Table of Content

20 August 2016, Volume 25 Issue 8

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Comparative studies of reconstruction methods for the long term NDVI dataset in the east of Northwest China

WANG Wei, GUO Ni, SHA Sha, HU Die, WANG Xiao-Ping, LI Yao-Hui

2016, 25(8):  1-13.  DOI: 10.11686/cyxb2015489

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A high-level time-series NDVI dataset is not only the basis for continuous monitoring of the land surface, but also an important tool for studying change related to climate and land use factors in terrestrial eco-systems. We reconstructed the noise component of the LTDR NDVI data for the east of Northwestern China where the ecosystem is fragile, using various time-series reconstruction methods. This paper use agrometeorological data and high-level NDVI data to evaluate the accuracy of different reconstruction methods. The results show that: 1) The vegetation or crop land cover is an important factor affecting fitted results of the various reconstruction methods. Each reconstruction method has a different noise reduction ability depending on differences in vegetation or crop growth characters; 2) The D-L reconstruction method has a better noise reduction ability and applicability in those areas of grassland, and woodland for which the annual average NDVI data is higher (NDVI≥0.3) and the NDVI curve has obvious seasonal changes; 3) The S-G reconstruction method has better fidelity ability and applicability in some areas of crop land in winter wheat and in areas of sparse vegetation for which annual average NDVI data are lower (NDVI<0.3) and where the NDVI curve have no obvious seasonal changes.

Monitoring of grassland herbage accumulation by remote sensing using MODIS daily surface reflectance data in the Qingnan Region

YANG Shu-Xia, ZHANG Wen-Juan, FENG Qi-Sheng, MENG Bao-Ping, GAO Jin-Long, LIANG Tian-Gang

2016, 25(8):  14-26.  DOI: 10.11686/cyxb2015455

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Monitoring of grassland herbage accumulation using remote sensing technology has a potentially important role in understanding seasonal changes in grasslands and optimizing animal husbandry and grazing management. In this study above ground biomass (AGB) and its spatial distribution was recorded using in-situ measurements during the growing seasons from 2010 to 2013 in southern Qinghai province, and regression models using in-situ AGB data and the corresponding daily surface reflectance product of Terra MODIS were established. The spatial analysis method was used to calculate four vegetation indices (NDVI_max, EVI_max, NDVI_mean and EVI_mean) using MOD09GA data, and the accuracy of the inversion models was then analyzed, and the spatial distribution of the NDVI mean values in the previous 10 years characterized. With the algorithms optimized in this way, we estimated the aboveground grassland biomass and its spatial distribution for the previous 10 growing seasons. It was found that the aboveground biomass gradually increases from northwest to southeast, and different grassland types have characteristic biomass differences. The biomass of mountain meadow was highest among the grassland types included in this 10 year study, and reached 1280 kg DW/ha in 2010. The biomass of alpine meadow, warm steppe, warm desert and marsh ranged between 244.9 kg DW/ha and 902.4 kg DW/ha, The biomass values of alpine meadow grassland, alpine desert, and alpine desert grassland were much lower, and were below 65 kg DW/ha. The elevation had a marked effect on biomass, with grassland biomass decreasing with increasing elevation above 3500 m. At elevations between 3500 and 4000 meters, peak biomass was 1358.8 kg DW/ha; between 4000 and 4500 meters, the biomass was below 920 kg DW/ha, and between 4500 and 5000 meters the biomass averaged approximately 574.2 kg DW/ha. Above 5000 meters elevation, the biomass averaged approximately 94.4 kg DW/ha. The trend of NDVI mean values in last 10 years indicates that most regions in the Three River Headwater region (The Yellow River, The Yangtze River, and The Mekong River), which span different administrative areas, can be categorized as showing ‘mild improvement’ or ‘improvement’. Overall, the trend in grassland vegetation status is positive.

Responses of greenhouse gas emissions to water table fluctuations in an alpine wetland on the Qinghai-Tibetan Plateau

WANG Dong-Xue, GAO Yong-Heng, AN Xiao-Juan, WANG Rui, XIE Qing-Yan

2016, 25(8):  27-35.  DOI: 10.11686/cyxb2016012

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A mesocosm experiment was conducted to study the effect of water table level on greenhouse gas (CO₂, CH₄, N₂O) emissions in alpine wetland on the Qinghai-Tibetan Plateau. Two treatments were adopted; stable water table (SW; about 0 cm or at soil surface) and dynamic water table (DW; 0 cm reducing to 45 cm and returning to 0 cm). The results showed that alpine wetland water table changes had no significant effect on soil dissolved organic carbon (DOC), but promoted transformations of ammonium (NH4+-N) and nitrate (NO3--N). The cumulative emissions of CO₂ were 235.2 and 209.7 g/m² for SW and DW treatment, respectively but were not significantly different. However, there was a significant treatment difference on CH₄ emissions. Cumulative emission of CH₄ for DW (0.86 g/m²) decreased by 52.18%, compared with SW (1.79 g/m²). The cumulative emission of N₂O for SW (6.72 mg/m²) was significantly higher than that for DW (7.36 mg/m²). There was a positive correlation between CO₂/CH₄ release and soil temperature in the alpine wetland with soil temperatures below about 10 ℃. The drop in the water table increased the sensitivity of CO₂/CH₄ release to soil temperature. Models of the response of CO₂, CH₄ and N₂O emissions to water table changes were different in alpine wetland on the Qinghai-Tibetan Plateau.

Effects of land use on soil microbial biomass and community structure in the loess hill region of west Henan

LIU Jing, ZHAO Yan, ZHANG Qiao-Ming, XU Shao-Jun

2016, 25(8):  36-47.  DOI: 10.11686/cyxb2016057

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In order to uncover the effects of different land use systems on soil microbial biomass and community structure characteristics, we selected five land use types; woodland, shrub land, orchard, abandoned farmland and farmland. We analyzed soil phospholipid fatty acids (PLFAs). Compared with the farmland, woodland increased soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) content by 225.38% and 206.19% respectively (P<0.05) while the MBC/total organic carbon (TOC) and MBN/TN value increased by 2.89 and 5.05 respectively (P<0.05). Shrub land increased soil MBC and MBN content by 265.73% and 245.03% respectively (P<0.05), the MBC/TOC and MBN/TN value increased by 3.00 and 5.57 respectively (P<0.05). Orchard management increased soil MBC and MBN content and MBN/TN value by 107.80%, 84.99% and 1.23 respectively (P<0.05). There was no difference in MBC and MBN and microbial biomass phosphorus (MBP) between the abandoned farmland and farmland soil (P>0.05). Bacterial and fungal PLFA in woodland soil increased by 17.87% and 24.27% respectively compared to farmland (P<0.05) while in shrub land these traits increased by 17.18% and 28.45% respectively (P<0.05). Orchard soil bacterial PLFA content was increased by 9.0% (P<0.05). Soil bacteria, fungi and actinomycetes PLFA in abandoned farmland and farmland were similar (P>0.05). The Shannon diversity index and Pielou evenness index of woodland and shrub land were significantly higher than other systems (P<0.05) while the Simpson dominance index was significantly decreased (P<0.05). The PLFA content of soil bacteria, fungi, and actinomycetes was significantly, positively correlated with TOC, MBC, total nitrogen (TN), available nitrogen (AN), MBN and bulk density (BD) (P<0.05 or P<0.01). The results showed that compared with farmland, abandoned farmland and orchard soil, soil microbial diversity of woodland and shrub land is enhanced; microbial species are uniformly distributed and community structure is relatively stable. This indicates that woodland and shrub land are superior for improving soil quality and microbial community structure diversity. The input of nutrients and the change of soil structure caused by different land use patterns is one of the reasons for the change of microbial community structure.

Changes in the spatial distribution and dynamics of soil organic carbon density in grasslands converted from farmland

TIAN Yao-Wu, HE Chun-Ling, LIU Long-Chang, WANG Ning, XU Shao-Jun, LIU Jing, LI Dong-Sheng

2016, 25(8):  48-55.  DOI: 10.11686/cyxb2015499

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The objective of this study was to explain changes in the spatial distribution and dynamics of soil organic carbon (SOC) in grasslands converted from farmland in the Lanlingxi watershed, Yichang City, and thus to provide a theoretical basis for assessments of the carbon sink function of abandoned farmland. The experimental scenario subsets included a control group (A₁) and a split-plot design with C₄ plant (Rhizoma cyperi) litter removal (B₀) versus double litter input (B₂) in 2008. Soil samples at different depths were collected at the end of March from 2008 to 2015. SOC density was determined and the results are as follows. 1) After the return of farmland to grassland, the balance of SOC density was disrupted and carbon sink functions initiated. The time taken for SOC density to reach a new dynamic equilibrium was 12 years. The annual rate of SOC sequestration was 263.5 g/m². 2) In 2008, SOC densities in the three experimental areas ranked in the order: B₂ (5504±245 g/m²)>B₀ (5476±267 g/m²)>A₁ (5392±306 g/m²); but by 2015 the rank order had changed to A₁ (6022±298 g/m²)>B₀ (5963±315 g/m²)>B₂ (5807±274 g/m²). Not only plant species but also the amount of litter can affect variations in organic carbon density. 3) SOC densities in the control (A₁) and litter removal (B₀) areas increased continuously during the study period, while the double litter area (B₂) fluctuated in 2009-2011 and then increased continuously. Control area (A₁) conditions were more conducive to the accumulation of SOC. 4) The changes in SOC affected by plant species and the amount of litter were mainly at the 0-20 cm soil layer, while at layers greater than 20 cm there was no change. SOC densities at different depths of farmland and grassland soils were significantly different (P<0.05). The spatial distribution of SOC density in all three experimental areas changed during the farmland-grassland succession process. The amounts of SOC accumulation varied significantly during the transition from farmland to grassland.

Effects of drying temperature on water loss and germination rates of leguminous forage seeds

MA Jin-Xing, TU De-Peng, KOU Jian-Cun, LIU Fang

2016, 25(8):  56-64.  DOI: 10.11686/cyxb2015508

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In order to understand the effects of drying temperature on the water loss and germination rates of seeds, seeds of 23 legume species were dried at (15±2) and (21±2) ℃ with (15±3)% relative humidity before they were put into the gene bank. The results showed that: 1) at 11 d the water contents of 14 species met the storage standard, below 7%, while all species with the exception of Coronilla varia met the standard at (21±2) ℃. 2) Compared with undried seeds, the drying temperature (15±2) ℃ had no effect on the seed germination rates of 11 species, increased the rates of 6 species and significantly decreased the rates of 6 species. The drying temperature (21±2) ℃ had no effect on 15 species, increased the germination rate of 5 species and decreased that of 3 species. In conclusion, the easily-dried seeds (Tephrosia candida, Lotus corniculatus, Trifolium pratense, Calopogonium mucunoides, Cajanus cajan, Medicago sativa, Astragalus adsurgens, Stylosanthes hamata, Pueraria lobate and S. guianensias) and the relatively-easy-dried seeds (Lespedeza bicolor, Caragana korshinskii and A. sinicus) should be dried at (15±2) ℃. Seeds that are more difficult to dry (T. repens, Macroptilium lathyroides, Onobrychis viciifolia, T. vesiculosm, Vicia sativa, T. incarnatum, Hedysarum leave, Macrotyloma uniflorum and Crotalaria pallida) should be dried at (21±2) ℃. The drying temperature for C. varia, which was very difficult to dry, requires further study.

Effect of different temperature and moisture conditions on seedling growth of Festuca sinensis

WANG Jian-Jun, WANG Zhi-Gang, MA An-Wei, LIN Wei-Hu, KUANG Yu, TIAN Pei

2016, 25(8):  65-73.  DOI: 10.11686/cyxb2015492

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Morphological characteristics of Festuca sinensis seedling growth were studied using the inner potted method under different temperature and moisture conditions. In order to explore the appropriate conditions for seedling growth, natural growth conditions were simulated by setting four soil moisture contents (80%, 65%, 50% and 35% field maximum water capacity, FWC) and three temperature levels (15, 20 and 25 ℃). The results showed that the emergence rate of F. sinensis was highest under the condition of 25 ℃ and 65% moisture content (P<0.05). The plant height of the control and other moisture treatments were significantly higher at 20 ℃ than the 15 and 25 ℃ treatments (P<0.05). Seedling stem diameter under the three temperature treatments all reached their highest scores under the 65% moisture content condition, while the lowest scores were recorded at 35% moisture content (P<0.05). At 15 and 20 ℃, blade width, plant tissue water content, plant height stress index and dry matter stress index were the largest at the 65% moisture condition and lowest at the 35% moisture condition. However, at 25 ℃ these factors decreased with the loss of soil moisture content, with the highest scores recorded at the 80% moisture condition. The root-shoot ratios of F. sinensis under the three temperature treatments increased with the loss of the soil moisture content, reaching maximum levels at 35%, significantly greater than the control and other moisture treatments (P<0.5). Under the 20 ℃ treatment, seedling root length was the largest at 35% moisture content, while under the 15 and 25 ℃ treatments it was largest at 50% moisture content and significantly greater than the control and other moisture treatments (P<0.05). Therefore, it is concluded that 20 ℃ temperature and 65% soil moisture content is the most suitable condition for the growth of F. sinensis seedlings.

Effects of salicylic acid on growth of Astragalus adsurgens seedlings under salt stress

WANG Bao-Zeng, ZHANG Yi-Ming, ZHANG Jiang-Li, BI Shu-Qing, KONG Hong

2016, 25(8):  74-80.  DOI: 10.11686/cyxb2016085

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Salicylic acid (SA) has emerged as a plant hormone involved in the processes of growth and development, and induced resistance to various abiotic stresses in plants. Studies of the effects of exogenous SA on the growth of Astragalus adsurgens under salt stress will uncover the underlying mechanisms of stress relief. Seedlings of A. adsurgens were treated with 200 mmol/L NaCl and different concentrations of SA (0.2, 0.4, 0.6, 0.8 & 1.0 mmol/L); growth and physiological indexes were subsequently determined. The results showed that, compared with NaCl treatment without SA, exogenous SA ranging from 0.4 to 0.8 mmol/L increased soluble protein content and the activity of superoxide dismutase (SOD) in leaves of A. adsurgens. Soluble protein content increased by 51.9% and 42.6% respectively under 0.6 and 0.8 mmol/L exogenous SA treatments and the activity of SOD increased significantly by 1.58 and 1.68 times under 0.4 and 0.6 mmol/L SA concentrations. Leaf membrane permeability was reduced by SA. SA at 0.4, 0.6 and 0.8 mmol/L reduced leaf conductivity by 19.2%, 26.6% and 18.1% respectively. The photosynthetic capacity of A. adsurgens was also enhanced by exogenous SA treatment. For example, the net photosynthetic rate increased by 1.21 and 1.43 times under 0.4 and 0.6 mmol/L SA treatment. All SA treatments resulted in increased plant height and dry weight in A. adsurgens seedlings. The optimal level of exogenous SA was 0.6 mmol/L. These results indicated that the growth of A. adsurgens under salt stress was enhanced by exogenous SA.

Effect of temperature stress on growth and metabolism in perennial ryegrass

WANG Ri-Ming, XIONG Xing-Yao

2016, 25(8):  81-90.  DOI: 10.11686/cyxb2015563

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In order to investigate the effects of high temperatures on growth, leaf membrane stability, chlorophyll content, photosynthesis, endogenous hormones and carbohydrate metabolism, two perennial ryegrass (Lolium perenne) cultivars with contrasting heat tolerance, ‘Premier’ (tolerant) and ‘Pinnacle’ (sensitive) were selected and treated under optimum (25 ℃/20 ℃) and high (35 ℃/30 ℃) temperatures in growth chambers for 21 days. The results demonstrated that leaf electrolyte leakage and abscisic acid (ABA) content increased while plant growth, chlorophyll content, photosynthesis and endogenous hormones auxin (IAA), gibberellin (GA₃) and cytokinin (ZR) decreased under high temperature, more so in Pinnacle than in Premier. Soluble sugars and fructans increased and subsequently decreased with prolonged temperature treatment, while starch content decreased in both cultivars under high temperature, but Premier maintained relatively high starch content compared to Pinnacle. Accumulating or maintaining high phytohormones levels, including ABA, GA₃, IAA and ZR, and carbohydrates including soluble sugars and fructans associated with cellular osmotic homeostasis and membrane stability, delayed leaf senescence, protecting photosynthetic apparatus from heat damage and maintaining photosynthetic capacity may all contribute to heat tolerance in perennial ryegrass.

Effects of silicon supply on the biomass and physiochemical features of tall fescue seedlings under different salinization conditions

SONG Rui, LIN Li-Guo, WANG Kang-Ying, SONG Hao-Ran, JIANG Yong-Bin, LIU Hui-Xia

2016, 25(8):  91-97.  DOI: 10.11686/cyxb2015501

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The effect of silicon supply on the biomass and physiochemical features of tall fescue seedlings was investigated under different salinization conditions using a water culture experiment. Biomass decreased as salt concentration increased, with 200 mmol/L proving to be the critical concentration for tall fescue seedlings. When salt concentration was less than 200 mmol/L, silicon addition significantly increased seedling biomass, indicating that the effectiveness of silicon on tall fescue is closely related to salt concentration. If the concentration was more than 200 mmol/L, there was no significant effect of silicon addition on biomass. Under water culture, the activities of SOD, CAT and POD were increased and the contents of malondialdehyde, proline and water soluble sugars, and relative conductivity, were decreased by adding silicon to seedlings under salt stress below the critical concentration. The most significant reduction in MDA content (18.05%) was when salt concentration was 100 mmol/L. The most significant decline in proline content (23.63%) was when salt concentration was 50 mmol/L. The results indicate that the adaptability to salinization of tall fescue seedlings is improved by adding silicon and that silicon may be directly involved in the seedlings’ physiochemical processes.

Effects of snow cover thickness on cold resistance and winter survival rates in alfalfa cultivars with different fall dormancies

YUE Ya-Fei, WANG Xu-Zhe, MIAO Fang, LU Wei-Hua, MA Chun-Hui

2016, 25(8):  98-106.  DOI: 10.11686/cyxb2015474

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Four alfalfa cultivars with different fall dormancies (rating 2 Alfaqueen, rating 5 Magna551, rating 8 WL525HQ, and rating 10 Sardi10) were used to study the effects of different snow cover thicknesses on cold resistance and overwintering survival rates. The four cultivars were maintained with 0, 10, and 15 cm winter snow depths. Temperatures were monitored for alfalfa canopy-level and soil surface (1-10 cm). Dynamic variation in malondialdehyde (MDA), soluble sugar (WSC) and soluble protein (SP) contents in collar and stand counts were recorded each fall and spring to assess winter injury. The results showed that without snow cover the winter survival rates of low fall dormancy alfalfa (2, 5) were 64% and 59% respectively, while all the high fall dormancy alfalfa (8, 10) died. With the exception of alfalfa with fall dormancy 10 (Sardi10), a snow cover thickness of 10 cm can ensure the winter safety of alfalfa, with the winter survival rate recorded at over 90%. Increasing snow cover thickness significantly moderated temperatures at alfalfa canopy-level and soil surface. Increased cover significantly improved the winter survival rate of different alfalfa (P<0.05). It increased the SP and WSC content of alfalfa collars in the non- and extremely non-fall dormancy cultivars, and decreased the MDA content. Membership function analysis showed that without snow cover the order of cold resistance and winter survival rate of the alfalfa cultivars was Alfaqueen>Magna551; with snow cover thickness of 10 cm, the order of cold resistance and winter survival rate was Magna551>Alfaqueen>WL525HQ>Sardi10; and with snow cover thickness of 15 cm, the order was Magna551>Alfaqueen=WL525HQ=Sardi10.

Nutrient content and digestibility of Fagopyrum dibotrys at various growth stages

HAN Yong, DEN Rong, DIAO Qi-Yu

2016, 25(8):  107-117.  DOI: 10.11686/cyxb2015491

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This study investigated the nutritive value, when fed to pigs, of Fagopyrum dibotrys at various growth stages. Crude protein (CP), amino acid (AA), trace element levels, among other parameters, and their digestibility characteristics within the terminal ileum were studied. Three growing Ba×Wild×Gao pigs, and having had an ileo-rectal anastomosis operation with a T fistula installed, underwent a 3×3 Latin square trial. The levels of organic matter (OM), CP, ether extract (EE), Ca, P, and crude fiber (CF) in F. dibotrys were 88.59%, 22.72%, 2.34%, 1.05%, 0.39%, and 13.51%, respectively, in the branching stage; were 89.10%, 20.57%, 1.69%, 1.25%, 0.42%, and 15.50%, respectively, in the bud stage, and were 89.63%, 17.54%, 1.37%, 1.29%, 0.46%, and 19.75%, respectively, in the early flowering stage. Essential amino acid (EAA), non-essential amino acid (NEAA), and total amino acid (TAA) contents in F. dibotrys were 9285, 7982, and 6244 mg/100 g, respectively, in the branching stage, were 14334, 10810, 9320 mg/100 g, respectively, in the bud stage, and were 23619, 18792, 15564 mg/100 g, respectively, in the initial bloom stage. Generally, nutritive value and digestibility characteristics of F. dibotrys decreased with increasing maturity (P<0.05), except for CF which increased. Specifically, the nutrient content and digestibility characteristics were significantly lower at the bud stage than at the branching stage (P<0.05), while the decline by early flowering was extremely significant (P<0.01). A gradual decline with increasing crop maturity was observed for CP, EE, EAA, TAA content and digestibility characteristics between the branching and the bud stages, again associated with an increase in CF; a comparatively faster rate of decrease was observed for nutrient content and digestibility characteristics between the bud and early flowering crop maturity stages. Three regression equations were developed to describe the relationship between in vitro digestibility values and the corresponding in vivo digestibility values for the three tested maturity states of F. dibotrys. In summary, F. dibotrys has high feeding value in terms of nutrient content, digestibility characteristics, and AA composition. Harvesting is recommended during the bud stage for F. dibotrys for maximum yield of total digestible nutrients. Regression equations developed in the present study can predict in vivo digestibility characteristics of F. dibotrys from in vitro data.

Heterologous expression of an SK2-type dehydrin gene (MrDHN3) from Medicago ruthenica enhances Escherichia coli tolerance under salt and high temperature stress

SHEN Ying-Fang, MA Chao, WU Xiao-Pei, ZHANG Ye-Meng, WANG Hai-Qing

2016, 25(8):  118-127.  DOI: 10.11686/cyxb2015510

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Medicago ruthenica, is an excellent legume in highland and cold regions, and is highly resistant to drought, cold and high salinity. Dehydrins (DHNs) are stress proteins involved in plant protective reactions against environmental stress. According to our previous RNA-sequence data, a DHN gene, MrDHN3, was cloned from young seedlings of M. ruthenica. Sequence analyses showed that the MrDHN3 gene contained a 666 bp open reading frame, putatively translated to 221 amino acids, and was an SK2-type acidic DHN. Amino acid sequence alignment showed that MrDHN3 shared the highest similarity (83%) with TrDHN3 and MtDHN3. Quantitative RT-PCR analysis showed that the expression of MrDHN3 was induced by dehydration, cold, high salinity stress and abscisic acid (ABA), which suggests that MrDHN3 is involved in abiotic stress responses. A prokaryotic expression vector was constructed and transferred to Escherichia coli so as to induce MrDHN3 over expression in E. coli. The survival and growth of the recombinant E. coli under salinity and high temperature stress conditions were determined. It was found that survival rates of recombinant E. coli after exposure to high salinity (0.5 mol/L NaCl, 0.5 mol/L KCl) and high temperature (55 ℃) stress were obviously higher than those of the control group. This suggests that MrDHN3 plays an important role in cell response to damage caused by salinity and high temperature stress. This research indicates a potential methodology for the genetic improvement of crops to improve stress tolerance.

Cloning and expression analysis of a lysine decarboxylase gene in Sophora alopecuroides

YANG Yi, LU Shan-Shan, LIU Ping, TIAN Lei

2016, 25(8):  128-135.  DOI: 10.11686/cyxb2015477

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In the biochemical metabolic processes of Sophora alopecuroides, a lysine decarboxylase (LDC) gene is one of the key enzyme genes involved in the process of Oxymatrine biosynthesis. In the present study, the full length of the LDC coding sequence in S. alopecuroides was cloned using a pair of specific primers designed based on the LDC sequence of Sophora flavescens and was named Sa-LDC (gene bank accession number: KM249871). Sa-LDC belongs to the Type Ⅲ Pyridoxal 5-phosphate (PLP)-Dependent enzyme supergene family, is comprised of a 1368 bps open reading frame (ORF) without intron, and has 97% identity with the LDC of Echinosophora koreensis and S. flavescens in GeneBank. Its nucleotide sequence encodes 455 amino acid residues whose putative protein had a relative molecular mass of 49.14 kD and the theoretical isoelectric point of 5.63 without signal peptide and transmembrane structure. Interestingly, the deduced amino acid sequence of Sa-LDC had the conserved amino acid residue (Phe³⁴⁰) in quinolizidine alkaloid producing plants. Therefore, the S. alopecuroides and other quinolizidine alkaloid producing plants were placed into a single group in the phylogenetic tree. In addition, the real time fluorescence quantitative PCR (qPCR) and high performance liquid chromatography (HPLC) results showed that both the LDC expression level and oxymatrine content were influenced by polyethylene glycol (PEG) stress, and that LDC expression and oxymatrine accumulation in S. alopecuroides were correlated.

Diversity of endophytic bacteria isolated from Kobresia during winter dormancy

YANG Cheng-De, WANG Yu-Qin, CHEN Xiu-Rong, ZHANG Zhen-Fen, XUE Li, WANG Ying, YAO Yu-Ling

2016, 25(8):  136-144.  DOI: 10.11686/cyxb2015368

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Twenty three strains of endophytic bacteria were isolated from the roots and seeds of dormant plants in winter of two species of Kobresia, using the dilution plate method. The isolated bacteria were identified by sequence analysis of their 16S rDNA. Then their biological properties, including antimicrobial activity, phosphorus solubilisation, nitrogen fixation and production of IAA, were determined. There were significant differences in the number of endophytic bacteria and their community composition in the roots and seeds of the two Kobresia species. Kobresia capillifolia had a higher species diversity of endophytic bacteria than Kobresia humilis. Endophytic bacteria were more abundant in roots than in seeds for K. humilis, but the opposite was true in K. capillifolia. The amount of endophytic bacteria was affected by the seed storage time. Twenty strains among the isolated endophytic bacteria displayed biological activity. including antimicrobial properties, phosphorus solubilisation, nitrogen fixation and production of IAA. The, numbers of strains with these respective capabilities were 35%, 55%, 45% and 25%, respectively, of the total number of bacteria. Fifteen taxa were identified among the 16S rDNA gene sequences of the endophytic bacteria isolated. They included the genera Bacillus, Phyllobacterium, Staphylococcus, Paenibacillus, Microbacterium, Promicromonospora and Sphingopyxis. Among these, Bacillus was the dominant species.

Screening of rhizobia of common vetch (Vicia sativa) in Qinghai, and assessment of symbiont salt tolerance

WANG Xue-Cui, MA Xiao-Tong, HAN Mei, CAO Wei-Dong, ZHANG Hong-Liang, BAI Jin-Shun, ZENG Nao-Hua, GAO Song-Juan, ZHOU Guo-Peng, WANG Yan-Qiu

2016, 25(8):  145-153.  DOI: 10.11686/cyxb2015497

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Common Vetch (Vicia sativa) is a traditional legume crop in China which is widely used as a green manure and for fodder. However, there has been little study to date of the rhizobia of common vetch. This study aimed to identify rhizobial strains of common vetch with superior symbiotic properties, and also greater salt tolerance. Root nodule samples were collected from the major production areas of common vetch in Qinghai, and 61 rhizobial strains were isolated and identified. Using a hydroponics inoculation technique and principal component analysis, 5 strains with stronger ability to promote nodulation and growth of the host plants were identified, and designated J1-3-2, J2-6-2, J3-12-1, J4-3-3 and J5-5-3. The salt tolerance of these 5 strains was examined by single plant culture. Strain J5-5-3 was tolerant of NaCl concentrations up to about 0.9%, while the other 4 strains could tolerate up to 1.2% NaCl concentration. Three distinct levels of salt tolerance were evident: J3-12-1 and J2-6-2 displayed the strongest tolerance, J1-3-2 and J4-3-3 displayed medium tolerance, and J5-5-3 the weakest tolerance. One strain from each of these groups was then evaluated in a pot experiment to asses nodulation of the host under differing salinity levels of 0.15% or 0.3% NaCl. When exposed to 0.15% NaCl concentration, the largest number of root nodules was observed in plants inoculated with J5-5-3, and no significant differences among the three rhzobial strains were found when exposed to 0.30% NaCl concentration. J3-12-1 and J5-5-3 inoculation resulted in increased dry weight (P<0.05) of the host plants under NaCl concentrations of 0.15% and 0.30%. Inoculation with strain J5-5-3 increased plant nitrogen content (P<0.05) under the two levels of NaCl stress and increased nitrogen uptake (P<0.05) under the 0.15% NaCl stress, while the strain J3-12-1 significantly increased the nitrogen uptake (P<0.05) of the host plants under 0.15% NaCl stress. It was concluded that the strains J3-12-1 and J5-5-3 are suitable as inoculant rhizobial strains to increase the biomass and nitrogen content of common vetch under salt stress.

An assessment of the level of control of two fungal pathogens by various plant growth promoting rhizobacteria

SUN Guang-Zheng, YAO Tuo, ZHAO Gui-Qin, LI Jian-Hong, CHEN Long, LIU Huan

2016, 25(8):  154-163.  DOI: 10.11686/cyxb2015353

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The capacity for dissolved phosphorus absorption, the nitrogenase activity and the secretion of auxin of 19 strains of plant growth promoting rhizobacteria (PGPR) acquired from five plant species were tested by molybdenum blue colorimetry, acetylene reduction assay and high performance liquid chromatography, respectively. All 19 strains were tested for ability to antagonize the fungi Fusarium oxysporum f. sp. cucumerinum and Bipolaris sorokiniana, using the panel confrontation method. Strains with antagonistic ability were identified at morphological, physiological biochemical, and molecular levels. It was found that Bacillus subtilis strain LM4-3 had stronger nitrogenase activity than other tested strains and reached 244.88 nmol C₂H₄/(mL·h), while B. subtilis strain LHS11-1 had the highest dissolved phosphorus absorption capacity (205.77 mg/L), and the strain PGRS-3 had the greatest secretion of auxin, reaching 40.78 μg/mL in the culture medium. Five bacterial strains were found to have antagonistic activity against F. oxysporum f. sp. cucumerinum, with B. subtilis strain FX2-1 providing up to 69.07% suppression. and 51.73% of its fermentation solution. Seven bacterial strains could efficiently antagonize B. sorokiniana, with B. subtilis strain FX2-1 achieving 78.17%, the fermentation solution of B. subtilis LHS11-1 rinsed up to 81.52%. Other bacterial species found to have plant growth promoting or to be antagonistic towards the above two pathogenic fungal species included Bacillus cereus, Bacillus pumilus, Bacillus simplex and Pseudomonas fluorescens.

Isolation and biological characteristics of the biological control fungi BC-1 for Echinochloa crusgalli

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

2016, 25(8):  164-171.  DOI: 10.11686/cyxb2015583

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There has been increasing effort in the research and development of biological herbicides because of their low toxicity. Myrothecium roridum, strain BC-1 was isolated from diseased Echinochloa crusgalli leaves in order to obtain a low toxicity and effective biological herbicide. The BC-1 strain was identified using its culture characters and 16S rDNA sequence analysis. The optimal mycelium growth media were PDA and PSA medium. The optimal culture temperature is 25-28 ℃, and optimal initial pH of culture media was 6-7. Darkness was beneficial for mycelium growth. The optimal mycelium growth carbon source is maltose, and the best nitrogen source was NH₄NO₃. Additionally, biocontrol testing showed that the E. crusgalli were all infested with BC-1 21 days after innoculation, and fresh weight inhibition was 93.7%. However, the fresh weight inhibition effects of BC-1 on Digitaria sanguinalis, Setaria viridis, Descuminia sophia and Amaranthus retroflexus were only 33.7%, 28.3%, -3.2% and 16.8% respectively. Crop safety analysis showed that the strain BC-1 was safe to Zea mays, Triticum aestivum and Oryza sativa. This study suggests that strain BC-1 has potential to be developed into an effective microbial herbicide with economic and social benefits.

The effect of herbicide application timing and dosage on control of Alopecurus myosuroides in winter wheat

GAO Xing-Xiang, SUN Zuo-Wen, LI Mei, FANG Feng, LI Jian, WU Jia-Jun, LEE Mao-Sheng

2016, 25(8):  172-179.  DOI: 10.11686/cyxb2016008

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Alopecurus myosuroides is a major weed in Europe. Originally, it was only found in Taiwan but now it is a worsening problem in mainland China, including Shandong, Hebei, and Shanxi. However, there is no information about control using chemical herbicides in China. Field experiments were conducted to determine the effectiveness of control and the response of winter wheat to different rates of eight herbicides spraying at different timings during the 2013-2014 growing seasons in Jinan, Shandong province. The results showed that pyroxsulam provided best control on A. myosuroides with a 97.1%-100.0% fresh weight (FW) reduction after application irrespective of application time. Mesosulfuron-methyl also gave good control with 80.1%-98.6% FW reduction. Pinoxaden produced good control (99.3%-99.9% FW reduction) if applied before winter, but was less effective applied during winter (74.1%-88.9% FW reduction) and spring (46.2%-75.8% FW reduction). Clodinafop-propargyl and fenoxaprop-p-ethyl had good effect with 81.1%-96.8% FW reduction applied before winter and in early spring but had reduced effectiveness applied during winter (41.4%-76.0% FW reduction). Isoproturon, traloxydim and flucarbazone-Na failed to control A. myosuroides at any applying timing.

Effects of living mulch on soil physical and chemical properties in orchards: a review

CAO Quan, SHEN Yu-Ying, WANG Zi-Kui, ZHANG Xiao-Ming, YANG Xuan

2016, 25(8):  180-188.  DOI: 10.11686/cyxb2015500

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A review has been undertaken to provide a basis for further research on and the application of living mulch practices in orchards. The effects of living mulch on soils’ physical and chemical properties make an important contribution to intensive, efficient, ecological and sustainable production. Forage cultivation can reduce soil bulk density by 4.7%-13.0% and improve the content of soil aggregates, thus enhancing hydraulic properties and water retention capacity. Forage cultivation can also help to raise rainfall interception and improve water use efficiency. Forage grass will compete for water with fruit trees in drought seasons, though adverse effects can be reduced by selecting appropriate grass varieties and strengthening field management. Forage grass cover can improve soil organic carbon (SOC) content. SOC can be improved by 19.6%-27.8% after planting forage grass for 6 years. The accumulation of SOC increases as the duration of forage planting increases. Living mulch can help to adjust soil temperature, which enhances microbial diversity and enzymatic activity. Living mulch will directly deplete soil nutrients, but the increase in the number of microorganisms can promote the decomposition of organic matter that increases nutrients. Moreover, legumes add nutrients through nitrogen fixation. Living mulch usually has a positive effect on soil nutrient accumulation.

Isolation and identification of high-quality lactic acid bacteria from wild forage silages on the Hulunbuir prairie

WANG Hong-Mei, SUN Qi-Zhong, TU Yan, SI Bing-Wen, SA Ru-La, NA Ya, DIAO Qi-Yu

2016, 25(8):  189-196.  DOI: 10.11686/cyxb2016092

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The objectives of this study were to identify lactic acid bacteria (LAB) from forage silages on the Hulunbuir prairie and screen LAB for desirable attributes. LAB strains were isolated from grass silages of four different communities and identified with classical identification and 16S rRNA analysis methods. Five strains: DME53, DMG108, DMC80, DMG138 and DMG139 were isolated and identified as Lactobacillus graminis, L. casei, L. plantarum, L. brevis and Pediococcus pentosaceus, respectively, in which DMG138 was identified as heterofermentative LAB while the other four strains were all homofermentative LAB. All five strains grew well at different temperatures, ranging from 5 to 45 ℃, and in 3.0% and 6.5% NaCl; an exception was that DMG139 grew poorly at 40 and 45 ℃. All strains generally grew well at pH ranging from 3.0-8.0; however, DME53 was inactive at pH 3.0. In conclusion, strain DMC80 demonstrated consistently desirable traits; strong acid production capacity, rapid fermentation rate and good tolerance of acidity and cold which could be used for the preparation of silage in Hulunbuir prairie.