Table of Content

20 January 2017, Volume 26 Issue 1

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Spatio-temporal dynamics of grassland net primary productivity and its response to climate change in the Temperate Eurasian Steppe 1982-2008

CHEN Yi-Zhao, LI Jian-Long, SUN Zheng-Guo, GANG Cheng-Cheng

2017, 26(1):  1-12.  DOI: 10.11686/cyxb2016079

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The Temperate Eurasian Steppe (TES) is the world’s largest continuous vegetation transition zone. Made up mainly of the Kazakh and Mongol Steppe. TES is a typical arid/semi-arid zone and sensitive to climate change. However, little is known about its net primary productivity (NPP), especially for the Kazakh Steppe. In this study, an improved boreal ecosystem productivity simulator (BEPS) model was used to simulate NPP in TES from 1982 to 2008. The BEPS algorithms for maximum carboxylation efficiency and autotrophic respiration were improved to make them more applicable to arid/semi-arid regions and then validated by long-term field observations in Kazakhstan, Inner Mongolia and Xinjiang. Results indicated that the improved model could enhance NPP simulation. Over the 27-year period from 1982 to 2008, the average TES NPP was 120 g C/m², of which 116.9 g C/m² was located in the Mongol Steppe and 122 g C/m² in the Kazakh Steppe. In a context of a regional “warming and drying” trend, the Mongol Steppe exhibited an obvious increasing NPP trend for the entire study period, while NPP in the Kazakh Steppe increased before 1991 and then decreased. The regional NPP showed a significant positive correlation with precipitation but was weakly correlated with temperature, suggesting that precipitation is the primary climatic factor that impacts regional grassland growth.

Soil respiration and carbon balance in fava bean farmland under conservation tillage

XIONG Ying, WANG Long-Chang, ZHAO Lin-Lu, DU Juan, ZHANG Sai, ZHOU Quan

2017, 26(1):  13-22.  DOI: 10.11686/cyxb2016089

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Soil respiration is an important process in carbon cycling. This study investigated effects of two tillage practices (ridge tillage and traditional tillage) and straw mulching at 0, 3750, or 7500 kg straw dry matter/ha on soil respiration of fava bean farmland. Six treatments applied were: traditional tillage without straw mulching (T), ridge tillage without straw mulching (R), traditional tillage+straw mulching at 3750 kg/ha (TS₁), ridge tillage+straw mulching at 3750 kg/ha (RS₁), traditional tillage+straw mulching at 7500 kg/ha (TS₂), and ridge tillage+straw mulching at 7500 kg/ha (RS₂). Soil respiration properties and carbon balance in dry-cropped farmland with a triple intercropping system of fava bean, maize, and sweet tomato were evaluated during the crop growth period, in a region of southwest China known as the purple hilly region. This study identified seasonal changes in soil respiration rate reflecting crop growth, with a peak in the middle of the fava bean growth cycle, and with a range from 0.885-10.213 μmol/(m²·s) in cropped soils, respectively. The soil respiration rates of the different treatments ranked TS₂>RS₂>RS₁>TS₁>T>R [4.096, 3.780, 3.441, 3.104, 2.850, 2.439 μmol/(m²·s), respectively]. Ridge tillage reduced soil respiration in fava bean farmland, whereas straw mulching treatment resulted in increased respiration corresponding to straw mulching levels. In soil planted with fava bean, the respiration rate at different crop growth stages ranked ripening<seedling<seed filling <branching< flowering and podding. Soil respiration during flowering, filling and podding stages contributed 50% of the total soil respiration. The contribution of root respiration to total soil respiration was 49.12% (range 37.02%-60.64%) when measured by a root biomass regression equation, but was 38.62% (range 19.49%-52.3%) when measured by root exclusion. The farmland system sequestered carbon during the life cycle of the fava bean crop with a net carbon sink ranging from 857.26 to 2236.25 kg C/(ha·yr). The treatments RS₂,TS₂,RS₁,TS₁, R increased carbon sequestration by 160.86%,101.44%, 30.78%, 47.63% and 110.41%, respectively (P<0.05), compared to the treatment T. This study indicated that ridge tillage and straw mulching conservation improved carbon sequestration in a fava bean farmland ecosystem, and the best treatment was RS₂ (ridge tillage+straw mulching at 7500 kg/ha).

Soil enzyme activities in alpine naked oat-artificial grassland in response to fertilizer and legume mix levels

LIU Wen-Hui, ZHANG Ying-Jun, SHI Shang-Li, HE Yong-Juan, SUN Jian, WEI Xiao-Xing

2017, 26(1):  23-33.  DOI: 10.11686/cyxb2016196

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To investigate the dynamics of soil enzymatic activity with regard to the combined effects of oat variety and different fertilizer and legume mixtures, an orthogonality experiment has been conducted in an alpine area. The experiment consists of three factors (oat varieties, fertilizer and legume mixtures) and four levels made up of (1) four oat varieties: Avena sativa cv. Qingyan No.1, A. sativa cv. Lena, A. sativa cv. Qinghai 444, A. sativa cv. Qinghai; (2) four fertilizer mixes: CK₀, urea (75 kg/ha)+NH₄H₂PO₃(150 kg/ha), organic manure (1500 kg/ha), urea (37.5 kg/ha)+NH₄H₂PO₃ (75 kg/ha)+organic manure (750 kg/ha); and (3) four Vicia sativa sow mixture rates: 0 kg/ha, 45 kg/ha, 60 kg/ha, 75 kg/ha. The results showed that appropriate combinations of oat variety, fertilizer mixes and legume sow rates can significantly improve soil enzymatic activities. The activities of soil urease, cellulose and invertase were respectively in the range of 400-900 μg/g, 80-180 μg/g and 4-7 mg/g in the cultivated alpine soil. Ranked from high to low, the factors that influenced soil enzymatic activities were first fertilizer mix, then variety, then legume mixture rate. Soil urease activity first increased and then decreased during the growth period, peaking at anthesis; cellulose activity first decreased and then increased, peaking at jointing stage; invertase activity had two periods of increase followed by decrease, with double peaks at the jointing and heading stages. Soil enzyme dynamics were calculated using the relative enzymes activity index and the relative enzyme activity comprehensive index. The highest soil enzymatic activities were recorded in the treatment consisting of the Qinghai 444 or Qinghai sweat oat variety mixed with 45 kg/ha V. sativa and fertilized with 37.5 kg/ha urea, 75 kg/ha NH₄H₂PO₃ and 750 kg/ha organic manure.

Microbial biomass, enzyme activity and composition of the fungal community in rhizospheric soil cropped with Artemisia annua for several years

LI Qian, YANG Shui-Ping, CUI Guang-Lin, HUANG Jian-Guo, LI Long-Yun, CHENG Yu-Yuan

2017, 26(1):  34-42.  DOI: 10.11686/cyxb2016091

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Artemisia annua (Qinghao, Asteraceae) is widely grown in Chongqing, China, for extracting the antimalarial drug, artemisinin. Many research studies focus on the release of allelochemicals into soils via leaching with rainfall percolation, on root exudation, and on decomposition of dead plant residues in the growing process of A. annua and on the inhibition of the growth and development of adjacent and subsequent crops by these allelochemicals, particularly artemisinin. Soil microbes play roles in nutrient transformation, organic matter recycling, toxicant decomposition, and hormone efflux, among others. However, little is known about the influence of continuous cultivation of this medicinal plant on soil microorganism populations. Therefore, rhizospheric soils cropped with A. annua for 1, 3, and 5 years were collected and analyzed by routine methods and Illumina MiSeq pyrosequencing to study microbial biomass, enzyme activity and fungal community components. Microbial biomass carbon (C) and nitrogen (N), and enzyme activities (dehydrogenase, urease and invertase) decreased, while C:N in microbes varied, and acid phosphatase activity increased in soils with this medicinal plant compared that in the soil without this plant. These results suggest that allelochemicals released from A. annua into the rhizosphere inhibited the metabolism, growth and reproduction of microorganisms. Principal component coefficients of fungal communities in soils varied significantly, indicating great changes of fungal community structures. In soil fungal communities, Ascomycota was the largest group, accounting for 66.10%-95.28% of the total taxa detected, and there was a significant change in the abundance of both fungal phyla and the top species during A. annua cultivation. Among the predominant fungi, 14 species were found in all soils, and only 1-3 unique species existed in each soil, suggesting that the soil was the most important factor governing the composition of the fungal community, but that community structure is also changed by A. annua cultivation. Erysiphe artemisiae and Puccinia tanaceti, two pathogenic fungi which only infect A. annua, were found in the soils cropped with A. annua. The presence of these two pathogenic fungi in soils would increase the risk of disease incidence in A. annua. Therefore, rotation is advisable when cropping A. annua. Although our study provided some information about fungal community composition and diversity in the soil cropped with A. annua, a large number of microorganisms detected remain unidentified, and the functions of microbes classified is also not clear. The results confirm that the understanding of soil microbial communities remains very poor. Further study should focus on determining the identity and function of bacterial members of the microbial community, as these could be important in maintaining soil quality and function in cropping systems.

Responses of soil microbial community functional diversity to Camponotus herculeanus ant-hill disturbance in alpine meadows

YANG You-Fang, ZI Hong-Biao, LIU Min, A DE Lu-Ji, CHEN Yan, WANG Chang-Ting

2017, 26(1):  43-53.  DOI: 10.11686/cyxb2016066

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To understand the function of the ants in the health and stability of an alpine meadow ecosystem we analyzed the effects of ant-hill disturbance on soil physical and chemical properties and microbial functional diversity in an alpine meadow using the Biolog-ECO microplate method. The results showed that while organic matter, total nitrogen, available nitrogen, available phosphorus and available potassium levels within the 0-10 cm soil depth were significantly higher than those in the 10-20 cm soil depth as expected (P<0.05), and that ant-hill disturbance had no significant effect on soil physicochemical properties (P>0.05). Ant-hill disturbance significantly improved soil microbial diversity index (specifically, values of Shannon-Weiner, Pielou, McIntosh and carbon utilization efficiency) and principal component analyses showed that ant-hill disturbance influenced soil microbial diversity and changed the microbial metabolism characteristics of soil microorganisms, to a status where carbohydrates, amino acids and carboxylic acid were the main carbon sources for the soil microbial community. Redundancy analyses indicated that metabolic rate and microbial functional diversity of soil microbial community was affected by soil nutrient levels. Therefore, the mining activities of the ants and associated accumulation of organic matter changed the soil microenvironment under the ant hills, resulting in changes to the soil microbial carbon source utilization and metabolism.

Grassland community species diversity and aboveground biomass responses to difference in cover soil thickness in restoration after mining damage

SUN Yong-Xiu, YAN Cheng, XU Hai-Liang, YAO Yan-Li

2017, 26(1):  54-62.  DOI: 10.11686/cyxb2016072

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This experiment examined different options for restoration of damaged steppe vegetation in the Kurt Kizu mining area, Xinjiang province, China. Different depths of cover soil (0, 10, 14, and 18 cm) were applied to mine-damaged steppe, and ground cover, height, aboveground biomass and species richness, diversity and evenness of the vegetation were measured. Key results were: 1) The number of species present and the diversity were highest when cover soil was applied at a thickness of 14 or 18 cm. The cover, height, and aboveground biomass of the vegetation generally increased with the thickness of cover soil, but the differences between 14 and 18 cm cover soil thickness were not statistically significant. 2) Species richness indices (R and Ma) ranked: 14 cm cover soil thickness>10 cm cover soil thickness>18 cm cover soil thickness>0 cm cover soil thickness, while diversity indices (D and H') ranked: 14 cm cover soil thickness>18 cm cover soil thickness>10 cm cover soil thickness>0 cm cover soil thickness. The community evenness indices (J_sw and Ea) showed an inverse ranking to richness and diversity with 0 cm cover soil thickness>18 cm cover soil thickness>10 cm cover soil thickness>14 cm cover soil thickness. 3) There was a low positive correlation between community productivity and Shannon-Wiener and Simpson indices. Therefore, for the Kurt Kizu mining area, considering economic cost against ecological benefits when restoring damaged steppe, the appropriate cover soil thickness for ecological restoration of grassland vegetation is 14 cm.

Effect of grazing on Stipa breviflora age dynamics and leaf traits

LIU Wen-Ting, WEI Zhi-Jun, LV Shi-Jie, WANG Tian-Le, ZHANG Shuang, HAI Song

2017, 26(1):  63-71.  DOI: 10.11686/cyxb2016277

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The regulation mechanism of plant population structure and function by herbivores is an important part of grazing ecology. A long-term grazing study in Xilingol was used to reveal the mechanisms of the regulation of plant responses to grazing through population age dynamics and leaf traits of Stipa breviflora in desert grassland. The result showed that few S. breviflora plants with base diameter of less than 4 mm survived. There was little difference between moderate grazing and no grazing. The frequency and proportion of age class Ⅲ plants was reduced 0.79 and 0.73 respectively by heavy grazing. S. breviflora population were relatively stable. Two way ANOVA showed that leaf height, leaf length, leaf dry weight, leaf erectness and leaf length-width ratio were sensitive to grazing in different age classes. By contrast, leaf width, leaf rolling index and leaf dry matter content were not affected by age class. Correlation analysis suggested that leaf width and leaf dry matter content changed synergistically with the age sensitive traits. Leaf rolling index was significantly negatively correlated with leaf dry weight, and was positively related with leaf erectness (e.g. age class Ⅲ and class Ⅰ). The study suggested that S. breviflora completed its life history and adapted to grazing by controlling population age and leaf traits in a metastable state.

Effects of different cutting height and frequency combinations on growth and production performance of hybrid giant napie

GUO Xiao, DENG Hong-Yu, HU Hua-Feng, LI Jian-Ping, HUANG An-Qun, BAI Chuang-Jun, TANG Jun

2017, 26(1):  72-80.  DOI: 10.11686/cyxb2016087

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This experiment was designed to explore the effects of cutting regime on growth characters and production performance of hybrid giant napie (Pennisetum sinense) planted on Yellow River flood plain, and consisted of a factorial combination of four cutting heights (cutting at 5,10,15 and 20 cm) and 4 cutting frequencies(cutting interval 30, 40, 60 and 120 d), to address some difficult problems with this species, including short utilization period, low yield, poor forage quality, and a high incidence of lodging with this cropplanted in Yellow River flood plain under continental climate. The cutting regime had a significant effect on the growth and production of hybrid giant napie. Multiple cutting within a growing season decreased stem to leaf ratio (S/L ratio) and leaf area index (LAI), while optimal cutting (cutting at 15-20 cm height and 60 d intervals) raised fresh biomass to dry matter ratio (F/D ratio), tiller density, and growth rate, compared to other treatments. More frequent and severe defoliation (cutting at 5 cm height and 30 d intervals) raised F/D ratio and number of single plant tillerings, noticeably decreased incidence of lodging, but decreased re-growth rate which was unfavourable to sustainable and efficient production of forage. The more favourable cutting regimes increased forage yield by 14.3%-17.3% compared to that (cutting only at 120 d cutting interval) and the annual forage yield reached 32 t DM/ha. Furthermore, optimal cutting decreased lodging, reducing losses of energy and nutrients at harvest. In conclusion, optimal cutting height and frequency, together with appropriate irrigation and fertilizer regimes were important to achievement of production potential, eliminating unnecessary losses in yield and forage quality.

Evaluation of Japanese soybean varieties in the Sichuan Basin, China

WU Hai-Jun, YANG Cai-Qiong, Nasir Iqbal, DENG Jun-Cai, DAI Wei, LIU Wei-Guo, YANG Feng, SHU Kai, DU Jun-Bo, YANG Wen-Yu, LIU Jiang

2017, 26(1):  81-89.  DOI: 10.11686/cyxb2016084

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In this study 17 soybean genotypes were introduced from Japan to the Sichuan Basin with an aim to assess their adaptability. Comparison of quality traits showed that variation in isoflavone content was highest; the coefficient of variation values were generally greater than 30% (apart from aglycone), while the coefficient variation for other seed compounds was around 10%. The soluble protein contents of the tested soybean seeds were relatively high while fatty acids, soluble polysaccharides and isoflavone were low. Principal component analysis and cluster analysis divided the 17 germplasms into five groups. Individually, Group-Ⅰ comprised high-oil varieties, their linoleic acid content were>55‰, suggesting that they could be used to produce high-oil hybrid varieties. Group-Ⅲ comprised high-protein varieties, potentially useful for developing varieties to produce soy raw materials; Group-Ⅴ comprised high-isoflavone varieties, which could potentially be used to produce varieties useful for functional food or fodder.

Studies of the floral organ characteristics and sexual breeding system of Fritillaria unibracteata

CHEN Yuan, XU Bo-Qiong, GUO Feng-Xia, BAI Gang, ZHANG Jin-Feng, ZHANG Yong

2017, 26(1):  90-98.  DOI: 10.11686/cyxb2016070

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To determine the flower characteristics and sexual breeding system for Fritillaria unibracteata, a combination of field tests and microscopy examination was used to study the flower conformation and pollination biology in order to provide scientific information to assist in plant breeding. This species has a single bisexual flower borne at the stem apex. Occasionally there are two flowers when cultivated for three years from bulbs. The immature bud is green and then turns a darker purple covered with light yellow flecks. The flowering period is from May to June but single flowers bloom only 6-8 days. The bell-shaped flower has six perianth segments in two whorls and six apopetalous stamens within, five of which are tightly circumfused to the pistil and the other independent. The epigynous ovary has three short splits on its hairy chapiter which are secretory. The ovary stands higher than the stamens in the young bud, but becomes shorter in mature, open flowers. The pollen quantity, and vigor is maximal on the first day of flowering and pollen is produced for three days. The pistil stigma in a 1.5 cm long green bud was already receptive. Anther dehiscence coincided with the peak in stigma receptivity but stigma receptivity lasted longer (over 6 days) than pollen production. The flower has over 6000 pollen grains and 160 ovules in single flower, resulting in a pollen to ovule (P/O) ratio of 37.5. The out crossing index (OCI) was 4 according to the flower size and behavior. Pollinators included wind and a few wasps, bees, spiders and other miscellaneous insects. Our results suggest that this species should possess a sexual breeding system with partial self-compatibility, heterogamy, and required pollinators.

Identification of soybean growth-promoting rhizobacteria and their effects on the growth and quality of Glycine max and Lotus corniculatus

ZENG Qing-Fei, WANG Qian, LU Rui-Xia, LIU Zheng-Shu, WU Jia-Hai, WANG Xiao-Li

2017, 26(1):  99-111.  DOI: 10.11686/cyxb2016063

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In order to screen combinations of rhizobacteria which have growth-promoting and quality-improving effects on local leguminous crops, phosphorus-solubilizing bacteria were isolated from soybean rhizospheric soils in the Bijie Region of Guizhou Province and rhizobium strains were isolated from soybean root nodules. Phosphorus-solubilizing strains with ratios of the diameter of the phosphorus-solubilizing halo to colony diameter of more than 2.20 were tested for their abilities of phosphorus-solubilizing, 3-indoleacetic acid (IAA)-secreting, organic acid and alkali production. Four superior phosphate-solubilizing strains were selected. For the isolated rhizobium strains, two highly efficient strains were screened out by means of back-inoculation and growth-promoting effect tests on soybean tube seedlings. The six selected strains were tested for antagonistic reactions and three types of bacterial suspension were prepared: phosphate dissolving only, rhizobia only and a mix of the two. These were immediately inoculated into Glycine max and Lotus corniculatus in pots to test their growth-promoting effects. The results showed that, compared to control, the rhizobia only inoculants had no effect on the plant height of G. max whereas the other two treatments could significantly increase height. All three treatments had significant promoting effects on G. max stem diameter, biomass, number of bean pods, weight of pods, seeds per pod and single seed weight. Among the three treatments, the mix of phosphate dissolving and rhizobia inoculants showed the best growth effects on soybean seedling plant height, stem diameter, aboveground biomass and underground biomass (respectively 21.26%, 40.79%, 15.88% and 42.19% higher than control). With regard to L. corniculatus, all three treatments could improve first and second harvest plant height, aboveground biomass, total nitrogen content, total phosphorus content and crude protein content. Again, the effects of the mixed treatment of phosphate dissolving with rhizobia inoculants were the highest (respectively 20.82%, 54.88%, 106.14%, 148.78%, 19.34%, 61.88% and 19.34% higher than control). The results thus indicate that combining phosphate-solubilizing with rhizobium bacteria strains produces a favourable interaction effect.

The effect of Phoma medicaginis on the photosynthetic physiology of Medicago sativa

FAN Qin, LI Yan-Zhong

2017, 26(1):  112-121.  DOI: 10.11686/cyxb2016275

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The yield and quality of Medicago sativa are seriously affected by the fungal pathogen Phoma medicaginis. A study has been undertaken using growth chamber pot experiments and the LI-6400/XT photosynthesis measurement system to investigate the effects of this pathogen on the photosynthetic physiology of M. sativa. The results showed that until 27 days post-inoculation (dpi) the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of M. sativa were reduced by P. medicaginis infection. In the early stages of infection there were little changes in intercellular CO₂ concentration (C_i) in the leaves. By 23 dpi, infected leaves showed significant reductions in photochemical quantum efficiency (F_v/F_m), PSⅡ reaction center of excitation energy capture efficiency (F_v'/F_m'), the relative quantum efficiency of PSⅡ photochemistry (Φ_PSⅡ), electron transfer rate (ETR), photochemical quenching (qP) and non-photochemical quenching (qN). Light compensation point, CO₂ compensation point and carboxylation efficiency (CE) also decreased. The results indicate that the photosynthetic electron transfer rate and capture efficiency, non-photochemical quenching (qN), and carboxylation efficiency (CE) decreased in leaves infected by P. medicaginis, leading to light suppression and a decrease in the assimilation of CO₂ that affect the growth and development of M. sativa.

The effect of cadmium on germination of Cosmos bipinnatus seeds and the alleviation effects of exogenous methyl jasmonate

LIU Yu-Jing, FENG Yi-Mei, LIU Xin-Yue, JIANG Yu-Lin, TAN Miao, JIANG Tian-Yi, YU Xiao-Fang

2017, 26(1):  122-130.  DOI: 10.11686/cyxb2016264

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A study has been undertaken to explore the effect of cadmium (Cd²⁺) on Cosmos bipinnatus seed germination and to discover the optimal treatment mode and concentration of exogenous methyl jasmonate (MeJA) under Cd²⁺ stress. Seeds were germinated on filter paper bedding and measurements taken of germination potential, germination rate, vigor index, plumule lengths, fresh weights, malonic dialdehyde (MDA) and the activity of antioxidant enzymes. The results showed that germination potential, germination rate, vigor index and plumule length reduced gradually with increases in Cd²⁺ concentration. C. bipinnatus seeds can endure low Cd²⁺ concentrations (<0.6 mmol/L), but their germination indexes were significantly inhibited by high concentrations (≥0.6 mmol/L). The performance of seeds pretreated with MeJA was higher than that of seeds subjected to Cd²⁺ and MeJA simultaneously. The optimal treatment concentration was 1.0 μmol/L MeJA which, compared to treatment with Cd²⁺ only, increased germination rate by 19.3%, vigor index by 73.0%, fresh weight by 28.1% and reduced MDA contents. The alleviation effect of low concentrations of MeJA on seed germination under Cd²⁺ stress was mainly through increasing peroxidase, catalase and glutathione reductase activity to scavenge reactive oxygen species and reduce lipid peroxidation of the membrane.

Functional analysis of two stress-related promoters in Medicago varia cultivar Xinmu No.1

CHAO Zhao-Xia, REN Yan-Ping, QIAN Jin, YAO Zheng-Pei, XU Lei, ZHANG Hua

2017, 26(1):  131-141.  DOI: 10.11686/cyxb2016071

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MvP5CS and MvNHX1 genes of the Medicago varia cultivar Xinmu No.1 and their promoter sequences have been successfully cloned in previous work. Based on this research, in this study two plant expression vectors, each containing Mvp5cs and Mvnhx1 promoters with a GUS gene as the reporter, were constructed and two tobacco transgenic plants with the promoter obtained by Agrobacterium-mediated method. PCR analysis showed that the two promoters had been stably integrated into the tobacco genome and GUS-staining proved that they have the function of activating gene expression. We explored this function by measuring GUS activity under four different abiotic stresses: drought, salinity, abscisic acid (ABA) and gibberellin (GA). The results showed that Mvnhx1 and Mvp5cs responded to the four stresses and had significant differences from the CaMV35S promoter. The Mvnhx1 promoter was superior to Mvp5cs under salt and ABA stress. After 48 h treatments of 100 and 150 mmol/L NaCl stress, the GUS activity of Mvnhx1 was 2.03 times and 3.23 times that of Mvp5cs. Under treatments of 25 and 50 μmol/L ABA stress, Mvnhx1 activity was significantly higher than the other two promoters. Mvp5cs was superior to Mvnhx1 under drought and GA stress. The GUS activity of the Mvp5cs was 2.22 times that of Mvnhx1 after 36 h treatment of drought stress. The Mvp5cs promoter reached its maximum value, which was 1.79 times that of Mvnhx1, after 36 h treatment with 70 μmol/L GA stress.

Biological characteristics of Lubao No.1 biological control agent (Colletotrichum gloeosporioides) and construction of a T-DNA insertional mutant library

LI Jian, LI Mei, GAO Xing-Xiang, FANG Feng, DONG Lian-Hong

2017, 26(1):  142-148.  DOI: 10.11686/cyxb2016238

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The application of Lubao No.1 microbial agent has been limited because of its degradation, although the strain shows high bio-herbicidal activity against Cuscuta chinensis. The results of an investigation of the biological characteristics of Lubao No.1 showed that the optimal mycelium growth medium was PDA medium. The optimal culture temperature is 25-28 ℃, and optimal initial pH of culture media was 5-8. Construction of a T-DNA insertional mutant library of Lubao No.1 using an Agrobacterium mediated transformation method, produced about 2300 positive transformants. Randomly selected transformants were all resistant to hygromycin B. A hygromycin gene fragment was amplified by PCR from all 20 tested mutants, indicating that the resistance of the transformants to hygromycin B was stable and was caused by the inserted T-DNA. This study laid the foundation for obtaining further applications of a genetically modified Colletotrichum strains with stable pathogenicity.

Identification of plant growth promoting rhizobacteria Astragalus membranaceus and their effectives

MA Cong-Yu, ZHANG Ying, MA Wen-Bin, LI Jian-Hong, YAO Tuo

2017, 26(1):  149-159.  DOI: 10.11686/cyxb2016263

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In order to obtain and study the performance of plant growth promoting rhizobacteria (PGPR) in Astragalus membranaceus, the root nodule, root morphology and rhizosphere soil of A. membranaceus were collected. Strains of rhizobium and phosphate solubilizing bacteria were isolated and assessed for the potentially useful characteristics of high nitrogenase activity in the rhizobium and high phosphate solubilisation and ability to secrete 3-indoleacetic acid (IAA) in the phosphate solubilizing bacteria. Potential PGPR strains were then identified using physiological and biochemical characteristics and 16S rDNA sequence analysis. Results showed there are large amounts of phosphorus-dissolving bacteria in the rhizospheres of A. membranaceus. The quantitative distribution of bacteria and PGPR shows a strong rhizosphere effect, with rhizosplan or surface of roots (RP)>soil adhering to roots (RS)>soil away from roots (NRS)>histoplan or interior of roots (HP). We have isolated 76 PGPR strains, composed of 1 rhizobium, 42 inorganic phosphate solubilizing and 33 organic phosphate solubilizing bacteria strains. There are 7 phosphate solubilizing strains with the ability to secrete IAA. A further 8 potential PGPR strains were identified (1 rhizobium and 7 phosphate solubilizing). 3 phosphate solubilizing strains were identified as Pseudomonas sp., 3 phosphate solubilizing strains as Bacillus sp., 1 phosphate solubilizing strain as Klebsiella oxytoca, 1 rhizobium strain as Rhizobium sp. This study has identified potential PGPR for the development of microbial fertilizers for A. membranaceus.

Effectiveness of different insecticides for control of aphids and thrips on alfalfa

LUO Lan, YUAN Zhong-Lin, SUN Juan

2017, 26(1):  160-167.  DOI: 10.11686/cyxb2016240

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Imidacloprid 10% wetable powder, cypermethrin 10% emulsifiable concentrate and chlorpyrifos 48% emulsifiable concentrate were compared for their ability to control aphids and thrips on alfalfa; their application safety and environment effects including residual effects were also assessed. Gas chromatography was used to assess chemical residue levels. At 1-7 days after treatment, the efficacy of imidacloprid, cypermethrin and chlorpyrifos against alfalfa aphids at application rates of 35.7 g a.i./ha (available ingredient/hectare), 75.0 g a.i./ha and 480.0 g a.i./ha were 80.83%-94.78%, 79.29%-87.80% and 90.93%-98.90%, respectively; against thrips efficacy were 78.33%-95.57%, 78.56%-91.67% and 92.78%-100.00%, respectively. The half-life of imidacloprid, cypermethrin and chlorpyrifos were 4.78, 3.69 and 2.48 days, respectively. Seven days after application residues of imidacloprid and chlorpyrifos in alfalfa were less than 0.5 mg/kg while cypermethrin residues did not drop below 0.5 mg/kg until 14 days after application. Based on the pesticide residue standards of the China and Codex Alimentarius Commission (CAC), the maximum residue limit (MRL) of imidacloprid, chlorpyrifos and cypermethrin were recommended at 0.5, 1.0 and 0.5 mg/kg, and the recommended safe application interval 7, 14 and 7 days respectively, in alfalfa.

Performance of Hu sheep in the cold, arid area’s of North-West China

MO Fu-Tao, LI Fa-Di, WANG Wei-Min, LA Yong-Fu, ZHANG Xiao-Xue, LIU Ting, TANG De-Fu, YUE Xiang-Peng, LI Fei, LI Chong, LI Wan-Hong, XIAO Jin-Yu, TAN Jian-Hua, WU De-Hu

2017, 26(1):  168-177.  DOI: 10.11686/cyxb2016076

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Hu sheep are one of the world’s rare localised sheep breeds; it is known for high fecundity, early maturity, rapid growth rates and being suitable for stabling. In order to understand the growth and development and enable better utilization of the traits of Hu sheep male sheep 3, 6, 12 and 24 months of age were assessed to determine live weight, the weight of different body components including the digestive tract weight, intestinal length, and meat quality traits. Results indicated that Hu sheep grow fastest between 3 to 6 months of age; after 6 months, relative growth rates begin to decline. Organ growth (heart, liver, spleen, lung, kidney, head and feet, skin and wool) increased with age between 3 to 6 months, though the head, feet, skin and wool were relatively stable, growth of remaining organs gradually reduced becoming stable by age 12 months. The growth rate of the rumen was always greater than growth in live weight, while the growth rate of the small intestine was less, with the exception of colorectal growth which was similar to live weight growth. Compared to 12 month old sheep, 6 month old male Hu sheep have better back fat thickness and eye muscle area with no difference in dress out and loin eye area. Meat colour darkened with age. It was concluded that the optimal age for slaughter was 6 months.

Cultivation and utilization of alfalfa in modern China

SUN Qi-Zhong, LIU Qian, TAO Ya, LI Feng, XU Li-Jun

2017, 26(1):  178-186.  DOI: 10.11686/cyxb2016054

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The cultivation and utilization of alfalfa in modern China is reviewed from traditional beginnings to its rapid development through a modern scientific approach. The introduction, domestication, cultivation, processing, storage and feeding, and characteristics of different varieties are described. An extensive literature review was used as the primary research tool. Results show that alfalfa is extensively utilized in modern China. Originally the adaptability of alfalfa was assessed in the northeast, north, northwest and southern areas of China. The biology and potential usefulness as forage were also assessed. Since the establishment of The Republic of China, the Chinese and American Agricultural Science and Technology inspection group have surveyed animal husbandry practices in China, and made suggestions on the development of forage crops. The development of alfalfa as an important forage crop has been rapid and its use in China widespread.

Advances in arbuscular mycorrhizal fungi and legumes symbiosis research

HE Shu-Bin, GUO Li-Xiang, LI Jing, WANG Yi, LIU Ze-Min, CHENG Yu-Yang, HU Tian-Ming, LONG Ming-Xiu

2017, 26(1):  187-194.  DOI: 10.11686/cyxb2016228

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Arbuscular mycorrhizal fungi (AMF), are widely distributed in the soil and plant roots of almost all agricultural ecosystems. In this symbiosis, AMF consumes carbohydrates produced by the host plant using the hyphae associated with the roots for growth and reproduction; at the same time arbuscular mycorrhizal hyphae enhance the capacity for root absorption, which provides nutrients needed for growth (such as phosphorus and nitrogen). Legumes can form symbiosis with arbuscular mycorrhizal fungi. Numerous studies indicate that arbuscular mycorrhizal fungi can improve legume growth, promote the absorption of mineral nutrients and water, and enhance biological nitrogen fixation capacity and stress resistance. The aim of this study was to enable better use of mycorrhizal fungi to promote legume production; the signal transduction mechanisms that may exist during the establishment of symbiosis were analyzed and the responses of legume yield and nutritional value to arbuscular mycorrhizal are discussed. The internal mechanisms of increased stress resistance due to arbuscular mycorrhizal are clarified, potential mechanisms of the interactions between arbuscular mycorrhizal and rhizobia are explored and the prospects for arbuscular mycorrhizal and legumes symbiosis studies in the future are addressed.

Overview and prospects for ecological safety threshold research

WANG Shi-Jin, WEI Yan-Qiang

2017, 26(1):  195-205.  DOI: 10.11686/cyxb2016075

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With global change intensifying, the ecological environment has been disturbed and damaged, resulting in increasingly evident ecological security problems. During the 21st century, ecosystem risk (or safety) assessment has become an internationally recognized discipline at the forefront of global change and ecology research. A key object of ecological safety research is to identify and understand the tolerance threshold of the different types of ecosystems at various scales and the processes of adaptive management of ecosystems under global change stress. This paper takes the different elements affecting ecosystems as the starting point to review the theory and application of the ecological safety threshold concept. The literature reveals the interrelationship between ecological steady-state processes and perturbations of climate change, impacting on carbon and nitrogen cycles, with a consequent need for changes to land and grassland use, and regional policy regimes, among others. Furthermore, improving detection of ecological safety thresholds in major ecosystems and the precision of forecasts about their behavior is pivotal to restoration of degraded ecosystems and the protection and management of the ecological environment. Because of the complexity of the changes to ecosystem processes induced by the various stress factors, and gaps in knowledge about the processes themselves, especially in relation to defining health and sustainability in different types of ecosystem, the determination and predictive capability pertaining to the ecological safety threshold is currently very limited, and there is still great uncertainty.

Effects of Mucaojing application time on alfalfa (Medicago sativa) production

MIAO Fu-Hong, SUN Juan, YANG Guo-Feng, TAN Zi-Heng, LIU Hong-Qing, YAN Di

2017, 26(1):  206-211.  DOI: 10.11686/cyxb2016096

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This research investigated the effect of Mucaojing (imazethapyr 5%) application time on the productivity of alfalfa on the Shandong peninsula. Plant height, biomass, crude protein (CP) content, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were assessed after application of Mucaojingat 4 stages. The results showed that Mucaojing application reduced plant height slightly when applied at emergence and seeding stages; biomass significantly increased (P<0.05) when Mucaojing was applied at seeding. Mucaojing did not affect leaf-stem ratio. CP was negatively correlated with application time; when applied at emergence CP content was significant higher (P<0.05) than treatment at the pre-sowing stage. NDF and ADF were significantly reduced (P<0.05), by Mucaojing application. In conclusion, the application of Mucaojing at the emergence stage increased alfalfa biomass and CP content under rain-fed conditions.