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    20 January 2019, Volume 28 Issue 1
    Influence of fertilization and root cutting on soil physicochemical properties and enzyme activities in a degraded Leymus chinensis steppe
    QIN Yan, LIU Wen-hui, HE Feng, TONG Zong-yong, LI Xiang-lin
    2019, 28(1):  5-14.  DOI: 10.11686/cyxb2018113
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    To improve the soil fertility of degraded Leymus chinensis steppe, influences of fertilization and root cutting on soil physicochemical properties and enzyme activities were studied. Key results were: 1) Soil organic carbon, total phosphorus, C/N, electrical conductivity and pH were not affected by fertilization and root cutting, but soil total nitrogen was reduced 14.5% by root cutting. 2) Grassland where root cutting was performed had higher soil enzymatic activity than fertilized grassland, and soil urease activity was responsive to agricultural practices, ranging from 0.82-2.26 mg $NH_{4}^{+}$ ·g-1 ·3 h-1. 3) Soil organic carbon level was positively correlated with soil total nitrogen, C∶N ratio, ammonium nitrogen, nitrate nitrogen and available nitrogen, but was negatively correlated with total phosphorus, electrical conductivity, pH and enzymatic activities. Hence, fertilization and root cutting improved soil available nutrients in degraded L. chinensis steppe, and root cutting provided an additional benefit of increased soil enzymatic activities, which may also contribute to the increase in soil nutrient transformation.
    Evaluation of agronomic traits and forage quality in summer-sown varieties of forage foxtail millet
    REN Xiao-li, CUI Ji-han, LIU Meng, ZHAO Yu, AI Yue-peng, LIU Fei, NAN Chun-mei, XIA Xue-yan, LI Shun-guo
    2019, 28(1):  15-26.  DOI: 10.11686/cyxb2018125
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    This study was designed to provide relevant information for the development of high-quality forage millet germplasm resources, and support informed breeding developments and guide feed formulation. The agronomic trait analysis included 17 summer-sown varieties of forage millet with measurement of fresh and hay yield, plant height, and stem:leaf ratio, among others. To assess nutritive value, crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were determined for the same 17 varieties. Three evaluation indexes were three used: the classification criterion of legume and gramineous forages in America, the relative feed value (RFV) and the grading index (GI), were also calculated, and the varieties ranked according to these criteria. It was found that: 1) The varieties S2014794, S20151375 and S2014742 had higher fresh and hay yield compared to others (the highest values of fresh and hay yield, respectively, were 37.26 and 18.92 t·ha-1); hence these varieties could be used as high-yield forage resources. The grain yields of varieties Hudewei 2, Zheng 10 and Z281 were high compared to other varieties, relatively higher, and the fresh and hay yield for these ranked medium to high among the tested cultivars of which were also in the middle and upper level; hence these varieties could be used dual purpose grain and forage production varieties. The varieties S2014907, S20151375, K2908 and K1955 had low stem:leaf ratios; while conversely Heng HN201026 and Hudewei 2 had high stem:leaf ratios, so these traits might indicate special uses for these varieties. Stem:leaf ratio also increased with crop maturity, through heading, grain filling, and seed maturation stages of crop development; Heng HN201026 and Hudewei 2 can be used as high-stalk resources. 2) The CP contents of varieties S2014907 and S2014742 (11.81% and 11.63%, respectively), which were higher (P<0.01) than other varieties. The contents of NDF in Zheng 10 and Jinlügu were 39.95% and 40.06% respectively, which were extremely significantly (P<0.01) lower than other varieties. The content of ADF in Sicao 4 was 14.73%, extremely significantly (P<0.01) lower than other varieties. There were different results by three grading methods of forage, but the general trend were same. By the classification criterion of legume and gramineous forages in America, the feeding value of forage millet is middle and upper level, and it is a better forage variety. The GI forage grading values were generally one unit lower than the corresponding RFV values. Based on the three grading methods, the feeding value of Zheng 10, K3970, Jinlügu, Sicao 4, K359, K2908, YC264 and Jicaogu 1 were superior to others, so these varieties could be used as high-nutritive-value resources.
    Comprehensive evaluation of cadmium tolerance of 14 switchgrass (Panicum virgatum) cultivars in the seedling stage
    HU Bing-yu, FANG Zhi-gang, LOU Lai-qing, CAI Qing-sheng
    2019, 28(1):  27-36.  DOI: 10.11686/cyxb2018101
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    Cadmium (Cd) is a common abiotic stress factor in the environment. Screening germplasm resources for Cd tolerance is an effective way to develop plants for use in biofuel production on land contaminated by heavy metals. Switchgrass (Panicum virgatum) has been identified by the U.S. Department of Energy as having very high potential as a biofuel substrate. Hence, 14 switchgrass cultivars under hydroponic culture were treated with 0 (control) or 10 μmol·L-1 Cd, and morphological and physiological traits were investigated. Root morphology data of switchgrass were obtained using an EPSON scanner and WinRHIZO software. Net photosynthetic rate was determined with the LiCor-6400 portable photosynthesis system and a spectrophotometer was used to determine root activity. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to examine Cd accumulation of switchgrass. Data for measured traits were transformed to units of statistical standard deviation by division by their standard error and aggregated with positive/negative sign reversal where relevant, so that Cd tolerance was additive across traits, and a composite index of Cd tolerance compiled. Lastly a cluster analysis was performed. It was found that Cd stress significantly reduced the root length, root surface area, number of root tips, total dry weight, net photosynthetic rate and root activity of different switchgrass cultivars to different degrees. Significant differences were found (P<0.01) among cultivars. According to composite index (D value), Kanlow was the most tolerant variety, while Foreburg was the least tolerant. On cluster analysis, the 14 switchgrass cultivars were classified into 3 Cd-tolerance types. One cultivar (Kanlow) had high Cd tolerance; 9 cultivars (Alamo, BoMaster, Carthage, Cave in Rock, Long Island, Newyork, Shawnee, Sunburst, Trailblazer) were medium-cadmium-tolerance types and 4 cultivars (Blackwell, Dacotah, Foresburg, Shelter) were Cd-sensitive types. It was also found that the cultivar Kanlow with high Cd tolerance had a strong ability to accumulate Cd. This study provides a theoretical basis for selecting suitable switchgrass cultivars for the cultivation of Cd-polluted land, and the results illustrate an operable method to evaluate the Cd tolerance of plant germplasm lines.
    Optimal cultivation conditions for forage triticale line C31, based on a response surface experiment
    LIU Jing, QU Guang-peng, TIAN Xin-hui, DU Wen-hua
    2019, 28(1):  37-49.  DOI: 10.11686/cyxb2018069
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    In order to identify the optimal cultivation conditions for forage triticale (Triticale wittmack) line C31, the effects of plant density, nitrogen fertilizer rate, and rainfall on hay yield and nutritional quality of triticale line C31 grown for forage, were studied. A regression prediction model for hay yield and nutritional quality of triticale line C31 was established based on the response surface method, which included 3 factors (plant density, nitrogen fertilizer rate, rainfall) and 5 levels. Key results were: 1) The 3 factors (plant density, nitrogen fertilizing rate, rainfall) all significantly affected the hay yield and nutritional quality of forage triticale (P<0.05). The interaction between rainfall and nitrogen fertilizer rate was significant for hay yield (P<0.05), while the interaction between rainfall and triticale plant density was significant for triticale nutritional quality (P<0.05). 2) In the multiple quadratic regression analysis, all 3 factors were shown to have highly significant effects on hay yield and nutritional quality of triticale (P<0.01), the results show that the regression model of hay yield and nutrient quality can represent the actual hay yield and nutrient quality of forage triticale. 3) Forage triticale line C31 was found to be suitable for growing in Hezuo, where the rainfall varied from 318 mm to 325 mm during the growth period of triticale. 4) Triticale line C31 was predicted to have the highest hay yield and nutritional quality when the rainfall was 322.07 mm during the growth period of triticale. At this predicted optimum rainfall, the nitrogen fertilizer rate indicated by the model was 289.17 kg N·ha-1, and modelled optimal plant density of triticale was 5.79 million seedlings·ha-1. Under these conditions the model predicted hay yield and nutritional quality of 16732.50 kg·ha-1 and 0.71, respectively. This study demonstrates a simple and effective method for evaluating the hay yield and nutritional quality of triticale germplasm under different growing conditions and suitable planting locations.
    Comparison of response mechanisms to low inorganic phosphate stress between alfalfa varieties Aohan and Victoria
    LI Zhen-song, LI Zhen-yi, ZHANG Qi-xin, HE Feng, WANG Yu-fei, WAN Li-qiang, LI Xiang-lin, TONG Zong-yong
    2019, 28(1):  50-59.  DOI: 10.11686/cyxb2018307
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    In order to compare the performance and adaptive mechanisms of two varieties of alfalfa under low inorganic phosphate (low-Pi) conditions, and to provide more information for improvement of Pi utilization efficiency and absorption efficiency in alfalfa, the varieties Aohan and Victoria were grown under low-Pi (5 μmol·L-1 KH2PO4) and normal Pi (500 μmol·L-1 KH2PO4) conditions. Morphological and physiological traits were measured at 10, 15 and 20 days. It was found that, the height, aboveground biomass and Pi content of both Aohan and Victoria were decreased under low-Pi stress; while the underground biomass, root-shoot ratio, total root length, root surface area and Pi utilization were increased. The net photosynthetic rate, stomatal conductance and transpiration rate were decreased significantly under low-Pi (P<0.05), but the decrease was much smaller in cultivar Aohan than in cultivar Victoria. The acid phosphatase activity of both was significantly enhanced (P<0.01), and for Aohan was significantly higher than that of Victoria (P<0.01). To sum up, low-Pi stress inhibited the growth of the above ground plant organs and promoted growth of the underground parts. The greater low-Pi tolerance of Aohan compared to Victoria is associated with greater increase in acid phosphatase activity under low-Pi in Aohan, and a lower reduction in photosynthesis under low-Pi. The contrasting responses of the two varieties under low-Pi stress indicate a potential mechanism for alfalfa tolerance to low-Pi.
    Effects of nitrogen management on photosynthetic characteristics and yield of maize in arid areas of central Gansu, China
    WANG Jin-bin, XIE Jun-hong, LI Ling-ling, Eunice Essel, PENG Zheng-kai, DENG Chao-chao, SHEN Ji-cheng, XIE Jian-hui
    2019, 28(1):  60-69.  DOI: 10.11686/cyxb2018096
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    Maize has become one of the major cultivated crops in arid farming areas of central Gansu, China because of the adoption of complete film surface mulching and adoption of double ridge-furrow planting. However, the high output of maize using this technology results in exhaustion of soil nutrients negatively influencing the sustainability of maize production. The objective of this study was to determine the effects of different nitrogen application rates on the photosynthetic characteristics, chlorophyll content (SPAD), leaf area index, dry matter accumulation and distribution and yield of maize. The study relied on a field experiment that was conducted in 2012 at Dingxi, Longzhong region. The treatments included four nitrogen rates (N0: 0 kg·ha-1, N1: 100 kg·ha-1, N2: 200 kg·ha-1, N3: 300 kg·ha-1) and two nitrogen application times (T1: 1/3 at sowing+1/3 at jointing+1/3 at flowering, T2: 1/3 at sowing+2/3 at jointing). The photosynthetic characteristics improved with increased nitrogen application rate, but there was no difference between T2N2 and N3; T2 enhanced the photosynthetic characteristics. N3 increased SPAD by 50.9%, 17.0%, and 2.7% respectively comparing N0, N1, and N2 at all stages. Leaf area index also improved with increased nitrogen application rate, but N2 and N3 were not different. SPAD and leaf area index under T2 were higher than T1. Dry matter during all growth stages was highest at N3 and lowest at N0 (N3>N2>N1>N0) and T2 was higher than T1. Grain yield and biomass were significantly higher with increased nitrogen rates; for example, grain yield and biomass were 79.2% and 68.4% higher for N3 than N0 respectively, and 65.9% and 51.4% higher for N2 than N0 respectively. T2 improved grain yield and biomass by 9.9% and 13.5% respectively, compared with T1. However, T2N2 and N3 were not different. The application of double furrow sowing technology, mulching with nitrogen applied at 200 kg·ha-1 rate, 1/3 applied at sowing+2/3 at jointing is suggested as a means of more sustainable maize production systems in arid areas of central Gansu, China.
    Effects of drought stress and rewatering on growth and physiological characteristics of invasive Aegilops tauschii seedlings
    WANG Ning, YUAN Mei-li, CHEN Hao, LI Zhen-zhen, ZHANG Ming-xin
    2019, 28(1):  70-78.  DOI: 10.11686/cyxb2018485
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    A weighting method was used to control soil water content to produce a soil water stress gradient. The effects of drought and rewatering on the changes of the morphological and physiological parameters of potted Aegilops tauschii seedlings were measured on the 28th day after imposition of watering treatments and the 7th day following rewatering. The relative water content, relative conductivity, malondialdehyde and proline content increased with increasing drought. Chlorophyll initially increased and then decreased during drought stress. Superoxide dismutase activity (SOD) increased in light drought and moderate drought stress, but initially increased and then decreased during strong drought. Leaf mass ratio and specific leaf area declined with drought stress, but root mass ratio and root∶shoot ratio increased with increasing stress. After rewatering, most indexes of physiological status such as relative water content and proline content recovered to the level of the control treatment (no water stress). These preliminarily results indicate that A. tauschii is well adapted to a high degrees of drought stress because of its ability to physiological metabolism.
    A study of the correlation between altitude and Medicago falcata phenotypic traits
    Ruozha·Zhaerhan, LI Qian, WANG Yu-xiang, ZHANG Bo
    2019, 28(1):  79-85.  DOI: 10.11686/cyxb2018114
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    Medicago falcata possesses an abundantly diverse array of phenotypic traits, which are influenced by habitat, and so are correlated with climatic gradients linked to altitude, latitude and longitude. This research aimed to characterise the genetic variation in M. falcata through study of correlation between the phenotypic characters of M. falcata and altitude. In this experiment, M. falcata (Variety Xinjiang) was used as the study material, and 18 phenotypic traits were studied, including plant height, number of branches, leaves, stems and flowers under the same latitude and longitude (N 43°43', E 86°94') over an altitude range of 2100-2350 m. These data provide a basis data for further research on genetic diversity and germplasm development in M. falcata. It was found that phenotypic traits are most variable with change in altitude. Plant height, leaf length, leaf width, internode length, stem diameter and floret length within inflorescences showed a trajectory across the altitude gradient of “declining-rising-declining” with decreasing altitude, with peak values at 2150 m of altitude. The values obtained for the phenotypic index ranged from 1.30%-22.83%, and the average coefficient of variation was 8.49%. There was a significant correlation between altitude and plant height, inflorescence length, petal length and keel width, with correlation coefficients of 0.490, 0.601, -0.449 and -0.421, respectively. Other phenotypic traits of M. falcata showed no significant correlation with altitude, and considering the data as a whole, an altitude of 2150 m is best suited for growth of M. falcata.
    Anatomy and histochemistry features of Phalaris arundinacea adapted to wetland environments
    WANG Xiao-e, ZHANG Fan, ZHANG Xia, ZHOU Cun-yu, YANG Chao-dong
    2019, 28(1):  86-94.  DOI: 10.11686/cyxb2018095
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    Reed canarygrass (Phalaris arundinacea) is a perennial herb adapted to wetland environments. The current work explores the anatomy and histochemistry of the adventitious roots, stems (rhizomes and culms), leaves and the permeability of apoplastic barriers of reed canarygrass. The anatomy and histochemistry of P. arundinacea were studied using an optical microscope and fluorescent microscope. Sections were stained with Sudan red 7B (SR7B) for suberin lamellae, with berberine hemisulfate-aniline blue (BAB) for casparian bands and lignified cell walls, phloroglucinol-HCl (Pg) for lignin and berberine hemisulfate-potassium thiocyanate for apoplastic permeability. Concentrated sulfuric acid digestion (AD) was used to detect the wavy casparian bands in young rhizomes and culms. The adventitious roots had a primary structure comprising epidermis, exodermis, cortex, endodermis and vascular cylinder with sclerenchyma; the stems comprised a cuticle, epidermis, peripheral mechanical ring, exodermis, cortex, endodermis, sclerenchyma ring with vascular bundles and pith cavity. The apoplastic barriers consisted of adventitious roots with a suberized and lignified endodermis and an exodermis, stems possessed a cuticle, suberized and lignified peripheral mechanical ring and a sclerenchyma ring, and rhizomes with endodermis and exodermis, culms only with exodermis. The air space consisted of pith cavities and cortical cavities in the stems, and aerenchyma in roots and leaves. This research revealed that reed canarygrass has the key constitutive, structural and histochemical features in roots and stems that allow it to grow in wetlands, be protected against oxygen leakage from aerenchyma, with-stand seasonal flooding and consequently, widely distributed. The anatomical structures and histochemical features of these perennial, rhizomatous grasses enhance our awareness of the biology of this species in native Asian and North American invaded habitats to select species for the restoration of degraded wetland of the Jianghan Floodplain and Three Gorges Reservoir Region of the Yangtze River.
    Effects on production performance, slaughter performance, apparent digestibility of nutrients and meat quality of partial substitution of corn concentrate with highland barley in a yak fattening system
    MIAO Jian-jun, PENG Zhong-li, GAO Yan-hua, GUO Chun-hua, WANG Ding, FU Yang-yang
    2019, 28(1):  95-107.  DOI: 10.11686/cyxb2018502
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    This study was conducted to investigate the effects of partial substitution of corn concentrate by highland barley in a yak fattening system. The experiment comprised a factorial combination of two levels of diet type (100% corn; 60% highland barley+40% corn) and three different concentrate∶forage ratios (CFR, 30∶70, 40∶60, 50∶50). Healthy Maiwa male yaks [n=36; 4 years of age; (144±21.0) kg body weight] were randomly divided into 6 groups, of 6 animals. Hence, the individual animals in each group were taken as experimental replicates. There was a pre-experimental period of 15 days, followed by a trial period of 180 days. Data collected included: production performance, slaughter performance, apparent digestibility of nutrients, muscle physical and chemical indexes, muscle tenderness and fiber characteristics of the yaks. It was found that: 1) Diet type and concentrate∶forage ratio had no significant effect on production performance (P>0.05). 2) The net meat percentage of the 60%-40% barley-corn group was significantly higher than that of the 100% corn group (P<0.05), but no significant differences between the two diet-type groups in dressing percentage and eye muscle area were observed (P>0.05). CFR had no significant effect on slaughter performance (P>0.05). There were significant interaction effects between the dietary types and concentrate∶forage ratios on the eye muscle area (P<0.05), and the best group was 60%-40% barley-corn with 40∶60 CFR. 3) Diet type had no significant impact on apparent digestibility of nutrients. However, compared with the 30∶70 CFR, the apparent digestibilities of organic matter (OM), gross energy (GE) and crude protein (CP) were significantly improved in the 40∶60 and 50∶50 CFR groups (P=0.002, 0.003 and 0.018, respectively). Significant interactions were observed between diet type and CFR, for the apparent digestibility of gross energy (GE), organic matter(OM), and ether extract (EE) (P<0.05), with the best group being 100% corn with 40∶60 CFR. 4) No significant difference was found between diet types for lightness value (L*), redness value (a*) and pH in the longissimus dorsi muscle (P>0.05), but the yellowness value (b*), drip loss and cooking loss of the 60%-40% barley-corn group were significantly lower than those of the 100% corn group (P=0.044, 0.048 and 0.003, respectively). With increasing CFR, cooking loss decreased (P=0.075). 5) Diet type had no significant effect on muscle tenderness (P>0.05). However, with increased CFR, shear force was decreased (P>0.05), muscle fiber diameter was decreased (P=0.059), muscle fiber density was significantly increased (P<0.05), and muscle fiber area was significantly decreased (P<0.05). In conclusion, a 60% substitution of highland barley in a corn concentrate diet in a yak fattening system, improved the slaughter performance, and meat quality. Considering all the data, the optimal dietary concentrate∶forage ratio for yaks in this study was 40∶60.
    Effects of seeding rate and row spacing on nutritional value of alfalfa in the arid oasis region of Gansu Province
    NAN Li-li, SHI Shang-li, GUO Quan-en, BAI Xiao-ming
    2019, 28(1):  108-119.  DOI: 10.11686/cyxb2018426
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    Seeding rate and row spacing are important cultivation details for alfalfa (Medicago sativa) need to be optimized to achieve high crop yield and forage quality. Therefore, an experiment to investigate the effect of seeding rate and row spacing on alfalfa performance was carried out in the arid oasis region of Gansu Province from 2014 to 2017. The experiment comprised four seeding rates (12.0, 16.0, 20.0 and 24.0 kg·ha-1) arranged in a randomized complete block design with three replicates, and three equal row spacings (10, 15, 20 cm) and two wide-narrow row spacings (60 cm+40 cm, and 60 cm+30 cm) randomly arranged as split plot treatments within the main plots. In wide-narrow row spacings, groups of 6 rows with a narrow spacing of 10 cm were separated by a wider spacing of 30 cm or 40 cm. It was found that seeding rate and row spacing did not have any significant effect on leaf∶stem ratio, but significantly affected nutritional parameters of alfalfa forage. Across the range of seeding rates and row spacings, herbage ether extract, calcium, and phosphorus contents were highest at intermediate plant densities. Crude protein content was highest (20.06%) at the 16.0 kg·ha-1 seeding rate and 20 cm row spacing combination, while the highest ether extract content (3.42%) was obtained at the 16.0 kg·ha-1 seeding rate with 15 cm row spacing. Calcium content was maximized (1.65%) at the 20 kg·ha-1 seeding rate and 20 cm row spacing, and phosphorus (P) content was maximized (0.19%) at the 3 lower seeding rates (12.0, 16.0 and 20.0 kg·ha-1) and row spacing of 20 cm. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents decreased with increasing seeding rates, while the NDF and ADF contents increased with increasing row spacings, and the lowest average NDF content (31.74%) was obtained at the 24.0 kg·ha-1 seeding rate and 10 cm row spacing. The lowest ADF content (25.64%) was obtained at the 24.0 kg·ha-1 seeding rate and 15 cm row spacing. The relative feed value (RFV) increased with increasing seeding rates and was highest at medium row spacings. Lastly, relative feed value was maximized (208.64%) at the 16.0 kg·ha-1 seeding rate and 20 cm row spacing. The nutritional values of alfalfa herbage different between growing years at the same seeding rate and row spacing. It was indicated from comprehensive evaluation of the main nutrients, that the optimal planting configuration for improving alfalfa nutritional value in this climate was a seeding rate of 20.0 kg·ha-1 and row spacing of 20 cm.
    Knock out of two splice variants of MYB 40 using the gene-editing technique CRISPR/Cas9
    LI Meng-zhan, YIN Hong-ju, LI Ding-ding, LIU Ya-qi, WANG Suo-min
    2019, 28(1):  120-127.  DOI: 10.11686/cyxb2018099
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    MYB transcription factors play important roles in various abiotic stress signaling pathways. In a previous study, we found that ZxMYB315 from Zygophyllum xanthoxylum is involved in plant responses to salt and drought stresses. In addition, the ortholog of ZxMYB315 in Arabidopsis, MYB40, has two splice variants, MYB40.1 and MYB40.2. Expression levels of both MYB40.1 and MYB40.2 are affected by salt treatment. However, the functions of these changes in response to abiotic stress are still unclear. In this study, we further analyzed the expression patterns of MYB40.1 and MYB40.2 under salt treatment. In particular, two heterozygous mutations for MYB40.1 and three heterozygous mutations for both MYB40.1 and MYB40.2 were generated using the gene-editing technique CRISPR/Cas9. These mutants now provide a foundation for studying functions and molecular mechanisms of MYB40 in various abiotic stress signaling pathways.
    Cloning and function analysis of the high temperature inducible promoter pMsMBF 1c in alfalfa (Medicago sativa)
    LI Xiao-dong, MO Ben-tian, MOU Qiong, LOU Fen, CHEN Wen-gui, CHEN Guang-ji, ZHANG Yu, HAN Yong-fen
    2019, 28(1):  128-137.  DOI: 10.11686/cyxb2018370
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    Plant thermotolerance is controlled by a complex and finely regulated network of transcription processes. High temperature inducible promoters can economically and efficiently activate or shut down the expression of key genes involved in regulating thermotolerance. Knowledge of these promoters is therefore important in plant functional genomics research and the molecular breeding industry. In the present study, a 1748 bp sequence upstream of MsMBF1c, which is a candidate gene involved in thermotolerance in alfalfa, was isolated using a digestion ligation PCR method, based on its coding sequence. Bioinformatics analysis showed that two conserved motifs representing the HSE and GATA binding sites involved in thermotolerance regulation existed in the MsMBF1c promoter region. There were 5 abscisic acid response cis-elements (ABRE, MYB2, MIC2, CBF and DPBF) and 2 MYB protein binding motifs in the MsMBF1c promoter region, which suggested MsMBF1c might regulate other abiotic stress response in addition to thermotolerance. A vector of pBI121-MsMBF1c::GUS was constructed and transformed into wild type Arabidopsis. The expression of GUS and AtMBF1c genes, was examined by qRT-PCR, and found to be up-regulated 5.4 and 4.8 fold, respectively, after heat stress. At the same time, histochemical staining analysis also showed the MsMBF1c promoter to be markedly induced by high temperature. To summarize, the MsMBF1c promoter was isolated and transformed into Arabidopsis, and was proved to be heat inducible by bioinformatics and gene expression data, and by histochemical staining analysis. This information provides technical and theoretical support for further investigation of heat regulation mechanisms and breeding of heat resistant alfalfa varieties.
    Correlation between oil content or fatty acid composition and expression levels of genes involved in TAG biosynthesis in flax
    LI Wen-juan, QI Yan-ni, WANG Li-min, DANG Zhao, ZHAO Li, ZHAO Wei, XIE Ya-ping, WANG Bin, ZHANG Jian-ping, LI Shu-jie
    2019, 28(1):  138-149.  DOI: 10.11686/cyxb2018321
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    Flax (Linum usitatissimum) is an oil crop containing abundant unsaturated fatty acids, especially α-linolenic acid. To better understand biosynthesis of these compounds, it is highly relevant to explore functions of genes in the TAG (triacylglycerol) synthesis pathway, which are associated with flax oil content and levels of various fatty acid components. In this study, the dynamic accumulation patterns of oil and fatty acid components in flax and the corresponding expression patterns of 7 key genes in the TAG synthesis pathway were determined in three varieties (lines) of flax identified as having significant differences in oil content or fatty acid composition. The correlations between expression patterns of 7 key genes, oil contents and unsaturated fatty acid levels were analyzed. It was found that seed oil and linolenic acid accumulate rapidly between 10 and 20 days after flowering in flax. However, the time course of the accumulation patterns of oil and linolenic acid differed significantly in the three varieties studied. Meanwhile, in the TAG synthesis pathway the 7 key genes (GPAT9, DGAT1, DGAT2, PDAT1, PDAT2, FAD2A, and FAD3A) were found to be expressed in different flax tissues at different stages of development, with the patterns of expression also differing among the three lines. The expression patterns of PDAT1, DGAT1, and DGAT2 were positively correlated with the dynamic accumulation pattern of oil content, and the pattern of PDAT1 was significantly positively correlated with the accumulation pattern of linolenic acid. In addition, the cumulative expression of PDAT1 in high oil and high-linolenic-acid flax germplasm is also significantly higher than that in low-oil and low-linolenic-acid material during seed development. Therefore, PDAT1 appears to be a key gene in the regulation of oil and linolenic acid content in different varieties (lines) of flax.
    De novo transcriptomic analysis for lignin synthesis in Cenchrus purpureus using RNA-seq
    WU Juan-zi, QIAN Chen, LIU Zhi-wei, PAN Yu-mei, ZHONG Xiao-xian
    2019, 28(1):  150-161.  DOI: 10.11686/cyxb2018303
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    Elephant grass (Cenchrus purpureus) is an excellent forage crop and a promising lignocelluloses energy crop; its stem characteristics are very important for forage and feedstock quality. In order to understand the gene expression profile of elephant grass stem in the absence of a reference genome, we performed de novo transcriptome sequencing and compared the transcriptome of stems with a high lignin content plant (HLCP) eg7 and a low lignin content plant (LLCP) eg87 in elephant grass using Illumina HiSeq 2000 platform. A total of 169630902 high qualities reads were obtained, which were then assembled into 87641 unigenes with an average length of 580 nt. All of the 87641 unigenes were compared against the non-redundant protein database (Nr), non-redundant nucleotide database (Nt), swisssprot protein sequence database (Swiss-Prot), gene ontology (GO), cluster of orthologous groups (COG) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases for functional annotation; a total of 62557 unigenes were annotated. Most homologous sequences were found between elephant grass with sorghum. 33323 unigenes showed significant differences in expression between eg7 and eg87 (control), 9704 (29.1%) genes were up-regulated and 23619 (70.9%) were down-regulated. GO and KEGG pathway analysis revealed that the genes related to photosynthesis-antenna proteins, photosynthesis, betalain biosynthesis, phenylpropanoid biosynthesis are genes of interest. 9 monolignol biosynthesis-related genes and 8 ClassⅢ peroxidase genes were selected as candidate genes. qRT-PCR analysis showed that the expression of 9 selected unigenes were consistent with the transcriptome data. Our study presented comprehensive transcriptomic data and gene function analysis of C. purpureus stem, providing a valuable resource for future studies of plant breeding in the genus Pennisetum and comparative genome analysis for C4 grasses.
    Effects of a Vicia villosa green-manure crop inoculated rhizobium during winter fallow, on soil fertility factors and fertilizer needs of a summer tobacco crop
    LIU Ming, CHEN Yuan-xue, CHEN Qiang, PENG Dan, YU Xiao, YANG Jun-wei, XU Kai-wei
    2019, 28(1):  162-169.  DOI: 10.11686/cyxb2018091
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    In order to investigate the effect on crop yield and soil fertility of Vicia villosa as a green manure crop in tobacco growing, a field experiment comprising three treatments was set up: winter fallow without a green manure crop (CK), a winter green manure crop of V. villosa not inoculated with rhizobium (V), and a winter green manure crop of rhizobium-inoculated V. villosa (VR). Plants of V. villosa were harvested for measurement at the beginning of flowering (187 days after planting) to determine their yield and nutrient levels, and then ploughed under, with tobacco planting following 45 days later. For tobacco planting on V and VR plots, fertilizer was applied at 80% of the rates recommended by the Guangyuan Tobacco Company for the CK treatment. Before planting tobacco and after harvest, soil samples were collected and physicochemical traits, enzyme activity and microbial populations were determined. Key results were: 1) Rhizobium inoculation enhanced vigor of the V. villosa green manure crop. Plant biomass and nutrient content, fresh grass yield, hay yield, root yield, nodule numbers, and plant height were all increased by 1.3% to 50.7%; total N, total P, and total K were increased by 1.8% to 5.0%; N, P, and K accumulation increased by 14.3% to 21.5%. 2) In the soil tests taken before planting tobacco, the VR treatment had increased soil nutrient content and microbial populations, compared with the CK treatment. Specifically, total N, organic matter, and available N, P, and K increased by 2.5% to 126.6%. Meanwhile, the activities of sucrase, catalase, phosphatase and urease were increased by 14.6% to 82.5%, while populations of bacteria, actinomycetes and fungi were increased by 85.3% to 236.9%. In the soil tests taken after harvesting tobacco, it was found that the VR treatment increased soil nutrient content and microbial populations, even with the 20% reduction in chemical fertilizer application. Total N, organic matter, and available N, P, and K were increased by 12.3% to 64.1%, the activities of sucrose, catalase, phosphatase and urease increased by 5.4% to 67.0%, compared to CK, while populations of bacteria, actinomycetes and fungi were increased by 65.1% to 473.3%. This finding that use of rhizobium-inoculatedd V. villosa (i.e. the VR treatment) can improve soil fertility status even with a 20% reduction in inorganic fertilise application, is of great significance to development of more sustainable tobacco leaf production practices.
    Isolation and screening of phosphate-solubilizing bacteria from the rhizosphere of Trifolium pratense and culture medium optimization
    LI Hai-yun, YAO Tuo, ZHANG Rong, ZHANG Jie, LI Zhi-yan, RONG Liang-yan, LU Xiao-wen, YANG Xiao-lei, XIA Dong-hui, LUO Hui-qin
    2019, 28(1):  170-179.  DOI: 10.11686/cyxb2018064
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    In order to optimize isolation and screening of phosphate solubilizing bacteria from the rhizosphere soil of Trifolium pratense (Cv. Minshan), a preliminary extraction using Pikovaskaia’s, PKOC1 and PKOC2 phosphate solubilizing media was carried out, and the 16S rRNA gene sequence was determined for the bacterial strains with excellent phosphate solubilizing ability. The separation and screening effect of PKOC2 was better than that of PKOC1 and Pikovaskaia’s. The composition of the culture medium was optimized using a response surface experiment design. The optimal composition so identified for the PKOC2 medium was: glucose 18.19 g·L-1, Ca3(PO4)2 5 g·L-1, MgCl2·6H2O 3.21 g·L-1, MgSO4·7H2O 0.25 g·L-1, KCl 0.2 g·L-1, (NH4)2SO4 0.08 g·L-1. It was found that 26 strains of phosphate solubilizing bacteria were isolated from T. pratense rhizosphere using these techniques. A preliminary identification of 7 isolated bacterial strains with excellent phosphate solubilizing ability using the strains 16S rRNA gene sequence indicated that a strain designated MHS4 was Bacillus cereus, strain MHS7 and MHS19 were Bacillus subtilis, strain MHS27 was Bacillus thuringiensis, strain MHS30 was Pseudomonas fluorescens, strain MHS31 was Pseudomonas gessardii, and strain MHS49 was Klebsiella oxytoca. To summarise, phosphate-solubilizing bacteria were abundant in the rhizosphere of T. pretense were abundant, and the optimized phosphate-solubilizing medium provided support for the screening of bacterial strains with excellent phosphate-solubilizing ability.
    Age structure of Calamagrostis macrolepis var. rigidula populations during vegetation restoration in coal ash storage pools
    WANG Rou-yi, SHENG Jun, JIA Jun-qi, LI Hai-yan, YANG Yun-fei
    2019, 28(1):  180-187.  DOI: 10.11686/cyxb2018100
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    The study of age structure of plant population is vital to analyze population dynamics and predict community succession trends. Age structures of tillers, rhizomes, tiller productivity, and rhizome storage capability of Calamagrostis macrolepis var. rigidula populations were studied during vegetation restoration in coal ash storage pools of a Coal fired power plant in the Horqin grassland regions. Age structures of C. macrolepis var. rigidula modules were analyzed under different restoration years (sample 1, spot 1 and spot 2 had been restored for 12 and 8 years respectively; sample 2, spot 1 and spot 2 had been restored for 16 and 12 years respectively) and livestock disturbance recorded. The results indicated that in sample 1, the number and biomass of tillers increased with age as did rhizome length whereas rhizome biomass was stable. The number and biomass of tillers, the length and biomass of rhizomes all increased with age in 12-year and 8-year restoration spots. In two samplings, tiller productivity decreased with increase of age. It reflects the regulation strategy of population priority to young age class with high viability under disturbance. Tiller productivity of each age in the second sampling was significantly lower than first sampling in the same restoration spot. In sample 2, rhizome storage capability was lower than those in sample 2 with the exception 1a rhizomes. The reason for the decline of material productivity in the second sampling in this study is that the management of the ash storage ponds was less than ideal resulting in the restoration areas being grazed by livestock. The decline of material productivity of grassland caused by free grazing was mainly due to the fact that the grazing intensity exceeded the carrying capacity of the restored grassland. For plant communities in the initial stages of restoration, it is very important to prevent disturbance from livestock.