Table of Content

20 July 2020, Volume 29 Issue 7

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Optimizing oat irrigation schedules in an alpine region using APSIM

MA Qian-hu, ZHANG Xue-mei, WANG Zi-kui, YANG Hui-min

2020, 29(7):  1-10.  DOI: 10.11686/cyxb2019455

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This research investigated optimization of irrigation schedules for oat production in an alpine region located in Haixi Prefecture of Qinghai Province, to provide technical guidance for oat production in the region. A field experiment was carried out at Jintai Farm in Wulan County, Qinghai Province, in 2017 and 2018. No irrigation was applied in 2017. Four irrigation treatments were set up in 2018: one irrigation at flowering stage (I₁), two irrigations at tillering stage and jointing stage (I₂), three irrigations at tillering stage, jointing stage and flowering stage (I₃), and no irrigation (N_I). Water applied at each irrigation was 50 mm. The APSIM (Agricultural Production Systems Simulation) model was calibrated with the data in I₃ in 2018, and validated with the data from the other irrigation treatments in 2018 and from unirrigated plantings in 2017. The yield and water use under different irrigation scenarios in different years were then simulated, and the optimal irrigation schedule for oat cropping in the study region was modelled. It was found that the highest yield and water consumption (significantly different from other treatments) occurred in I₃ in 2018, while, the water use efficiency was highest in I₂. Dry matter yield in 2017 was higher, and water use efficiency greater than in the treatments I₂, I₁ and N_I in 2018. The root mean squared error (RMSE) of the simulated and measured values of dry matter yield and soil moisture were 0.94 t·hm^-2 and 4.96 mm respectively in model calibration, and were 1, 3, 4 and 8 d in the four key phenological periods (sowing-emergence, sowing-flowering, sowing-filling and sowing-harvesting). The RMSE of the simulated and measured values of dry matter yield and soil moisture were 1.03 t·hm^-2 and 7.13 mm respectively in model validation, and were 1, 1, 5 and 10 d in the four key phenological periods in 2017. The results showed that APSIM-oat, after calibration, was reliable in simulating soil water content and yield. The calibrated model was used to simulate the dry matter yield, water use efficiency and irrigation water production efficiency of oats under 10 irrigation scenarios. The results showed that a scenario involving irrigation at tillering and jointing, with 50 mm water applied at each irrigation, was the optimal irrigation regime in 2017. (In 2017, annual rainfall was below average, while in 2018 annual rainfall was above average. The results have reference value for water-saving irrigation management of forage oat plantings in the study area.

Soil structure and fractal characteristics of different land categories in a karst rocky desertification area

LUO Nan, SHU Ying-ge, CHEN Meng-jun, XIAO Sheng-yang

2020, 29(7):  11-22.  DOI: 10.11686/cyxb2019522

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This research studied soil properties in different stages of grassland ecological restoration in a karst area. Specifically, the size distribution of soil particles, and the fractal dimension of soil aggregates and micro-aggregates were evaluated for farm cropland (FC), land in conversion from cropland to grassland (CCG), grassland (G), and forest and grass intercropped land (FGI), in a karst mountainous. These four spatially separated land categories were considered to represent a land restoration time series. Results were obtained from a combination of field sampling and laboratory analysis, and the relationship between fractal dimension of soil aggregates and soil physical and chemical properties was also analyzed. It was found that during the process of ‘rocky desertification restoration', the proportion of larger-diameter micro-aggregates and aggregates increased across the ecological restoration time series, while the proportion of smaller-diameter soil peds decreased. However, the mechanical composition of soil showed an opposite trend. The mean weight diameter (MWD) ranking of soil micro-aggregates in 0-10 cm soil layer was: FGI=G>FC>CCG. Quantitatively, the MWD of soil micro-aggregates in CCG was 0.15, 0.15 and 0.11 lower than other grassland types, which was 0.15, 0.15 and 0.11 lower (P<0.05), respectively, than that of FGI, G, and FC land. Soil micro-aggregate MWD in 10-20 cm soil layer ranked G>FGI>FC>CCG, and values for CCG were 8.26% and 13.18% lower (P<0.05), respectively, than those for FGI and G. The soil structure characteristics were weakest in CGC land. Across the ecological restoration time series, the fractal dimensions of soil micro-aggregates and aggregates ranked in descending order: CCG>FC>FGI>G, while the fractal dimensions of soil particles ranked in descending order: G>FGI>FC>CCG. These results indicate that soil structure in this karst mountain area is gradually improved with ecological restoration, and the soil fractal dimensions reflect soil restoration status in the karst rocky desertification area to some extent. At the same time, the fractal dimension of these soils correlates well with their physical and chemical properties. The fractal dimension of micro-aggregates and aggregates can better represent the strength of soil structure and erosion-resistance. In the process of ecological restoration and control of rocky desertification, human input that shortens the time needed to return farmland to grassland or accelerates increase of vegetation coverage, can effectively reduce soil erosion and improve the ecological environment of the region.

Effects of seasonal regulation of grazing intensity on soil erosion in desert steppe grassland

SUN Shi-xian, DING Yong, LI Xia-zi, WU Xin-hong, YAN Zhi-jian, YIN Qiang, LI Jin-zhuo

2020, 29(7):  23-29.  DOI: 10.11686/cyxb2019409

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Overgrazing is an important cause of grassland degradation and desertification affecting large land areas. The aim of this project was to investigate the effects on soil erosion of seasonal regulation of grazing intensity. Litter biomass, sand collection in winter and spring and the particle size of the soil surface layer were evaluated under six grazing intensity treatments in Stipa breviflora desert steppe in a randomized complete block design. It was found that: 1) The more that litter biomass was preserved in winter and spring, the stronger the sand-fixation ability of the grassland, and the proportion of ‘flow sand' under moderate grazing intensity (45.16%), which was lower than that of heavy grazing. 2) With increase in grazing intensity, the amount of loose sand of various particle sizes increased significantly. Severe grazing increased the proportion of particles of size >0.25 mm and <0.05 mm, compared to that of ungrazed or lightly grazed treatments, while the proportion of particles sized 0.25-0.10 mm was lowest under severe grazing. 3) Heavy grazing in autumn increased the amount of loose sand in grassland. Therefore grazing practice in desert grassland should be to reduce stocking rate in autumn. Based on these results, it was concluded that unreasonable grazing utilization of grassland reduces the windbreak and sand fixation capacity of the vegetation, resulting in surface roughening. In the desert steppe, maintenance of no less than 32.93 g·m^-2 litter in winter and spring was conducive to reducing wind erosion.

Water distribution characteristics of soil profiles in five land use types under rotational cropping in the Hill and Gully Regions on the Loess Plateau

MA Tao, LV Wen-qiang, LI Ze-xia, CHEN Ai-hua, DONG Yan-li

2020, 29(7):  30-39.  DOI: 10.11686/cyxb2019582

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In order to explore the water distribution characteristics of soil profiles in the cropping systems in the Hill and Gully Regions on the Loess Plateau, five land use categories were selected for study: Mulched corn field (YMD), fallow 2 years (XGA), fallow 4 years (XGB), waste grassland (HCD), and alfalfa field (MXD); and the soil moisture content was measured in various soil layers to 200 cm depth. It was found that, for the 0-20 cm soil depth at P<0.05, the soil moisture content of the five land use categories ranked YMD>XGA>XGB>HCD=MXD. Soil moisture content for the 0-20 cm soil depth in the YMD category was 20.28%, and exceeded that in categories XGA, XGB, HCD, MXD by factors of 1.38, 1.40, 1.94 and 2.91, respectively. With increase in soil depth, the soil moisture profile of YMD showed a ‘double-peak' pattern. Soil moisture content in HCD and MXD categories decreased with depth in the upper layers, to a value stable across the deeper layers. For XGA and XGB categories, the trend in soil moisture content with increasing depth was an initial increase, followed by a zone of decrease with depth, and then basically stable with increasing depth. Soil moisture spatial variability in all layers of XGA and MXD categories was moderate, and low in HCD. For YMD, soil moisture spatial variation was moderate, except for the soil layers 80-100 cm and 180-200 cm, which had low variation. For XGB, soil moisture contents of the 0-180 cm soil layers were moderately variable, but the soil moisture variation of the 180-200 cm soil layer was greater. Across the 200 cm soil depth surveyed, the average coefficient of variation for water content of the soil profile of the 0-200 cm layer was 40.75%, 38.02%, 30.91%, 27.06%, 4.12%, respectively, for XGB, XGA, MXD, YMD and HCD, land use categories. Soil water use in XGA and XGB land use categories was primarily from the 0-40 cm soil layers, while in HCD it was from the was 0-20 cm soil layer; for YMD it was from 0-120 cm; for MXD, it was from 0-40 cm and from 120-200 cm. The rotational fallow system has important effects on soil profile moisture differences, spatial variation in soil moisture, and grading. The soil moisture conditions under mulched corn were the best, and the information from this study provides a theoretical basis for the optimal allocation of land use patterns and design of crop rotation fallow patterns in the Hill and Gully Regions on the Loess Plateau.

Effects of four different soil-covering measures on vegetation restoration of coal mine spoils in an alpine area

WANG Rui, LI Xi-lai, ZHANG Jing

2020, 29(7):  40-51.  DOI: 10.11686/cyxb2019446

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Reconstructing the soil matrix by covering coalmine spoils with soil is a key method for ameliorating the soil properties of the spoils, and accelerating vegetation recovery in minefields located in high-elevation frigid areas. In this study, a field experiment was conducted in the Shengxiong coal minefield at Muli, Qinghai Province. Field experiment treatments involved covering coalmine spoil with soil to four depths [0 (Control), 5, 10, and 15 cm] to identify the outcomes in each case and identify optimal vegetation restoration methods. Five forage species were trialed in this study: Elymus nutans, Festuca sinensis, Poa crymophila var. ‘Qinghai', Poa pratensis var. ‘Qinghai', and Puccinellia tenuiflora. It was found that ground cover of E. nutans was the highest among the tested species, and its height increased with time. The average vegetation cover after 3 years for the four soil cover treatments ranked: 15 cm (74.6%)>10 cm (70.8%)>5 cm (64.3%)>control (58.8%). During the study period, the difference in plant density between different treatments became progressively more significant. There was an extremely significant difference in the yield of aboveground biomass between the control plot and the soil-covered plots (P<0.01). The highest yield of aboveground biomass (453.6±38.4) g·m^-2 occurred in the treatment with 10 cm soil cover. This was nearly 2 times higher than in the control treatment. A significantly positive correlation was observed between soil nitrogen concentration and height (r= 0.578) and density (r=0.6198) of herbage (P<0.05). Similarly, there was an extremely significant positive correlation between aboveground biomass yield and soil available nitrogen content (r=0.839, P<0.01). In turn, soil organic matter content was significantly correlated with plot biomass yield (r=0.592, P<0.05). It is estimated that the cost of covering with soil to 5, 10 and 15 cm depth is, respectively, 20000, 40000 and 60000 CNY·hm^-2. The results demonstrate that soil covering can effectively promote plant growth and improve the height, ground cover and density of vegetation. Soil covering of mine spoil to 10 cm depth is an economical and effective method to restore the vegetation in open mining areas in alpine grassland.

QTL analysis of tiller number in Miscanthus

WANG Yan-cui, YU Wei-li, WANG Shu-kai, GE Chun-xia, ZHANG Guo-bin, CHEN Cui-xia

2020, 29(7):  52-59.  DOI: 10.11686/cyxb2019456

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Miscanthus is a tall, perennial plant of the grass family, with highly efficient C₄ photosynthesis and therefore has potential to become an important bioenergy crop. Tiller number is one of important agronomic traits of Miscanthus and plays an extremely important role in yield regulation. We used two established interspecific genetic linkage maps of Miscanthus floridulus and M. sacchariflorus for quantitative trait locus (QTL) analysis of tiller number, together with the tiller number phenotype data from Tai'an in 2014, 2015 and Dongping in 2015. Results showed that the frequency of the tiller number phenotype followed the normal distribution of continuous variation, according with the hereditary characteristics of quantitative traits. A total of sixteen QTLs were identified for tiller number using a multiple-QTL model. The single QTLs explained 11.4%-21.5% of the phenotypic variation and the logarithm of odds (LOD) values of these QTLs ranged from 3.06 to 6.09. Three of the QTLs were detected repeatedly 3 times: qmfTI-2 explained 12.7%, 12% and 15.5% of the phenotypic variation, qmsTI-1 explained 12%, 12.1% and 19.8% of the phenotypic variation and qmsTI-2 explained 21.5%, 20.2% and 13.4% of the phenotypic variation. Three of the QTLs were detected twice, of which qmfTI-1, qmfTI-3 and qmsTI-4 explained, respectively, 12.4% and 11.4%, 13.8% and 13.2%, and 12.1% and 14.3% of the phenotypic variation. Through the QTL analysis of tiller number of Miscanthus, our study provides a good foundation for molecular marker-assisted breeding and improvement of Miscanthus germplasm resources.

Cloning, subcellular localization and expression analysis of the RVE8 gene from Festuca arundinacea

LUO Wei, SHU Jian-hong, LIU Xiao-xia, WANG Zi-yuan, MU Qiong, WANG Xiao-li, WU Jia-hai

2020, 29(7):  60-69.  DOI: 10.11686/cyxb2019452

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The circadian clock is a complex regulatory network that promotes plant growth in the ever-changing environment. REVEILLE8 (RVE8) is an important gene in the circadian clock. In order to explore the molecular mechanism, the FaRVE8 gene of leaves from Festuca arundinacea was cloned by RT-PCR and RACE. It was found that the full length of FaRVE8 was 1881 bp, the open reading frame was 1236 bp, encoding 411 amino acids, which belonged to a MYB-like factor. The phylogenetic analysis showed that it is closely related to Brachypodium distachyon, Aegilops tauschii, and Hordeum vulgare. Real-time fluorescence quantitative analysis of FaRVE8 expression in F. arundinacea leaves under different light treatments showed that FaRVE8 was expressed under different light treatments and showed obvious circadian rhythm. Subcellular localization indicated that FaRVE8 is localized in the nucleus, and FaRVE8 may play an important role in the nucleus. These above studies indicate that the FaRVE8 gene plays an important role in regulating biological rhythms, laying the foundation for further study of the function and molecular regulation mechanisms of the FaRVE8 gene.

Effect of exogenous abscisic acid on seedling establishment of Epichloё gansuensis-Achnatherum inebrians symbiont

CUI Xue-lian, XIA Chao

2020, 29(7):  70-80.  DOI: 10.11686/cyxb2019570

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Achnatherum inebrians is a perennial bunchgrass of the Poaceae family, widely dispersed in the arid and semi-arid grasslands of northwest China. It forms a reciprocal symbiosis with Epichloё endophyte. The presence of the endophyte provides A. inebrians strong resistance to various stresses, making it more competitive. Both seed germination and seedling growth are important stages of plant growth, determining the future competitiveness of plants. In the present study, a gradient of five different abscisic acid (ABA) concentrations was set up to explore how exogenous ABA affects endophyte-infected (E+) and endophyte-free (E-) A. inebrians seed germination and seedling growth. It was found that the germination rate, embryo length and radicle length of both E+ and E- A. inebrians seeds were significantly promoted when treated with 2.0 mg·L^-1 ABA solution. The net photosynthetic rate, root:shoot ratio, root area, root diameter, root volume and number of roots of the seedlings were higher when treated with 1.0 mg·L^-1 ABA than those in the CK group. In contrast, the germination A. inebrians seeds and seedling growth were inhibited when treated with 4.0 mg·L^-1 ABA solution. These results indicate that the interaction between Epichloё endophyte and an appropriate concentration of ABA improves seeds germination and seedling growth, and enhances the photosynthetic capacity of A. inebrians.

Potential allelopathic effects of water extracts of three grasses on germination of their own seeds and seedling growth

LIANG Jun, QUAN Xiao-long, ZHANG Jie-xue, SHI Hui-lan, DUAN Zhong-hua, QIAO You-ming

2020, 29(7):  81-89.  DOI: 10.11686/cyxb2020031

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Knowledge of the allelopathic potential of grass species is of great theoretical and practical significance for unraveling the degradation mechanisms in sown perennial pastures in alpine regions. The purpose of this study was to explore the potential allelopathic effects of Elymus nutans, Poa crymophila, and Festuca sinensis. Water extracts were prepared from whole plants and from plant powder of the perennial grass species. The effects of water extract on seed germination and seedling growth were investigated by laboratory bioassay. The whole plant extract of E. nutans significantly reduced the germination rate of E. nutans, P. crymophila and F. sinensis by 10.6, 7.0 and 21.4 percentage points (P<0.05), respectively, compared with the control. Seedling growth of the three grass species was also inhibited by the extract. The whole plant extract of P. crymophila inhibited the root length of E. nutans, P. crymophila and F. sinensis seedlings, the inhibition rates were 41.9%, 61.5% and 32.1%, respectively. The whole plant extract of F. sinensis significantly inhibited the dry weight of P. crymophila and E. nutans seedlings (P<0.05) by 51.2% and 46.4%, respectively. The powder extracts of E. nutans, P. crymophila, and F. sinensis significantly reduced (P<0.05) the germination rate, germination index, seedling height and root length of their own seeds and seedlings and those of other species. The different extracts of the three grasses had autotoxic and allelopathic effects on the germination and seedling growth of their own seeds and the those of other species, and the allelopathic effect of the powder extracts on the three grasses was stronger than that of whole plant extracts. A multivariate evaluation of the allelopathic effects of different extracts of the three grasses on their own seed germination and seedling growth of the other grass species ranked the allelopathic activity in the order: P. crymophila>E. nutans>F. sinensis. It is recommended to consider the inter-species allelopathic effect when establishing mixed seeding pasture in the Tibetan plateau area.

Effects of super absorbent polymers on growth and physiological characteristics of Sophora davidii vs. Panjiang seedlings under drought stress

ZHANG Yu-jun, SHANG Yi-shun, WANG Pu-chang, DING Lei-lei, ZHANG Wen, ZOU Chao

2020, 29(7):  90-98.  DOI: 10.11686/cyxb2019510

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In order to investigate the effect of super absorbent polymers (SAP) on the growth and drought resistance of shrub seedlings under drought stress conditions, a pot experiment to study the growth and physiological indexes of the Sophora davidii vs. Panjiang seedlings under different SAP application regimes was conducted. The results demonstrated that a low concentration of SAP increased plant height, stem diameter, leaf length and leaf width of S. davidii seedlings under drought stress. SAP applied at a concentration below 2% effectively increased the concentrations of soluble protein, soluble sugar and proline in the leaves of S. davidii seedlings, and increased the enzyme activity of superoxide dismutase, peroxidase and catalase. These findings indicate that SAP (less than 2% concentration) increases the drought resistance of S. davidii seedlings. A principal component analysis and multivariate data evaluation indicated that the water-retention effect of three tested SAP types were: Wote SAP>potassium salt-type SAP>agroforestry drought-resistance SAP. The Wote SAP (2% concentration) provided the best promotional effect on the growth of S. davidii seedlings and reduction of drought stress damage. The results of the present investigation provide a theoretical basis to enhance drought tolerance and achieve water-savings during cultivation of S. davidii, and can be readily adopted and applied in Karst mountain areas with cultivated S. davidii.

The relationship between endogenous hormone content and apomixis rate of wild Kentucky bluegrass in Gansu Province

LIU Yan, YU Mei-ling, ZHANG Ran, NIU Kui-ju, LI Yu-zhu, ZHANG Jin-qing, MA Hui-ling

2020, 29(7):  99-111.  DOI: 10.11686/cyxb2019454

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To investigate the relationship between apomixis rate and endogenous hormone levels in Kentucky bluegrass, eight wild Kentucky bluegrass strains with different apomixis rates, collected in Gansu Province, were studied. Fresh spikelets were harvested at different development stages, and the contents of zeatin (ZT), indole-3-acetic acid (IAA), trans-zeatin-riboside (ZR), gibberellin (GA₃) and abscisic acid (ABA) were determined, and the relationship between apomixis development and endogenous hormone levels analyzed. It was found that: ZT and ZR contents showed a downward trend during early spikelet development, and were lowest 2 days after heading, then ZT content gradually increased and ZR content began to decline after peaking at flowering stage. GA₃ and IAA showed a trend of first increasing and then declining, but GA₃ content reached a peak 2 days after heading, while IAA content was highest during the flowering stage. In addition, during the early stages of spikelet development, there was no significant change in ABA levels in genotypes with low apomixis (Gannan, Qingshui, Sunan and Lanzhou), but showed a decreasing trend in highly-apomictic genotypes (Longxi, Qinzhou, Dingxi and Longnan). However, ABA levels sharply increased from flowering to milk ripening, and then decreased sharply in two genotypes. Correlation analysis showed that the apomixis rate was positively correlated with ZT, ZR, ABA, (ZT+ZR)/IAA and (ZT+ZR)/ABA; negatively correlated with GA₃, IAA/ABA and GA₃/ABA; but failed to correlate with IAA. Therefore, high ZT, ZR and low ABA contents, (ZT+ZR)/IAA and (ZT+ZR)/ABA ratio are associated with promotion of apomictic ovule development, while high GA₃ content appears to promote ovule development by the sexual pathway.

Effect of NaCl on the adaption of Atriplex canescens under osmotic stress

GUO Huan, Pan Ya-qing, BAO Ai-ke

2020, 29(7):  112-121.  DOI: 10.11686/cyxb2019394

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Secretohalophyte Atriplex canescens is a C₄ perennial shrub with excellent resistance to salinity and drought. Our previous study showed that the transport of excessive Na⁺ into leaf salt bladders and contribution of the elevated Na⁺ concentration to leaf osmotic potential (Ψ_s) improves water status of plants and is a primary strategy in salt tolerance of A. canescens. The external application of 100 mmol·L^-1 NaCl can substantially stimulate the growth of A. canescens. To investigate whether NaCl could help to alleviate deleterious impacts of osmotic stress on the growth of A. canescens, five-week-old seedlings were subjected to two osmotic stress levels (-0.2 and -0.5 MPa) induced by D-sorbitol in the presence or absence of an additional 100 mmol·L^-1 NaCl. It was found that under osmotic stress, the addition of NaCl obviously improved the growth of A. canescens. Leaf relative water content was increased, net photosynthetic rate was enhanced and significantly more negative Ψ_s was induced. Furthermore, exogenous NaCl significantly increased Na⁺ concentration in stem, leaf tissues and leaf salt bladders as well as enhancing the Na⁺ contribution to leaf Ψ_s, with little adverse effect on K⁺ accumulation in stem and leaf tissues. In addition, the content of free proline and betaine in plants was significantly increased in the presence of NaCl under osmotic stress, and their contributions to leaf Ψ_s were significantly increased by additional NaCl under osmotic stress. This suggests that compatible solutes, in addition to functioning as protectants, are also involved in osmotic adjustment to further alleviate the deleterious impacts of osmotic stress. In summary, the appropriate concentration of NaCl does effectively alleviate the adverse impacts of osmotic stress on the growth of A. canescens.

Effects of dietary concentration:roughage ratio on rumen fermentation and flora population structure in Hu sheep

ZHAN Jin-shun, YANG Qun, HU Yao, WU Yan-ping, HUO Jun-hong

2020, 29(7):  122-130.  DOI: 10.11686/cyxb2019435

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To study the effects of dietary concentration:roughage ratio on fermentation and flora population structure in Hu sheep, forty healthy lambs with similar body weight and good body condition were randomly divided into four groups with ten sheep per group (5 male and 5 female). Sheep in each group were fed total mixed ration with concentration:roughage ratio of 70:30 (A), 60:40 (B), 50:50 (C) or 40:60 (D), respectively. The experimental period was 70 days containing a 14-day pre-experiment adaptation period and a 56-day experiment. It was found that: 1) The concentrations of ammonia nitrogen, propionic acid, butyric acid and valeric acid in group B were significantly higher than those of group D (P<0.05). 2) In total, 875 operational taxonomic units (OTUs) were detected, and 725 of these OTUs (82.86% of total OTUs) were shared by all four treatment groups. Group A possessed six unique OTUs, while group D had one unique OTU. The number of phyla, and Shannon diversity index were significantly higher in group A than in groups C and D (P<0.05), while the Simpson index was significantly lower in group A than that of groups B and C (P<0.05).The bacterial diversity in group C was significantly different from that in group A and group B (P<0.05). 3) At the phylum level, the relative abundance of Actinobacteria, and Spirochaetae in group A was significantly higher than the abundance in groups C and D (P<0.05). At the genus level, the relative abundance values for Lachnospiraceae_ND3007, Treponema_2, Weissella, Anaeroplasma, Brevibacterium, Pseudobutyrivibrio, an uncultured rumen bacterium and Roseburia were significantly higher in group A than in group D (P<0.05). The relative abundance of Lachnospiraceae_XPB1014 and Uncultured_Bacteroidales_BS11 in group A was significantly lower than those of group C and D, respectively (P<0.05). In conclusion, a high concentration:roughage ratio enhanced microbial richness and diversity in rumen of Hu sheep, and thus promoted rumen fermentation.

Genetic diversity analysis and multivariate evaluation of agronomic traits of 50 oat germplasm lines in northwest Sichuan

LEI Xiong, YOU Ming-hong, BAI Shi-qie, CHEN Li-li, DENG Pei-hua, XIONG Yi, XIONG Yan-li, YU Qing-qing, MA Xiao, YANG Jian, ZHANG Chang-bing

2020, 29(7):  131-142.  DOI: 10.11686/cyxb2020062

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This research aimed to objectively evaluate the genetic diversity of agronomic traits in 50 oat germplasm accessions. Twenty seven agronomic traits were evaluated; a morphological diversity index was calculated for each of them; and correlation, cluster and principal component analyses were performed for 16 selected quantitative traits among them. It was found that the trait with the highest genetic diversity index was panicle length (H'=2.04), and the highest coefficient of variation (63.36%) was for vegetative tiller number. The yield of fresh grass, hay yield, plant height, tiller number, and a number of other traits showed a very significant positive correlation (P<0.01). Cluster analysis divided the 50 oat germplasm accessions into four major groups. Group Ⅰ was characterized by high grass yield and plant height, a greater number of internodes and spikelets, and sturdy stems. This group was considered to provide excellent parent material for breeding projects involving multiple target traits. Group Ⅱ comprised mid-late maturing germplasm, without obvious beneficial traits. Group Ⅲ comprised medium-value germplasm, with potential for breeding high for yield and tillering ability. Group Ⅳ included late flowering germplasm, with heavier stems, which would provide excellent parent material for breeding lodging resistant varieties. The principal component analysis reduced the 16 analyzed traits to 4 principal components which cumulatively explained 69.00% of the data variation. The first principal component was closely related to forage yield; for the second principal component, the highest loading coefficient was for vegetative tillers per plant. For the third principal component accessions were primarily differentiated on the number of reproductive branches. The fourth principal component mainly reflected the number of stem nodes. Tin summary, the 50 evaluated oat germplasm accessions introduced from northwestern Sichuan and from abroad, have wide genetic diversity. Multivariate evaluation of measured traits indicated that accessions ‘Golden Yellow', ‘Lightning', ‘Golden Rain Ⅱ', and ‘Bambull Ⅱ' can be used as parents to improve local oat varieties.

Correlation between SSR diversity and ear traits of maize inbred lines

DING Yong-fu, WANG Ji-liang, CHEN Fen-qi, ZHUANG Ze-long, BAI Ming-xing, LU Yan-tian, JIN Bing-bing, PENG Yun-ling

2020, 29(7):  143-153.  DOI: 10.11686/cyxb2019448

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Ear-conformation traits directly affect the yield per plant of maize. This research aimed to provide an in-depth analysis of the genetic diversity of ear traits in maize inbred lines, and identify molecular markers associated with target traits. Pairs of SSR primers (n=145) were used to analyze the genetic diversity of 186 maize inbred lines in the study. A total of 652 alleles were detected. The average number of alleles was 4.5 per inbred line, and the average polymorphic information content of markers was 0.478. Using Structure software, 186 inbred lines were divided into 5 subgroups (Lyuda red cob, Tang sipingtou, Lancaster, P group and Reid). Using general linear model analysis, we found 14 markers related to the following 9 panicle traits: the number of kernel rows, ear diameter, cob diameter, ear length, bald length, number of kernels per row, grain weight per spike, 100-kernel weight, and cob weight. The tag contribution to phenotypic variation ranged from 0.0211 to 0.2159. A total of 8 ear-conformation trait tags were detected by an MLM (mixed linear model) correlation analysis model, and for these tags the phenotypic variation ranged from 0.0174 to 0.1243. These tags were located on chromosomes 1, 2, 3, 4, 5, 7, 8, 9, 10. This detailed analysis correlating maize genetic diversity for ear traits with SSR occurrence lays a foundation for the discovery of genes conveying superior allelic variation, for genetic studies of complex traits and for molecular marker-assisted breeding.

Effect of high plant density on yield of maize variety ‘Zhenghong No. 6'

HU Yue-qiu, XU Kai-wei, LONG Ling, JIANG Fan, ZHOU Yuan, QIU Chuan-zhi, LI Jian-bing, CHEN Yuan-xue

2020, 29(7):  154-162.  DOI: 10.11686/cyxb2019431

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The aim of this research was to explore the potential to achieve increased yield of maize variety Zhenghong No. 6 through high plant density under normal fertilisation rates. Field trials were set up in Zhongjiang County in the central hilly region of Sichuan. Five planting densities were set up: 5.25 (CK, actual production density), 6.00, 6.75, 7.50 and 8.25×10⁴ plants·ha^-1, and the growth, lodging and yield of Zhenghong No.6 compared under the different planting densities. It was found that as planting density increased, plant height, cob length, and leaf area index all increased, while stem diameter decreased. With each stepwise increase in plant density of 750 plants·ha^-1, plant height increased on average by 6.47 cm and cob height from the ground by 2.13 cm, while the maximum leaf area index increased by 0.46, and stem diameter decreased by 0.46 mm. With greater plant density, single-plant dry weight decreased (CK, 231.5 g·plant^-1; 8.25×10⁴ plants·ha^-1, 185.1 g·plant^-1) but the crop biomass increased (CK 12153 kg·ha^-1; 8.25×10⁴ plants·ha^-1, 15271 kg·ha^-1). Across the range of tested plant densities, with increasing density, the percentage dry matter allocation to leaves and stem sheaths increased, while the allocation to stem initially increased and then decreased. Within-plant dry matter allocation was grain (~55%)>stem (~15%)>leaf (~10%)>cob>leaf sheaths>bract leaves, and proportions of each responded differently to increasing density. A calculation of % dry matter translocation at grain-fill crop development stage showed that leaf ‘translocation ratio' reduced from 18.67% to 15.04% across the tested plant density range, while stem sheath translocation ratio was greatest (20.52%) at 6.75×10⁴ plants·ha^-1. With increase in planting density, the incidence of lodging and stalk-folding increased significantly, while the incidence of empty ears, drooping ears, and double ears decreased; the ear number per ha^-1 increased significantly; ear length, ear diameter, ear grain number, 1000-kernel weight and the harvest index showed a downward trend, and bare tip length tended to increase. The grain yield was highest at 7.50×10⁴ plants·ha^-1 (10419 kg·ha^-1 and 38.02% greater than the control). Thus, it can be seen that dense planting of maize increases the risk of stalk lodging and folding, and within a certain density range, the increase in the dry matter productivity of the population more than compensates for for the decrease in productivity per plant, resulting in higher yield. Based on simulation modelling, the optimal planting density for spring maize variety Zhenghong No. 6 in the hilly region of central Sichuan under the conditions of this experiment is 7.94×10⁴ plants·ha^-1.

Background and achievements of China's subsidy and award policy for farmers and herdsmen

LI Xin-yi, YIN Xiao-fei, ZHOU Xiao-li, LI Ping

2020, 29(7):  163-173.  DOI: 10.11686/cyxb2019453

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China's ‘subsidy and award' policy for farmers and herdsmen which was implemented in 2011 is a project designed to benefit rural people, and to provide the largest practicable amount of capital and benefit to the largest possible number of people in grassland regions. It is a key measure to reconcile the conflicting needs of human populations, and of grassland and livestock husbandry by encouraging and supporting farmers and herdsmen to use the grassland in a reasonable way and develop an ecologically sustainable grassland-livestock industry. This has been achieved by providing farmers with subsidies and awards. The central government has continually reviewing the policy details for optimum impact, and improving the support level. Based on the ‘four-to-provinces' and ‘five-to-households' principle, local governments have shown astute attention to regional practices and local innovation, when administering the policy. Significant ecological, economic and social progress has been achieved since the inception of this policy. However, there is still a coordination gap and lack of congruence between production and ecological considerations, and the conflicts between needs of people, and management considerations of grassland and livestock systems remain incompletely resolved. Further adjustment needs to occur in the subsidy and award policy framework, aimed at promoting grassland protection, regeneration, and management, as well as sustainable development of the grassland industries.

Advances in research on the roles of tannins in plant-soil nitrogen cycling

ZONG Wen-zhen, GUO Jia-hao, JIA Yun-long, ZHENG Yong-xing, YANG Xu, HU Fang-di, WANG Jing

2020, 29(7):  174-183.  DOI: 10.11686/cyxb2019445

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Tannins are secondary metabolites produced by higher plants. Tannins and tannin-linked organic nitrogen complexes play an important role in the nitrogen cycling at the plant-soil interface. The mechanisms by which tannins participate in the nitrogen cycling mainly include complexing organic nitrogen, affecting soil microbial activities and soil enzyme activities. Previous studies have not explored the complexation capacity of tannins to various organic nitrogen compounds, and the degradation mechanism of mycorrhizal fungi and saprophytic fungi on tannin-linked organic nitrogen complexes. Therefore, this review focuses on the complexation capacity of tannins to bind with various organic nitrogen compounds, the degradation mechanism of the complexes, the inhibition of soil enzyme activities by tannins and the influences of tannins on activities of soil microorganisms. Roles such as slowing of litter decomposition, inhibition of net nitrogen mineralization, and effects of tannins on net nitrification and nitrogen fixation in the nitrogen cycle is summarized. The findings of this review indicate that tannins can complex most of the organic nitrogen compounds; the structure and concentration of the tannins present can significantly affect the inhibitory actions of tannins on soil enzyme activities and net nitrogen mineralization, and soil microbial activity and diversity. These conclusions lay a foundation for further understanding of the role of tannins in nitrogen cycling at the plant-soil interface.

Effect of early mashed and pelleted concentrate starter supplementation on animal performance and development of the gastrointestinal tract in lambs

SUN Da-ming, YIN Yu-yang, WU Jian-liang, LIU Li-xiang, MAO Sheng-yong, LIU Jun-hua

2020, 29(7):  184-192.  DOI: 10.11686/cyxb2019432

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The aim of this study was to investigate the effect of early mashed and pelleted concentrate starter supplementation on animal performance and development of the gastrointestinal tract in pre-weaned lambs. The findings may provide a basis for the use of pellets in ruminant husbandry. In the present study, 18 newborn Hu lambs with similar birth weights were selected and separated from the ewes at 12 days of age and fed with goat milk powder (goat milk powder:water=1:10). After a three-day acclimation period, they were randomly divided into a control group (n=9, Con) and a treatment group (n=9, TG). The Con lambs received mashed concentrate ad libitum while the TG lambs received pelleted concentrate ad libitum. The two groups of lambs were given the same daily ration of milk powder (600 mL·d^-1). All lambs had free access to clean drinking water throughout the experimental period. During the experimental period, the feed intake of the lambs was recorded daily, and the lambs were weighed weekly to determine their weight gain. At the end of the feeding trial (42 days), all lambs were slaughtered, skinned and each part of the gastrointestinal tract was weighed. Tissue samples from various parts of the gastrointestinal tract were collected and sections were taken for epithelial morphometry. The results obtained revealed that pellet supplementation significantly (P=0.047) increased average daily feed intake of lambs at the age of 6 weeks compared to the control group. Pellet supplementation also significantly increased the average daily gain of lambs aged 4 weeks (P=0.030) and 5 weeks (P=0.019). Pellet supplementation significantly increased body weight of lambs aged 4 weeks (P=0.048), 5 weeks (P<0.001), and 6 weeks (P<0.001). There was no significant (P>0.05) difference between the two groups of lambs in the weight or length of the gastrointestinal tract. However, the length (P<0.001) and width (P<0.001) of the rumen papillae, and absorptive area of ruminal epithelium (P=0.038) were significantly increased by pellet supplementation. The gastrointestinal epithelial structure was observed using hematoxylin eosin staining and it was found that, compared with mashed concentrate, pellet supplementation significantly increased the thickness of the stratum granulosum of the rumen epithelium (P=0.027). The treatment group was observed to have significantly higher duodenal villus height (P<0.001) and ratio of villus height to crypt depth (P<0.001) but had a significantly lower duodenal crypt depth (P=0.010) compared to the control group. The pellet supplementation also significantly reduced jejunal crypt depth (P=0.010) and increased the ratio of jejunal villus height to crypt depth (P=0.087), but did not affect the jejunum villus height (P=0.258). The pellet supplementation significantly increased ileal villus height (P<0.001) and ratio of villus height to crypt depth (P=0.002), but the ileal crypt depths of lambs in both groups were similar (P=0.761). There was no significant difference in the thickness of the cecal epithelium (P=0.266) and colonic epithelium (P=0.526) between the two groups of lambs. These results show that pellet supplementation significantly promoted the development of the rumen epithelium and intestinal epithelium of the lambs, but did not affect the development of the hindgut epithelium.

Comparative analysis of slaughter performance and meat composition between different sexes in Cha Wula yaks

ZHANG Qiang, Dawayangla, JI Qiu-mei, XIN Jing-wei, ZHANG Cheng-fu, ZHU Yong, Luosangdunzhu, Cidanyangji, SUN Guang-ming, JIANG Hui

2020, 29(7):  193-198.  DOI: 10.11686/cyxb2019406

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In order to research the slaughter performance and meat quality of yak cows in Cha Wula district, ten 8-year-old yaks (5 males and 5 females) were randomly selected to determine slaughter performance and muscle quality. It was found that the female yaks had a higher dressing out percentage, net meat yield, and bone-meat yield than males. However, the eye muscle in male yak was of greater diameter than in the females. The analysis of nutrient composition of yaks showed that the contents of vitamin A, E, B₁₂, cysteine, histidine, arginine, calcium, selenium and fatty acids in male yaks were higher than those in female yaks (P<0.05). The results showed that Cha Wula yak meat is rich in highly nutritional components, and therefore is able to provide high quality animal protein for human consumption. In conclusion, compared with male yak meat, female yak meat is superior.