Table of Content

20 July 2024, Volume 33 Issue 7

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Vegetation classification of UAV remote sensing images in desert steppe based on object-oriented technology

Jie SHE, Ai-hong SHEN, Yun SHI, Na ZHAO, Feng-hong ZHANG, Hong-yuan HE, Tao WU, Hong-xia LI, Yi-ting MA, Xiao-wen ZHU

2024, 33(7):  1-14.  DOI: 10.11686/cyxb2023319

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Exploring suitable remote sensing classification methods for desert grassland vegetation and clarifying the types of plant species and their distribution in desert grassland areas can improve the ability of fine biodiversity monitoring in desert grassland， which is of great significance for the protection and management of desert grassland as well as for the sustainable development of ecosystems within the landscape. This research studied the typical vegetation of Stipa breviflora， Convolvulus tragacanthoides， Salsola laricifolia， Ephedra rhytidosperma in the desert grassland of the floodplain fan at the eastern foothill of Helan Mountains. We used remote sensing images from unmanned aerial vehicles （UAVs）， processed by object-oriented classification and regression tree （CART）， K-nearest neighbor （KNN）， random forest （RF） and support vector machine （SVM） classification methods， combined with the feature selection algorithm to optimize the image features. We then selected the optimal features for the study of desert grassland vegetation classification， and its refinement. It was found that： 1） Feature selection can effectively improve the classification accuracy and should be fully utilized， and the highest classification accuracy is achieved when the selected feature combination has a contribution degree greater than 1.00%； 2） Based on the vegetation spectral and texture features mined from UAV remote sensing images， combining with the object-oriented classification method can effectively achieve the refined classification of the typical vegetation of the desert grassland at the eastern foothills of the Helan Mountains. In this research the RF classification accuracy was the highest， and the overall classification accuracy reached 87.77% with a Kappa coefficient of 0.79. The results of this study provide a reference for the study of vegetation classification in desert grasslands. This research will be of great significance for the conservation and management of desert grassland biodiversity and ecological sustainable development.

Comparison of vegetative propagation characteristics of modules between Leymus chinensis and Carex duriuscula clonal populations in a restoration succession series in northeast degraded grassland

Li-li LIU, Yue-lin WANG, Hai-yan LI, Ji FENG, Li-shuang CHU, Yun-fei YANG, Li-shi LAN, Jian GUO

2024, 33(7):  15-24.  DOI: 10.11686/cyxb2023299

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Populations of clonal herbaceous plants mainly regenerate by vegetative propagation. The age structure of modules of rhizomatous herbaceous plants generated by vegetative propagation is an important factor in population status analysis， and in the prediction of vegetation and restoration succession dynamics. In this study， we analyzed and compared the age structures of tillers and rhizomes， the productivity of tillers， the storage capacity of rhizomes， and the vegetative propagation capacity of both tillers and rhizomes at different ages between two major clonal herbaceous species， Leymus chinensis and Carex duriuscula， at five stages of restoration in the succession of degraded grassland in northeast China. The tillers of L. chinensis and C. duriuscula showed an expanding age structure， and the rhizomes exhibited a stable or expanding age structure at each stage of restoration succession. The tiller productivity and rhizome storage capacity of L. chinensis were greater than those of C. duriuscula at different stages of restoration succession. With the process of grassland restoration succession， the storage capacity of rhizomes of L. chinensis in the first age class showed a significant increasing trend， and the productivity of tillers of C. duriuscula in the second age class showed a significant decreasing trend. At the stages of restoration succession when L. chinensis and C. duriuscula coexisted， the vegetative propagation capacity of L. chinensis rhizomes was higher than that of C. duriuscula. Overall， the age structure characteristics of the modules of L. chinensis and C. duriuscula were similar at various stages of restoration succession. However， with the process of grassland restoration succession， the vegetative propagation strategy of the L. chinensis population to enhance the vegetative propagation capacity of young and prime tillers was more conducive to the maintenance and expansion of the population than that of the C. duriuscula population to only increase the vegetative propagation capacity of young tillers. Therefore， L. chinensis gradually replaced C. duriuscula as the dominant species in the community during succession.

Effect of grazing exclusion on soil carbon， nitrogen， and phosphorus contents and enzyme activity and stoichiometry in Seriphidium transiliense desertgrasslands

Si-yuan LI, Zong-jiu SUN, Bing-jie YU, Chen-ye ZHOU, Lei ZHOU, Li ZHENG, Hui-xia LIU, Hua-wei YE

2024, 33(7):  25-40.  DOI: 10.11686/cyxb2023310

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It is important to determine the changes in soil enzyme activity and enzyme stoichiometry during grazing exclusion to understand how vegetation restoration affects soil nutrient availability， and to elucidate the mechanisms of nutrient cycling in ecosystems. In this study， therefore， the responses of soil in sagebrush desert grassland to 6 years of grazing exclusion were initially analyzed by measuring soil carbon （C）， nitrogen （N） and phosphorus （P） contents， as well as soil enzyme activities and their stoichiometry. The results showed that： 1） There were no significant changes in soil organic C， total N， and total P contents， soil C/P， soil N/P， soil leucine aminopeptidase， alkaline phosphatase activities and soil enzyme C/N， in the 0-20 cm soil layer after grazing exclusion. The activities of β-1， 4-glucosidase in April and β-1， 4-N-acetylglucosaminidase in July Manasi showed an increasing trend， compared with those in the control， after grazing exclusion； 2） Grazing exclusion significantly affected the soil C/N in July Manasi， increased soil enzyme C/P in April， and decreased soil enzyme N/P values in July Manasi. In a vector analysis， the vector lengths of all samples increased significantly in April after grazing exclusion， and the vector lengths of all samples before and after grazing exclusion were greater than 45°， suggesting that the soil microorganisms in the study area were mainly limited by C and P； 3） The results of a redundancy analysis showed that soil C， N， and P contents and their stoichiometric characteristics explained 56.03% of the variance in soil enzyme activity and stoichiometric and vector characteristics after grazing exclusion. These results indicate that soil organic C content may be the main factor influencing the activity of soil enzymes and their characteristics in sagebrush desert grasslands.

Effects of Chinese milk vetch combined with reduced chemical fertilizer on soil phosphorus adsorption and desorption characteristics in different years

Cheng-lan ZHANG, Chun-zeng LIU, Yu-hu LYU, Ben-yin LI, Lin ZHANG, Li DING, Guang-hui DU, Xiang-ning ZHANG, Chun-feng ZHENG, Ji-shi ZHANG, Min LI, Wei-dong CAO

2024, 33(7):  41-52.  DOI: 10.11686/cyxb2023300

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The aim of this study was to clarify the dynamic effects of Chinese milk vetch coupled with reduced chemical fertilizer on soil phosphorus adsorption and desorption characteristics in different years. This long-term field study was conducted in Xinyang， Henan province. The experimental design consisted of a control （no fertilizer， CK） and four treatments： fertilizer only （CF）， 22500 kg·ha^-1 Chinese milk vetch+80% fertilizer （G+80% CF）， 22500 kg·ha^-1 Chinese milk vetch+60% fertilizer （G+60% CF）， and 22500 kg·ha^-1 Chinese milk vetch+40% fertilizer （G+40% CF）. We determined the change trends of soil phosphorus adsorption and desorption characteristics， as well as their relationships with soil physicochemical properties in 2011， 2016， and 2020. The results showed that the Langmuir isothermal adsorption equation provided a good fit for the adsorption characteristics of soil phosphorus （R²=0.9804-0.9949， P<0.01）. The maximum phosphorus adsorption capacity （Q_max） of soil samples from the G+80% CF， G+60% CF， and G+40% CF treatments decreased from 2011 to 2020， whereas the phosphorus adsorption constant （K） and maximum phosphorus buffer capacity （MBC） increased over the same time period. Compared with their respective values in 2011， the Q_max of the G+80% CF， G+60% CF， and G+40% CF treatments had decreased by 11.30%， 12.95%， and 15.47%； K had increased by 20.73%， 22.50%， and 27.27%； and the MBChad increased by 8.63%， 6.43%， and 6.28% in 2020. In contrast， in the CF treatment， the Q_max of soil phosphorus increased with increasing age， whereas K and MBC decreased with increasing age. Compared with their respective values in 2011， the Q_max of soil phosphorus had increased by 8.80%， K had decreased by 12.20%， and MBC had decreased by 2.97% in 2020. In all treatments， the soil phosphorus adsorption saturation （DPS） did not show any consistent changes over the experimental period. The average desorption rate of soil phosphorus decreased during the experimental period in the CK and CF treatments， initially decreased and then increased in the G+80% CF and G+40% CF treatments， and showed a decreasing trend in the G+60% CF treatment. Compared with CK， the application of reduced chemical fertilizer coupled with Chinese milk vetch decreased the Q_max of soil phosphorus and increased the K， MBC， DPS， and average desorption rate of soil phosphorus in the same year. The results of correlation analysis showed that Q_max was significantly positively correlated with soil cation exchange capacity （CEC）， MBC was significantly negatively correlated with CEC， DPS was significantly positively correlated with alkali-hydrolyzed nitrogen （AN） and available phosphorus （AP）， and the desorption rate （DR） was significantly negatively correlated with available potassium （AK） and pH. The results of a redundancy analysis revealed that CEC， AP， and AK were the primary factors affecting soil phosphorus adsorption and desorption characteristics， with contribution rates of 26.7%， 18.5%， and 16.2%， respectively （P<0.05）. In summary， our results indicate that the adsorption and desorption of soil phosphorus are mainly affected by the soil CEC， AP， and AK. Long-term application of Chinese milk vetch coupled with reduced chemical fertilizer decreased P adsorption and increased P desorption in soil， while the long-term application of fertilizer alone had the opposite effect. Considering the adsorption and desorption characteristics of soil P and soil physical and chemical properties， the best effects were obtained by reducing chemical fertilizer usage by 20%-40% combined with 22500 kg·ha^-1 Chinese milk vetch. Our findings provide scientific guidance for reasonable fertilization in the rice-growing area of south Henan province.

Genome-wide identification and expression analysis of the Hsp70 gene family in wheat and its ancestral species

Yi WU, Ya-lan FENG, Tian-ning WANG, Ji-hao JU, Hui-shu XIAO, Chao MA, Jun ZHANG

2024, 33(7):  53-67.  DOI: 10.11686/cyxb2023334

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Heat shock protein 70 （Hsp70） exerts a crucial influence on plant development and response to biotic and abiotic stresses. In order to explore the evolutionary relationships， functions and expression patterns of the Hsp70 gene family in wheat （Triticum aestivum）， this study conducted a comprehensive bioinformatics analysis of the Hsp70 gene family in Triticum urartu， Aegilops speltoides， Triticum turgidum， Aegilops tauschii and common wheat， and the expression patterns of some Hsp70 genes under different exogenous hormones and environmental stress were analyzed by RT-qPCR. The results showed that， respectively， from the five species， 30， 41， 60， 28 and 94 Hsp70 genes were identified. Phylogenetic analysis showed that the members of the Hsp70 family in the five species were divided into 5 subfamily groups， and the number of members in each group was not equal. Most of the members are distributed in Group I， and most of the Hsp70 members in the same subfamily have similar gene structures and conserved motifs. Further comprehensive analysis of chromosome localization and repetition events of the Hsp70 gene in the five species revealed that the Hsp70 gene was unevenly distributed on each of the chromosomes， and a total of 12 tandem repeat events and 110 fragment replication events were found from the five species， indicating that fragment replication events promoted the expansion of the Hsp70 gene family in wheat. The analysis of cis-acting elements showed that there were various light response elements， stress response elements， hormone response elements and growth as well as development regulatory elements in the promoter region of Hsp70 gene in the five wheat species. In addition， RT-qPCR results indicated that particular Hsp70 genes in the five wheat species had varying degrees of response under different hormone treatments and stress. The expression of eight Hsp70 genes was up-regulated under high temperature and drought stress. The identification of the Hsp70 gene in wheat and its ancestral species and elucidation of its evolution provides a theoretical basis for further research on the function of the Hsp70 gene in wheat growth and development， as well as its response mechanism under stress.

Identification of AKR gene family members in Halogeton glomeratus and salt tolerance analysis of the root salt stress response gene HgAKR42639

Zhen-huan ZHANG, Li-rong YAO, Jun-cheng WANG, Er-jing SI, Hong ZHANG, Ke YANG, Xiao-le MA, Ya-xiong MENG, Hua-jun WANG, Bao-chun LI

2024, 33(7):  68-83.  DOI: 10.11686/cyxb2023335

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In order to explore the biological function of the AKR gene family and the salt tolerance of the root salt stress response gene HgAKR42639 in Halogeton glomeratus， the aldo-keto reductase gene （AKRs） was identified based on full-length transcriptome sequencing of H. glomeratus， and the protein sequence encoded by AKRs in H. glomeratus was analyzed by bioinformatics methods. The target gene expression， physiological indexes and sodium and potassium content in roots of H. glomeratus and the Arabidopsis thaliana HgAKR42639 gene were measured under 200 mmol·L^-1 NaCl stress for 0， 6， 12， 24 and 48 hours. We found that 23 HgAKRs were identified from the H. glomeratus transcriptome， encoding amino acid sequences ranging from 165 to 664 aa， and the prediction of subcellular localization was mainly in the cytoplasm. AKR protein conserved domains were highly similar with 3 motifs， and there were core elements， enhancing elements and stress response elements in the analysis of promoter cis-acting elements. The results of qRT-PCR showed that the relative expression of HgAKR42639 increased initially and then decreased in both H. glomeratus roots and A. thaliana， and the expression of HgAKR42639 peaked at 24 hours. With increase in exposure time to salt stress， the activities of catalase （CAT）， peroxidase （POD）， superoxide dismutase （SOD） and the proline content showed an increasing trend， while the contents of malondialdehyde （MDA） and soluble protein showed a downward trend， reaching their lowest levels at 24 hours. The content of Na⁺ and K⁺ decreased under the salt stress treatment for 24 hours， and K⁺/Na⁺ reached the maximum value. In summary， the AKR family genes of H. glomeratus were obtained in this study， and the results provide a theoretical basis for further research on the molecular mechanism of regulation of response to salt stress in AKR genes in H. glomeratus. This research provides a foundation for further verification of the HgAKR42639 gene role in salt tolerance.

Screening and verification of SgMPK6-interacting proteins of Stylosanthes

Fang WANG, Shi-zi ZHANG, Rong-hui DAI, Li-yun YANG, Li-juan LUO, Ling-yan JIANG

2024, 33(7):  84-93.  DOI: 10.11686/cyxb2023273

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The mitogen-activated protein kinase （MAPK） cascade plays a key role in regulating plant immunity. Anthracnose is a serious disease affecting the production of Stylosanthes （Stylo）. The SgMPK6 gene of Stylo has been shown to function in resistance against anthracnose， which is caused by Colletotrichum gloeosporioides. To investigate the interacting proteins downstream of SgMPK6 in the response to C. gloeosporioides infection， a yeast two-hybridization technique was used to screen the cDNA library of Stylo using the SgMPK6 kinase domain as the bait. Seventy-four potential interacting proteins were obtained. The interactions between the SgMPK6 kinase domain and the bHLH transcription factors SgbHLH32， SgbHLH33， and SgbHLH44 were verified in yeast two-hybrid experiments. Phosphorylation site analysis revealed that all three transcription factors contained MAPK phosphorylation sites. The results of qRT-PCR analyses showed that SgbHLH32， SgbHLH33， and SgbHLH44 were significantly up-regulated in Stylo by C. gloeosporioides infection. Together， these results suggest that SgbHLH32， SgbHLH33， and SgbHLH44 are substrates of SgMPK6 and may be involved in resistance against anthracnose. The results of this study provide a basis for further analysis of the role of SgMPK6 in resistance to C. gloeosporioides infection.

The effect of tail-docking on adipocyte structure and lipid metabolism-related gene expression in Lanzhou fat-tailed sheep

Shu-zhen SONG, Cai-ye ZHU, Li-shan LIU, Xu-ying GONG, Rui-rui LUO

2024, 33(7):  94-104.  DOI: 10.11686/cyxb2023417

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The objective of this study was to observe the effect of tail docking on the number and structure of adipocytes， and gene expression related to lipid metabolism in Lanzhou fat tailed sheep. The results help in clarifying the molecular regulation mechanism leading to redistribution of fat after tail docking in fat-tailed sheep. Eighteen Lanzhou fat-tailed lambs （5 d old and weighing 3.79±0.12 kg） from eighteen ewes were randomly divided into a control （C） group and a test （T） group， with nine lambs in each group. Tails of lambs in the T group were ligated with rubber bands. The two groups were fed with same formula diet after weaning at 2 months； the trial period was 240 days. At the end of the experiment， samples were collected for analysis. It was found that： 1） With respect to the longissimus dorsi and visceral fat， tail-docking had an observable effect on gene expression related to formation of tail fat and subcutaneous fat. For T sheep， SCD， LEP， PLIN1 expression levels were higher， and LPL， FAS， PEPCK expression levels were lower in the tail， SCD was higher and LEP， ADPN， FABP4， PLIN1 were lower in subcutaneous fat， LPL， ADPN， PEPCK， UCP1 were lower in kidney fat and PEPCK was lower in omental fat （P<0.05） than for C sheep. In addition， SCD expression was higher， PEPCK and PLIN1 expression levels were significantly lower in longissimus dorsi of T than of C sheep （P<0.05）. 2） Intramuscular fat was significantly higher in the T than in the C group （6.96% and 6.05%， respectively）. Similarly， lipid droplets in the longissimus dorsi were significantly increased in T group sheep compared to C （4.28% and 3.04%， respectively； P<0.05）， while the area ratio of lipid droplets increased by about 1%， the area ratio of lipid droplets in tail fat decreased by 10% （87.58% and 97.58% for T and C groups， respectively）， and the diameter of adipocytes was significantly decreased （P<0.05） in tail fat from sheep in the T group. 3） Transmission electron microscopy observation showed that the fat cells in the tail were filled with large fat droplets， the nucleus and cytoplasm were squeezed to the edge of the cell by these large fat droplets， and the cytoplasm at the edge of the cell contained organelles such as mitochondria， endoplasmic reticula， golgi apparatus， autophagosomes and small lipid droplets in Lanzhou fat-tailed sheep. Compared to the C group， the single lipid droplets were smaller， and the glycogen granules were more numerous in the cytoplasm in fat cells in tail-docked sheep. To summarize， the results showed that tail-docking early in the life of Lanzhou fat-tail sheep increased the area ratio of fat droplets in the longissimus dorsi and decreased the area ratio of fat droplets in tail fat. Moreover， tail-docking changed the expression of genes related to fat metabolism. The distribution of fat deposits is indicated to be regulated by the genes related to fat metabolism： SCD， PLIN1， LPL， FAS， PEPCK and others.

Effects of mineral salt brick supplementation in the warm season on growth performance， rumen fermentation， blood， and hair mineral content of grazing yaks

De-yu YANG, Wen-zhi HUANG, Yu-zhe FENG, Bin XUE, Xiao-wei ZHANG, Zhan-hong CUI

2024, 33(7):  105-118.  DOI: 10.11686/cyxb2023317

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To investigate the effect of supplementary feeding of mineral salt bricks on yak productivity under grazing conditions， two controlled grazing experiments were carried out. Twelve healthy male yaks， aged 2.5 years old with similar body weight ［（139±6） kg］， were randomly divided into two groups： a whole grazing group （CG Group） and a grazing group with supplementary feeding of mineral salt bricks （SG Group）. Each group included six animals as replicates. The study focused on the effects of supplementary feeding of mineral salt bricks in the warm season on the growth performance， rumen fermentation， blood， and hair mineral content of grazing yaks. The total weight gain of yaks in the CG Group was 20.75 kg， with an average daily weight gain of 244 g·d^-1. In contrast， the total weight gain of yaks in the SG Group was 39.45 kg， with an average daily weight gain of 464 g·d^-1， which was 90.12% higher than the CG Group. The dry matter digestibility of yaks in the SG Group was significantly higher than that of the CG Group（P<0.05）. In contrast， the crude protein digestibility， ether extract digestibility， and neutral detergent fiber digestibility of the SG Group were significantly lower than those of the CG Group on the 30th and 90th day of the experiment（P<0.05）. Similarly， the acid detergent fiber digestibility of the SG Group was also found to be significantly lower than that of the CG Group on the 30th and 60th day of the experiment （P<0.05）. Furthermore， the yield of butyric acid， valeric acid， total volatile fatty acids and NH₃-N in the rumen of the SG Group was significantly higher than that of the CG Group （P<0.05）. On the 30th day of the experiment， there was no significant difference in rumen liquid pH between the CG Group and the SG Group （P>0.05）. However， on the 60th and 90th day of the experiment the rumen liquid pH of the SG Group was significantly lower than that of the CG Group （P<0.05）. The contents of Ca， P， K， Mg， and Fe in the serum of yaks in the CG Group were not significantly different from those in the SG Group on the 30th day of the experiment （P>0.05）. Nevertheless， the contents of Na and Co in the CG Group were significantly higher than those in the SG Group （P<0.05）. Conversely， the contents of Cu， Zn， and Mn in the serum of yaks in the SG Group were significantly higher than those in the CG Group （P<0.05）. Moreover， the contents of Ca， P， and Na in the CG Group were not significantly different from those in the SG Group on the 60th and 90th day of the experiment （P>0.05）. On the other hand， the contents of Fe， Cu， Zn， Mn， Mg， K， and Co in the SG Group were significantly higher than those in the CG Group （P<0.05）. The hair mineral content analysis showed that on the 30th day of the experiment， the contents of Ca， Mg， Na， K， and Mn in the hair of yaks in CG Group were not significantly different from those in the SG Group （P>0.05）. Nevertheless， the contents of Fe in the hair of yaks in the CG Group were significantly higher than those in the SG Group （P<0.05）. Meanwhile， the contents of Cu， and Zn in the SG Group were significantly higher than those in the CG Group （P<0.05）. On the 60th and 90th day of the experiment， the contents of Ca， Na， and K in the CG Group were not significantly different from those in the SG Group （P>0.05）. However， the contents of Mg， Cu， Zn， Mn， and Fe in the SG Group were significantly higher than those in the CG Group （P<0.05）. In conclusion， supplementation of mineral salt bricks in the warm season improved the body weight gain of yaks， nutrient digestibility of yaks foraging grass， rumen fermentation of yaks， metabolism of mineral elements in blood and deposition of mineral elements in hair. Additionally， mineral salt bricks also enhanced the mineral nutrition balance for grazing yaks during the warm season to more fully realize the growth potential of yaks.

A study of the protein requirements of 20-35 kg Chuanzhong black goats

Shang-lin YANG, Xuan WU, Qiao-hui LUO, Tai-hua HUANG, Zheng-fan ZHANG, Hai-tao SHI, Chun-hua GUO

2024, 33(7):  119-129.  DOI: 10.11686/cyxb2023323

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This study was conducted to determine the protein requirements of Chuanzhong black goat wethers with body weight ranging from 20-35 kg. One aim was to provide data for the improvement of goat feeding standards in China. A total of twenty-two 2.5-month-old Chuanzhong black goat wethers （BW=19.97±5.47 kg） were selected. Four kids were used in an initial comparative slaughtering trial， the eighteen remaining kids were used in a feeding and digestion-metabolism trial. The pre-feeding period was 14 days， and the formal trial was 82 days. Animals were divided into 3 treatments： an ad libitum feeding group （AL Group）， a 75% ad libitum feeding group （AL75 Group） and a 60% ad libitum feeding group （AL60 Group）. There were thus 6 kids （replicates） per treatment， and 1 kid per replicate. A digestion-metabolism study was performed 4 days before the end of the feeding test to collect all feces and urine. When the average weight of the test kids in the AL Group reached 35 kg， the feeding test was ended， and 4 kids （a total of 12） close to the average weight of the group， were selected for slaughter in each group. The carcasses were cryopreserved to be tested. It was found that： 1） the final body weight in the AL Group was significantly higher than that of the AL60 Group （P<0.01）. The net weight gains， average daily gains and dry matter intakes in the AL75 Group and the AL60 Group were significantly lower than those in the AL Group （P<0.01）. The ratio of feed to weight of the AL60 Group was significantly higher than that of AL Group and the AL75 Group （P<0.05）. 2） The live weights， fasting weights， carcass weights and net meat weights of goats in the AL Group were significantly higher （P<0.01） than those in the AL75 Group and AL60 Group. There were no significant differences in slaughter rates， net meat rates， carcass net meat rates and meat-to-bone ratios （P>0.05）. The bone weights of the AL Group were significantly higher than those in the AL75 Group and the AL60 Group （P<0.05）. 3） The differences in heart， spleen， and lung organ index of goats in the three treatment groups were not significant （P>0.05）； the AL Group liver organ index was significantly higher than that of the AL75 Group and the AL60 Group （P<0.01）， and the kidney organ index decreased significantly （P<0.01） with decrease in feeding level. 4） The maintenance net protein requirement of the 20-35 kg Sichuan black goats was determined as 1.60 g·kg^-1·BW^-0.75·d^-1； while the net protein requirement for growth of goats with a daily gain of 100-300 g·d^-1 （Np_g） was 13.13-40.13 g·d^-1， and the total protein requirement （Np_r） was 28.26-63.15 g·d^-1. These findings for Chuanzhong black goats provide a data reference for the improvement of local sheep and goat meat production and breeding standards in China.

Induced formation method and germination characteristics of chlamydospores by Fusarium oxysporum f. sp. medicaginis

Xiang-ling FANG, Shi-yang XU, Zhi-biao NAN

2024, 33(7):  130-141.  DOI: 10.11686/cyxb2023316

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Chlamydospores are the main survival structure of Fusarium oxysporum in soil， and the number and germination status of chlamydospores in soil directly affects the occurrence and severity of the disease. In this study， we established a system to induce chlamydospore production by F. oxysporum f. sp. medicaginis （Fom） by culturing the pathogen on synthetic low nutrient agar （SNA） medium， synthetic low nutrient agar with filter （SNAF） medium， or in two-salt solution （KH₂PO₄ and MgSO₄·7H₂O） with glucose or magnesium carbonate at a range of concentrations. The chlamydospore induction system was verified， and the effects of different carbon and nitrogen sources on chlamydospore germination were studied. The T6 and T9 strains of Fom produced many chlamydospores after static culture for 7 days in the two-salt solution with glucose at 2 mg·L^–1， producing 4.2×10⁵ and 5.1×10⁵ chlamydospores per mL， respectively. Both T6 and T9 produced more chlamydospores under static culture than under shaking culture （4.2- and 2.8- times， respectively， at 7 days of culture）. All Fom strains produced many chlamydospores after 7 days of culture in the two-salt solution， with a rapid increase of 2.3- times compared with 3 days， followed by slow increases at 14 and 21 days， with an average increase of only 1.2- times from 7 to 21 days of culture. Comparing all the carbon and nitrogen sources， glucose and ammonium chloride had the strongest promoting effects on the germination and germ tube growth of chlamydospores， whereas lactose and urea had the weakest effects. The results show that chlamydospore formation by Fomstrains requires a trace amount of a carbon source and a low-oxygen environment， and the germination and growth of chlamydospores require suitable carbon and nitrogen sources. These findings provide new insights into effective management of soil-borne diseases in alfalfa through controlling the primary infection source， i.e.， the chlamydospores of the pathogen.

Identification of the pathogen causing downy mildew in Angelica sinensis in Gansu Province

Qian-li ZHU, Xiang HE, Yang-yang ZHANG, Jiang-shan NIE, Chang-qing WANG, Guang-xin LU

2024, 33(7):  142-150.  DOI: 10.11686/cyxb2023257

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The aim of this work was to identify the pathogen causing downy mildew in Angelica sinensis in Yuzhong County， Lanzhou City， to provide a theoretical basis for field diagnosis and control of the disease. The pathogen was preliminarily identified by recording disease symptoms and by observing its morphology under a microscope. Hyphae were collected from diseased plants and the DNA was extracted. The 28S rDNA D1/D2 region and the mitochondrial DNA （mtDNA） gene cytochrome c oxidase subunit II （cox2） were sequenced， and phylogenetic trees were constructed based on the sequencing results. The disease primarily affected the leaves. At the onset of the disease， irregular chlorotic spots appeared on the front side of the leaves， followed by the development of a frosty white mildew layer. Eventually， the chlorotic spots became brown dead spots， and in severe cases， the entire plant died. The morphology of the sporangiophores and sporangia were consistent with those of Plasmopara angelicae. The 28S rDNA D1/D2 region displayed 99.87% sequence similarity to that of Plasmopara pimpinellae HV 634， while the cox2 gene exhibited 100% sequence similarity to that of P. pimpinellae TCM-155. Phylogenetic analysis revealed that the Plasmopara species infecting Apiaceae plants were clustered together and were more distantly related to Plasmopara species infecting host plants from different families. Molecular identification based on the 28S rDNA D1/D2 region sequence and cox2 gene sequence corroborated the close relationship between the pathogen and P. pimpinellae that parasitizes members of the Apiaceae. Additionally， morphological identification confirmed the downy mildew on A. sinensis as P. angelicae， consistent with the membership of A. sinensis in the Apiaceae family. This study is the first comprehensive report on the pathogen responsible for downy mildew in A. sinensis in China.

Allelopathic effects of aqueous extracts of fallen leaves of Acer truncatum on three medicinal plants

Kun-fei RUAN, Tian-qi WANG, Ning-ning BI, Shao-tong SHI, Sen LI, Zhong-hua LIU

2024, 33(7):  151-159.  DOI: 10.11686/cyxb2023304

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In this study， we determined the effects of aqueous extracts from fallen leaves of Acer truncatum on three medicinal plants： Glycyrrhiza uralensis， Scutellaria baicalensis，and Platycodon grandiflorus. The overall aim was to provide a theoretical basis for cultivating medicinal herbs in A. truncatum forests in Beijing. The effects of an aqueous extract from fallen leaves of A. truncatum at a range of concentrations on seed germination and seedling growth of the three medicinal plants were determined. The leaf litter extract of A. truncatum showed “low promoting and high inhibition” effect on the seed germination of G.uralensis and S. baicalensis， respectively， and inhibited the seed germination of P. grandiflorus. The leaf litter extract of A. truncatum most strongly inhibited the seed germination and seedling growth of P. grandiflorus， followed by S. baicalensis and then G. uralensis. The chlorophyll content in the leaves of all three medicinal plants was lower in those treated with the leaf litter extract of A. truncatum than in the controls. As the concentration of the A. truncatum leaf litter extract increased， the superoxide dismutase activity increased in leaves of S. baicalensis seedlings， and the catalase activity in leaves of S. baicalensis and G. uralensis seedlings first increased and then decreased. The malondialdehyde content in leaves of the three medicinal plants first increased and then decreased as the concentration of the A. truncatum leaf litter extract increased. Overall， these results show that S. baicalensis and G. uralensis are suitable for cultivation in A. truncatum forests， but P. grandiflorus is not.

A study of the mutagenic effect in red clover induced by N⁺ and Ar⁺

He-shan ZHANG, Jiao-yun LU, Wei ZHU, Hong TIAN, Jun-bo XIONG, Xin-jiang WU, Yang LIU

2024, 33(7):  160-171.  DOI: 10.11686/cyxb2023438

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Ion implantation technology is an effective means to create new plant germplasm lines. In order to explore the biological effect on red clover （Trifolium pratense） induced by ion implantation， the seeds of T. pratense cv. ‘Emu 5’ were implanted with N⁺ ions at energies of 30 or 50 keV and doses of 5×10¹⁴ or 5×10¹⁵ ions·cm^-2 （N3014， N3015， N5014 or N5015， respectively） or Ar⁺ ions with energies of 30 or 50 keV and a dose of 5×10¹⁴ ions·cm^-2 （Ar3014 and Ar5014， respectively）. The germination characteristics and biological characteristics of irradiated seeds were studied and the variation in agronomic traits， including plant height， branch number per plant， flower number per plant， flower number per inflorescence， leaf length， leaf width， inflorescence length and inflorescence width， was analyzed. We found that the epidermis of red clover seed displayed an obvious ‘burn’ phenomenon after ion implantation， and the color of seed coat changed from yellowish brown to black-brown. Compared to control （CK）， the Ar3014 treatment numerically increased seed germination， while the N3014 and N3015 treatments numerically decreased seed germination； however， these trends were not statistically significant. The N5014 treatment significantly decreased germination by approximately 10% compared to CK and the N5015 and Ar5014 treatments both significantly decreased germination by more than 30%. Radicle volume and length were both significantly increased， compared to CK， by the two N30 irradiation treatments. The irradiated seeds （M₁ generation） were grown and allowed to set seed， which was also grown to produce an M₂ generation. This cycle was repeated twice more to produce M₃ and M₄ generation seeds. The mean values of measured traits in M₂ generation plants were usually significantly lower than those in CK plants （P<0.05）， but showed greater character variation among mutagenic plants， which provided a basis for further screening of mutant materials. N⁺ and Ar⁺ mutagenic treatments at energies of 50 keV showed greater mutagenic effects than those observed at 30 keV， but the majority of mutations were adverse characters. The mutagenic effect was optimal for red clover in the N3014 and N3015 treatments and after four generations of breeding， eight mutant materials from the M₄ generation with stable characters， potentially usable for breeding purposes， were obtained. Our study provides basic data for mutation breeding in red clover.

Induction and molecular and cellular identification of polyploid Lilium davidii var. unicolor

Yong-yao FU, Li CAI, Feng-yao LI, Wen-jun YANG, Wen-ji XU, Si-jia JIANG, Li-ping YANG

2024, 33(7):  172-181.  DOI: 10.11686/cyxb2023294

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Lilium davidii var. unicolor is the most important edible sweet lily in China. To cultivate new， high-quality germplasm of L. davidii var. unicolor， bulblets growing in vitro were treated with different concentrations of colchicine， and mutagenic seedlings were obtained via adventitious bud induction. The variant lines were further identified by chromosome ploidy level， morphological， and inter simple sequence repeat （ISSR） molecular marker analyses. The results indicated that treatment of the bulblets with 0.15% colchicine for 48 h was the optimal induction method， leading to the maximum mutation rate of 58.06%. Two fast-growing seedlings with stable morphological variations were selected for chromosome ploidy analysis by flow cytometry and tableting in the root tip. The proportion of cells containing 36 chromosomes in the root tip of one induced line was 80%， indicative of a homozygous triploid. Compared with the control， the seedlings of the mutated lines showed significant differences in the leaf， bulblet， and roots. The guard cells were larger and the stomatal density was significantly reduced in the mutated lines compared with the control. Analyses of ISSR markers revealed genetic variations in the two mutagenic lines compared with the control， with mutation rates of 19.64% and 20.91%， respectively. Together， these results provide an important basis for obtaining triploid germplasm of L. davidii var. unicolor， and for breeding of new lily materials using colchicine treatment.

Effects of the Epichloë gansuensis endophyte on the physiological status of Achnatherum inebrians under different nitrogen concentrations

Mao-hua DENG, Rong ZHENG, Bei-chen WANG, Chao WANG, Rong-gui LIU, Han-wen ZHANG, Zheng-he WANG, Jian-feng WANG

2024, 33(7):  182-191.  DOI: 10.11686/cyxb2023314

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Nitrogen is an essential macronutrient for plant growth and development， and endophytic fungi can influence nitrogen metabolism in the host. The endophyte Epichlo? gansuensis forms a symbiotic relationship with Achnatherum inebrians， also known as drunken horse grass. The effect of endophytic fungi on the host’s nitrogen metabolism is dependent on the surrounding nitrogen concentrations. In this study， A. inebrians plants infected with the Epichlo? gansuensis endophyte （E+） or not infected （E-） were grown under low （0.01 mmol·L^–1 N） and normal （7.5 mmol·L^–1 N） nitrogen levels for 6 months. The harvested materials were analyzed to determine leaf dry weight， hydrogen peroxide （H₂O₂） content， malondialdehyde （MDA） content， and other physiological and biochemical indices. The results revealed that： 1） Under low-nitrogen conditions， compared with E- A. inebrians plants， E+ A. inebrians plants showed significantly increased plant height， dry weight， tiller number， glucose-6-phosphate dehydrogenase （G6PDH） activity， reduced glutathione （GSH） content， and nitrogen content， and significantly decreased MDA and H₂O₂ contents. However， the carbon （C） and phosphorus （P） leaf contents， and the C∶N， C∶P， and N∶P ratios in the plants did not differ significantly between the E+ and E- plants. 2） Under normal-N conditions， compared with E- plants， E+ plants showed significantly increased plant height， but no significant difference in dry weight， tiller number， MDA and H₂O₂ contents， and GSH and G6PDH activity. Taken together， these findings suggest that E. gansuensis infection can enhance the growth of A. inebrians under low-nitrogen conditions by increasing G6PDH activity and GSH content， reducing H₂O₂ and MDA content， and promoting nitrogen uptake， thereby increasing leaf dry weight and tiller numbers. However， the impact of E. gansuensis on A. inebrians plants under normal N levels is limited.

Meta-analysis of the effects of arbuscular mycorrhizae on the yield and quality of wheat

Shou-xia XU

2024, 33(7):  192-204.  DOI: 10.11686/cyxb2023289

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Wheat （Triticum aestivum） is one of the most important grains cultivated by humans， and as such， it plays a key role in ensuring food security. Achieving higher and more stable yields and better quality of wheat grains is an important scientific issue. Arbuscular mycorrhizae （AM） are the most widespread symbionts in plant roots， and can improve plant nutrition， yield， and quality. Many studies have demonstrated that AM can promote wheat plant growth and improve grain yields. In this study， a meta-analysis was conducted to evaluate the effects of AM fungi on the grain yield and quality of wheat based on 171 published reports. This allowed for the systematic and comprehensive evaluation of the roles of AM in wheat production and the identification of AM fungi species or genera that consistently increase wheat grain yield and quality. The results of the meta-analysis indicated that AM can increase wheat grain yield by up to 24.2% as a result of increasing grain number per spike （by up to 17.1%） and the thousand-grain weight （by up to 15.7%）. In addition， AM can improve wheat quality by increasing protein content （by up to 15.7%） and the contents of nutrients such as phosphorus and zinc （by up to 15.2% and 21.5%， respectively）. Improvements in the yield and quality of wheat grains by AM may be attributed to the improvement of wheat shoot nutrition and leaf chlorophyll content， because AM can increase the concentrations of nitrogen， phosphorus， calcium， and zinc by up to 8.4%， 16.2%， 91.2%， and 11.3%， respectively， in the shoots of wheat plants， and the leaf chlorophyll content by up to 27.5%. Furthermore， different genera or species of AM fungi have significantly different effects on wheat yield and quality， and those in the genus Funneliformis have more significant and stable effects on wheat grain yield and quality. In summary， this study comprehensively evaluated how and to what extent AM affect wheat grain yield and quality， and identified which AM fungi consistently promote wheat plant growth and grain yield and quality. These results provide a theoretical and practical basis for the application of AM in wheat production and the selection of the best AM fungi to improve wheat grain yield and quality.

Effects of snow addition on soil phosphorus availability in an alpine meadow of the Tibetan Plateau

Xiang-jiao TAN, Kui-cai DONG, Hua ZHANG, Chuan-chuan TANG, Yan YANG

2024, 33(7):  205-214.  DOI: 10.11686/cyxb2023328

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Deeper snow cover in winter may change soil phosphorus cycling in alpine meadow grassland ecosystems through effects on soil temperature and moisture. A field experiment involving snow addition was conducted at an alpine meadow in the permafrost region of the Tibetan Plateau. Snow fences were used to contain snow to simulate increased depth of snow cover. The results showed： 1） Snow addition significantly increased temperature and moisture in the top 0-10 cm soil horizon in the growing season （from May to September）. 2） Snow addition significantly increased soil total phosphorus， available phosphorus and Al-P in the 0-10 cm and 10-20 cm soil horizons， but decreased soil organic phosphorus and Ca₂-P contents. The Ca₈-P content decreased in the 0-10 cm soil depth and increased in the 10-20 cm soil depth. 3） Redundancy analysis showed that the key factors affecting soil phosphorus forms were soil total nitrogen， organic matter and soil hydrothermal state. Therefore， it was confirmed that snow addition improved soil organic phosphate mineralization rate by changing soil physical and chemical properties， including total nitrogen content， organic matter content， hydrothermal state and soil phosphatase activity. Snow addition also promoted phosphorus release from slow-acting phosphorus sources such as Ca₈-P and Al-P， and improved soil phosphorus availability.