Frontiers of Agriculture in China

ISSN 1673-7334

ISSN 1673-744X(Online)

CN 11-5729/S

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A simulation model assisted study on water and nitrogen dynamics and their effects on crop performance in the wheat-maize system: (II) model calibration, evaluation and simulated experimentation
Hongzhan Lü, Weili LIANG, Guiyan WANG, David J. CONNOR, Glyn M. RIMMINGTON
Front Agric Chin. 2009, 3 (2): 109-121.

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The test on the model with data collected from two years’ field experiments revealed an ability to satisfactorily simulate crop parameters such as LAI, biomass accumulation and partitioning, yield, and variables influencing crop growth and development as nitrogen uptake by crops and partitioning in different organs, and dynamics of soil water and nitrogen including infiltration and leaching. With the model, crop yield, water use efficiency (WUE), nitrogen use efficiency (NYE) and water-nitrogen leaching at specific soil layers under various water and nitrogen management practices were simulated to provide data used as references for designing sustainable nitrogen and water management practices.

The outputs of the simulated experiment with various treatments of irrigation and nitrogen application indicated that crop yield was closely related to water and nitrogen application, crop water use was positively related to irrigation amount, and nitrogen fertilization could improve the crop water use and WUE within certain limits. This is a valuable evidence to be considered in water-saving farming. Nitrogen uptake had a positive relation to nitrogen application, while irrigation to some extent improved its uptake by crops and hence increased NYE. Additionally, irrigation and fertilization had great effects on nitrogen leaching. Thus, in order to improve WUE and NYE, the model showed how nitrogen application and irrigation should be well coordinated.

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Influences of nitrogen fertilizer application rates on radish yield, nutrition quality, and nitrogen recovery efficiency
Yulin LIAO*, Xiangmin RONG*, Qiang LIU*, Meirong FAN, Jianwei PENG, Guixian XIE, Yulin LIAO, Shengxian ZHENG*, Meirong FAN*
Front Agric Chin. 2009, 3 (2): 122-129.

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Radishes (Raphanus sativus L.) were grown in plastic pots in a screenhouse to investigate the influences of nitrogen fertilizer application rates (NFAR) on yield, nitrate content, nitrate reductase activity (NR), nutrition quality, and nitrogen recovery efficiency (NRE) at commercial mature stage. Five N-rate treatments, 0.644, 0.819, 0.995, 1.170, and 1.346 g?pot-1, were set up in the screenhouse pot experiments, and nitrogen fertilizer (unlabeled N and 15N-labeled fertilizer) was applied as basal dressing and topdressing, respectively. The results indicated that the fresh and dry weight yields of radish increased with the increase of NFAR at the range of 0.099 to 0.180 g N?kg-1 soil, decreased at 0.207 g N?kg-1 soil, and accordingly there was a significant quadratic relationship between the fresh and dry weight yields of radish and the NFAR. At the high addition of urea-N fertilizer, the nitrate content accumulated in the fleshy roots and leaves due to the decline in NR activity. From 0.644 to 0.819 g N?pot-1 NR increased most rapidly, the highest NR activity occurred at 0.819 g N?pot-1, and the lowest NR activity happened at 1.346 g N?pot-1. Soluble sugar and ascorbic acid initially increased to the highest value and then decreased, and, contrarily, crude fiber rapidly decreased with the increase of NFAR. Total N uptake (TNU), N derived from fertilizer (Ndff), and N derived from soil (Ndfs) in radish increased, except that Ndfs relatively and slightly decreased at the rate of 0.207 g N?kg-1soil. The ratio of Ndff to TNU increased, but the ratio of Ndfs to TNU as well as NRE of N fertilizer decreased with the increase of NFAR. Therefore, the appropriate NFAR should be preferably recommended for improving the yields and nutrition qualities of radish and NRE of N fertilizer.

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Correlation between allele sizes of microsatellites and phenotypic variations in rice landraces
Yawen ZENG, Shuming YANG, Juan DU, Xiaoying PU, Hongliang ZHANG, Zichao LI, Luxiang WANG, Jiafu LIU, Fenghui XIAO
Front Agric Chin. 2009, 3 (2): 130-139.

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Yunnan is one of the largest centers of genetic diversity in the world. Allele size of microsatellites associated with phenotypic traits of rice landraces in Yunnan, Southwest China, was investigated based on 20 SSR markers and 23 phenotypic traits, as well as eight mineral elements in brown rice within the core collection of 629 accessions; and there was a significant correlation for 182 (r = 0.083*-0.438**) of 620 pairs among these markers and traits, as well as elements. Surprisingly, there was a significant correlation for 94 of 180 pairs between the allele size of microsatellites and grain traits, and 48 of 160 pairs between allele size of microsatellites and panicle traits. In these rice landraces, 309 alleles were detected, with an average of 15.5 alleles per marker, ranging from 5 (RM60) to 40 (RM257). There was a significant correlation between the allele size of 20 SSR markers and some phenotypic traits, such as the significant correlation of 17 (r = -0.085*--0.438**) pairs between the allele size of RM224 and 23 phenotypic traits, as well as eight elements. The allele size of microsatellites was more associated with grain or panicle traits than that of plant traits or element contents in brown rice. Grain length/width ratio and 1-2 internode length, as indica-japonica classification traits, in which two traits were closely associated with the allele size of 14 SSR markers ranging from 0.089* to -0.438**. Therefore, allele size of SSRs was associated with phenotypic traits (especially in grain traits), as well as elemental contents in brown rice.

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A multiplex PCR method for detection of Clavibacter michiganensis subsp. michiganensis with co-amplification of its host DNA
Yan ZHANG, Wenxiang YANG, Yaning LI, Daqun LIU, Ting ZHANG
Front Agric Chin. 2009, 3 (2): 140-145.

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A multiplex PCR assay system was developed for the detection of Clavibacter michiganensis subsp. michiganensis (Cmm), which combined two tests in one reaction mixture. Cmm-specific primers PSA-4/PSA-R and Solanum lycopersicum–specific primers NS-7-F/NS-8-R (internal PCR control primer) were combined in one PCR reaction mixture with Cmm and plant DNA as template. The primer sets could amplify the target product successfully. Different combinations and concentrations of primers and annealing temperatures were tested, respectively. The detection level of the optimized multiplex PCR assay was up to 5×102 cfu·mL-1. To verify the applicability of this system, it was employed to detect Cmm in tomato seeds and plantlet samples. Seeds mixed with Cmm and diseased plantlets were detected successfully. The multiplex PCR system will avoid false-negative results and provide a reliable method for the detection of Cmm.

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Early stage SSH library construction of wheat near isogenic line TcLr19 under the stress of Puccinia recondita f. sp. tritici
Aihua YAN, Lifeng ZHANG, Yunwei ZHANG, Dongmei WANG
Front Agric Chin. 2009, 3 (2): 146-151.

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cDNA library of wheat near isogenic line TcLr19 was constructed with suppression subtractive hybridization (SSH) 16 h after inoculation with race 366 of Puccinia recondita f. sp. tritici. This SSH library included 1337 positive clones and the insert sizes ranged from 200 bp to 600 bp, 237 clones were selected according to the result of reverse northern blotting, and then 35 ESTs were sequenced. EST similarity analysis was finished by comparing sequences with BLAST software in the non-redundant database of GenBank. The results showed that they were related to many biological processes including signal transduction, transcription regulation and hypersensitive response.

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Symptoms and histopathological study of Anoplophora glabripennis larvae infected with Metarhizium (Metsch.) Sorokin MS01
Baohui WANG, Jianwei ZHENG, Dazhuang HUANG, Da WANG, Xiaoyong HAN, Xiaohong WANG
Front Agric Chin. 2009, 3 (2): 152-158.

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Some changes in color and morphology of Anoplophora glabripennis larvae were observed when infected with Metarhizium (Metsch.) Sorokin MS01. Paraffin sections show the spores of MS01 attached to the cuticle of A. glabripennis larvae at 24 h post inoculation (hpi). At 36 hpi, the conidium germinated and penetrated through the cuticle. After 48 h of inoculation, the endocuticle was disintegrated and the germ tubes passed through the epithelial layers into the hemocoel and multiplied, and then invaded the tissues near the penetration point, such as the fat body, muscle, tracheal tissue, malpighian tubule, alimentary canal, etc. The infected larvae were dead and most tissues and organs were infected and disintegrated with the multiplication of the mycelium for 3 days. The hyphae emerged through the cuticle and formed a hyphal layer on the surface of the dead insect and the conidium emerged five days after inoculation.

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Biological characteristics of Bacillus thuringiensis strain Bt11 and identification of its cry-type genes
Tinghui LIU, Wei GUO, Weiming SUN, Yongxiang SUN
Front Agric Chin. 2009, 3 (2): 159-163.

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A novel strain of Bacillus thuringiensis Bt11, isolated from soil samples in China, was classified and characterized in terms of its crystal proteins, cry genes content. The Bt11 strain showed high toxicity against Spodoptera exigua and Helicoverpa armigera neonates. Bt11 strain shares morphological and biochemical characteristics with the previously described Bacillus thuringiensis subsp. kurstaki. SDS-polyacrylamide gel electrophoresis revealed that crystals were composed of several polypeptides ranging from 20 to 130 kDa, of which the 35, 80, and 130 kDa proteins were the major components. PCR-RFLP with total DNA from strain Bt11 and specific primers for cry1, cry2, cry3, cry4/10, cry7, cry8, cry9, and cry11 genes revealed that cry1Aa, cry1Ab, cry1Ia, and cry9Ea genes were present.

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Mycorrhizal and dark septate endophytic fungi under the canopies of desert plants in Mu Us Sandy Land of China
Yanqing WU, Xueli HE, Tiantian LIU
Front Agric Chin. 2009, 3 (2): 164-170.

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Biodiversity of arbuscular mycorrhizal colonization and spore density was investigated in 20 desert plants (dominant or common species) collected from different locations of Mu Us Sandy Land of China. We observed three mycorrhizal types including Arum-type,Paris-type, and an intermediate type among the plants. Another type of potentially beneficial fungi associated with roots of all species was also observed, namely, dark septate endophytic fungi (DSEF). Of the 20 sample plants examined, all species were coinfected by the two target fungi (Arbuscular mycorrhizal fungi (AMF) colonization of Salix psammophila and DSEF colonization of Periploca sepium were as low as 4%). Based on this investigation, we speculated that the DSEF are ubiquitous in desert ecosystems and can co-occur with AMF in desert plants, functioning much like mycorrhizal fungi. Further studies will be required to elucidate interactional mechanisms with AMF and the mechanisms operating in desert ecosystem.

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Mechanism of herbicidal action of the component I from Pythium aphanidermatum
Jiao XU, Wenchao XU, Lihui ZHANG, <NativeName DisplayOrder="Western" Language="chs"><GivenName>Chuan</GivenName><FamilyName>LI</FamilyName></NativeName>
Front Agric Chin. 2009, 3 (2): 171-177.

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The herbicidal mechanism of the components extracted from Pythium aphanidermatum was examined in this study. Component I was isolated using the HPD500 macroporous adsorption resin and HPLC. Its impact on seed germination and plant growth of weeds was determined and the contents of MDA, superoxide anion radical, and the activities of hills and roots were examined. The root length of weed plants was inhibited under illumination while the stem height was inhibited evidently under darkness. The relative electric conductivity of Digitaria sanguinalis and Amaranthus retroflexus under illumination was 94.55 μS·cm-1 and 58.75 μS?cm-1, respectively, whereas that under darkness was 85.25 μS?cm-1 and 36.25 μS?cm-1, respectively. The MDA contents of Digitaria sanguinalis and Chlorella pyrenoidosa were 0.08385 μmol·L-1 and 0.1742 μmol?L-1 under illumination, respectively, while those were 0.0129 μmol?L-1 and 0.01935 μmol?L-1 under darkness, respectively. Simultaneously, superoxide anion radical content was higher under illumination than under darkness. These results showed the photosynthesis was affected by component I extracted from Pythium aphanidermatum.

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Effects of aqueous leaf extracts of P. at different ages on the growth and photosynthetic characteristics
Meiqiu ZHU, Ying WANG, Bingxiang LIU, Lili ZHANG, Hui WANG, Yuxin YUAN, Kejiu DU
Front Agric Chin. 2009, 3 (2): 178-185.

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Through the outdoor potted plant trials, the allelopathic potential of Populus tomentosa was tested against its species in the growth, chlorophyll content, and photosynthetic and chlorophyll fluorescence characteristics with aqueous extracts (0.01, 0.02, 0.05, and 0.1 g?mL-1) obtained from leaves at different individual ages (1, 20, and 45 years old). The results showed that seedling height, basal diameter, fresh and dry weights, quantity of chlorophyll, the ratio of chlorophyll a/b, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), efficiency of primary conversion of light energy of PSII (Fv/Fm), potential activity of PSII (Fv/F0), and photochemical quenching (qP) of the seedlings gradually decreased with the increase of extract concentration of all three ages when compared with the controls. The older the P. tomentosa used for extract preparation, the greater the percentage declined in the aforementioned parameters. Moreover, at the four concentrations used, there was a significant difference between treatments with the extracts from 1- and 45-year-old plants (except for qP), but occasionally, the effects were not obvious between the 1- and the 20-year-old plants, or the 20- and 45-year-old plants. The intercellular CO2 concentration (Ci) treated with the extracts from the 1-year-old decreased at the lowest concentration, whereas it increased at higher concentrations. The Ci treated with aqueous leaf extracts from the 20-year-old decreased at the lower concentrations and increased to similar levels to that of the control at the higher concentrations. Ci was always close to control levels in 45-year-old extract treatments. All the aqueous leaf extracts of P. tomentosa at all ages caused an increase of the initial fluorescence (F0). The older P. tomentosa used for the preparation of aqueous leaf extracts caused a greater percentage decline in F0. The nonphotochemical quenching (qN) increased significantly at lower concentrations of all P. tomentosa extracts, whereas it decreased significantly at higher concentrations. It seemed that aqueous leaf extracts from P. tomentosa were harmful to the photosynthetic structure of its own seedlings, inhibited seedling growth, and led to an eventual decrease of biomass. Extracts from older P. tomentosa leaves had more negative effects on the seedling growth of poplar. The effects on photosynthesis are the more important mechanism of the allelopathy of poplar.

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Growth responses of Kentucky bluegrass (Poa pratensis L.) to trinexapac-ethyl applied in spring and autumn
Guangyu FAN, Xiuju BIAN, Huibin LI, Zhao MENG, Shengyao LIU
Front Agric Chin. 2009, 3 (2): 186-189.

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The practices with low clippings production to save time, money, or landfill space, were favored by turf managers. Understanding the responses of Kentucky bluegrass (Poa pratensis L.) to Trinexapac-ethyl (TE) would facilitate recommendations regarding its safe and effective use in Northern China. The objectives of this study are (1) to investigate the effects of TE on vertical growth, clipping yield, leaf width, and chlorophyll content of Kentucky bluegrass, and (2) to compare the seasonal application impacts of TE. Both spring and autumn experiment results demonstrated that Trinexapac-ethyl applied to Kentucky bluegrass suppressed the vertical grass growth and significantly reduced the Kentucky bluegrass clippings production within a few weeks after initial treatment. Applied trinexapac-ethyl enhanced Kentucky bluegrass leaf width in both spring and autumn experimental periods. Discoloration on leaf tips was observed and lasted for four weeks when the same TE rate of 0.191 mL?m-2 was applied in early autumn. Darker leaves with higher chlorophyll content compared with non-TE-treatments appeared after the initial four weeks of the treatment in autumn and the treatment for the entire spring.

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Effects of Bt transgenic crops on soil ecosystems: a review of a ten-year research in China
Wenke LIU
Front Agric Chin. 2009, 3 (2): 190-198.

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Bacillus thuringiensis (Bt) transgenic cotton is the unique Bt transgenic crop planted on a large scale in China, and its commercialized varieties and hectareage had increased rapidly in China during the past decade (1997-2006) with broad geographic distribution for the economic, environmental, and health benefits. In 2004, the planting area of Bt transgenic cotton in China ranked first worldwide with up to 370 × 106 hm2. In addition, Bt transgenic rice varieties in field tests have been close to approval for commercialization. However, ecological risks, a complex issue of Bt transgenic crops on soil ecosystem is urgently faced in China due to more than 60 varieties transferred single or bivalent Bt genes grown under diverse geographic regions. Two main pathways, biomass incorporation and root exudates, are involved in the effects of Bt transgenic crops on soil ecosystems. In this paper, the research results in recent years in China involved in the effects of Bt transgenic crops (Bt transgenic cottons and rice) on soil ecosystems were summarized with special attentions paid to the release and persistence of Bt toxins, and the toxicology to microorganisms, as well as the change of soil biochemical properties in soils where Bt transgenic crops were planted or incubated with their biomass. In addition, the complexity and current research defaults of ecological risk evaluation of Bt transgenic crops in China were highlighted.

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Cell reprogramming for the creation of patient-specific pluripotent stem cells by defined factors
Huiqun YIN, Hongguo CAO, Yunhai ZHANG, Yong TAO, Xiaorong ZHANG, Heng WANG
Front Agric Chin. 2009, 3 (2): 199-208.

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Pluripotent stem cells (PSCs), characterized by being able to differentiate into various types of cells, are generally regarded as the most promising sources for cell replacement therapies. However, as typical PSCs, embryonic stem cells (ESCs) are still far away from human clinics so far due to ethical issues and immune rejection response. One way to avoid such problems is to use stem cells derived from autologous somatic cells. Up to date, PSCs could be obtained by reprogramming somatic cells to pluripotent state with approaches including somatic cell nuclear transfer (SCNT), fusion with stem cells, coculture with cells’ extracts, and induction with defined factors. Among these, through reprogramming somatic cells directly by retroviral transduction of transcription factors, induced pluripotent stem (iPS) cells have been successfully generated in both mouse and human recently. These iPS cells shared similar morphology and growth properties to ESCs, could express ESCs marker genes, and could produce adult or germline-competent chimaeras and differentiate into a variety of cell types, including germ cells. Moreover, with iPS technique, patient specific PSCs could be derived more easily from handful somatic cells in human without immune rejection responses innately connected to ESCs. Consequently, generation of iPS cells would be of great help to further understand disease mechanisms, drug screening, and cell transplantation therapies as well. In summary, the recent progress in the study of cell reprogramming for the creation of patient-specific pluripotent stem cells, some existing problems, and research perspectives were suggested.

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Effect of a Chinese herbal formula Astragalus immunomodulator on immune function of chickens
Qingru ZHANG, Guojun JIANG, Shupeng LI, Xiuhui ZHONG
Front Agric Chin. 2009, 3 (2): 209-215.

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In order to investigate the immunomodulatory effects and the mechanism of a Chinese herbal medicine, Zengmiansan (Astragalus immunomodulator), on immune function of chickens, three hundred 1-day-old chickens were assigned randomly into 5 groups, i.e., the blank control group, the Chinese herbal medicine Zengmiansan (ZMS)-treated group, the cyclophosphamide group, the cyclophosphamide plus levamisole group, the cyclophosphamide plus ZMS group and the control group. All chickens were immunized with Lasota vaccine by nose-drip or eye-drop at the age of 6 days. Newcastle Disease (ND) antibody titers, growth indexes of the spleen, thymus and bursa of Fabricius, the concentrations of CD4+ lymphocytes and CD8+ lymphocytes in spleen, thymus and peripheral blood, and the apoptosis of splenocytes, thymocytes and bursa of Fabricius cells were observed at the ages of 14, 21, 28 and 35 days, respectively. Our results indicated that the NDV antibody titers of chickens in the Chinese herbal medicine ZMS-treated group at the ages of 14 and 21 days were significantly higher than that of the other groups (P<0.01). The growth indexes of immune organs, the concentrations of CD4+ lymphocytes and the ratio of CD4+/CD8+ T lymphocytes of chickens in the Chinese herbal medicine ZMS- treated group at the ages of 14, 21 and 28 d were significantly higher than those of the other groups (P<0.01). The apoptotic splenocytes, thymocytes and bursa of Fabricius cells of chickens in the ZMS-treated group were significantly lower than the other groups (P<0.01) at the ages of 14, 21 and 28 days.

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Ecological studies on medaka in a remained habitat in Qinhuangdao, Hebei, China
Zhiguo LI, Huiguang FU
Front Agric Chin. 2009, 3 (2): 216-220.

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Ecological studies were carried out in the remaining habitat for medaka (Oryzias latipes), a marsh in the suburbs of Qinhuangdao City, Hebei Province, China. Sewage released from villages increases the nutrient levels in open water areas of the marsh, while in cattail (Typha angustifolia) and reed (Phragmites communis) beds the nutrient levels are decreased. There are fewer zooplanktons in the cattail and reed beds than in the open water areas. Sampling fishes with trap nets showed that medaka lived in dense populations in the cattail and reed beds, while the other three fish species, wild goldfish (Carassius auratus), topmouth gudgeon (Pseudorasbora parva), and mud loach (Misgurnus bipartitus), occupied the open water areas in the marsh. A little amount of paradise fish (Macropodus chinensis) was also found in the marsh. Japanese freshwater shrimps (Macrobrachium nipponense) were found only in the influx canal from waterworks. Indoor aquarium experiments showed that the wild medaka in this marsh was easily cultured with commercial feed similar to domesticated strains. Some ecological aspects of the medaka were discussed based on the observations of the fish in the marsh.

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Effects of different selenium sources and levels on serum biochemical parameters and tissue selenium retention in rats
Fei HAN, Daiwen CHEN, Bing YU, Wenli LUO, Daiwen CHEN, Bing YU
Front Agric Chin. 2009, 3 (2): 221-225.

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A total of 54 female Wistar rats were allotted to nine treatments by weight and fed basal diet or diets containing Se of 0.05, 0.10, 0.15, or 0.20 mg?kg-1 diet provided with either Se yeast or sodium selenite for 10 days. The results showed the following: (1) Selenium yeast had better effects compared with sodium selenite on increasing serum superoxide dismutase activities (P<0.05). Addition of Se yeast or sodium selenite increased the activities of serum gluthathione peroxidase (P<0.01); (2) According to slope ratio assay, the bioavailability of Se from Se yeast was 132.1%, 205.7%, 140.0%, and 107.2% of that from sodium selenite when glutathione peroxidase activities and Se contents in serum, kidney, and liver were used as indicators. It is concluded that Se from Se yeast has higher bioavailability than Se from sodium selenite.

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Regulation of the type IIb sodium-dependent phosphate cotransporter expression in the intestine
Bin WANG, Yulong YIN
Front Agric Chin. 2009, 3 (2): 226-230.

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Phosphate (Pi) plays important roles in growth, development, bone mineralization, energy metabolism, nucleic acid synthesis, cell signaling, and acid–base regulation. The rate of intestinal absorption of Pi is a major determinant of Pi homeostasis. The type IIb sodium-dependent Pi cotransporter (NaPi-IIb) is responsible for intestinal Pi absorption. Many physiological factors regulate the rate of Pi absorption via modulating the expression of NaPi-IIb in the intestine. In this review, we summarize the role of these factors in the regulation of NaPi-IIb expression in the intestine.

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