soil system serves as a comprehensive evaluation index to measure the complementarity and integration of grassland ecosystem components， and is an important tool in implementing the quantitative management of grassland. This study was conducted in Yeniugou Township， Qilian County， Qinghai Province， and three different grazing management systems were compared： all feed from grazing in winter， winter grazing+supplemental feeding， and winter enclosure （no grazing）. We constructed an evaluation system composed of vegetation factors and soil factors， and used the entropy power method to determine the weight of each index， and formulated a model to score the degree of synergistic coupling of the vegetation-soil system. It was found that there were significant differences in the Shannon-Wiener index and Patrick richness index of vegetation communities under the different grazing managements， and the grassland in the grazing+supplementary forage winter feeding system had the highest score， while that where grazed grassland comprised the total feed supply had the lowest score. There were significant differences in the contents of soil total carbon， total nitrogen， total phosphorus， ammonium nitrogen， nitrate nitrogen， available potassium， and available phosphorus with different grazing management， and the highest soil system score was found in the grassland with no winter grazing， and the lowest in the grazed grassland with no feed supplementation. The score for the degree of synergistic coupling under the different grazing management systems ranked： enclosure （0.510）>grazing+supplementary feeding （0.482）>all feed from grazing （0.397）. For the above three winter grazing systems， the grassland ecosystem could be categorized， respectively， as ‘barely coordinated vegetation-soil system lacking development’， ‘bordering on disordered vegetation-soil coordination lacking development’， and ‘mildly disordered vegetation-soil coordination with development recession’. In conclusion， winter enclosure of animals with no grazing by animals of grassland in the Qilian Mountain area was the most conducive to the health and stability of the ecosystem， among the three grazing systems evaluated， but still exhibited a less than optimal level of vegetation-soil coordination.

Analysis of herders’ willingness to pay for snow disaster weather-index insurance—A case study in the Gannan Pastoral area

Fu-ning LI, Tian-shu CHAI, Ze-ping QIN, Zeng TANG

2024, 33(12):  13-22.  DOI: 10.11686/cyxb2024046

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Weather-index insurance is a novel insurance product that has gained widespread recognition globally. However， its application in alpine grassland pastoral areas remains unexplored. Herders’ demand for insurance products directly influences the applicability and promotion potential of index insurance schemes. In this study， we investigated herders’ willingness to pay （WTP） for snow disaster index insurance， and the associated influencing factors， in the Gannan grassland pastoral area using the contingent valuation method （CVM）. The overall aim of this study was to provide scientific support for the development of index insurance as a part of the insurance industry in the study area. The key findings of our study are as follows： 1） The average WTP for index insurance in the study area significantly exceeds the current livestock insurance premium； 2） However， it is still lower than the premiums associated with the offered indexed insurance schemes； 3） Large-scale and specialized herders exhibit a higher WTP for new index insurance products. Together， these results suggest that herders in the study area are willing to pay a higher premium for index insurance products offering enhanced protection. Nevertheless， the high cost of index insurance currently restricts its potential to replace existing lower-cost， high-coverage insurance options. At this stage， it can serve as a complementary product to address the security needs of some large-scale and specialized herding operations. Moving forward， implementing differentiated insurance subsidy policies will be crucial to strengthen the insurance protection capacity within the study area.

Effects of photovoltaic power station construction on plant community and soil characteristics

Ping-an BAO, Bo JI, Guo SUN, Na ZHANG, Xu-dong WU, Jian-long HE, Zhan-jun WANG, Ying TIAN

2024, 33(12):  23-33.  DOI: 10.11686/cyxb2024117

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This research investigated the impact of photovoltaic （PV） power station construction on vegetation and soil in a desert steppe. Two PV power stations in Ningxia with a post-construction vegetation recovery time of one and two years were selected for study and data were collected for three categories of site： between PV panels （BJ）， under PV panels （BX）， and outside the PV power station （control， CK）. Vegetation surveys were conducted and soil sampling carried out， and the plant community characteristics of soil physical and chemical properties were compared under the different treatments and their relationships analysed. The results revealed that the vegetation cover， aboveground biomass and diversity index were the highest in the CK plot after one year of vegetation restoration. The contents of soil organic matter （SOM）， soil total phosphorus and potassium （TP and TK） and soil available phosphorus （AP） in the photovoltaic power station area were significantly higher than those in the control area outside the photovoltaic power station. After 2 years of vegetation restoration， plant community species diversity indices， TK， available nitrogen （AN） and AP were significantly higher for both BJ and BX sites than for CK site. Plant community cover and aboveground biomass were positively correlated with pH， and negatively correlated with electrical conductivity （EC）， SOM and AN. Shannon-Wiener index was positively correlated with EC， SOM and AN. Soil pH and SOM content are the most important factors affecting the characteristics of plant communities in this study. The results show that the construction of a photovoltaic power station has a negative impact on the vegetation community and soil physical and chemical characteristics， but that subsequently there is at least partial recovery from the ecological damage resulting from power station construction.

The geographic distribution pattern and factors influencing the spread in China of the invasive alien plant Cenchrus longispinus

Yu-xuan HAN, Rui WANG, Li-fen HAO, Hai-bin YUAN, Ke-jian LIN

2024, 33(12):  34-44.  DOI: 10.11686/cyxb2024054

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The invasion of Cenchrus longispinus has caused great harm to the northern grassland and the ecotone of agriculture and grazing land in China. Most of the studies have focused on the biological characteristics of， and control measures for C.longispinus， but its invasion and spread mechanisms， geographical distribution pattern and factors influencing these in China are not clear. Hence， we reconstructed the invasion history of C. longispinus in China using data from herbarium specimens， literature， field surveys， and other sources. This spatial analysis approach revealed the spatial distribution pattern of C. longispinus， and the spatiotemporal heterogeneity of its spread. We selected 8 environmental factors based on principal component analysis to identify the key factors that influence distribution and spread patterns. C.longispinus first invaded Jinzhou City， Liaoning Province in 1963， then spread to the southeastern part of Inner Mongolia and western Jilin， where it has formed an invasion infestation and is still spreading. It has also spread to western Inner Mongolia since 2010 and formed a new infestation. The spread of C.longispinus in Liaoning Province shows anisotropy， mainly spreading north and west， with little spread to the southwest. C. longispinus was recorded in Chaoyang District， Beijing and Qinhuangdao， Hebei Province in the 1970s， but subsequently did not spread. The heterogeneity of the direction and pattern of C. longispinus spread in Liaoning and Beijing after introduction may be due to its inability to establish a stable and growing population after introduction. The factor analysis results of the introduction and establishment area show that soil calcium carbonate content， annual average precipitation， surface soil sand content， and surface soil carbon to nitrogen ratio are the key factors affecting whether C. longispinus can establish after introduction. In future risk assessments， the adaptability and reproductive capacity of C. longispinus populations in different soil environments should be considered. To better understand risk of spread， the reproductive growth characteristics and invasiveness in different environments should be fully analyzed. Such data will provide scientific support for accurately identification of areas at risk of colonization and will assist formulation of efficient monitoring and control measures to inhibit further C.longispinus spread.

Estimation of alfalfa yields on the basis of unmanned aerial vehicle multi-spectral and red-green-blue images

Yu-fei BAI, Hang YIN, Hai-bo YANG, Zhen-hua FENG, Fei LI

2024, 33(12):  45-58.  DOI: 10.11686/cyxb2024045

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Yield is a key component of the economic output of alfalfa （Medicago sativa） pasture. Timely and accurate quantification of alfalfa yield is useful to improve nutrient management and optimize planting patterns. The traditional method to estimate yield in pasture relies on destructive sampling， and there is a certain time lag in obtaining the results. In contrast， unmanned aerial vehicle （UAV）-based monitoring technologies can quickly obtain information to model yield in a non-destructive manner. However， the spectral and spatial resolutions cannot be balanced based on image information from a single sensor， so a comprehensive analysis of crop growth is impossible. It is difficult to effectively improve the accuracy of estimates based on a single UAV image. Therefore， the aim of this study was to explore the potential to combine multi-source image information from UAVs to estimate alfalfa yield during harvesting. In this study， red-green-blue （RGB） and multispectral （MS） images were collected during the alfalfa harvesting period. Based on spectral， texture， and wavelet features extracted from the RGB and MS images， two machine learning algorithms involving partial least squares （PLSR） and Gaussian process regression （GPR） algorithms were used to evaluate the robustness of the alfalfa yield estimation model. The results show that the wavelet features of RGB images were more effective for the comparison of color index and texture features. The combination of the two types of features improved the accuracy of alfalfa yield estimates to some degree. The GPR alfalfa yield estimation model combining three types of features （color index， texture， and wavelet） had high accuracy （training set coefficient of determination R²=0.76， validation set coefficient of determination R²=0.63， and RPD=1.61）. For MS images， the model built based on texture features was the most accurate （training set coefficient of determination R²=0.76， validation set coefficient of determination R²=0.63， and the ratio of prediction to deviation RPD=1.61）. The alfalfa yield estimation model based on texture features was slightly better than that based on spectral index features， and the GPR alfalfa yield estimation model constructed by combining the two types of features was very accurate （training set coefficient of determination R²=0.83， validation set coefficient of determination R²=0.58， and RPD=1.55）. The accuracy of the alfalfa yield estimation model was significantly improved when the RGB image and MS image features were fused. Particularly， the GPR model with three kinds of feature parameters （multi-spectral index， multi-spectral texture， RGB wavelet feature） was the most accurate in estimating alfalfa yield （coefficient of determination R²=0.83 in the training set， coefficient of determination R²=0.75 in the validation set， and RPD=1.98）. In conclusion， the GPR algorithm provided the best estimation results， and the estimation accuracy was improved by 13.6% compared with that of the PLSR model. These results provide a reference for remotely monitoring artificial grassland and estimating yield in the future.

Estimation of relative water content in bermudagrass leaves based on hyperspectroscopy

Qi-kun YU, Wen LI, Li-si TANG, Yu HAN, Pei-ying LI, Zong-jiu SUN

2024, 33(12):  59-72.  DOI: 10.11686/cyxb2024039

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Hyperspectral techniques have been widely used to monitor the degree of drought stress and screen for drought-resistant plant materials. In this study， 18 bermudagrass genotypes were subjected to natural drought for 12 days. The soil water content and leaf relative water content of each material were determined， and hyperspectral photos were obtained at different timepoints during the drought treatment using an SVC HR-768 portable spectrometer. The spectral reflectance， which was processed using a combination of hyperspectral Savitzkye Golay smoothing and Savitzkye Golay smoothing+first derivative， was used as the independent variable， and characteristic bands that were well correlated with the relative water content of leaves and， on the basis of Pearson’s correlation and continuous projection analyses， were common among all the materials screened. Then， an inversion model of the relative water content of bermudagrass leaves was established using three machine-learning algorithms： the BP neural network， support vector machine， and random forest algorithms. The main results were as follows： 1） Five Savitzkye Golay smoothing+first derivative characteristic bands were screened out using the continuous projection algorithm； the bands were located at 406， 569， 706， 736， and 786 nm， respectively， and showed high correlations （P>0.5） with the relative water content of bermudagrass leaves. The covariance among the bands was weak， so these bands could be used as sensitive bands for drought monitoring. 2） The coefficient of determination （R² ） and root-mean-square error （RMSE） of the random forest inversion model based on the sensitive wavebands were 0.939 and 8.552， respectively， which were 5% and 8% higher， respectively， than those of the support vector machine and BP neural network models. Thus， the random forest inversion model showed the best prediction effect and universality. The R² of the test set was 0.925， and the RMSE was 9.008. The results of our study provide technical support for the development of a non-destructive and high-precision method to monitor the relative water content of bermudagrass leaves using hyperspectroscopy.

Effects of potassium application level on the growth， tuber quality， and yield of Cyperus esculentus in the Northern wind-sand area

Zi-qi CAO, Xiao-qing ZHAO, Xiang-qian ZHANG, Jian-hui WU, Fan ZHANG, Dan LIU, Zhan-yuan LU, Yong-feng REN

2024, 33(12):  73-83.  DOI: 10.11686/cyxb2024037

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In this study， the effects of the potassium （K） fertilizer application rate on the growth， physiology， biochemical indexes， tuber quality， and yield of Cyperus esculentus were determined， with an overall aim to provide theoretical support for the optimization of K fertilization for C. esculentus growing in the Northern Wind-Sand Area. A pot experiment with the C. esculentus cultivar Zhongyousha 1 was conducted in which K fertilizer was applied at four different levels： 0 （K₀）， 0.15 （K₁）， 0.30 （K₂） and 0.45 g·kg^-1 （K₃）. The growth， physiology， biochemical indexes， tuber quality， and yield were analyzed. The results showed that， compared with the control （K₀）， all the treatments resulted in significantly increased values for plant height， tiller number， single leaf area， maximum root length， and root volume of C. esculentus. The highest activities of acetyl-CoA carboxylase and soluble starch synthas and the largest amount of starch and fat in tubers （229.03 mg·g^-1 and 21.98%， respectively） were in the K₁ treatment （K applied at 0.15 g·kg^-1）， but the values of these parameters were not significantly different from their respective values in the K₂ treatment. The highest contents of unsaturated fatty acids and total fatty acids in the tubers （16.53 and 20.07 g·100 g^-1， respectively） were in the K₂ treatment. The highest total in the tubers sugar content （217.86 mg·g^-1） was in the K₃ treatment. The whole plant dry weight and yield of C. esculentus increased as the potassium application rate increased， and showed the highest values in the K₃ treatment， but these values were not significantly different from those in the K₂ treatment. Based on the quality， yield， and nutrient utilization rate of C. esculentus， we concluded that a K fertilizer application rate of 0.30 g·kg^-1 can enhance its growth and development in the Northern Wind-Sand Area， improve the activities of enzymes and other indexes related to quality， and increase dry matter accumulation and tuber yield.

Effect of manganese sulfate on photosynthesis and nitrogen metabolism of cultivated Indian barnyard grass seedlings under saline-alkali stress

Chang-zhuang LIU, Yu-zhao TAO, Ming LI, Xiao-ming ZHANG

2024, 33(12):  84-98.  DOI: 10.11686/cyxb2024056

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Soil salinization reduces plant uptake of manganese， seriously affecting the growth and yield of crops. However， it is unclear if exogenously supplied manganese sulfate can improve crop growth under soda solonetz conditions. In this experiment， two Mn supplementation treatments， manganese sulfate seed soaking and fertilization， were applied to cultivated Indian barnyard grass （Echinochloa frumentacea）， to investigate the physiological response to manganese sulfate of crop seedlings at V5 growth stage under saline-alkali stress. It was found that saline-alkaline stress significantly reduced the chlorophyll content and decreased the optimal/maximal quantum yield of PSⅡ （F_v/F_m） of Indian barnyard grass seedlings. This inhibition affected the performance of chlorophyll fluorescence parameters in the light response curve and led to a significant decrease in photosynthetic efficiency. Additionally the activities of key enzymes involved in nitrogen assimilation， such as nitrate reductase and glutathione synthetase decreased while the nitrate nitrogen content increased， ultimately this imbalance disrupted the carbon and nitrogen metabolism balance， inhibiting shoot growth. More dry matter was allocated to the roots， resulting in a significant increase in the root∶shoot. For saline-alkali-inhibited seedlings， application of manganese sulfate fertilizer or seed dipping treatment， promoted the development of the root system， enhancing nitrogen absorption ability， and increasing the activity of key enzymes involved in nitrogen metabolism. This led to effective accumulation of free amino acids and enhanced overall nitrogen assimilation efficiency in the plant. Additionally， manganese supplementation promoted the accumulation of chlorophyll and carotenoids， increased the F_v/F_m， and improved energy transfer within the photosystem. Consequently， the photosynthetic capacity of crop seedlings under salinity stress was significantly increased， resulting in improved crop growth. Comparing the seed soaking and fertilization treatments， fertilization was more effective in reducing the damage caused by saline-alkali stress and in balancing the overall carbon and nitrogen metabolism of the crop.

Allelopathic effects of aqueous extracts from Reaumuria soongorica and Salsola passerina on seedling growth

Yu-ying WANG, Pei-fang CHONG, Jian-xi ZHANG, Hang-hang LIU, Xin-guang BAO, Xue-ying WANG

2024, 33(12):  99-110.  DOI: 10.11686/cyxb2024036

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Plants can enhance their competitiveness through allelopathy. It has been observed that the desert plant Reaumuria soongorica grows better with Salsola passerina than it does alone. The aim of this study was to determine whether this phenomenon is related to allelopathy. Pot experiments were conducted to determine the effects of aqueous extracts of different organs of 1-year-old R. soongorica and S. passerina plants at a range of concentrations （0.02， 0.04， 0.06， and 0.08 g?mL^–1） on the growth and physiology of seedlings. We found that at the same mass concentration， leaf extracts of R. soongorica and S. passerina had the strongest allelopathic inhibitory effect on plant growth， followed by stem extracts， and then root extracts. This order of allelopathic effects of aqueous extracts of R. soongorica and S. passerina on seedling growth was the same， on the whole， for all extract concentrations. The treatments at a concentration of 0.02 g?mL^–1 had the weakest inhibitory effects， and those at 0.08 g?mL^–1 had the strongest inhibitory effects. In general， the aqueous extracts of R. soongorica organs had a stronger inhibitory effect on the growth of S. passerina seedlings than the aqueous extracts of S. passerina organs had on R. soongorica seedlings. In summary， there is an allelopathic interaction between R. soongorica and S. passerina. Therefore， when establishing artificial vegetation in desert areas， allelopathy between species should be considered， and appropriate planting methods should be selected to achieve the best revegetation outcomes. These findings provide insight for planning the ecological restoration and protection of desert ecosystems.

Ovule development before and after fertilization and seed formation dynamics of Medicago sativa cv. Xinmu No.4

Abudilimu YUERENSA·, Wei ZHAO, Xiao-wei WANG, Yan HUANG, Ai-qin ZHNAG

2024, 33(12):  111-121.  DOI: 10.11686/cyxb2024028

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The phenomenon of “more ovules and less seeds” at the fruit level is a common problem in seed production， in which the process of sexual reproduction is crucial. It is important to study the dynamics of ovule development and seed formation before and after fertilization to reveal the mechanism of the formation of seed yield. In this study， we explored ovule development before and after fertilization， the fertilization process， and the seed-setting pattern of Medicago sativa cv. Xinmu No. 4 by observations of paraffin sections stained with fluorescent dyes. We also conducted artificial controlled experiments to explore the factors restricting the formation of seed yield from the viewpoint of sexual reproduction. The main results of our study are as follows： 1） Before fertilization， there were no abnormalities in ovule development， and there was no location effect on the distribution of the vascular bundle on the ventral sutures. However， during fertilization， 19.6% of mature embryo sacs were coated with callus and could not be fertilized normally. 2） The pollen germination rate and pollen tube growth rate were higher after cross-pollination than after self-pollination. After entering the ovary， the pollen tubes preferentially reached the middle and base of the ovary， and fertilized the ovule in these positions. 3） Under natural conditions， on the second day after pollination， the middle and base parts of the ovule expanded， and on the third to sixth day after pollination， the proportion of the enlarged parts of the ovule had further increased. Subsequently， the basal part of the ovule became further enlarged and the middle to upper parts of the ovary began to abort. Finally， the seed setting pattern was formed with high ovule abortion rates at both ends of the pod and a low ovule abortion rate in the middle. 4） Resource restriction not only affected the number of ovules that formed before fertilization， but also increased the abortion rate of enlarged ovules after fertilization. In summary， many factors affect the development of ovules and the formation of seeds in M. sativa cv. Xinmu No. 4， including callose deposition， the fertilization sequence， resource allocation， and location effects. The low fertilization rate caused by callose deposition and high abortion rate of ovules after fertilization M. sativa cv. Xinmu No. 4 were identified as the main factors affecting seed yield.

A study of autotoxic effects of soil extract from continuously cropped Codonopsis pilosula var. modesta on seed germination and seedling growth

Ying-yu CHEN, Ya-juan QIU, Xiao-ling SHAO, Yu-fang HUANG, Fu-de YANG, Lin-jie CHEN, Hong-gang CHEN, Tian-peng XIE

2024, 33(12):  122-133.  DOI: 10.11686/cyxb2024048

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Autotoxicity is one of the serious problems in Codonopsis pilosula var. modesta cultivation. The purpose of this study was to investigate the autotoxicity effects of soil extract from continuously cropped C. pilosula var. modesta on seed germination and seedling growth， and to screen out potential autotoxic compounds of C. pilosula var. modesta. Rhizosphere soil of C. pilosula var. modesta continuously cropped for 1， 2 and 3 years was collected； extracts from the collected soil were prepared， and germination and seedling growth tests for C. pilosula var. modesta were conducted. Potentially autotoxic compounds in the rhizosphere soil extracts were identified by gas chromatography-mass spectrometry （GC-MS）. It was found that the soil extract for all three continuous cropping durations had an effect of “low promotion and high inhibition” on the seed germination and seedling growth of C. pilosula var. modesta. However， the inhibition effect of continuous cropping for 3 years was the strongest， and that of continuous cropping for 1 year was the weakest. The chlorophyll content and the catalase， peroxidase and superoxide dismutase in leaves initially increased and then decreased with increase in soil extract concentration， and the contents of malondialdehyde and proline increased with increase in soil extract concentration. Again， these effects were strongest for extracts from soils after three years of continuous cropping. The GC-MS analysis detected， respectively， 12， 18 and 8 different potentially autotoxic compounds （including hydrocarbons， alcohols， ketones and fatty acids）， in extracts from soils continuously cropped for 1， 2 and 3 years. In summary， extracts from soils continuously cropped with C. pilosula var. modesta had autotoxic effects on seed germination and seedling growth. Autotoxicity is one of the causes of continuous cropping vigor loss in C. pilosula var. modesta.

A study of the diversity of cultivable seed-borne bacteria in Poa pratensis and the growth-promoting characteristics of 18 bacterial strains

Jin-jing XIE, Shao-wei ZHU, Rong HUANG, Jie YANG, Xuan HOU, Zhen-fen ZHANG

2024, 33(12):  134-146.  DOI: 10.11686/cyxb2024086

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This study investigated the diversity of cultivable seed-borne bacteria of Poa pratensis to identify strains with superior plant growth-promoting properties. The cultivable seed-borne bacteria of three varieties of P. pratensis were isolated by the dilution plate method and 30 bacterial isolates were obtained. Through 16S rRNA sequence analysis， 18 representative isolates with different morphological characteristics were identified and phylogenetic trees were constructed. It was found that the isolated cultivable seed-borne bacteria so identified belonged to the phyla Firmicutes， Actinobacteria and Proteobacteria， and included six genera， Bacillus， Paenibacillus， Pseudomonas， Curtobacterium， Stenotrophomonas and Erwinia. Among them， Bacillus is the common genus of three varieties. The nitrogen fixation， indole-3-acetic acid-producing， phosphorus solubilization and extracellular enzyme （protease， cellulase and amylase） production of the 18 bacterial taxa were determined and it was found that strains designated BM8 and KTJ14 possessed all three of the above functions. In addition， the biofilm formation ability and swimming motility of the strains were determined by crystal violet staining and swimming medium， and the correlation between these two traits and the growth-promoting function of isolated taxa is discussed. A strain designated KTJ16 had the strongest biofilm formation ability， and the swimming motility of taxa designated SW5 and KTJ18 was significantly stronger than that of other taxa. Based on multiple characteristics， the strains with superior growth-promoting characteristics were determined to be BM8， SW5， KTJ14， KTJ16 and KTJ18.

Rhizosphere bacterial diversity and the effects of soil sterilization on the growth of two varieties of Medicago ruthenica under drought stress

Jing XING, Wen-qiang FAN, Jia-ni WANG, Feng-ling SHI

2024, 33(12):  147-159.  DOI: 10.11686/cyxb2024029

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Drought， as one of the environmental factors that severely affects plant development and crop production， requires an efficient but environmentally neutral approach to mitigate its harmful effects on plants. Soil microorganisms are known to interact with plants to ameliorate the adverse effects of environmental factors， but there is still a need to verify whether soil microorganisms play a critical role in protecting plants under drought stress. In this study， to reveal the roles of soil microorganisms in the response of Medicago ruthenica to drought stress， we compared the growth phenotypes and physiological characteristics of two cultivars of M. ruthenica （Mengnong No.2 and Mengnong No.1） growing in sterilized and unsterilized soil under drought stress. In addition， we performed high-throughput sequencing analyses of 16S rRNA extracted from the rhizosphere soils of plants under drought stress or well-watered conditions to detect differences in microbial communities in the rhizosphere of M. ruthenica under drought stress， and to determine which bacterial taxa play a key role in the drought response. The results show that， compared with plants of Mengnong No.1 and Mengnong No.2 growing in sterilized soil， those growing in unsterilized soil showed higher values for plant height， dry weight of aboveground and belowground parts， and catalase activity， and lower values for proline and malondialdehyde contents. Meanhile， in the rhizosphere soils of well-watered plants of Mengnong No.2 and Mengnong No.1， Proteobacteriaaccounted for 72.83% and 67.65% of rhizosphere bacteria， respectively， and Rhizobium accounted for 5.28% and 3.65%， respectively. In Mengnong No.2 and Mengnong No.1 under drought stress， the relative abundance of Proteobacteria in the rhizosphere bacterial community was decreased by 8.42% and 4.76%， respectively， and the relative abundance of Rhizobium was increased by 1.69% and 2.35%， respectively. On the basis of these results， we identified Rhizobium as the core taxon related to drought resistance in M. ruthenica. Under well-watered conditions， Mengnong No.2 had more rhizobia in its rhizosphere than did Mengnong No.1， so it was better able to respond quickly to drought stress. In conclusion， the results of this study demonstrate that the soil microbiome plays an active role in plants’ resistance to drought stress， that rhizosphere microorganisms can improve the drought tolerance of M. ruthenica， and that microbial composition and abundance are regulated by drought stress and the host plant. The large differences in microbial communities in the rhizosphere between the two varieties of M. ruthenica suggest that the process of microbial enrichment is closely related to plant genotype.

Effects of maize continuous cropping on soil microbial community structure based on metagenomic analysis

Chen-yang ZHANG, Meng-jun JIN, Yong-feng XU, Cheng-de YANG

2024, 33(12):  160-174.  DOI: 10.11686/cyxb2024042

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The aim of this study was to explore the effects of maize （Zea mays） continuous cropping on soil microorganisms. Soil samples were collected from the Ganzhou District of Zhangye City from fields continuously used to cultivate maize for 5， 10， 15， 20， and more than 21 years， and from Linze County from fields continuously used to cultivate maize for 10， 15， 20 and more than 21 years. The soil samples were subjected to metagenomic analyses. The results showed that the soil bacterial abundance in the two areas increased and then decreased as the number of years of continuous cropping increased， and the diversity continued to decrease with extended continuous cropping. Across the time series， the relative abundance of the dominant phyla Proteobacteria and Actinobacteria in Ganzhou District initially increased and then decreased， and had further significantly decreased at 20 years of continuous cropping （P<0.05）. The relative abundance of Acidobacteria in Linze County continued to decline， and was significantly lower at 20 years of continuous cropping than at 10 years （P<0.05）. With increasing number of years of continuous cropping， fungal abundance and diversity continued to increase. The relative abundance of the fungal genera Colletotrichum and Fusarium in Ganzhou District was significantly increased （P<0.05） at 15 and 20 years of continuous cropping， and that of Fusarium in Linze County fluctuated at 15 and 21 years of continuous cropping. Analyses of beta diversity revealed that the structure of soil bacterial and fungal communities differed significantly， depending on the number of years of continuous cropping. In Ganzhou District， metabolic pathways， microbial metabolism， carbon metabolism， and pyruvate metabolism functions of the microbial community were significantly lower （P<0.05） at 10 years than at 5 years of continuous cropping. In Linze County， metabolic pathways， biosynthesis of secondary metabolites， and pyruvate metabolism functions were significantly （P<0.05） higher at 20 years than at 10 years of continuous cropping. In contrast， two-component system functions were significantly （P<0.05） lower at 20 years than at 10 years of continuous cropping. The results of this study indicate that the duration of continuous cropping affects the diversity， community structure， and functions of soil microbes. The decrease in the relative abundance of Proteobacteria and Actinobacteria and the increase in the relative abundance of Colletotrichum and Fusarium in Ganzhou District， and the decrease in the relative abundance of Acidobacteria and the increase in the relative abundance of Fusarium in Linze County might contribute to maize continuous cropping decline. The results of our study provide a basis for unravelling the microbiological mechanism of continuous cropping decline.

Identification and biological characterisation of Fusarium root rot pathogens of white clover

Xu-ke ZHANG, Hong-fei XIA, Guo-li CHEN, De-zhou LI, Xiao-wei ZHANG, Ke-mei LI, Li-li WANG

2024, 33(12):  175-187.  DOI: 10.11686/cyxb2024109

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To determine the pathogenic species and biological characteristics of root rot in white clover （Trifolium repens） in Xinjiang， root fungi were isolated from symptomatic white clover roots collected from 11 counties （cities） in Xinjiang. The isolated fungi were identified through morphology and multi-gene sequences including ITS， EF1-α， and RPB2. Among the isolates obtained， Fusarium avenaceum accounted for 51.69%， Fusarium oxysporum 17.42%， Fusarium redolens 4.50%， and Fusarium equiseti 26.40%. Pathogenicity assays revealed all four Fusarium species to be pathogenic to white clover roots， with the following ranking of pathogenicity： F. oxysporum>F. redolens>F. equiseti>F. avenaceum. Biological characteristic results showed F. avenaceum grew well at 15-25 ℃， while the optimal mycelial growth temperature for the other three Fusarium species was 25 ℃. All four Fusarium species exhibited optimal mycelial growth at pH 7-9， with no significant differences observed under different light conditions. F. oxysporum and F. avenaceum showed optimal mycelial growth on potato dextrose agar and inulin， while F. redolens and F. equiseti grew better on Czapek's medium， with better utilization of polyol carbon sources. The optimal nitrogen source for F. avenaceum and F. equiseti was peptone， while the other two pathogens grew better on beef extract. Sporulation was best at 25-30 ℃ and pH 6-8 for all four Fusarium species. Under different light conditions， except for F. oxysporum and F. redolens showing significantly increased sporulation under 12-hour light-dark alternation， no significant differences were observed in sporulation among the species. Optimal sporulation media were potato saccharose agar for F. oxysporum and F. redolens， and oatmeal aga and corn meal agar for F. avenaceum and F. equiseti， respectively. Optimal carbon sources for sporulation were sorbitol， glucose， maltose， and soluble starch for F. avenaceum， F. oxysporum， F. redolens， and F. equiseti， respectively. The optimal nitrogen source for the former two pathogens was potassium nitrate， while for the latter two， it was yeast extract. The lethal temperature for F. oxysporum and F. redolens was 64 ℃ for 10 minutes， while for F. avenaceum and F. equiseti， it was 55 ℃ for 10 minutes. Except for F. oxysporum， the other three pathogens represent first-time occurrences on white clover and are considered newly recorded pathogens of that plant species.

Effects of dietary supplementation with bile acid on ileal epithelial morphology， microflora composition， and relative transcript levels of IFN-γ in the ileal mucosa of goats with subacute ruminal acidosis

Yue CHEN, Pin SONG, Man-man HOU, Xiao-ran YANG, Li-ping LIU, Ying-dong NI

2024, 33(12):  188-200.  DOI: 10.11686/cyxb2024024

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The aim of this study was to investigate the effect of dietary supplementation with bile acid on intestinal mucosal structure， intestinal microflora composition， and the relative transcript levels of IFN-γ （encoding interferon γ）and IfnGR1 （encoding the IRN-γ receptor）in the ileal mucosa of goats with subacute ruminal acidosis （SARA） induced by a high-concentrate diet. Fifteen 3-month-old male goats （mean weight， 18.19±2.83 kg） were selected and implanted with permanent rumen fistulas by surgery. After a 2-week recovery period， the goats were randomly divided into three groups： a control group （CON）， a subacute ruminal acidosis group （SARA）， and a SARA plus bile acids treatment group （SARA+BA）， with five goats in each group. Goats in the CON group were fed with a low-concentrate diet （concentrate∶forage=3∶7）， those in the SARA and SARA+BA groups were fed with a high-concentrate diet （concentrate∶forage=7∶3）， and those in the SARA+BA group were fed with an additional 3 g of bile acid through the rumen fistula every day for 6 weeks. At the end of the experiment， the goats were slaughtered and the ileal epithelial tissues were sampled to analyze their morphology， the characteristics of goblet cells and paneth cells， and the transcript levels of IFN-γ and IfnGR1 in the mucosa. In addition， the ileal digesta were collected to analyze the composition of the microbial community. The results showed that， compared with the CON group， the SARA group showed an irregularly shaped brush border of the ileal epithelium， indicative of a degree of injury， but no significant difference in the number of cup cells and paneth cells in the villi and crypt （P>0.05）. Compared with the CON group， in the SARA group， the transcript levels of IFN-γ and IfnGR1 in the ileum mucosa were decreased （0.05<P<0.1）， the diversity of the microbial community （Ace and Shannon’s indexes） in the ileum contents was decreased （P<0.05）， and the relative abundance of the phylum Firmicutes in the microbial community in the ileum was significantly increased （P<0.05）. Compared with the CON group， the SARA group showed significantly lower relative abundance of Unclassified_f_Lachnospiraceae， Ruminococcus and Christensenellaceae_R-7_group （P<0.05） and significantly higher relative abundance of Erysipelotrichaceae_UCG-006 and Clostridium_sensu_stricto_1 （P<0.05） in the microbial community. Compared with the SARA group， the SARA+BA group had a smoother brush border of the ileal epithelium， the epithelial structure was complete， the villi height was significantly increased （P<0.05）， and the number of paneth cells was significantly increased （P<0.05）， but the number of cup cells in the villi and crypt was not significantly different （P>0.05）. Also， compared with the SARA group， the SARA+BA group showed increased transcript levels of IFN-γ in the mucosa （0.05<P<0.1）， increased transcript levels of IfnGR1 （P<0.05）， significantly increased bacterial diversity （Ace index） in the ileum microbial community （P<0.05）， and a lower relative abundance of the phylum Firmicutes （P<0.05）. At the genus level， the beneficial bacteria Unclassified_f_Lachnospiraceae， Ruminococcus and Christensenellaceae_R-7_group were more abundant in the SARA+BA group than in the SARA group （P<0.05）， and the harmful bacteria Erysipelotrichaceae_UCG-006 and Clostridium_sensu_stricto_1 were significantly less abundant （P<0.05）. In conclusion， feeding bile acid to goats with subacute ruminal acidosis improved the morphology and structure of the ileum of SARA goats， alleviated the disturbance of the microflora in the ileum， and alleviated damage to the ileum mucosa of SARA goats by up-regulating the relative mRNA expression levels of anti-inflammatory factor IFN-γ and receptor IfnGR1 in the mucosa.

Toxicity of 10 insecticides to alfalfa aphid Therioaphis trifolii and thrip Odontothrips loti and assessment of their field efficacy

Bin PENG, Xiao-ning CUI, Bo ZHANG, Bo-xin XI, Gui-xin HU, Tuo YAO, Chang-ning LI, Kui-ju NIU, Feng-mei CHANG, Jian-hai BAI

2024, 33(12):  201-213.  DOI: 10.11686/cyxb2024053

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Therioaphis trifolii aphid and Odontothrips loti thrip are the most important pests threatening alfalfa （Medicago sativa）production in China. This study， conducted in Minqin county， Gansu Province， aimed to identify highly effective and low-toxicity biopesticides against T. trifolii and O. loti for field control. We investigated the field population dynamics of these two insect species through the clapper boarding method. The toxicity of 10 different insecticides against T. trifolii and O. loti was determined using the leaf dipping method in laboratory， and the field control efficacy was also evaluated in spraying tests. The results showed that the population densities of T. trifolii and O. loti were highest during the second and third alfalfa regrowth cycles， and the peaks occurred on July 9 and August 10， in the alfalfa bud stage. Laboratory toxicity results indicated that veratrine and matrine were the most toxic to T. trifolii and O. loti， while imidacloprid， β-cypermethrin， rotenone， spinetoram and avermectin were intermediate， and spirotetramat exhibited the least toxicity. Field control efficacy of matrine and rotenone against T. trifolii aphids ranged from 73.47% to 85.16%， and for O. loti thrips ranged from 70.11% to 88.61% during the period from seven to 14 days after application. The control efficacy of spinetoram and avermectin against T. trifolii ranged from 67.80% to 82.00%， and for O. loti ranged from 83.67% to 92.55% in the same period. Based on our results， the high-efficiency and low-toxicity rotenone， matrine， avermectin and spinetoram are recommended as the preferred chemicals for spray control of T. trifolii and O. loti in the field production of alfalfa.

Research progress on assessment of losses in grassland due to diseases， pests，weeds and rodents

Wan-qing DONG, Zi-yuan MA, Ying-de LI, Ya-jie WANG, Rong-chun ZHENG, Zhi-biao NAN, Ting-yu DUAN

2024, 33(12):  214-223.  DOI: 10.11686/cyxb2024049

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Diseases， pests， weeds and rodents can be defined as organisms that detrimentally impact the ordinary life， production activities， and survival of human beings within constrained conditions. In the field of grassland conservation， harmful organisms mainly refer to pathogenic microorganisms， pests， noxious weeds， and rodents. Grassland pests are not only important components of grassland ecosystems， but also important factors threatening grassland production and ecological security. The harm caused by diseases， pests and weeds runs through the pre-plant production level， plant production level， animal production level and post-biological production level of the whole grassland agricultural ecosystem， and causes huge losses in various production stages， which seriously threaten the ecological security of grassland and the economic development of animal husbandry in China. Presently， research on the disease， pest and weed induced losses in grassland is characterized by fragmentation， with the associated assessment methods and models being less developed and systematic compared to those in the agricultural domain. Therefore， this study reviewed the domestic and international research on grassland disease， pest and weed loss assessment， and categorized the indexes， methods and models of loss assessment in four categories： diseases， pests， noxious weeds and rats， and briefly evaluated the advantages and disadvantages of different methods and models as well as their scope. This research aims to provide theoretical knowledge to underpin for grassland protection.