Table of Content

20 December 2022, Volume 31 Issue 12

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Grassland quality response to climate change in Xinjiang and predicted future trends

Chen CHEN, Chang-qing JING, Wei-kang ZHAO, Yu-feng XU

2022, 31(12):  1-16.  DOI: 10.11686/cyxb2021458

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Grassland is a major vegetation type in Xinjiang Province， and is an important component of carbon source-sink calculations. It is therefore important to ecological management decisions to understand the factors driving changes in grassland quality and likely future trends in those changes. We used geographic information maps to eliminate the interference of human activities and determine changes in grassland status and areas of stable grassland from 1980 to 2020， and analyzed changes in grassland quality and its response to climate change using data such as normalized vegetation index （NDVI）， vegetation net primary productivity （NPP）， and meteorological data， among others. We here estimate changes in grassland quality in Xinjiang and predict grassland quality changes from 2021 to 2040 using the Thornthwaite Memorial model and other models. We found that： 1） The grassland quality in Xinjiang was generally increasing， with a statistically significant rate of ongoing increase. The grassland cover and quality in mountainous areas of Xinjiang was high， while that at the desert edge was low. 2） The main driving forces for grassland quality changes in Xinjiang are temperature and precipitation. The correlation between grassland quality and precipitation was positive. Temperatures exceeding a certain limit were found to inhibit grassland quality. Sensitivity to temperature and precipitation decline was found to be greater when vegetation cover was lower. 3） The grassland quality and its temporal and spatial changes in Xinjiang can be reflected by climatic productivity. The lower the grassland cover， the stronger was the link between grassland quality and climate factors. 4） Under currently predicted climate change scenarios， the quality of low-cover grassland will be improved in the future， while the quality of other categories will tend to decrease. This information on grassland quality in Xinjiang and its predicted future trends can assist in formulating ecological protection measures and in other ways， such as compilation of carbon stock inventories.

Climate and land-use change jointly determine the spatial-temporal changes of ecosystem services in Hainan and Haibei Tibetan Autonomous Prefectures， Qinghai Province

Xiao-min FAN, Xin JING, Bo-wen XIAO, Xiao-liang MA, Jin-sheng HE

2022, 31(12):  17-30.  DOI: 10.11686/cyxb2021470

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Evaluating the spatial-temporal dynamics and driving factors of ecosystem services is fundamental to the understanding of how to maintain and improve those ecosystem services. Alpine regions are both a hotspot of ecosystem service supply， and sensitive and vulnerable to climate change. However， there are few systematic studies investigating the joint role of land-use change and climate change in shaping the spatial-temporal dynamics of alpine ecosystem services. Here， we first used models of ecosystem services to quantify changes in seven ecosystem services and in ecosystem multiserviceability from 2000 to 2015 in Haibei and Hainan Tibetan Autonomous Prefectures on the northeastern Qinghai-Tibetan Plateau. Next， we investigated the relative importance of climate change， population density change， land-use change and the interactions between climate change and land-use change effects on ecosystem services using generalized linear models. We found that ecosystem services increased in the south while decreased in the north from 2000 to 2015. Land use change （relative contribution was 34%） was the major factor affecting food supply. Net ecosystem productivity （NEP） was affected by temperature change （relative contribution was 77%）. Water purification （nitrogen and phosphorus retention）， soil retention， water yield and water retention were affected by precipitation change （relative contributions were 63%， 48%， 74%， 86% and 75%， respectively）. Ecosystem multiserviceability was also affected by precipitation. In addition to the service of soil retention， the effects of climate change （i.e. precipitation and temperature） on other ecosystem services and ecosystem multiserviceability varied with land-use change （interaction， P<0.001）. Our study highlights that realizing the sustainable development of ecosystem services needs to pay attention to both land-use change and the interactions between climate change and land-use change and optimizing the spatial-temporal allocation of ecosystem services to improve ecosystem multiserviceability in alpine regions.

Effects of Ligularia virgaurea on plant and soil nutrient levels and soil microbial biomass characteristics in degraded alpine grassland

Yu-qin WANG, Mei-ling SONG, Rui ZHOU, Hong-sheng WANG, Hua LIU, Xiu-lian ZHU, Yu-shou MA

2022, 31(12):  31-40.  DOI: 10.11686/cyxb2021467

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Ligularia virgaurea is considered to be an important indicator species of vegetation degradation in alpine meadows. A study of grassland ecosystem vegetation， soil and microbial nutrient cycling would make a significant contribution to understanding its invasion mechanism. An area with L. virgaurea invasion was studied. Chemical agents were used to remove the competitive advantage of L. virgaurea， and the subsequent changes in the nutrient levels of vegetation functional groups， soil nutrients and soil microbial biomass were measured and analyzed. We found that the carbon （C） content of Cyperaceae in the study area was increased. The nitrogen contents of Poaceae and Fabaceae and the phosphorus （P） content of Fabaceae were significantly increased， while the P content of Cyperaceae was significantly decreased （P<0.05）， and C content in L. virgaurea was significantly higher than that in other functional groups （P<0.05）. Across functional groups， the C∶N was significantly higher in Cyperaceae than in Fabaceae and forbs （P<0.05）， and C∶P of Cyperaceae was significantly higher than that of other functional groups （P<0.05）. Stoichiometrically， there was a negative correlation between C content and N or P content， and a positive correlation between N content and P content. The total nitrogen content of soil increased significantly in the study area after chemical treatment of L. virgaurea， and the contents of available nitrogen， total potassium and available potassium and the C∶N decreased significantly， while N∶P increased significantly （P<0.05）. L. virgaurea caused an increase in soil microbial biomass （and also microbial C， N， and P） and increased soil microbial activity. Microbial C∶N and C∶P ratios in the study area were also higher than those in the control area， and microbial N∶P was slightly lower than that in the control area， indicating that the demand for N in L. virgaurea is greater than the demand for P. The plant contents and stoichiometric ratios of plant C， N， and P were linked to soil and soil microbial biomass nutrient levels and stoichiometric ratios. Results of a redundancy analysis showed that soil levels of C， N， and P in the study area were highly correlated with those in microbial biomass， and the P content of plants was significantly related to that of soil and microbial biomass （P<0.05）， and the nutrient requirements of each functional group of plants in the control area were evenly distributed， which shows that the nutrient distribution pattern in grassland was affected by L. virgaurea.

High-resolution leaf area index inversion based on the Kernel Ridge Regression algorithm and PROSAIL model

Heng-liang GUO, Xiao LI, Yu FU, Bao-jin QIAO

2022, 31(12):  41-51.  DOI: 10.11686/cyxb2021468

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Accurate estimation of leaf area index （LAI） plays an important role in ecological， environmental and climate change research. Large-scale LAI estimates can be obtained from satellite remote sensing technology， but they rely on a large amount of ground-measured data with and they have low spatial resolution， which often does not meet the needs of high-precision and large-scale research. In this study， using surface reflectance data with a spatial resolution of 30 m， we tested an inversion method combining the Kernel Ridge Regression （KRR） algorithm and the PROSAIL physical model to invert LAI without a large number of ground measured data. First， the sensitivity analysis was performed on the input parameters of the PROSAIL model to determine the input parameters and generate the simulated data sets. Then， the KRR model inversion between the simulated reflectance and LAI was established. For comparison， we linked two other models， the Multilayer Perceptron （MLP） algorithm and the Random Forest Regression （RFR） algorithm， with the PROSAIL model， to perform high spatial resolution LAI inversion. Finally， we used ground measured data to compare the outputs and performance of the three inversion models. We found that the LAI inversion accuracy of the KRR-PROSAIL model was the highest with an R^{\mathrm{2}} of 0.8089 and root-mean-square error （RMSE） of 0.2492. The inversion accuracies of the PROSAIL model linked with MLP and RFR were inferior with R² values of 0.7726 and 0.7118， respectively and RMSE values of 0.2781 and 0.2432， respectively. Based on this study we recommend the combination of the Kernel Ridge Regression algorithm and PROSAIL models to invert satellite data to LAI for improved accuracy and high spatial resolution of the inverted LAI data. This methodology provides a method for rapid and accurate inversion of regional high-precision LAI information.

Response of grain yield and related agronomic traits of oilseed flax to diversified cropping rotations

Hai-di WANG, Yong ZHANG, Yu-hong GAO, Bing WU, Bin YAN, Zheng-jun CUI, Yi-fan WANG, Xue ZHANG

2022, 31(12):  52-65.  DOI: 10.11686/cyxb2021469

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This research aimed to identify a suitable planting pattern for oilseed flax production in a dry-farming region. A long-term field experiment was started in 2012 with a 4-year crop rotation cycle， designed to measure the effects on flax crop performance of previous crop， and various patterns of flax planting interval within the four-year rotation， compared with continuous flax cropping. Crop parameters measured included plant height， stem diameter， dry matter accumulation and distribution， and the experiment included six different crop rotation patterns： Flax→flax→flax→flax ［（F）FFF］； Flax→wheat→potato→flax ［（F）WPF］； Flax→potato→flax→wheat ［（F）PFW］； Flax→flax→wheat→potato ［（F）FWP］； Flax→wheat→flax→potato ［（F）WFP］ and flax→wheat→potato→wheat ［（F）WPW］. Results for the ninth year showed significantly increased grain yield （29.89%-109.57%） in crop rotation treatments compared with continuous cropping of oilseed flax. The ranking of the six tested rotations for yield was： （F）WPW>（F）FWP>（F）WFP>（F）PFW>（F）WPF>（F）FFF. The grain yield of oilseed flax was significantly affected by previous crop， frequency and years interval of flax cropping and number of years of continuous flax cropping. Yield was increased by 54.45%-59.29% under wheat stubble and potato stubble compared with oilseed flax stubble， and increased by 30.66% and 109.57%， respectively， under 50% and 25% frequencies， compared with 100% frequency. The grain yield of oilseed flax under two-year continuous cropping was higher by 29.89% than four-year continuous cropping， and increased with increase in years interval between flax crops. Correlation analysis identified a significantly positive correlation between oilseed flax grain yield and effective capsule number， branch number and 1000-seed weight. The effective capsule number， branch number and 1000-seed weight of oilseed flax under rotation treatment were increased by 35.88%-108.91%， 15.47%-46.19% and 14.61%-16.34%， respectively （P<0.05）， compared with continuous cropping. In addition， the high grain yield of oilseed flax was accompanied by an increase in plant height， stem diameter and dry matter accumulation and these increases were， respectively， 5.11%-42.24%， 2.77%-39.92% and 31.25%-117.89% under the rotation regimes， compared with continuous cropping. Reduction in the number of years of continuous cropping years， change of crop stubble， decreased flax planting frequency and increased of interval between flax crops also improved flax crop performance. In summary， crop rotation improved the vigor of oilseed flax， resulting in greater plant height and stem diameter， improved dry matter accumulation and distribution， leading to increased branch number， effective capsule number and 1000-seed weight， and increase in the crop yield of oilseed flax. The results indicated that a multiple-crop rotation pattern was an effective way to avoid the yield reduction caused by continuous cropping in oilseed flax. The rotation： Flax→wheat→potato→wheat performed best among those tested and can be recommended as an appropriate cropping rotation for oilseed flax production in the dry region of northwest China.

Effects of plastic film mulching on soil moisture， soil temperature and root growth of Angelica sinensis in cold and humid areas

Yong-wei MI, Cheng-wen GONG, Wu-ping SHAO, Yun-xia PENG

2022, 31(12):  66-75.  DOI: 10.11686/cyxb2022052

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This research investigated Angelica sinensis production systems with the objective of identifying opportunities for yield increase and improved mulching practice for management of the soil water and soil thermal environment， and to provide direction for further detailed study of technology and its application in A. sinensis production. The experiment included three planting systems： Hole seeding under ridging with plastic-film mulching （LS）， trenching and slant planting under film-side cultivation （MC） and trenching and slant planting in open field （LD） and studied vertical soil moisture and temperature profiles and root development in each case. It was found that in the leaf development growth stage film mulching increased soil water content in the 0-20 cm soil horizon， compared with LD， by 22.94% in LS and 14.57% in MD （P<0.05）. However， due to rainfall， there was no significant difference in soil water content among different treatments in later growth stages. Mulching also significantly increased the average daily temperature in the 0-15 cm soil horizon， with LS and MC resulting in mean increases of 1.04 and 0.61 ℃， respectively， compared with LD. During the growth period， the daily variation in soil temperature had a sinusoidal pattern with the amplitude of the diurnal variation decreasing with increasing soil depth and the maxima and minima delayed by 1 h for every 5 cm increase in soil depth. Mulching also alleviated the temperature drop overnight and reduced the temperature difference between day and night. When soil temperatures in the 0-15 cm horizon were greater than 14 ℃， the root growth of A. sinensis in the mulching treatments was rapid， and the fresh weight of single roots was significantly higher than that of LD mode. The stem diameter and single root fresh weight were therefore significantly increased in film mulching treatments compared with LD treatment， but there was no significant difference in root length. The soil water content of 0-20 cm horizon was significantly positively correlated with the root length， stem diameter and fresh weight of single roots， which played a homogenizing role in the composition of crude drug yield. In conclusion， film mulching resulted in obvious retention of soil moisture and temperature increase and thus an improved growth environment in the root zone of A. sinensis. Mulching alleviated the slow growth of A. sinensis caused by low temperature and water deficit in spring and would also alleviate water deficit later in the season. Mulching can be recommended as a cultivation system for A. sinensis production in cold and humid areas.

Evaluation of adaptability of naked oat varieties in the alpine region of North China based on the AMMI model and GGE Biplot

Xing-yu WANG, Jing CHENG, Sheng GAO, Mo-han LI, Man-xia YANG, Jun-yong GE, Hai-tao ZHOU, Yun-xia LI, Hua-dong ZANG, Wen-bo ZUO

2022, 31(12):  76-84.  DOI: 10.11686/cyxb2021475

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In order to comprehensively evaluate the productivity， stability and adaptability of varieties of naked oats， as well as the discriminative power and representativeness of testing sites in the alpine region of North China， data for six naked oat varieties and six testing sites in 2019 were analyzed and evaluated using the AMMI （additive main effects and multiplicative interaction） model and GGE （genotype main effect plus genotype-environment interaction） biplot. It was found that analyses of naked oats regional trial results using the two methods together reduced the statistical error and increased the ability to declare variety means significantly different， compared to traditional ANOVA methods. It was found that genotype， environment， and genotype×environment interaction effects all contributed to differences in grain yield. Variety 200910-28-4-3（G₂） showed the best performance in both grain yield and stability of yield across sites， followed by varieties 200910-5-2 （G₃） and 200910-22-1（G₄）. In terms of the selection of regional adaptability test sites for varieties， Ulanqab pilot in Inner Mongolia had both good representativeness and strong discriminability， and was the most ideal test site. Chongli Shizigou Seed Farm and Zhangbei Base were also comparatively good test sites. This study provided a scientific evaluation of methodology for performance testing of naked oat varieties in the alpine region of north China and the results basis will assist future breeding and promotion.

Diurnal changes in photosynthesis and photosynthetic product partitioning in alfalfa in response to phosphorus application

Yan-liang SUN, Kong-qin WEI, Xuan-shuai LIU, Jun-wei ZHAO, Sheng-yi LI, Chun-hui MA, Qian-bing ZHANG

2022, 31(12):  85-94.  DOI: 10.11686/cyxb2021489

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This research explored the effect of different levels of phosphorus application on diurnal variation in photosynthesis and partitioning of photosynthetic products in alfalfa under drip irrigation. In particular， the relationship between photosynthetic product levels in the plant and leaf photosynthetic parameters of alfalfa was clarified. Four phosphorus （P₂O₅） application levels of 0 （CK）， 50 （P₁）， 100 （P₂） and 150 kg·ha^-1 （P₃） were used as treatments in a field experiment. Leaf photosynthetic parameters were measured with a Li-6400 portable photosynthesis instrument on sunny days from 10：00-20：00 during the early flowering stage， together with environment factors and sugar and starch content in the leaves， stems and roots. A feature of the results was a ‘photosynthetic noon-break’ phenomenon across all phosphorus application treatments， and stomatal limitation was the main factor responsible for the mid-day decline of net photosynthetic rate （P_n）. Photosynthetically active radiation had the greatest impact on the P_n of alfalfa leaves， while atmospheric CO₂ concentration， atmospheric temperature， and atmospheric environmental factors such as relative humidity and vapor pressure deficit based on leaf temp also affected P_n. Principal component analysis showed that alfalfa photosynthetic efficiency in the four P-treatments ranked P₂>P₁>P₃>CK. At the 100 kg·ha^-1 phosphorus level （compared to CK）， the hay yield of alfalfa was increased significantly， the soluble sugar contents of leaves， stems， and roots were increased by 11.6%， 5.0% and 4.6%， respectively， and the starch contents were increased by 15.2%， 9.6% and 5.3%， respectively. Higher overall levels of soluble sugar and starch typically manifested as greater concentration increases in leaves， and relatively smaller increases in roots and stems. The diurnal troughs in P_n， transpiration rate， leaf internal CO₂ concentration and water use efficiency （WUE） of alfalfa leaves were less marked in the P treatments， compared with the control treatment. Therefore， appropriate phosphorus application can increase the photosynthetic efficiency of alfalfa leaves， thereby significantly promoting crop growth and development. At the phosphorus （P₂O₅） application rate of 100 kg·ha^-1 （P₂）， the alfalfa photosynthetic enhancement effect was the most pronounced.

Functional analysis of glycine decarboxylase H-protein gene MsGDC-H1 in Medicago sativa

Chun-xue WEI, Fei HE, Lei XU, Xiao LI, Li-xia ZHANG, Ming-na LI, Lin CHEN, Jun-mei KANG, Qing-chuan YANG, Rui-cai LONG

2022, 31(12):  95-105.  DOI: 10.11686/cyxb2021477

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Photorespiration is essential for C₃ plants， allowing oxygenated photosynthesis by removing 2-phosphoglycolate. H-protein is one of the key components of glycine decarboxylase （GDC）， which converts glycine to serine during photorespiration. The MsGDC-H1 gene was cloned from Medicago sativa. The cloned gene encoded 166 amino acids and had a conserved lipoyl-binding domain and a conserved N6-lipoyllysine site. Phylogenetic analysis showed that MsGDC-H1 was closely related to glycine decarboxylase H-protein （GDC-H） in other dicotyledons. The expression pattern analysis showed that MsGDC-H1 was highly expressed in leaves and was induced by light. To explore the effects of MsGDC-H1 on Arabidopsis thaliana growth， photoinduced stem-leaf specific promoter ST-LS1 and constitutive promoter CaMV 35S were used to drive MsGDC-H1 expression （ST-LS1：：MsGDC-H1； CaMV 35S：： MsGDC-H1）. MsGDC-H1 is heterogeneously expressed in A. thaliana. Biomass， starch and soluble sugar content and photosynthetic rate of overexpressed plants were evaluated. Data analysis showed that CaMV 35S：：MsGDC-H1 overexpression （G series） inhibited A. thaliana growth. The starch content of G series was increased by 34%-67% compared with A. thaliana in which ST-LS1：：MsGDC-H1 was overexpressed （GS series）， and was increased by 7.3%-33.7% compared with wild type （WT） A. thaliana； The soluble sugar content was decreased by 36%-38% compared with GS series and increased by 44.3%-49.7% compared with WT A. thaliana. Compared with WT， GS series plants grew faster， starch content was not significantly different （P>0.05）， and soluble sugar content was significantly increased （P<0.05）. The experiment results show that MsGDC-H1 plays an important role in regulating photosynthetic rate， carbohydrate synthesis and growth of A. thaliana， and can be used as a candidate gene in genetic engineering breeding to improve alfalfa yield in the future.

Identification of CAX gene family and expression profile analysis of response to abiotic stress in alfalfa

Guo-xiang ZHANG, Wei-leng GUO, Ming-yu BI, Li-shuang ZHANG, Dan WANG, Chang-hong GUO

2022, 31(12):  106-117.  DOI: 10.11686/cyxb2021471

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Ca²⁺/H⁺ reverse transporter proteins （CAX） are an important group of transmembrane transporters， which plays important roles in regulating Ca²⁺ balance， resisting abiotic stresses and transporting heavy metal ions in plants. Using bioinformatics methods， we performed a genome-wide identification of CAX gene family occurrence in alfalfa. In this work， the physicochemical properties， structural characteristics， phylogenetic relationships， cis-acting elements and chromosome locations of CAX gene family members were analyzed. Fifteen MsCAX genes were identified and these were distributed on 15 alfalfa chromosomes with 22 pairs of segmental duplication events. Further analysis showed that they encoded 367-460 amino acids with isoelectric points ranging from pH 5.2 to 6.5. All of them were hydrophobic proteins. Phylogenetic analysis showed that MsCAXs were divided into two subfamilies， and members of the same subfamily had similar genetic structures， conserved motifs， and the number of transmembrane domains. The promoter region of MsCAXs contained the light， hormone and stress-responsive elements. The expression patterns of six MsCAXs genes in response to abiotic stress were analyzed by qRT-PCR. It was found that all six MsCAX genes were significantly down-regulated under drought and low temperature stress， and three MsCAX genes were up-regulated under salt and saline-alkali stress. These results indicate that MsCAX gene has different expression patterns under different abiotic stresses. The results provide a reference for further exploration of the functions of the MsCAX gene family.

Regulatory effects of butanediol on the expression level of endogenous hormones and related genes in creeping bentgrass under heat stress

Ning ZHAO, Hui-ling MA, Ran ZHANG, Jin-qing ZHANG, Yi SHI

2022, 31(12):  118-132.  DOI: 10.11686/cyxb2021493

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This research investigated ways to improve the heat resistance of creeping bentgrass （Agrostis stolonifera） in the context of use as a turfgrass in a global warming environment. Potted seedlings of the variety Penn A4 were studied under a simulated high temperature environment （37 ℃/32 ℃， day/night） and subjected to treatments involving foliar spraying of 300 μmol?L^-1 2，3-butanediol （BD） to examine effects on leaf endogenous hormone content and the related gene expression. Seedlings received a BD pretreatment before being exposed to heat stress for 0， 7 or 42 days before BD pretreatment， and then were allowed to recover at optimal temperature for 10 days. For seedlings subject to 7 days of heat stress it was found that BD application increased the levels of cytokinin， gibberellins （GA₃） and jasmonic acid， decreased levels of auxin， salicylic acid， abscisic acid， and 1-aminocyclopropane carboxylic acid， and decreased the expression of related genes， thereby accelerating transpiration-driven cooling and plant vegetative growth. In addition， in plants subject to 42 days of stress， BD pre-treatment up-regulated the expression levels of various hormone-related genes， and reduced leaf hormone content by promoting endogenous hormone transport， thus inhibiting plant vegetative growth， and an energy saving whereby Penn A4 seedlings were able to resist long-term heat stress， and improving their survival probability. In summary， by regulating endogenous hormone metabolism to accelerate the growth rate and transpiration-induced cooling of Penn A4 under short-term stress， and by inhibiting the senescence and growth rate of plants under long-term stress， BD improved heat tolerance of Penn A4 creeping bentgrass.

Estimation of genome size for Psammochloa villosa by flow cytometry and K-mer analysis

Tao LIU, Yu-ping LIU, Gui FU, Ting LV, Feng LIU, Yu ZHANG, Dan-dan SU, Ya-nan WANG, Chang-yuan ZHENG, Xu SU

2022, 31(12):  133-145.  DOI: 10.11686/cyxb2021491

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The genus Psammochloa belongs to Poaceae and contains only one species （Psammochloa villosa）. P. villosa has characteristics typical of sand-plants， including a rhizomatous growth habit and clonal integration， and is a dominant species in non-fixed sand dunes on the Inner Mongolia Plateau in China. The present study measured the genome size of P. villosa by combing flow cytometry and K-mer analysis， built an optimized system for determination of DNA content （C value） in diploid species via selecting Achnatherum splendens as an internal standard， and Orinus kokonorica，and Aegilops squarrosa as external standards. We found that： 1） The P. villosa fluorescence peak in flow cytometry was 2.54 times that of O. kokonorica， and 1.35 times that of A. splendens. Relative fluorescence intensity of P. villosa was much smaller than for A. squarrosa. The genome size of P. villosa was estimated to 1580.10±5.02 Mb. 2） Using K-mer analysis， the genome size of P. villosa was estimated to be about 1563.54 Mb， the hybridity rate was 1.15%， and the proportion of repeated sequences was 66.27%. Therefore， the genome of P. villosa is a complex genome with high heterozygosity and high repetition. 3） It is recommended that the sequencing strategy should be based on CLR or HiFi mode from the PacBio platform， and sequencing depth should be higher than 20×. The accurate determination of genome size of P. villosa has both added to knowledge of DNA content in a member of the tribe Stipeae （Poaceae）， and provided data useful for genome sequencing， evolutionary genomics research， germplasm resource development and utilization， and species conservation. The result may provide an indication of genomic size for closely related species of Stipeae.

Identification of a WRKY gene family based on full-length transcriptome sequences and analysis of response patterns under salt stress in Halogeton glomeratus

Qian CHEN, Xiao-yun XU, Jun-cheng WANG, Li-rong YAO, Er-jing SI, Ke YANG, Xiao-ling WEI, Xiao-le MA, Bao-chun LI, Xun-wu SHANG, Ya-xiong MENG, Hua-jun WANG

2022, 31(12):  146-157.  DOI: 10.11686/cyxb2021478

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WRKY is a plant-specific transcription factor that plays an important role in plant growth， plant development and plant stress responses. This research aimed to identify members of the WRKY gene family in Halogeton glomeratus， explore their evolutionary relationships and elucidate the expression response pattern of HgWRKY genes under salt stress. From the full-length transcriptome data of H. glomeratus， the WRKY gene family members were identified and analyzed by bioinformatics methods， and their relative expression levels under salt stress were detected by qRT-PCR. A total of 31 HgWRKY genes were identified from H. glomeratus，with the coded amino acid number of identified HgWRKYs ranging from 220 to 611. All HgWRKY proteins had complete conserved WRKYGQK sequences at the N-terminal. Subcellularly， all HgWRKYs were located in the nucleus， and HgWRKY20 and HgWRKY21 were also located in mitochondria. Based on phylogenetic analysis， the 31 detected HgWRKYs can be divided into three groups： Ⅰ （8 members）， Ⅱ （22 members）， Ⅲ （1 member）. Group Ⅱ contained five subgroups： Ⅱ-a （1 member）， Ⅱ-b （2 members）， Ⅱ-c （1 member）， Ⅱ-d （15 members） and Ⅱ-e （3 members）. Motif 1 and Motif 2 were the characteristic motifs of the HgWRKYs family， and these were found to be relatively conserved in the evolutionary process. The qRT-PCR results indicated that HgWRKYs were mainly expressed in roots with tissue specificity， and the expression levels of HgWRKY19， HgWRKY23 and HgWRKY27 genes were the highest at 24 h. These three were therefore selected as candidate genes for salt stress response， in order to provide a basis for further study of the molecular mechanisms of HgWRKY genes in response to salt stress.

Screening of antifreeze-thawed lactic acid bacteria and their effects on oat silage fermentation quality and aerobic stability

Hai-ping LI, Hao GUAN, Zhi-feng JIA, Wen-hui LIU, Xiang MA, Yong LIU, Hui WANG, Li MA, Qing-ping ZHOU

2022, 31(12):  158-170.  DOI: 10.11686/cyxb2022087

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The effects of freeze-thaw conditions on the fermentation quality and aerobic stability of oat silage were investigated. Four strains of freeze-thaw-resistant lactic acid bacteria （LAB） with rapid growth and efficient acid production were screened from 437 strains， which had been isolated from the Qinghai-Tibetan Plateau. Based on physiological and biochemical characteristics and 16S rRNA gene sequence alignment， the four strains were identified as Lactobacillus plantarum 157 （LP157）， L. plantarum 160 （LP160）， Lactobacillus brevis 248 （LB248）， and Lactobacillus pentosus 260 （LPE260）. In order to investigate their effects on the fermentation quality， nutrient composition， microbial counts and aerobic stability of oat silage under freeze-thaw conditions， seven treatments were tested as follows： 1） LP157； 2） LP160； 3） LB248； 4） LPE260； 5） LP160+Lactobacillusrhamnosus 753 mixture （MIX）； 6） A commercial bacterial silage additive （COM）； 7） The same amount of sterilized distilled water （CK）. All treatments were ensiled for 60 days at a constant temperature of 20 ℃ and under a 20 ℃/-5 ℃ regime alternating every 12 h （freeze-thaw）. LP inoculation improved silage quality： The pH and dry matter loss in silages inoculated with LP157， LP160， LB248 and LPE260 were significantly lower than CK （P<0.05） and lactic acid and acetic acid contents were significantly higher than CK （P<0.05）， and the growth of spoilage micro-organisms such as coliform bacteria， yeast and mold were inhibited， both with fermentation at constant 20 ℃ and under freeze-thaw conditions. After aerobic exposure for 5 days， the pH and NH₃-N of silages treated with LP157， LP160， LB248 and LPE260 were significantly （P<0.05） lower than CK， MIX and COM. The aerobic stability of oat silage was improved， especially when inoculated with LP160 （70 h vs. CK 11 h）. The results show that the four screened strains can be used as effective LAB inoculants for silage preparation in the freeze-thaw environment of the Qinghai-Tibetan Plateau.

Symbiotic compatibility of different rhizobia strains with important Chinese milk vetch （Astragalus sinicus） cultivars

Dan-na CHANG, Xiao-tong MA, Guo-peng ZHOU, Song-juan GAO, Rui LIU, Wei-dong CAO

2022, 31(12):  171-180.  DOI: 10.11686/cyxb2021465

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Symbiotic compatibility of different rhizobia strains with important Chinese milk vetch （CMV） cultivars was studied to identify rhizobia with a broad host compatibility high nitrogen fixation ability for CMV crop inoculation， with a view to improving CMV nitrogen fixation ability and performance. Eight rhizobia strains isolated from different geographic CMV production regions and eight important CMV cultivars were used in the research. A hydroponic tube test showed six of the eight rhizobia strains could establish good symbiosis with all of the eight tested CMV cultivars. Four rhizobia strains with better symbiosis were re-tested in a vermiculite pot experiment in which the effective nodule number， nodule fresh weight， nitrogenase activity， dry weight， and nitrogen accumulation of CMV were recorded and analyzed. It was found that compared with the uninoculated control， rhizobia inoculation significantly increased the dry weight and nitrogen accumulation of CMV. Across the eight tested CMV cultivars and four rhizobia strains， CMV shoot dry weights were 3.23-7.12 times higher and root dry weights were 1.64-4.12 times higher in inoculated than in uninoculated plants. Similarly， shoot nitrogen accumulation was 12.72-37.84 times higher， and root nitrogen accumulation 5.42-13.63 times higher in inoculated plants than in the control treatment. There were also differences between CMV cultivars and rhizobia strains in nitrogen fixation ability. The eight cultivars tested differed in their response to inoculation. CMV cultivars Yijiangzi and Ningbodaqiao were generally more responsive， and cultivar Xinzi No.1 was generally less responsive. For cultivars Yijiangzi and， Ningbodaqiao， shoot dry weight was 1.78-1.87 times higher； root dry weight was 1.68-1.99 times higher； shoot nitrogen accumulation was 1.14-2.08 times higher and root nitrogen accumulation was 1.74-2.40 times higher than for cultivar Xinzi No. 1. Among the four rhizobia strains re-tested in the pot trial， strain 7653R was superior to the other three （13005， 13025 and 13052）. Averaged over the eight tested CMV cultivars， the effective nodule number was 1.17-1.19 times higher； the nodule fresh weight was 1.15-1.22 times higher， and nitrogenase activity was 1.38-1.45 times higher for rhizobia strain 7653R than for the other 3 strains. ANOVAs for CMV and rhizobia strain effects and their interaction showed that the contribution of rhizobia strains to effective nodule number， nodule fresh weight， nodule dry weight， and nitrogen accumulation was 50.79%-87.64%， compared with a 7.17%-32.83% contribution of CMV cultivars. Symbiotic compatibilities among different rhizobia strains and the main CMV cultivars were elucidated， and these data provide a knowledge base for further screening of rhizobia strains with excellent field performance.

Identification and biological characterization of the pathogens responsible for sclerotinia rot in Codonopsis pilosula

Jing-jing JIANG, Hui DU, Ai-chang CHEN, Xue-ping LI, Min-quan LI, Yong-hong QI

2022, 31(12):  181-190.  DOI: 10.11686/cyxb2021462

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The aim of this study was to isolate and characterize the causal pathogen and study the biological characteristics of sclerotinia rot of Codonopsis pilosula. Pathogen material was obtained by tissue isolation. The isolated fungal species were comprehensively evaluated in terms of their morphology， rDNA-ITS sequence， RPB2 gene of RNA polymerase Ⅱ， and biological characteristics. The pathogens were identified as Sclerotinia nivalis and Sclerotinia sclerotiorum， and of the two， S. nivalis was the dominant species. The optimum temperatures for mycelium growth and sclerotia formation of S. nivalis were 20 and 15 ℃， respectively， while corresponding values for S. sclerotiorum were 25 and 25 ℃. The optimum pH for mycelium growth was 6 for both species， while optimum pH for sclerotia formation was 6 for S. nivalis and 7 for S. sclerotiorum. The optimum culture medium was 100% potato dextrose agar （PDA）. The mycelial growth rate approach was applied to test the toxicity of adiacylamine， which exhibited inhibitory activity with EC₅₀ on S. nivalis at 0.2625 mg·L^-1 and on and S. sclerotiorum at 0.4165 mg·L^-1. In summary， this is the first report of S. nivalis and S. sclerotiorum causing sclerotinia rot on C. pilosula in China， and the data presented provide a reliable scientific proof of the pathogen diagnosis and a theoretical basis for the development of prevention measures.

Precision grazing management of grassland： Concept， theory， technology and paradigm

De-li WANG, Ling WANG, Guo-dong HAN

2022, 31(12):  191-199.  DOI: 10.11686/cyxb2022047

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With the development of human understanding of the multi-functionality of grassland， coupled with the increasing demand for grassland ecological services， animal production and pastoral living， it is necessary to update the concept of grassland management， develop higher level livestock grazing and feeding technology based on multidisciplinary theories， and establish a more effective grassland grazing management paradigm. This study considers both the background and characteristics of the grassland resources and modern multi-dimensional social demands， and develops the concept of precise grassland grazing management which encompasses the versatility and stability of the grassland ecosystem and sustainability as the goal and the use of grassland science， animal science， ecology and other multi-disciplinary theories， based on the habitat conditions， especially the vegetation characteristics， livestock classes and their requirements， and livestock-vegetation interactions. Through multi-dimensional， effective and directional regulation of the livestock grazing process， the grassland management and utilization paradigm of synergistic balance between production and ecological functions can be finally realized. Also， the concepts and connotations of precise grazing and its relevant theoretical bases are systematically explained， including the plant compensatory growth mechanism， the intermediate disturbance hypothesis， the theory of diversifying grazing livestock， mechanisms of plant-animal interactions， nutrition regulation principles and versatility synergy. These concepts form a scientific basis for the regulation of grazing pressure and livestock assembly. In conjunction with this coverage， the key points in precision grazing are reviewed， such as dynamic optimal stocking rate （threshold）， mixed grazing （species and proportion）， remote sensing information options （satellite， unmanned aerial vehicle monitoring， large scale data processing） and other related supporting technologies. Finally， the authors sum up the concept of grassland multifunctionality as a goal of “combining productive function and ecological service in a win-win manner”， so providing a precise grazing management paradigm. This approach provides a principle for the integration of natural grassland grazing， grassland grazing with supplementary feeding， and drylot feeding， reflecting region-wide whole industry regulation of livestock grazing pressure/assembly and provision for animal nutrition， while aiming for grassland grazing systems to achieve an overall “livestock-vegetation balance”. Such a system will generate high quality animal products and sustainable ecological services. Precise grazing management of grassland is advanced， practical and extensive， and therefore is a desirable choice for future grassland management with great potential and prospect.

Challenges in research on rhizomatous clonal plants

Chao-qun BA, Qun MA, Hai-yang WANG, Zhi-min LIU

2022, 31(12):  200-207.  DOI: 10.11686/cyxb2021424

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Rhizomatous clonal plants are a category of clonal plants in which daughter ramets are formed by spreading underground stems. Their particular distinction of having a subsurface connection system provides them a range of unique reproduction and growth modes and also unique adaptations to their local environment. However， because relevant research techniques are not well developed， the differences between rhizomatous and other clonal plants in phenotypic plasticity， clonal integration， foraging behavior and clonal division of labor， are not yet well understood and the potential to harness their behavior to prevent weed invasion， to mitigate climate change， to reduce ecosystem degradation or to promote ecosystem ecological restoration is also unclear. In view of this， through a review and summary of relevant recent research， we have identified knowledge gaps for further research. We recommend immediate research effort in the following areas： 1） Innovation in research methodology for identification and selection of beneficial plasticity traits； 2） The mechanisms by which various environmental factors affect clonal integration outcomes； 3） Development of a complete foraging model that comprehensively combines plant and environmental characteristics.