Table of Content

20 October 2024, Volume 33 Issue 10

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Root distribution characteristics of typical herbaceous plants and their effects on soil physicochemical properties on the Loess Plateau

Fang LIU, Pei-pei WANG, Yu-ying CAO, Jun-e LIU, Zheng-chao ZHOU

2024, 33(10):  1-13.  DOI: 10.11686/cyxb2023446

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Extensive vegetation restoration has been implemented to control serious soil erosion on the Loess Plateau， China， and the ecological environment has improved. Understanding the beneficial effects of plant roots on soil properties will be helpful for further systematic research aimed at optimizing vegetation restoration on the Loess Plateau， and will provide a scientific reference for subsequent ecological restoration in this area. In this study， we focused on Stipa bungeana and Artemisia gmelinii growing naturally on the Loess Plateau. Land that had been abandoned for 1 year served as the control. The root characteristics of the two plant species and soil physicochemical properties were determined， the distribution of roots in different size classes and its relationship with the soil physicochemical properties were analyzed. The results showed that： 1） There were significant differences in root characteristics between S. bungeana and A. gmelinii. Compared with A. gmelinii， S. bungeana had higher root length density （RLD） and root surface area density （RSAD）. In addition， the proportion of very fine roots （diameter， D<0.5 mm） was higher in S. bungeana （94.73%） than in A. gmelinii （90.20%）. Compared with S. bungeana， A. gmelinii had an obvious taproot advantage， with a higher root mass density， mean diameter， and root volume density. The proportions of coarse roots RLD （16.28%） and RSAD （32.85%） were significantly higher in A. gmelinii than in S. bungeana. 2） Compared with bare land， the plots with S. bungeana and A. gmelinii showed significantly better soil structure and stability. The roots of S. bungeana and A. gmelinii were concentrated in the 0-20 cm soil horizon， which had the greatest influence on the physicochemical properties of the topsoil. The soil aggregate stability and soil water retention were highest in the plots containing A. gmelinii， and the mean weight diameter （MWD） （2.04 mm）， capillary water capacity （24.69%）， and saturated water content （34.93%） of soil in those plots were 4.33-times， 1.36-times， and 1.31-times higher than their respective values in soil in bare land. The soil organic matter （SOM） content （7.23 g·kg^-1） was highest in the plots containing S. bungeana. 3） The plant root characteristics significantly affected soil properties. The RLD and RSAD of fine roots had the most significant effect on soil physicochemical properties， and were significantly negatively correlated （P<0.05） with soil bulk density and positively correlated with soil porosity （P<0.05）. The proportion of very fine roots （D<0.5 mm） was significantly positively correlated （P<0.01） with SOM content. The results of principal component analysis showed that the MWD， SOM content， and soil water content were the soil properties showing the largest differences between plots containing S. bungeana and those containing A. gmelinii.

Prediction of the potential distribution of Curcuma in China under current and future climate scenarios

Peng WANG, Zheng JIN, Ting YU, Kang-qiang QIN, Xin-ya SANG, Jian-ping TAO, Wei-xue LUO

2024, 33(10):  14-27.  DOI: 10.11686/cyxb2023435

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Curcuma species are important medicinal herbs in China， and are crucial for the sustainable development of Chinese herbal medicine resources. However， the potential distribution pattern of Cucurma species in China under climate change is still unclear. To study the potential spatial distribution characteristics of Curcuma species under climate change in China， we selected the three most representative species， namely Curcuma phaeocaulis， Curcuma longa， and Curcuma aromatica， for detailed analyses. The MaxEnt model （maximum entropy） and geographic information system （ArcGIS） methods were applied， and along with records of the present distribution of these three Curcuma species and environmental factors in their distribution area such as climate， topography， and soil， were used predict the potential habitat of the three species under current and future climate scenarios. The results showed that the area under receiver operating characteristic curve （AUC） values of the three Curcuma species predicted by the MaxEnt model were all greater than 0.95， indicating that the prediction results had high accuracy. At present， the three species are mainly distributed in the provinces of Yunnan， Guangxi， Guangdong， Fujian， Taiwan， and Hainan， with C. longa having the largest area of suitable habitat and C. aromatica having the smallest. During the 2090s， under the SSP245 climate scenario， there is a trend for all three species to expand their distribution towards the northeast in China with the maximum area of suitable habitat. Under the SSP370 and SSP585 climate scenarios， only small areas of the three species will undergo contraction and expansion of the fitness zone. The mean temperature of the driest season was identified as the key factor affecting the potential distribution of C. phaeocaulis， while the mean annual precipitation was identified as the key factor affecting the potential distribution of C. longa and C. aromatica. In conclusion， the three species of Curcuma are mainly distributed in southern China and will tend to expand northward under climate change. On the basis of these results， the Conservation Departments in some identified provinces can carry out planting to expand the growing area of Curcuma， which will help to enhance the economic and ecological benefits of this genus.

Spatial and temporal distributions of drought on the Loess Plateau during the growing seasons of 2001-2020

Li-jing LIU, Jing WU, Chun-bin LI, Xiu-hong CHANG

2024, 33(10):  28-36.  DOI: 10.11686/cyxb2023470

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Based on MODIS actual evapotranspiration （ET） and potential evapotranspiration （PET） inversion of crop water stress index （CWSI）， the spatial and temporal variability of drought during the growing season in the Loess Plateau was investigated， and bias correlation analysis was conducted between the CWSI and the degree of vegetation cover （NDVI） to investigate the influence of the driest month on the NDVI during the growing season. The results showed that： 1） The multi-year average value of CWSI in the growing season of the Loess Plateau was 0.777， which reflected a moderate drought state， and the spatial distribution showed a pattern of lighter drought in the southeast and more severe drought in the northwest， together with greater drought severity in areas with lower elevation of 1200-1700 m. 2） The overall CWSI in the growing season showed a significant decreasing trend across years from 2001 to 2020， with the drought degree being the highest in 2001 and the lowest in 2018. Within the growing season， the Loess Plateau had the highest degree of drought in April； and the lowest degree of drought in August. Specifically， as the growing season progressed， the drought level transitioned from severe drought to moderate drought and light drought， and then from light drought to moderate drought. 3） Analyzed from the perspective of vegetation types， the surveyed areas of desert and grassland were in severe drought； the surveyed areas of meadow， cultivated vegetation， and scrub were in moderate drought； and the surveyed areas of coniferous and broadleaf forests were in light drought， and the CWSI of the different vegetation types showed a fluctuating and decreasing pattern during the vegetation growing season. The study provides a scientific basis for ecological early warning and drought prediction in the Loess Plateau region.

Point pattern analysis based on null models of populations in fixed sand at the southeastern edge of the Tengger Desert

Wen-jie QU, Lei WANG, Xin-guo YANG, Jian-jun QU, Li ZHANG, Bo ZHANG, Xiang-bo SUN

2024, 33(10):  37-45.  DOI: 10.11686/cyxb2023444

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The spatial distribution patterns of vegetation populations result from the combined effects of populations’ biological characteristics， intraspecific relationships， and interspecific relationships. Understanding the spatial distribution patterns of plants is of great significance for elucidating how plants adapt to their ecological environment， and how populations maintain diversity. In this study， we analyzed vegetation populations in fixed sandy lands on the southeast edge of the Tengger Desert. Areas where the sandy lands have been fixed for 30 to 40 years were selected for analysis. The formation of spatial patterns of five common plant species， namely Eragrostis minor， Setaria viridis， Chloris virgata， Salsola collina， and Grubovia dasyphylla， was analyzed and tested using point pattern analyses. The null models used in the tests of spatial randomness were the complete spatial randomness model， the Poisson cluster model， and the nested double-cluster model. According to the results， the populations were ranked from highest to lowest density， as follows： E. minor， S. viridis， C. virgata， G. dasyphylla， and S. collina. When using the complete spatial randomness null model， the population of E. minor showed a trend towards changing from an aggregated distribution to a uniform distribution and then to an aggregated distribution at the scale of 0-1000 cm.The other four species appeared to have aggregated distributions， and the scale of aggregated distribution reduced as population density decreased. Using the Poisson cluster null model， E. minor， G. dasyphylla， and S. collina showed an aggregated distribution at 0-35 cm scales， but a random distribution at other scales. S. viridis， showed an aggregated distribution at scales of 0-55 cm and 405-835 cm， and C. virgata at scales of 0-75 cm and 465-945 cm， but a random distribution at other scales. Using the double-cluster null model， the five species showed random distributions at 0-1000 cm scales， that is， small clusters were spread across large clusters. In conclusion， the restriction of seed dispersal， the “fertile island” effect of shrubs， and the characteristics of the algal crust may determine the patchiness of populations of common plants in areas with 30-40 years of sand fixation on the southeast edge of the Tengger Desert.

Anatomical and histochemical features of the wetland plants Eremochloa ophiuroides and Hemarthria altissima

Ge-ge QIN, Lian HAN, Xin-yu HE, Yu-sheng WANG, Fan REN, Zi-shun CHEN, Cun-yu ZHOU, Chao-dong YANG, De-bao TAN, Xia ZHANG

2024, 33(10):  46-54.  DOI: 10.11686/cyxb2023453

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Eremochloa ophiuroides and Hemarthria altissima are two wetland plants distributed in the Jianghan Plain area. These two species can survive in both terrestrial and wetland environments， and are able to adapt to seasonal floods in the Jianghan Plain. The selection of wetland plants and flooding-tolerant plants plays an important role in vegetation restoration in the various wetlands and drawdown zone in the middle reaches of the Yangtze River. To explore the mechanisms of water resistance reflected by the differences in anatomy and in structures related to environmental adaptability （e.g.， the aerenchyma and apoplastic barrier） between E. ophiuroides and H. altissima， we studied the anatomical and histological features of the roots and stems of these two species. To explore aspects of anatomy， sections of various plant parts were prepared， subjected to histochemical staining， and observed and photographed under a microscope. The results indicate that： 1） E. ophiuroides and H. altissima have anatomical structural characteristics that allow them to adapt to wetland environments and are typical wetland plants. These structural features include aerenchyma （stem air cavity and root schizo-lysogenic aerenchyma） and apoplastic barriers （endodermis， exodermis， suberization tissue， and cuticles）. The roots of both E. ophiuroides and H. altissima have an endodermis and exodermis， as well as suberized and lignified secondary walls. 2） The stem of H. altissima has a suberized and lignified peripheral mechanical ring and vascular bundle sheath， as well as a pith cavity. The stem of E. ophiuroides has a peripheral mechanical ring that is lignified but not suberized， a sclerenchyma ring and vascular bundle sheath cells， and a pith cavity and cortical aerenchyma. The stolons and rhizomes of H. altissima have a continuous suberized sclerenchyma ring， peripheral mechanical ring， and a vascular bundle sheath. The stolons of E. ophiuroides have a discontinuous lignified （but not suberized） peripheral mechanical ring. These findings indicate that H. altissima is better adapted to a submerged environment than is E. ophiuroides.

Cloning and salt-tolerance functional analysis of alfalfa MsBBX20 gene

Xin-yue ZHOU, Qing-xue JIANG, Hui-li JIA, Lin MA, Lu FAN, Xue-min WANG

2024, 33(10):  55-73.  DOI: 10.11686/cyxb2023460

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The BBX family of transcription factors is involved in plant growth and development processes such as photomorphogenesis， flowering physiology， shade avoidance， seed development， hormone signaling， and responses to environmental stress. Medicago sativa， commonly known as alfalfa， is a forage crop with strong salt tolerance and high forage quality， and has been called the “queen of forages”. Uncovering and investigating the molecular mechanisms of the alfalfa MsBBX20 gene in response to abiotic stress can reveal the biological basis for alfalfa stress resistance and provide new genetic resources for molecular breeding for stress resistance. The MsBBX20 gene cDNA sequence was cloned using RT-PCR and 3′/5′ RACE PCR techniques， and bioinformatics analysis showed that its CDS is 834 bp long， encoding 278 amino acids， and the protein is a member of the zinc finger protein family. The expression pattern of MsBBX20 in different alfalfa tissues and under various abiotic stresses was analyzed using qRT-PCR technique. Subcellular localization was performed by transiently expressing MsBBX20 in Allium cepa epidermis via a gene gun. The MsBBX20 promoter sequence， with a length of 1737 base pairs， was cloned and its cis-acting elements were analyzed. This promoter can efficiently drive the expression of the GUS reporter gene in the leaves， stems， and roots of Nicotiana tabacum. The MsBBX20 promoter sequence was linked to the pCAMBIA-1301 vector containing the GUS gene， and then transiently transformed into N. tabacum and GUS activity in different tissues was analyzed by histochemical staining. A pCAMBIA3301-MsBBX20 plant overexpression vector was constructed and genetically transformed into wild-type Arabidopsis thaliana using the Agrobacterium-mediated method， A. thaliana lines overexpressing MsBBX20 were thus obtained. Transgenic lines of A. thaliana were treated with different concentrations of salt solution （150， 200， and 300 mmol·L^-1 NaCl） and the malondialdehyde （MDA） content and antioxidant enzyme activity of different lines were analyzed. Evolutionary analysis indicated that the MsBBX20 protein of alfalfa is most closely related to the TpBBX20 of red clover （Trifolium pratense）. The MsBBX20 protein is localized to the nucleus. The MsBBX20 gene is most highly expressed in flowers and can respond to various abiotic stresses such as drought， salt， cold， abscisic acid， gibberellin， and light. Transgenic A. thaliana lines overexpressing MsBBX20 were obtained， and three highly expressed positive lines were selected for functional validation. Under different concentrations of NaCl， the MDA content of A. thaliana lines overexpressing MsBBX20 was significantly lower than the control， while the activities of superoxide dismutase， catalase， and peroxidase were significantly higher than the control. The MsBBX20 gene， a zinc finger protein transcription factor from alfalfa， is highly expressed in flowers and can respond to a variety of abiotic stresses and exogenous hormone treatments， indicating that MsBBX20 may be involved in multiple stress response processes in alfalfa. Further research demonstrated that MsBBX20 may enhance the resistance of transgenic A. thaliana to salt stress by regulating the plant’s antioxidant enzyme system， mitigating oxidative damage to plant cells caused by stress， and thereby improving plant salt tolerance.

A study of the mechanism of nitrate nitrogen-induced cytokinin enhancement of strontium enrichment in Avena sativa

Lin QI, Yun BAO, Ying-bo YANG, Xiao-ling WANG, Wei ZHAO

2024, 33(10):  74-82.  DOI: 10.11686/cyxb2023466

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This research investigated the effect of nitrate nitrogen on strontium enrichment ability of oat （Avena sativa） seedlings. The oat variety “Neimengkeyi-1” was used in the experiment. Three levels of strontium （0， 400 and 800 mg·kg^-1） and two levels of nitrate nitrogen （0 and 100 mmol·L^-1） were applied as treatments in a pot experiment. After 30 days of nitrate nitrogen treatment， the strontium uptake and distribution patterns， growth index， and leaf cytokinin concentration of the oat seedlings were examined. It was found that： 1） The dry weight of oat seedlings decreased with increasing concentration of strontium. However， nitrate nitrogen alleviated the inhibitory effect of the strontium on the growth of the oats. 2） The ability of oat tissues to accumulate strontium ranked： root>leaf>stem. Nitrate nitrogen promoted the accumulation of strontium and increased the strontium translocation of strontium within oat seedlings. 3） The cytokinin concentration increased with increase in the nitrate nitrogen concentration. The cytokinin concentration was positively correlated with the translocation factor. In conclusion， capacity for strontium accumulation was strongest in the roots. Nitrate nitrogen enhanced increase in cytokinin concentration on exposure to strontium and the resistance to strontium in oats. This study provided data applicable to strengthening phytoremediation of strontium contaminated soil.

A multi-trait evaluation of production performance and nutritional quality of different oat varieties in the Sanjiangyuan area

Jin-lan WANG, Xiao-jun WANG, Qi-lin LIU, Guo-ling LIANG, Ze-liang JU, Hong-mei SHI, Xiao-bing WANG, Pei WEN, Qingmeiranding, Wen LI

2024, 33(10):  83-95.  DOI: 10.11686/cyxb2024038

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The objective of this research was to identify oat （Avena sativa） varieties providing high yield and quality， suitable for planting in the Sanjiangyuan area. Fifteen oat varieties were selected for testing， and their agronomic traits， yield traits and quality traits evaluated， in connection with oat variety introduction in Banma County and Zhiduo County. The piecewise structural equation model was used to explore how varieties， region and their interactions affected nutritional quality via agronomic traits and yield traits， and a multi-criterion decision model-TOPSIS （technique for order preference by similarity to an ideal） was used to perform an integrated evaluation of the various indexes of tested oat varieties， thus identifying varieties with high performance and suitable for planting in the Sanjiangyuan area， and providing supporting data for forage production in this area. It was found that： None of the 15 oat varieties achieved seed maturity and completed the growth period. The plant height of A. sativa cultivars Qingyan No.2， Qingyan No.5 and Qingyin No.1 （82.2-89.7 cm） were higher than other oat varieties. The hay yields of A. sativa cultivars Qingyan No.4， Qingyan No.3 and Qingyan No.5 （1012.3-1167.1 g·m^-2） were highest， while the crude protein contents of A. sativa cultivars Qingyin No.2， Longyan No.1 and A. sativa cv. Qingyan No.5 （7.6%-8.1%）. were higher than those of other varieties. The cultivar Qingyan No.5 had lower stem∶leaf， acid detergent fiber and neutral detergent fiber contents， and accordingly relative feeding value was higher than other cultivars. The sructural equation model analysis showed that varieties， region and their interactions indirectly affected the nutritional quality of oats， mainly through oat yield and height. The integrated multi-trait evaluation using a TOPSIS model showed that A. sativa cultivars Qingyan No.5 and Qingyan No.3 not only provided high yield performance， but also had high nutritional quality. These two oat varieties are therefore recommended for planting in the Sanjiangyuan area.

Effects of 3-indoleacetic acid on lead accumulation and physiological properties of Cynodon dactylon under lead stress

Cheng-qiang ZHU, Shao-fu WEN, Run-hai JIANG, Mei ZHANG, Zhi-hong CAI, Yue-chen HE, Xin CHEN, Xiu-li HOU

2024, 33(10):  96-107.  DOI: 10.11686/cyxb2023463

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This research explored the stress alleviation effect of exogenous auxin in Pb-stressed plants of Cynodon dactylon， a naturally lead tolerant species， and the underlying physiological mechanism. In a pot experiment， the foliar surface of C. dactylon under 324.4 mg·kg^-1 soil Pb stress was sprayed with different concentrations （0， 1， 10， and 100 mg·L^-1） of 3-indoleacetic acid （IAA） along with 5 and 10 mg·L^-1 of polar transport inhibitor of IAA （NPA）. Plant growth， physiological response， Pb accumulation in the roots， and its translocation to the shoots were systematically investigated. The findings demonstrated that exogenous IAA significantly increased the contents of IAA and cytokinin （CTK）， and lowered the abscisic acid （ABA） level and indoleacetic acid oxidase （IAAO） activity， which promoted an increase in plant height， root length， and above- and belowground dry weight of C. dactylon under Pb stress. Among the different IAA treatments， foliar spraying of 10 mg·L^-1 IAA exhibited the most pronounced stress alleviation effect. Compared to the control， foliar spraying of 10 mg·L^-1 IAA increased plant height， root length， aboveground and belowground dry weight by 32.4%， 30.1%， 32.2%， and 25.5%， respectively. Meanwhile， the contents of chlorophyll a， chlorophyll b， and carotenoids in plants treated with 10 mg·L^-1 IAA were 1.35， 1.36， and 1.21 times those in the control， and the contents of Ca²⁺ and soluble protein in leaves and roots were also significantly increased. Foliar spraying of 10 mg·L^-1 IAA also improved the antioxidant indexes in C. dactylon， which was demonstrated by the significantly decreased malondialdehyde （MDA） content and increased peroxidase （POD） activity as compared to the control treatment. More importantly， foliar spraying of 10 mg·L^-1 IAA promoted the adsorption of Pb by roots， and inhibited the Pb translocation from root to shoot. In contrast， foliar spraying of NPA aggravated the growth inhibition effect of Pb on C. dactylon. This effect exerted dose dependence on NPA， with 10 mg·L^-1 NPA exhibiting the strongest inhibitory effect， as well as reducing the chlorophyll fluorescence， and decreasing photosynthetic pigment contents， and increasing the shoot uptake of Pb， which led to a rise of MDA content. In summary， foliar spraying of 10 mg·L^-1 IAA exerted the best growth promotion and stress alleviation effects on C. dactylon. Exogenous IAA improved C. dactylon plant growth by stimulating hormone mediated stress response， enhancing photosynthetic capacity， and promoting anti-oxidative capacity. Exogenous IAA also increased cellular Ca²⁺ and soluble protein contents， which impeded the translocation of Pb from root to shoot， ultimately decreasing the level of membrane lipid peroxidation and oxidative damage induced by Pb stress. The results from the present study extend knowledge of mechanisms underlying Pb tolerance of C. dactylon and indicate a strategy for alleviating Pb poisoning in plants by applying exogenous IAA.

Diversity of seed-borne fungi in Phleum pratense and their effects on seed germination and seedling growth

Qin SHEN, Rong-chun ZHENG, Zhi-biao NAN, Ting-yu DUAN

2024, 33(10):  108-122.  DOI: 10.11686/cyxb2023383

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Timothy grass（Phleum pretense） is a perennial， tufted grass belonging to the Poaceae family. It is commonly used as a forage crop， and is highly valued for its productivity and high quality as forage. It is a significant source of pasture and income for herders in Min County， Gansu Province， China. However， little is known about the diversity and pathogenicity of seed-borne fungi in timothy grass. In this study， we used a combination of traditional culture-based methods and high-throughput sequencing to investigate the diversity and pathogenicity of seed-borne fungi in timothy grass. Using traditional culture-based methods， 13 fungal species in nine genera were isolated from the three tested Timothy grass varieties. The five most commonly isolated species were Alternaria alternata， Fusarium avenaceum， Lichtheimia corymbifera， Epicoccum nigrum， and Aspergillus chevalieri. High-throughput sequencing revealed the presence of fungi from 27 genera across two phyla， predominantly Ascomycota and Basidiomycota， including genera such as Alternaria， Aspergillus， Phaeosphaeria， and Fusarium. At the species level， the prevalent species were A. alternata， Gibberella avenaceum， Mycosphaerella tassiana， Alternaria metachromatica， and Parastagonospora nodorum， and there were significant differences in the α and β diversity of the seed-borne microbial community among the three tested timothy grass varieties. Eight of the seed-borne fungal isolates significantly reduced the germination rate （by 9.78%-30.67%） and vigor （by 10.69%-32.08%） of timothy grass seeds （P<0.05）. Aspergillus pseudoglaucus resulted in the lowest germination rate of timothy grass seeds， while A. alternata and A. pseudoglaucus significantly increased the mold rate of seeds. The findings of this research provide a theoretical basis for the utilization of timothy grass and the prevention of seed-borne diseases.

Evaluation of resistance of different alfalfa varieties to Paraphoma root rot

Shi CAO, Hui-xia LI, Shou-rong CAO

2024, 33(10):  123-134.  DOI: 10.11686/cyxb2024001

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Alfalfa （Medicago sativa） Paraphoma root rot （APRR） is a disease previously unknown in the world that has been identified and reported by our research team. This study evaluated the disease resistance of 30 different alfalfa varieties to root rot caused by Paraphoma radicina. In this evaluation， the incidence rate， disease index， height， root length， and above- and belowground biomass per plant were determined for 30 different alfalfa varieties， both domestic and international， after inoculation with P. radicina through root dipping. The standard deviation coefficient allocation weighted method was used to provide a multivariate evaluation of their resistance to the disease. The D value represents the comprehensive evaluation of each variety’s disease resistance. A higher D value indicates greater resistance， while a lower D value indicates lower resistance. The study found that the M. sativa varieties Longwei 3010， Magnum Ⅱ and Gannong No.3 had composite evaluation values （D） of 0.972， 0.955， and 0.916， respectively. All three varieties showed high resistance to APRR， with D values greater than 0.9. Caoyuan No.3 and Gongnong No.1 exhibited poor disease resistance， with D values of 0.003 and 0.113， respectively， both less than 0.2. The other tested varieties had intermediate disease resistance. The study has identified three varieties with strong disease resistance to APRR， providing husbandry information for alfalfa production and the prevention and control of the disease by planting resistant varieties.

Exogenous melatonin mediates the antioxidant system and phenylpropanoid metabolism to induce resistance to leaf spot disease in oat

Zheng WANG, Xin LI, Jian-gui ZHANG, Ji-kuan CHAI, Gui-qin ZHAO, Kui-ju NIU

2024, 33(10):  135-146.  DOI: 10.11686/cyxb2023426

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The aim of this work was to determine how exogenous melatonin affects the resistance of oat （Avena sativa） to leaf spot disease caused by the pathogen Drechslera avenae. Seedlings of the oat cultivar ‘Molasses’ were subjected to foliar spraying with melatonin （0， 10， 100， 250， 500， and 1000 μmol·L^-1） followed by inoculation with the pathogen. At 9 days after inoculation， the disease index was calculated， and physiological indicators and the transcript levels of genes related to the antioxidant system and phenylpropanoid metabolism were determined. The results showed that leaf spot disease significantly inhibited oat plant growth， but the disease index was significantly decreased when melatonin was applied. The degree to which the disease index was decreased differed depending on the melatonin concentration. The in vitro induction efficiency of the pathogen， the activities of catalase and phenylalanine ammonia lyase， and the transcript level of the gene encoding ascorbate peroxidase were highest in the 100 μmol·L^-1 melatonin treatment， and were 50.72%， 80.32%， 3.88%， and 148.00% higher than their respective values in the control. The lowest superoxide anion production rate and malondialdehyde content were in the 250 μmol·L^-1 melatonin treatment， and were 28.27% and 86.62% lower than their respective values in the control. Compared with the control， in the 250 μmol·L^-1 melatonin treatment， the activities of superoxide dismutase， peroxidase， ascorbate peroxidase， cinnamic acid-4-hydroxylase， and 4-coumaric acid∶CoA ligase were increased by 128.23%， 137.14%， 74.00%， 52.65%， and 26.73%， respectively； the contents of lignin， total phenols， and flavonoids were increased by 1.40%， 10.33%， and 13.70%， respectively， and the transcript levels of genes encoding superoxide dismutase， peroxidase， catalase， phenylalanine ammonia lyase， 4-coumaric acid∶CoA ligase， and cinnamic acid-4-hydroxylase were increased by 352.56%， 80.32%， 65.71%， 26.65%， 52.65%， and 20.11%， respectively. Seedlings treated with 500 μmol·L^-1 melatonin showed the lowest hydrogen peroxide content （75.45% lower than that in the control） and the highest chlorophyll content （81.35% higher than that in the control）. According to the above results， the best concentration of melatonin for inducing resistance to leaf spot in oat plants is 250 μmol·L^-1. The results of this study demonstrate a new approach for the control of leaf spot disease in oat.

Effects of rotation with a green manure crop on soil quality and microbial nutrient limitation in a tobacco field in Yunnan

Wen-jun ZHAO, Rui LIU, Zheng-xu WANG, Yu FENG, Kai-zheng XUE, Kui LIU, Zi-he XU, Wei-dong CAO, Li-bo FU, Mei YIN, Hua CHEN

2024, 33(10):  147-158.  DOI: 10.11686/cyxb2023431

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We investigated the effects of rotating tobacco （Nicotiana tabacum） with green manure crops， with an aim to provide theoretical and technical support for selecting suitable green manure for rotation systems in tobacco fields in Yunnan Province. The field experiment， which started in 2017， aimed to test the effects of green manure rotation on tobacco yield， soil quality， nutrient cycling-related enzyme activity， and microbial nutrient limitations in a tobacco field. The experiment consisted of four treatments， i.e.， winter fallow-tobacco rotation （WF）， radish （Raphanus sativus）-tobacco rotation （RD）， smooth vetch （Vicia villosa）-tobacco rotation （SV）， and ryegrass （Lolium perenne）-tobacco rotation （RG）. Compared with the WF treatment， the SV treatment increased tobacco yield by 6.8% in 2019； and the RD and SV treatments increased tobacco yield by 6.4% and 8.4% in 2022， respectively. Compared with 2019， in 2022， the soil organic matter （SOM）， total nitrogen （TN）， available phosphorus （AP） and available potassium （AK） contents were increased， but the soil pH value and total phosphorus （TP） contents were decreased. In 2022， compared with the WF treatment， the SV treatment decreased the TP content by 22.9%， and the RG treatment increased the SOM and AK contents by 9.7% and 73.6%， respectively. Additionally， compared with the WF treatment， the RD， SV， and RG treatments increased soil nitrate-nitrogen contents by 97.1%， 75.9%， and 26.0%， respectively， and increased the dissolved organic nitrogen contents by 228.8%， 85.0%， and 96.7%， respectively. Overall， the soil quality area index was significantly higher in the RD and RG treatments （by 27.0% and 15.6%， respectively） than in the WF treatment. Compared with the WF treatment， the green manure rotation treatments significantly increased the activities of carbon metabolism-related enzymes （β- glucosidase， β-xylosidase， α-glucosidase） by 48.8% to 262.1%， the amount of the nitrogen-related compound L-leucine-7-amido-4-methyl coumarin by 59.3% to 125.0%， and the activity of a phosphorus-related enzyme （alkaline phosphatase） by 312.0% to 435.9%. Compared with the WF treatment， all of the tobacco-green manure rotation treatments resulted in reduced microbial carbon limitation， but increased microbial phosphorus limitation. In conclusion， rotation of tobacco with smooth vetch and radish increased tobacco yield and improved soil quality in the tobacco field. These rotations proved to be effective methods to achieve clean tobacco production and sustainable soil management in the tobacco fields of Yunnan Province.

Optimization of extraction process of Neolamarckia cadamba leaf polyphenols and its effect on Stylosanthes guianensis silage

Pei-shan HUANG, Mei-qi ZANG, Wei-ling ZHANG, Jun-jian CHEN, Li-xuan LIU, Qing ZHANG

2024, 33(10):  159-170.  DOI: 10.11686/cyxb2024016

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The purpose of this study was to investigate the optimal ultrasonic-assisted extraction conditions of Neolamarckia cadamba leaf polyphenols （NCLP） and its effect on Stylosanthes guianensis silage quality. The Box-Behnken design experiment in response surface analysis was used to optimize the process conditions of ultrasonic-assisted extraction ofNCLP. There were 3 treatments in the silage experiment： No addition （control， CK）， 1%NCLP and 2% NCLP. After 30 days of ensiling， the nutrient composition and fermentation quality of S. guianensis silages with the above three treatments were measured. The results showed that the optimum extraction conditions were： a methanol concentration of 71%， a liquid∶solid of 30 mL·g^-1， an extraction time of 37 min， and ultrasonic power of 250 W. Under the optimal conditions， the NCLP content was 136.82 mg Gallic acid equivalent（GAE）·g^-1 DM. Compared with the control group， the NCLP addition treatments significantly reduced（P<0.01） the pH value， ammonia nitrogen content and rate of dry matter loss in S. guianensis silage， and significantly increased（P<0.01） lactic acid bacteria number， lactic acid and acetic acid content. Furthermore， the addition of 2% NCLP caused a significant decrease in the content of neutral detergent fiber and acid detergent fiber of the silage （P<0.05）， while the contents of true protein increased significantly （P<0.05）. In conclusion， the study obtained the optimum extraction process for the NCLP and found that NCLP had a positive effect on the fermentation quality of S. guianensis leaf silage， and the effect of 2% NCLP was better than that of 1% NCLP.

The important role of oat in reinforcing the foundation of food security

Qing-ping ZHOU, Xiao-wei HU, Hui WANG, You-jun CHEN

2024, 33(10):  171-182.  DOI: 10.11686/cyxb2023439

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In this study， we analyzed the role of oat as a dual-purpose crop in reinforcing the foundation of food security. There is an emphasis on a food crop production strategy based on forage， taking into account an all-encompassing approach to food， including territorial resource development and utilization， ecological balance， and international and domestic markets. Oat， as a dual-purpose crop， is recommended to farmers in China. Oat grain is essential for food security and is considered to be a staple and functional food. Meanwhile， oat hay is a premium forage for ruminants. Feeding oat hay to animals can increase the quality of animal products， relieve pressure on other feed grains， and contribute to a diversified food security system. Furthermore， because oat plants are resistant to cold， drought， and poor soils， the potential to grow oat crops in medium- and low-yield fields， idle winter fields， and the degraded grassland needs to be explored further. In a food crop production strategy based on forage， a combination of oat grain for food security and oat hay for the forage industry can lay a solid foundation for food security and promote territorial resource development and utilization， thereby contributing to the development of modern agriculture in China.

The dialectical relationship between “sourcing food from croplandstoring grain in the land” and “sourcing food from grasslandstoring grain in the grass” from the perspective of agricultural ethics——On the “Farmland Protection” in chapter Chapter 2 of the Food Security Law

An ZHAO, Ying BAI

2024, 33(10):  183-193.  DOI: 10.11686/cyxb2023423

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From the perspective of agricultural ethics， there is a complementary and win-win relationship between sourcing food from cropland and sourcing food from grassland through forage for animal production. Focusing on Chapter 2， “Farmland Protection，” of the Food Security Law promulgated in 2023， it is believed that farmland protection is not about preserving area only， but also about preserving water， soil， fertilizer， diverse planting practices， and the diversity of agricultural systems. In this study， a combination of several research methods including a literature review， field research， and case studies， was used to understand the interaction between the rigid constraints of resources such as cultivated land area and quality， structural problems relating to the unsuitability of particular land areas for crop planting， and the unsustainable expectation of continuous incremental increase in crop yields over time. Achievements have been made in scientific research， and in policies to improve cultivated land and increase the amount of reserve land， through diversified planting of food crops of various kinds and forages. Six counties in the Yellow River Basin were selected for surveys of food and forage crop rotation and replanting. Various categories of farm system were studied， including： systems with two crops per year， intercropping of different species， and mixed food crop and silage production. Three commonly practiced farming systems were taken as case studies： alternate-row mixed cropping of food and forage plants， broadcast-sown mixed food and forage species crops， and monoculture forage crops. Our results indicate that changes in the patterns and technology of crop and forage planting are the key to changes in future organization of the agricultural sector. Especially after the annual grain yield reaches the food safety threshold of 400 kg per person， higher grain production targets should not be pursued， but instead the “forage for animal production” strategy should be implemented in a timely manner to protect farmland. A focus on forage production for animal husbandry is more conducive to enhanced agricultural ethics outcomes and represents an innovative application of ethics in plant production. It is recommended to separately calculate the planting of human food and animal forage crops， and to develop a diversified planting model for these two categories of crops， according to local conditions.

Effect of bacterial enzyme complexes on the quality of silage made from Chinese medicine crop residues

Tian-xin GUO, Shi-shi RUAN, Xiang GUO, Jia-qi ZHAN, Qiu-yu LIANG, Xiao-yang CHEN, Wei ZHOU, Qing ZHANG

2024, 33(10):  194-202.  DOI: 10.11686/cyxb2023422

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The aim of this study was to investigate the effects of adding different enzymes and Lactobacillus plantarum （LP） on the dynamics of silage fermentation and the quality of silage made from Chinese medicine residues. Residues of four Chinese medicine plant species （Astragalus sp.， Dioscoreae rhizome sp.， Poria cocos sp.， and Bupleuri radix sp.） were mixed with different combinations of LP and enzymes ［cellulase （CE）， pectinase （PE）， and xylanase］， and the fermentation quality of these silages and a blank control （CK） was analyzed after 3， 7， 15， and 34 days of ensiling. The results showed that after 34 days of ensiling， the pH value and fiber content were significantly lower （P<0.05）， and the soluble carbohydrate content was significantly increased （P<0.05） in the treatment groups compared with CK. The addition LP and enzymes significantly reduced the neutral detergent fiber and acid detergent fiber contents of Chinese medicine crop residues during ensiling. During the ensiling period， the soluble carbohydrate content increased in the LP+CE treatment group， and the amount of ammonia nitrogen was significantly lower in the LP+CE and LP+PE treatment groups than in CK， indicative of a lower rate of protein degradation. Thus， the addition of LP and enzymes effectively improved the quality of silage made from Chinese medicine crop residues.