Table of Content

20 July 2021, Volume 30 Issue 7

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Changes in forage quality and its relationship with plant diversity under fertilization and mowing in Hulun Buir meadow steppe

Xin-lei XU, Yan-tao SONG, Jing-dong ZHAO, Yun-na WU

2021, 30(7):  1-10.  DOI: 10.11686/cyxb2020434

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This research explored the effect of fertilization and mowing on the nutritional quality of forage in Hulun Buir meadow steppe and its relationship with plant diversity. A mown area was established at the Erguna Forest-Steppe Ecotone Research Station， CAS， in 2016. The experimental plots comprised fertilized and unfertilized treatments and six stubble cutting heights. Sampling was carried out in August 2019 and the nutritional components of the samples were determined and their relationship with plant richness was analyzed. It was found that the crude protein content and relative feeding value of forage under the fertilization treatment was significantly higher than without fertilization treatment， while the herbage acid detergent fiber content without fertilization treatment was significantly higher than under fertilization. The crude protein， crude fat， water soluble carbohydrate， relative forage quality and milk yield were the highest when plots were mowed at 3 cm stubble height， while the contents of neutral detergent fiber and acid detergent fiber were the highest when plots were unmown. There was no significant interaction between fertilization and mowing. The relative forage quality， relative feeding value， milk yield， non-fibrous carbohydrate and Ca contents were positively and significantly correlated with species richness； the neutral detergent fiber content was negatively and significantly correlated with species richness， indicating that increase in species diversity improves the nutritional value of forage. Therefore， management methods that maintain high plant species richness in plant communities may be more effective for livestock production in Hulun Buir grassland.

Analysis of spatial variability of soil available nitrogen in Xilingol grassland

Shuai CHANG, Hong-bo YU, Qiao-feng ZHANG, Zi-ce MA, Yue-xuan LIU, Xiang LI

2021, 30(7):  11-21.  DOI: 10.11686/cyxb2020253

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The content of soil available nitrogen （AN） is an important index of soil nutrient levels， and AN plays an important role in the stability of the grassland ecosystem and in plant community development. This research used field sampling， laboratory analyses and data processing， using a Geographic Information System platform combined with geostatistical methods， to determine AN spatial variation characteristic in Xilingol grassland and factors affecting it. There were 30 sampling sites across six administrative regions， with sampling to 50 cm depth in six soil depth bands： 0-5 cm， 5-10 cm， and thereafter in 10 cm increments. It was found that： 1） The soil AN level displayed significant spatial different law in Xilingol grassland. In the horizontal direction， the content of AN in each depth of soil layer was banded and tends to gradually decrease from east to west. Vertically through the soil horizons， the soil AN content decreased with depth and gradually stabilizes. The soil AN content was at the lower middle level. There was a strong spatial correlation between the AN content of each layer of soil， and its spatial variation was mainly affected by structural factors， and all moderate variability. 2） The soil AN content in different grassland types displayed a similar decreasing trend with soil depth. In the 0-30 cm soil horizon， the AN level ranked： meadow grassland>typical grassland>desert grassland. In the 20-50 cm soil horizon， the AN level ranked： typical grassland>meadow grassland>desert grassland. 3） There was a very significant correlation between AN content in all soil layers （P<0.01）. There was no obvious correlation between soil AN and available potassium， but soil AN had a very significant positive correlation with soil organic matter and available phosphorus （P<0.01）， and a very negative correlation with soil pH （P<0.01）.

Evaluating the deep-horizon soil water content and water use efficiency in the alfalfa-wheat rotation system on the dryland of Loess Plateau using APSIM

Gulnazar Ali, Hai-ning TAO, Zi-kui WANG, Yu-ying SHEN

2021, 30(7):  22-33.  DOI: 10.11686/cyxb2020271

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Rainfall on the Loess Plateau is limited and variable （350-650 mm·y^-1）. The problem of deep soil desiccation caused by continuous planting of alfalfa has aroused widespread attention. Alfalfa and food crop rotation is an effective way to restore soil moisture of alfalfa fields and improve the sustainability of forage cropping systems. However， there is still a lack of research on the effects of long-term rotation on the soil water environment and water use efficiency. The agricultural production systems simulator （APSIM） has extensive adaptability and can accurately simulate the impact of tillage management on the resource utilization of crop systems. Based on experimental data from Changwu， Zhenyuan， and Qingyang experimental stations in the dryland of Loess plateau for continuous alfalfa cropping and alfalfa based rotations， this study firstly verified the APSIM model in simulating deep soil moisture and alfalfa long-term production， and then simulated the effects of 81 different 38-year rotation patterns on farmland soil moisture， dry matter production， nitrogen absorption and water use efficiency. It was found that the APSIM model simulated the yield of alfalfa with high accuracy. The determination coefficient （R²）， mean square error （RMSE） and mean absolute error （MAE） for alfalfa yield were 0.65， 0.23 t·hm^-2 and 0.17 t·hm^-2， respectively， and the normalized mean square error （NRMSE） was 29.2%. The model could also accurately simulate the soil moisture content for the 0-1000 cm layer in long-term continuous alfalfa and alfalfa rotation cropping systems. The R²， RMSE， MAE and NRMSE were 0.73， 0.021 t·hm^-2， 0.017 t·hm^-2 and 11.7%， respectively. The determination coefficients of the simulation results in the rotation system was 0.83， RMSE， MAE and NRMSE were 0.024 t·hm^-2， 0.018 t·hm^-2 and 11.8%， respectively. The 81 rotation scenarios modelled comprised alfalfa and wheat rotation periods of 2， 4， 6， 8， 10， 12， 14， 16， 18 years respectively. The results showed that with increasing length of alfalfa rotation in the system， the soil water content became extremely low， falling to between 0.10-0.15 in the 0-1000 cm depth with rapid loss from the 400-600 cm soil horizon. When the alfalfa rotation period was more than 12 years， all rotation patterns experienced soil water deficit. Among the 81 scenarios， the total yields of 12-year alfalfa rotated with 14-， 16-， or 18-year wheat （L12W14， L12W16 and L8W16） were the highest. The system nitrogen uptake increased with increase in the number of the years planted with alfalfa， and decreased sharply after more than 10 years of wheat planting. After rotations of alfalfa exceeding 8 years， the water use efficiency of the system decreased with the increase in the number of years planted with alfalfa. Considering the soil water environment and water use efficiency， it is suggested that optimum length of alfalfa planting in an alfalfa-wheat rotation system in the study area should be 4-6 years， and the duration of the wheat rotation should be more than four years. The results provide guidance for dryland alfalfa management and forage-grain crop rotation practices on the Loess Plateau.

Effects of precipitation on carbon， nitrogen and microbial characteristics of biological soil crusts in a desert steppe of Northern China

Xu-dong WU, Qi JIANG, Xiao-bin REN, Hong-qian YU, Zhan-jun WANG, Jian-long HE, Bo JI, Jian-min DU

2021, 30(7):  34-43.  DOI: 10.11686/cyxb2020516

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Biological soil crusts are fundamental components and surface landscape in arid regions， and the main source of soil nutrients also depends on them. However， the rainfall pattern affects the stability of the regional ecosystem in the desert region of Northern China. This paper aims to investigate the effects of precipitation on soil organic carbon， total nitrogen and microbial characteristics of biological soil crusts in a desert steppe. The precipitation was regulated by the measurement of artificial rain using rainwater shed and sprinkler irrigation technologies， in order to evaluate precipitation effects on the biological soil crusts in desert steppe compared with natural precipitation. 12 precipitation treatments （6 m×6 m） were set up at the test station in early March 2018， where 3 m wide buffer zone was designed between each time. Control conditions of precipitation were designed via the rainwater shed and sprinkler irrigation system， comprising 3 precipitation treatments， natural precipitation （CK）， -50% （50% reduction in precipitation）， and +50% （50% increase in precipitation）. Each treatment had 4 replicates for statistical evaluation of the reproducible. In the same period， small weather stations were set up in the test area. We collected soil samples from each site stratified into three soil depths： the crust layer （0-0.5 cm）， a middle layer （0.5-3.0 cm） and deep layers （3-10 cm）. There were three main findings： 1） The -50% was conducive to the accumulation of soil organic carbon （C） and soil microbial carbon （SMB-C） and increased the presence of soil fungi， while also increasing the soil total nitrogen （TN） content and presence of fungi in the crust layer and middle layer. +50% increased the number of soil bacteria in each soil layer， the crust layer and the soil microbial biomass nitrogen （SMB-N） content in the middle layer， and significantly reduced the soil C∶N， SMB-C∶SMB-N in each soil layer and number of fungi： ratio of number of bacteria， the contents of SOC， SMB-C， SMB-N， and the number of bacteria and fungi under different precipitation treatments all decreased significantly with soil depth； 2） Bacteria were more sensitive to precipitation reduction， while fungi were more resistant to aridity than bacteria. Soil bacteria and fungi had different adaptation strategies to changes in precipitation. 3） The -50% treatment was beneficial to the restoration of soil nutrients， especially to the restoration of soil nutrients in the middle layer underlying the crust layer， while the +50% treatment resulted in slight degradation of the crust layer and decreased deep layer soil nutrients.

Isolation of a beneficial hydrogen sulfide-producing bacterial strain that reduces lead uptake by Medicago sativa and aids remediation of Pb-contaminated soil

Qian-qian ZHOU, Ya-jian ZHANG, Jing ZHANG, Tu-tong YIN, Xia-fang SHENG, Lin-yan HE

2021, 30(7):  44-52.  DOI: 10.11686/cyxb2020265

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This research explored the roles of hydrogen sulfide-producing bacteria in preventing forages from absorbing heavy metals and in remediation of soil contaminated by heavy metals. From alfalfa growing at a locality contaminated by nearby mining activities， a bacterial strain， Sar15， with high hydrogen sulfide production was isolated. Sar15 was found to synthesize indole-3-acetic acid （IAA）， siderophores and urease， and to reduce the concentration of Pb²⁺ in solution by 60% （P<0.05）. Using 16S rDNA analysis the strain Sar15 was identified as Proteus penneri. A field experiment was then conducted to evaluate the potential influence of this hydrogen sulfide-producing bacterial strain on the growth ofalfalfaand its role in the inhibition of Pb uptake by alfalfa in Pb-contaminated farmland. It was found that P. penneri strain Sar15 was the most efficient in producing hydrogen sulfide and could colonize on the roots of alfalfa. Compared with the control， the strain Sar15 increased the dry weight of alfalfa and significantly reduced its Pb content by 44%-45% （P<0.001）. P. penneri strain Sar15 also increased the rhizosphere soil pH and enzyme activity， reduced the available Pb content in the rhizosphere soil， and reduced the toxicity of Pb to alfalfa. Inoculationof P. penneri strain Sar15 has the potential to mitigate moderately Pb-contaminated soil and ensure safe forage production.

Screening for plant growth-promoting rhizobacteria that promote cadmium absorption and accumulation and their effects on annual ryegrass

Hui-li WU, Wei TIAN, Yan-ling JI, Lai-qing LOU, Qing-sheng CAI

2021, 30(7):  53-61.  DOI: 10.11686/cyxb2020252

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Some plant growth-promoting rhizobacteria （PGPR） have the ability to promote plant growth and increase heavy metal absorption. Therefore， there is an opportunity to improve the efficiency of phytoremediation by inoculating the rhizosphere of plants which accumulate a large biomass with relevant strains of bacteria. In this study， 30 cadmium （Cd）-tolerant PGPR strains were isolated from soil of the plant rhizosphere in cadmium-contaminated areas. Based on the results of indole-3-acetic acid secretion， phosphorus dissolution， 1-aminocyclopropane-1-carboxylate deaminase production， iron carrier and growth promotion experiments， two PGPR strains designated Pi01 and Ma02 were selected and inoculated onto two cultivars of annual ryegrass with contrasting cadmium tolerance， IdyⅡ and Wasehope， and the effects on the growth and cadmium accumulation of ryegrass were measured. A pot culture test was carried out using soil contaminated with Cd at a concentration of （19.5±0.42） mg·kg^-1， and the two PGPR strains， Pi01 and Ma02， were inoculated onto the two cultivars of annual ryegrass. The biomass and Cd accumulation of both ryegrasses were significantly increased by inoculation with Pi01 and Ma02. In addition， inoculation with PGPR increased chlorophyll content， photosynthetic parameters， and extractable Cd concentration in the rhizosphere. Therefore， the two selected PGPRs， Pi01 and Ma02， can promote the growth of annual ryegrass and increase its accumulation of cadmium.

A study of rodent community structure in the Annanba wild camel national nature reserve

Cui-cui TIAN, Shu-hai BU, Duo-liang ZHOU, Jian-quan LIU, Yong-xiang ZHOU, Xue-li ZHENG

2021, 30(7):  62-71.  DOI: 10.11686/cyxb2020263

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In this study， a ‘quadrat trap’ method was used to investigate rodent communities of 10 different habitat types at 25 survey sites in the Annanba wild camel national nature reserve from 2018 to 2019， in order to understand rodent community structure and diversity. Our project captured 124 rodents， belonging to nine species， six genera， and three families. Among these， the most commonly trapped species were Dipus sagittal， Meriones meridianus and Meriones tamariscinus. A cluster analysis and PCA diagram show that the rodents of Annanba reserve were mainly divided into two communities； there was a desert drought-tolerant rodent community widely distributed in all habitats of the reserve， and a drought-tolerant and hygrophilous mixed rodent community mainly distributed in habitats characterized by Form. Phragmites australis and Form. Myricaria platyphylla. Among the 10 habitat types surveyed， the richness index and diversity index of Form. P. australis habitats were higher than other habitats. In addition to environmental factors， the observed diversity pattern may have shaped by the two factors： the number of species and the evenness of species distribution. The altitudinal distribution of rodent populations was marked by a large number of species distributed at altitudes of 1400-1800 m and 2600-3000 m， i.e. lower numbers at mid-altitude， and higher numbers at both lower and higher altitudes. This study showed that habitat type and altitude affect the rodent community structure in the Annanba nature reserve.

Analysis of genetic structure and fingerprinting in oat varieties based on SCoT markers

Jin LI, Shi-yong CHEN, Xu ZHAO, Hao-qi TIAN, Zhi-hua CHEN, Qing-ping ZHOU

2021, 30(7):  72-81.  DOI: 10.11686/cyxb2020596

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The genetic diversity and fingerprinting of 36 forage oat varieties used in China were analyzed using start codon targeted polymorphism markers （SCoT）. In this research 15 primers were selected from 80 SCoT primers， and a total of 146 bands were amplified. The number of polymorphic bands amplified by different primers ranged from 3 to 9， with an average of 6.4. The proportion polymorphic bands （PPB） was 65.75%. The average effective number of alleles， and values of Nei’s gene diversity and Shannon’s information index were 1.46， 0.27， and 0.38， respectively. The DNA fingerprints of 36 oat varieties were constructed using 14 sites from 4 core primers， which could identify and discriminate the tested oat varieties efficiently. The DICE genetic similarity coefficient of all tested oat varieties was 0.7596-0.9507， with an average of 0.8473. The unweighted pair group method with arithmetic average cluster analysis based on genetic similarity coefficients showed that the tested varieties could be divided into 4 groups. There was no obvious correlation between genetic similarity and geographical origin. The results of population structure analysis revealed the genetic composition of the oat varieties， and showed that 32.1% of foreign oat varieties have mixed sources， while only 25.0% of Chinese domestic varieties have mixed sources. It also showed that the domestic oat varieties have narrow genetic bases and single genetic components. The results provide genetic data for cultivar identification， and a theoretical foundation for breeding and analysis of genetic relationships of oats.

Screening and identification of target fragments with low cyanide traits of sorghum-sudangrass hybrid using BSA-SSR

Guo-fang WU, Xiao-xia YU, Zhuo YU, Dong-sheng YANG, Qian-qian LU

2021, 30(7):  82-92.  DOI: 10.11686/cyxb2021016

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In this study， bulk segregant analysis using simple sequence repeat markers （BSA-SSR） was used to screen and identify DNA fragments linked to low hydrocyanic acid content of sorghum-sudangrass hybrids. By PCR amplification using nine pairs of suitable SSR primers screened， 26 SSR target fragments related to low cyanide traits in sorghum-sudangrass hybrids were discovered. After PCR product recovery， partial purification， and sequence analysis， the base sequences of these DNA fragments linked to low cyanide content were obtained. Sequence comparison using the BLASTn database showed that two ‘low cyanide’ target fragments， TF8 （101 bp） and TF16 （586 bp） had， respectively， 95.4% and 97.0% homology with sorghum phosphoribulokinase chloroplastic gene XM_021458168.1 and sorghum clone BAC 88M4 gene AY661656.1， but there was no mention of hydrocyanic acid regulation in the functional annotation of these two genes. However， there are a number of variations in the DNA base sequences. The TF8 fragment has three base substitutions and one insertion， resulting in the replacement of an alanine and a glycine with cysteine， a threonine with alanine， and deletion of a glycine. Fragment TF16 has one base A missing， resulting in alanine deletion. Based on these results it is inferred that TF8 and TF16， two low cyanide target fragments， regulate the expression of a low hydrocyanic acid content trait. These results lay a foundation for further research on the detailed mapping and marker-assisted breeding of the major QTLs for low hydrocyanic acid content of sorghum-sudangrass hybrids.

Effects of different roughage combinations on in vitro rumen fermentation characteristics of Jinnan cattle

Dan-dan ZHANG, Yuan-qing ZHANG, Jing CHENG, Guang JIN, Bo LI, Dong-cai WANG, Fang XU, Rui-feng SUN

2021, 30(7):  93-100.  DOI: 10.11686/cyxb2020264

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The objective of this experiment was to study the effects of different roughage combinations of whole plant corn silage， wheat straw， and alfalfa silage on rumen in vitro fermentation characteristics of Jinnan cattle. Whole plant corn silage， wheat straw， and alfalfa silage were fermented in different ratios （80∶10∶10， 70∶10∶20， 70∶20∶10， 60∶10∶30， 60∶20∶10， 60∶30∶10， 50∶10∶40， 50∶20∶30， 50∶30∶20， 50∶40∶10， 0∶100∶0， 100∶0∶0， 0∶0∶100， respectively）. Gas production （GP）， in vitro dry matter degradation rate （IVDMD）， pH， ammonia nitrogen （NH₃-N）， and volatile fatty acid （VFA） were measured， and the single factor associative effects index （SFAEI） and multiple factors associative effects index （MFAEI） of the different feedstuff ratios were calculated. It was found that GP differences among the different roughage combinations were extremely significant （P<0.01）. The GP gradually increased with increase in the proportion of whole plant corn silage； the pH of each group was maintained at 6.68-6.89 （P<0.01） and NH₃-N was 14.31-26.01 mg·100 mL^-1 （P<0.01）. With the proportion of whole plant corn silage constant， IVDMD increased as the proportion of alfalfa silage was increased. Differences in rumen VFA levels among the different feedstuff ratios were also extremely significant （P<0.01）. The concentration of acetic acid and total volatile fatty acid （TVFA） in the 60∶30∶10 formulation was significantly higher than in other formulations （P<0.05）， and the concentration of propionic acid was also the highest （13.99 mmol·L^-1） in this formulation. The ratio of acetic acid to propionic acid ranged from 2.76-3.20， and there was no significant difference between the formulations （P>0.05）. The MFAEI of the various feed formulations was positive， and the MFAEI of the 70∶20∶10 formulation was the highest （0.9343）. In conclusion， in this study， the largest associative effects occurred when the proportion of whole plant corn silage， wheat straw and alfalfa silage was， respectively， 70∶20∶10.

Analysis of plasma and milk fatty acid and metabolite composition in lactating dairy cows with differing tolerance to subacute ruminal acidosis

Tao ZHANG, Ying-yu MU, Wang-pan QI, Chang-zheng GUO, Ji-you ZHANG, Sheng-yong MAO

2021, 30(7):  101-110.  DOI: 10.11686/cyxb2020482

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The present study aimed to explore the differences in plasma and milk metabolism of dairy cows with different subacute rumen acidosis （SARA） tolerance. Twelve fistulated Holstein dairy cows in mid lactation ［days in milk=（114±22） d］ were selected and fed the same diet consisting of 60% forage and 40% concentrate mixture. On days 20 and 21 of the trial period， the rumen pH was monitored at 0， 2， 4， 6， 8， and 12 h after morning feeding. Milk samples were collected before feeding in the morning and evening. Blood samples were collected from the jugular vein 6 h after morning feeding. All the milk and blood samples were stored in liquid nitrogen for subsequent fatty acid composition and metabolome analysis. Cows with the lowest and highest ruminal pH were assigned into the susceptible （SUS， n=4） and tolerant （TOL， n=4） groups， respectively. The fatty acid composition results showed that the proportions of ≤C16 fatty acids in the blood and milk were significantly increased in the SUS group （P<0.05）， while the proportions of >C16 fatty acids were significantly decreased （P<0.05）. The levels of the saturated fatty acids （SFA） and monounsaturated fatty acids （MUFA） in the milk were significantly decreased in the SUS group （P<0.05）. The LC-MS metabolomics results revealed that the L-phenylpyruvate was significantly reduced， while the levels of remaining MG （18：0/0：0/0：0）， 9-HODE， niacinamide， isovalerylcarnitine， phosphocreatine， L-glutamic acid， and 12（13） Ep-9-KODE were substantially increased in the SUS group. The results of milk metabolome analysis indicated that the levels of 1-stearoylphosphoglycerolserine and sphingosine were significantly increased， while the levels of 14 different metabolites were significantly decreased in the SUS group （P<0.05）， including glyceryl-phosphoryl-ethanolamine， glycerol 3-phosphate， and orotic acid. These differential metabolites were mainly involved in glycerophospholipid metabolism （P<0.05）， glycerolipid metabolism， and pantothenate and CoA biosynthesis. In conclusion， the fatty acids and metabolic profiles in the plasma and milk of cows with different tolerance to SARA were different. For the SUS group， the amino acid metabolism and the de novo synthesis ability of milk fat was enhanced in the plasma， while the ability to absorb long chain fatty acids from blood was weakened. At the same time， the levels of phospholipid， orotic acid and other nutrients were decreased in the milk， which indicated that the quality of milk was reduced for the SUS cows.

Effects of different levels of jujube powder on slaughter characteristics and meat quality of Northern Shaanxi white cashmere goats

Wang-bin SUN, Qi FU, Rui-lin XUE, Wei-ping WANG, Qian ZHANG, Ping FENG

2021, 30(7):  111-121.  DOI: 10.11686/cyxb2020526

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The research evaluated the effect of different dietary levels of jujube （Zyzyphus lotus） fruit powder on slaughter characteristics and meat quality of Northern Shaanxi white cashmere goats. Forty healthy goats with an average initial body weight of （20.15±1.63） kg were randomly selected and allotted to 5 dietary groups （Control， and Diets I to IV， 8 goats per group）. The control group was fed a basic diet， and the experimental groups I to IV were fed diets with 10%， 15%， 20%， and 25% jujube powder， respectively. After a pre-experiment adaptation period of 10 days， during which all goats were fed the basic diet； The five diets as described above were established and continued for a formal experiment of 70 days. All goats were slaughtered at the end of the experiment， and meat samples were measured the difference of muscle fiber characteristics， appearance quality， and fatty acid and amino acid contents. It was found that： 1） Dressing out and net meat percentages in all four groups receiving jujube powder were significantly higher than in the control group， and bone：meat in the control group and groups I and II were significantly higher than in groups III and IV （P<0.05）. 2） Intramuscular fat content in the control group was significantly lower than that in groups I， II， III and IV （P<0.05）. 3） The shear force， muscle fiber area and diameter of group III were significantly lower than in the other four groups （P<0.05）. 4） The contents of glutamic acid （C16：0） and stearic acid （C18：0） in group III were significantly lower than in the control group and group I （P<0.05）， while arachidonic acid （C20：4n6） and α-linolenic acid （C18：2n6c） in group IV were significantly higher than in the control group and group I （P<0.05）. 5） Aspartic acid， glutamic acid and alanine in group IV were significantly higher than that in the other four groups （P<0.05）. The addition of jujube powder in the experimental diets improved meat tenderness， which was beneficial to the accumulation of minerals， unsaturated fatty acids， amino acids and other nutrients in meat. As a result， the goat meat has higher nutritional value. Considering all the data， the meat quality was the best when Northern Shaanxi white cashmere goats were fed a diet with 20% jujube powder.

Effects of silage additives on quality and in vitro rumen fermentation characteristics of first season ratoon rice whole silage

Shi-yu ZOU, Si-kui CHEN, Qi-yuan TANG, Dong CHEN, Yuan-wei CHEN, Pan DENG, Xu-lai HUANG, Fu-qiang LI

2021, 30(7):  122-132.  DOI: 10.11686/cyxb2020256

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This experiment was conducted to investigate effects of silage additives on quality and in vitro rumen fermentation characteristics of first season ratoon rice whole-crop silage. The experiment compared three fermentation-enhancing preparations of bacterial and enzyme additives， added at 500 g·t^-1 fresh weight when ensiling whole crop ratoon rice， and a control （CK， 500 g·t^-1 water）. The additive treatments were： N₁， Lactobacillus plantarum （60%）+cellulase （30%）+xylanase （10%）； N₂， L. plantarum （70%）+Enterococcus faecalis （20%）+cellulase （5%）+hemicellulase （5%）； N_3，L. plantarum （30%）+E. faecalis （60%）+cellulase（5%）+hemicellulase （5%）. The silages were sampled after 45 d after ensiling， and the silage quality and in vitro rumen fermentation characteristics analyzed. The results were as follows： 1） After ensiling， the gross energy， total digestible fiber， and acetate values of the N₁， N₂ and N₃ silages were significantly higher than those of CK group （P<0.05）， while the contents of neutral and acid detergent fiber and ammoniacal nitrogen∶total nitrogen of the N₁， N₂ and N₃ groups were significantly lower than those of the CK group （P<0.05）. Among treated silages， the neutral detergent fiber level of the N₂ group was significantly lower than that of N₁ and N₃ groups （P<0.05）. 2） After 24 h in vitro fermentation， the 24 h cumulative gas production， the gas production of rapid degradation and the potential gas production of the N₂ group were significantly higher than for the N₁， N₃ and CK groups （P<0.05）， and the potential gas production of the N₁ group was significantly higher than for the CK group （P<0.05）. The N₁ and N₂ groups had lower pH than the N₃ and CK groups （P<0.05）， and the contents of acetate and ammonia of N₂ group were significantly higher than those of the N₁， N₃ and CK groups （P<0.05）. The propionate contents of the N₁ and N₂ groups were significantly higher than those of N₃ and CK groups （P<0.05）； the acetate∶propionate ratio of the N₂ group was significantly lower than that of N₃ and CK groups （P<0.05）； the degradation rates of dry matter and crude protein of N₂ and N₃ groups were significantly higher than those of N₁ and CK groups （P<0.05）； the degradation rates of organic matter， neutral detergent fiber and acid detergent fiber values of the N₂ group were significantly higher than for N₁， N₃ and CK groups （P<0.05）. In conclusion， it is suggested that silage additives should be supplemented with E. faecalis， cellulase and hemicellulaseunder the premise that L. plantarum is the main agent required to produce first season ratoon rice whole silage with improved nutritional value in actual production.

Effects of various moisture-absorbing roughages on the fermentation quality and aerobic stability of napier grass silage

Xiang YIN, Yong-qi WANG, Xin-qin LI, Jing TIAN, Xiao-ya WANG, Jian-guo ZHANG

2021, 30(7):  133-138.  DOI: 10.11686/cyxb2020257

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In south China， napier grass often has a high moisture content at harvest and as a result the fermentation quality of direct-cut silage is poor. In order to improve the quality of napier grass silage， the effects of various moisture-absorbing roughage materials on the silage fermentation quality and aerobic stability were studied. There were five silage treatments； four of these being napier grass with an added roughage material at 10% fresh grass weight and the fifth a Control （napier grass with no additive）. Roughages tested were rice bran， wheat flour， dried soybean curd residue and wheat bran. The fermentation quality and aerobic stability of the silages were analyzed 60 d after ensiling. It was found that all additive treatments significantly increased the dry matter （DM） content （P<0.01）， reduced the buffering capacity （P<0.05）， and increased the lactic acid content （P<0.01） of the respective silages， compared with the control. The addition of wheat flour significantly increased the concentrations of butyric acid （0.81% DM） and NH₃-N （14.40% TN， P<0.05）； the other roughage additives had no significant effect （P>0.05） on silage quality. The butyric acid and NH₃-N contents of silage with added dried soybean curd residue were only 0.04% DM and 9.75% TN， respectively. After the silage was exposed to the air， the aerobic stabilities of the silages with added wheat flour and dried soybean curd residue were better than the others. Based on multivariate analysis of nutritional characteristics， silage fermentation quality and aerobic stability， the addition of dried soybean curd residue produced the best silage.

Metal accumulation characteristics and physiological response of Kummerowia striata to manganese stress

Xin-hang LI, Ze-hua XIAO, Xue-shao KUANG, Wu-min WANG, Liang-yu LUO, Wen-sheng LIU

2021, 30(7):  139-147.  DOI: 10.11686/cyxb2020259

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This research studied the tolerance mechanism of plants to manganese stress. Individual plants of Kummerowia striata were collected from localities contaminated or not contaminated by heavy metals and cultivated under different concentrations of manganese ［0 （Control）， 1000， 5000， 10000， 15000， 20000 μmol·L^-1］. The effects of manganese stress on the phenotype， physiological and biochemical features， and manganese accumulation characteristics of K. striata from these two sources were evaluated. It was found that， as the concentration of Mn increased： 1） The root dry weight， shoot dry weight， and root∶shoot ratio of K. striata from both localities decreased； when the concentration of Mn was in the range 5000-20000 μmol·L^-1， compared with the Control， the shoot and root dry weight of plants from the contaminated locality decreased by 4.34%-27.71% and 19.00%-66.06%， respectively； while the shoot and root dry weight for plants from the uncontaminated locality decreased by 16.33%-49.77% and 27.90%-77.54%， respectively. 2） The contents of chlorophyll， soluble sugar and proline and the activities of superoxide dismutase and peroxidase in leaves of K. striata from the two localities showed a pattern of initial increase and then decrease with increasing Mn exposure， while the content of soluble protein gradually decreased and the content of malondialdehyde gradually increased. 3） The Mn content of the roots， stems， and leaves of K. striata from both localities increased. When grown at the Mn concentration of 20000 μmol·L^-1， the Mn content of K. striata sourced from the contaminated and uncontaminated areas was 16.53 and 13.41 times than that of the Control， respectively. Therefore， the Mn accumulation capacity and Mn tolerance of the K. striata from the contaminated locality are higher than in plants sourced from the uncontaminated locality. High activities of antioxidant enzymes appear to be an important physiological mechanism of K. striata tolerance to high Mn stress.

Effects of exogenous trehalose on growth regulation and total flavonoid content of Glycyrrhiza uralensis seedlings under NaHCO₃ stress

Fu-zhi LIU, Ying-fang ZHANG, Yuan CHEN

2021, 30(7):  148-156.  DOI: 10.11686/cyxb2020269

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In this study， aseptic plantlets of Glycyrrhiza uralensis generated by tissue culture were used to study the stress effects of NaHCO₃ at 50 mmol· L^-1 with and without exogenous trehalose addition to mitigate stress effects. The biomass， chlorophyll content， concentrations of osmotic regulation substances， antioxidant enzyme activities and total flavonoid contents in the plantlets were monitored. It was found that NaHCO₃-stressed seedlings showed significantly lower biomass， chlorophyll content， concentration of K⁺， total flavonoid contents and antioxidant enzyme （superoxide dismutase， peroxidase， catalase） activities， and significantly higher malondialdehyde （MDA）， proline， soluble sugar and Na⁺ concentrations. Those plantlets treated with 15 mmol·L^{-1trehalose showed significantly improved biomass， chlorophyll content， concentration of K+， total flavonoid content and antioxidant enzyme activities， together with reduced MDA， proline， soluble sugar， and Na+ concentrations. In summary， the application of exogenous trehalose under NaHCO₃ stress had a major beneficial effect on the growth of G. uralensis plantlets and enhanced their alkali-resistance ability of the seedlings. This study provides a theoretical basis for understanding the mechanism of exogenous trehalose enhancement of the alkali-resistance capacity of G. uralensis plantlets.}

Damage to the AsA-GSH cycle of soybean leaves under waterlogging stress at in seed filling period growth stages and the mitigation effect of uniconazole

Shi-ya WANG, Dian-feng ZHENG, Nai-jie FENG, Xi-long LIANG, Hong-tao XIANG, Sheng-jie FENG, Xin-xin WANG, Guan-qiang ZUO

2021, 30(7):  157-166.  DOI: 10.11686/cyxb2020249

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This research explored the effect of spraying uniconazole （S3307） on two different soybean varieties under waterlogging stress. The waterlogging-tolerant variety Kenfeng 14 and the waterlogging-sensitive variety Kenfeng 16 were studied in pot experiments. The degree of membrane lipid peroxidation as indicated by malondialdehyde （MDA） concentration， and levels of reactive oxygen species （ROS） and peptide ascorbic acid-glutathione （AsA-GSH） in soybean leaves under waterlogging stress at growth stage R5 （seed filling period） were evaluated. AsA-GSH circulatory system damage was detected and S3307 had an alleviating effect. The results showed that waterlogging stress at the R5 growth stage significantly increased the MDA content in the leaves of the two tested soybean varieties and accelerated the accumulation of ROS. A greater increase was observed in the waterlogging-sensitive variety Kenfeng 16 than in Kenfeng 14. After foliar spraying with S3307， the concentration of non-enzyme antioxidants and the activities of key enzymes were increased， and the MDA concentration of leaves was reduced. S3307 inhibited the accumulation of ROS， reduced the damage caused by waterlogging stress to the membrane system， and assisted the maintenance of a high level of key enzyme activity and non-enzymatic antioxidant concentrations. The benefits of S3307 application persisted after plants were returned to normal soil water levels， S3307 and promoted the recovery of the two soybean varieties to a normal growth status. The recovery ability of waterlogging-tolerant variety Kenfeng 14 was better than Kenfeng 16. In summary， waterlogging stress had contrast effects on the AsA-GSH cycle in the leaves of two soybean varieties with different waterlogging tolerances. S3307 partially alleviated the damage caused by the waterlogging stress.

An investigation of multiple crop planting options when following wheat with mixed-cropped forage rape and oats in the Jilin area of northeast China

Ying-liang YUAN, Dan TANG, Ying LU, Gui-xia RAN, Yan-qin GUO

2021, 30(7):  167-178.  DOI: 10.11686/cyxb2020551

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This research explored multiple cropping planting options when following wheat with mixed cropping of forage rape and oats in the Jilin area of northeast China. The experiment comprised two control treatments and 36 mixed-cropped treatments. The control treatments were forage rape sown alone at 15 kg·ha^-1 and oats sown alone at 220 kg·ha^-1. The mixed-cropped treatments were a factorial combination of forage rape and oats sown at 50%， 60%， 70%， 80%， 90% or 100% of control rates， designated A to F， respectively， for variation in sowing rate of oats， and subscript 1 to 6， respectively， for variation in sowing rate of forage rape. There were three replicates making 108 plots in total. Samplings were conducted at bolting， full bloom， and pod-set growth stages to evaluate crop performance， and results were analyzed according to Grey System theory. It was found that at bolting stage， the hay yield of the experimental crops ranged from 3999.89 kg DM·ha^-1 to 5367.28 kg DM·ha^-1， the crude protein content ranged from 10.16% to 13.99%， the content of neutral detergent fiber ranged from 49.88% to 64.51%， and the content of acid detergent fiber ranged from 36.88% to 41.52%. At full bloom stage， the hay yield of the experimental crops ranged from 5102.35 kg DM·ha^-1 to 6453.52 kg DM·ha^-1， the crude protein content ranged from 11.28% to 16.01%， the neutral detergent fiber content ranged from 57.99% to 69.37%， and the acid detergent fiber content ranged from 33.88% to 48.80%. At pod setting stage， the hay yield of the experimental crops ranged from 5737.16 kg DM·ha^-1 to 6988.16 kg DM·ha^-1， the crude protein content ranged from 9.25% to 13.12%， the content of neutral detergent fiber ranged from 57.10% to 68.88%， and the content of acid detergent fiber ranged from 32.99% to 41.01%. As determined by multivariate analysis， for earlier harvest， the C₁ treatment （forage rape 7.5 kg·ha^-1， oats 154 kg·ha^-1） was optimal and had forage yields of 5281.23 kg DM·ha^-1 and 6152.52 kg DM·ha^-1 at the bolting and full flowering growth stages， respectively； for later harvest the C₂ treatment （forage rape 9 kg·ha^-1， oats 154 kg·ha^-1） was the best and the forage yield was 6988.16 kg DM·ha^-1 at the pod-set growth stage.

Advances in artificial inoculation technology for grass-endophytic fungi

Chun-jie LI, Ming-xiao LANG, Zhen-jiang CHEN, Zheng-feng WANG, Tai-xiang CHEN

2021, 30(7):  179-189.  DOI: 10.11686/cyxb2020267

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Epichloё fungal endophytes of grasses not only improve the competitiveness of the host plants in plant communities， but also cause toxicoses in livestock. These dual effects have attracted widespread scientific attention both domestically in China and internationally. However， the use of Epichloё endophyte as a resource is limited due to its host-specificity. With the development and application of molecular biology and genomics， more and more novel endophytes have been discovered. Meanwhile， grass tissue culture regeneration systems have been developed and established. These points of progress have supplemented the traditional methods of artificial inoculation of grass endophytes to some extent. Screening endophytes with excellent characteristics， then establishing symbionts that are non-toxic to livestock and thereby improving host quality as a livestock feed， and resistance to biotic and abiotic stress through artificial inoculation， are the research directions and hotspots in the present and future. This study reviewed the existing techniques for artificial inoculation of endophytes in grasses， and found that the main inoculation methods currently are： Sterile seedling inoculation， injection inoculation， seed inoculation， callus inoculation， and adult plant inoculation. Among these， the sterile seedling inoculation method is widely used and the technique is becoming well adopted， but this method and injection inoculation are harmful to plants and increase seedling mortality. The potential success rate of the callus inoculation method is high， however the procedures for mature tissue culture regeneration are currently still developing， hence this method is less used. The seed slit inoculation method is an attempt at a new inoculation method； This method is simple and easy to operate， but there is no successful example. The seed soaking inoculation method causes little physical damage to plant tissues， so the seedling survival rate is high， which can effectively improve the success rate of inoculation. Through research and exploration of existing artificial inoculation techniques， it should be possible to develop the artificial inoculation methods for use with other microorganisms， and at the same time explore new inoculation methods with higher success rate and better compatibility， to broaden the range of symbiotic endophytes available for use in grasses， and so obtain more symbionts with better traits.

Investigation and pathogen identification of common root rot of Qingke barley （Hordeum vulgare var. nudum）

Xue-ping LI, Mei-jin LIU, Shi-yang XU, Jian-wei GUO, Yong-hong QI, Min-quan LI

2021, 30(7):  190-198.  DOI: 10.11686/cyxb2020270

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Qingke barley （Hordeum vulgare var. nudum） is a food and forage crop specifically adapted to the Qinghai-Tibet Plateau in China. Qingke barley has strong cold resistance and short-growth period traits， unique to this variety and making it suitable for use in a cold area at an altitude of more than 4200 meters. However， in recent years Qingke barley crops have been seriously affected by root rot. From June to August 2016， an investigation was carried out on Qingke barley in Gannan Prefecture of Gansu Province， and Haidong and Haibei Prefectures of Qinghai Province， to understand the factors influencing root rot incidence at the seedling and adult-plant growth stages and to collect samples of infected roots. It was found that common root rot was rife in China’s North-West Qinghai-Tibetan Plateau in the Prefectures surveyed. Disease incidence was approximately 5% to 15% within each entire field. Qingke barley， after becoming infected by this disease， will show yellow green leaves； the heads turn white and the seeds are empty. Infected seedlings look weak or die， their roots becoming black， rotted or cracked. Root sections were cut out from the junction of diseased and healthy roots of infected plants. In the laboratory， the root samples were dipped in 70% alcohol for 2-3 s， disinfected in 0.1% mercury bichloride solution for 10 s， rinsed 4 times with sterile water， and dried on sterilized filter paper. Then， the root section ends were sliced with a sterile scalpel and the middle root section so obtained was placed on potato dextrose agar （PDA） and incubated at 25 ℃. About 3-4 days later， two hyphae ends emanating from the root section were transferred to another PDA plate. The fungus was purified by single spore separation and subcultured on a new potato sucrose agar （PSA） plate. The classification status of pathogens was determined by combining morphological characteristics with molecular biological identification. The pathogens were Bipolaris sorokiniana and Alternaria alternata. The pathogenicity was measured and the symptoms similar to those reported from diseased crops of Qingke barely were observed in the inoculated plants. The morphology of the reisolated fungus was consistent with the inoculated one. No symptoms were observed on the control plants. As far as we know， this is the first report in the world of B. sorokiniana and A. alternata causing root rot of Qingke barley. This identification of the causative agents provides a theoretical foundation for development of prevention and control measures for Qingke barley root rot.