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2012 Vol. 11 No. 4 Previous Issue    Next Issue

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Crop Genetics · Breeding · Germplasm Resources
PHYSIOLOGY & BIOCHEMISTRY · TILLAGE · CULTIVATION
PLANT PROTECTION
ANIMAL SCIENCE · VETERINARY SCIENCE
AGRICULTURAL ENVIRONMENT, ECOLOGY AND ENERGY
AGRICULTURAL ECONOMICS AND MANAGEMENT




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Crop Genetics · Breeding · Germplasm Resources

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Characterization and Molecular Mapping of a Stripe Rust Resistance Gene in Synthetic Wheat CI110 REN Qiang, LIU Hui-juan, ZHANG Zeng-yan, FENG Jing, XU Shi-chang, PU Zong-jun , XIN Zhiyong 2012, 12(4): 521-·527.  DOI: 10.1016/S1671-2927(00)8571 Abstract ( )   PDF in ScienceDirect   Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.). To diversify stripe rust-resistant resources for wheat breeding programs, a CIMMYT synthetic wheat line CI110 was identified to be resistant to 28 isolates of Pst, including 6 Chinese prevalent races CYR28-CYR33. Genetic analysis indicated that a single dominant gene was responsible for the stripe rust resistance in CI110, temporarily designated YrC110. A molecular map, harboring YrC110 and 9 linked SSR markers, was constructed through simple sequence repeat (SSR), and bulked segregant analysis. These linked markers and YrC110 were assigned on the short arm of chromosome 1B using the Chinese Spring nullisomic-tetrasomic and ditelosomic stocks. Gene postulation based on seedling reaction patterns to 30 Pst isolates suggested that the resistance gene YrC110 seemed different from the other known resistance genes tested, such as Yr9, Yr10, Yr15, Yr24, and Yr26/YrCH42. Four SSR markers Xbarc187150, Xgwm18227, Xgwm11223, and Xbarc240292 distinguished YrC110 from Yr10, Yr15, Yr24, and Yr26/YrCH42, and could be used as diagnostic ones for YrC110 in wheat resistant breeding programs against stripe rust.

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Mapping of Quantitative Trait Loci for Adult Plant Resistance to Stripe Rust in German Wheat Cultivar Ibis  BAI Bin, REN Yan, XIA Xian-chun, DU Jiu-yuan, ZHOU Gang, WU Ling, ZHU Hua-zhong, HEZhong-hu , WANG Cheng-she 2012, 12(4): 528-536.  DOI: 10.1016/S1671-2927(00)8572 Abstract ( )   PDF in ScienceDirect   The German wheat cultivar Ibis has excellent adult plant resistance (APR) to stripe rust in Gansu, a hotspot for stripe rust in China. To elucidate the genetic basis of APR to stripe rust in Ibis, 237 F3 lines derived from the cross Ibis/Huixianhong were evaluated at Tianshui, Gansu, in the 2008-2009 and 2009-2010 cropping seasons, and at Chengdu, Sichuan Province, China, in the 2009-2010 cropping season. Inoculations were conducted with a mixture of several prevalent Pst races in both locations. Maximum disease severity (MDS) data showed a continuous distribution of response, indicating quantitative nature of resistance to stripe rust in Ibis. The broad-sense heritability of MDS was 0.75 based on the mean values averaged across three environments. A total of 723 simple sequence repeat (SSR) markers were used to map the QTL for APR by inclusive composite interval mapping (ICIM). QTLs mapping to chromosomes 2BS and 6BS, designated as QYr.caas-2BS.1 and QYr.caas-6BS.1, respectively, explained 4.1-40.7% of the phenotypic variance in MDS across environments. The major effect QTL QYr.caas-2BS.1, flanked by Xgwm148 and Xwmc360, was consistently detected at all three sites as well as the averaged data over three environments, accounting for 40.7, 24.2, 5.2 and 29.9% of phenotypic variance, respectively. The molecular markers closely linked to this QTL have potential for use in marker-assisted selection and gene pyramiding to improve the durability of stripe rust resistance in wheat breeding.

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Genetic Analysis of Cryotolerance in Cotton During the Overwintering Period Using Mixed Model of Major Gene and Polygene ZHANG Xin, LI Cheng-qi, WANG Xi-yuan, CHEN Guo-ping, ZHANG Jin-bao , ZHOU Rui-yang 2012, 12(4): 537-544.  DOI: 10.1016/S1671-2927(00)8573 Abstract ( )   PDF in ScienceDirect   The joint analysis of the mixed genetic model of major gene and polygene was conducted to study the inheritance of cryotolerance in cotton during the overwintering period. H077 (G. hirsutum L., weak cryotolerance) and H113 (G. barbadence L., strong cryotolerance) were used as parents. Cryotolerance of six generation populations including P1, P2, F1, B1, B2, and F2, from each of the two reciprocal crosses H077×H113 and H113×H077 were all investigated. The results showed that cryotolerance in cotton during the overwintering period was accorded with two additive major genes and additivedominance polygene genetic model. For cross H077×H113, the heritabilities of major genes in B1, B2, and F2 were 83.62, 76.84, and 90.56%, respectively; and the heritability of polygene could only be detected in B2, which was 7.76%. For cross H113×H077, the heritabilities of major genes in B1, B2, and F2 were 67.42, 68.95, and 83.40%, respectively; and the heritability of polygene was only detected in F2, which was 6.51%. In addition, the whole heritability in F2 was always higher than that in B1 and B2 in each cross. Therefore, for the cryotolerance breeding of perennial cotton, the method of single cross recombination or single backcross should be adopted to transfer major genes, and the selection in F2 would be more efficient than that in other generations.

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A Modified Method for the Development of SSR Molecular Markers Based on Redundant EST Data and Its Application in Soybean ZHAO Xue, CHANG Wei, HAN Ying-peng, TENG Wei-li , LI Wen-bin 2012, 12(4): 545-555.  DOI: 10.1016/S1671-2927(00)8574 Abstract ( )   PDF in ScienceDirect   EST-derived SSR marker has been developed in many species, but few methods of high efficiency have been reported for the exploitation of EST-SSR markers. Thus, a high efficiency method for mining millions of redundant EST data is needed. A modified method for the EST-SSR development with high efficiency was established based on the redundant EST data of soybean in this study. The method achieved its function through classifying ESTs according to the same SSR motif and detected candidate loci with redundant sequences. In this study, a total of 80 polymorphic EST-SSR markers of soybean were developed, 50 of them were exploited by this modified method which proved the higher speed and efficiency of this method. All the 80 polymorphic EST-SSRs were mapped on soybean physical map through in silico mapping and 15 markers were integrated on a genetic map constructed in previous study. A software named hpSSR (high polymorphic SSR) was programmed based on the concept of the up-built method for EST-SSR development. This method is not only pragmatic for EST-SSR exploitation in soybean, but also effective for the development of the marker in other species if the redundancy EST data is available.

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Assessment of Genetic Relationship of Foxtail Millet with Its Wild Ancestor and Close Relatives by ISSR Markers LI Wei, ZHI Hui, WANG Yong-fang, LI Hai-quan , DIAO Xian-min 2012, 12(4): 556-566.  DOI: 10.1016/S1671-2927(00)8575 Abstract ( )   PDF in ScienceDirect   Inter simple sequence repeat (ISSR) analysis was applied to samples of foxtail millet and its wild ancestor and other close relatives of the genus Setaria in order to detect domestication-related geographical structure and phylogenetic relationship of those species. Eighty-one accessions of nine Setaria species that originated from different regions were used in this study. Fourteen out of the 27 ISSR primers screened amplified successfully and a total of 156 markers were scored for all the accessions, with a high level of polymorphism being detected. The dendrogram based on UPGMA cluster analysis showed clear geographic structure among foxtail millet and its wild ancestor green foxtail, which implies that northern China is the domestication center for both the Chinese and European foxtail millet landraces used in this study. This result did not support the hypothesis that China and Europe are independent domestication centers for foxtail millet proposed by several previous studies based on morphological and isozyme data. The dendrogram also clearly classified the Setaria sample used into two groups, a viridis and a pumila groups. The viridis group was composed of S. viridis, S. italica, S. faberii, S. verticillata, S. leucopila, and S. queenslandica, and the pumila group consisted of S. parviflora and S. pumila, which is consistent with the recently proposed hypothesis of multiple origin of Setaria species. The phylogenetic relationships among different species are discussed.

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Construction and Analysis of Suppression Subtractive cDNA Library from Fertile Disk Floret Buds of Zinnia elegans  PANG Rui-hua, MA Guang-ying, LOU Xue-yuan, BAO Man-zhu , YE Yao-mei 2012, 12(4): 567-575.  DOI: 10.1016/S1671-2927(00)8576 Abstract ( )   PDF in ScienceDirect   In order to isolate genes related to anther development and understand molecular basis of male sterility, cDNA library of Zinnia elegans was constructed using suppression subtractive hybridization (SSH) approach. 672 different expressed clones were selected from the fertile disk floret buds. PCR results showed that cDNA inserts were ranged from 100 to 750 bp. 303 positive clones screened by dot-blot hybridization were sequenced. 273 out of 303 sequenced clones produced readable sequences; these sequences represent 87 non-repetitive sequences. The homology alignment showed that 76 expressed sequence tags (ESTs) had functional annotations in GenBank, the other 11 ESTs without any homology to the known gene. In addition, 87 ESTs were divided into 17 groups according to MIPS of Arabidopsis thaliana database. Sequence data from the cDNA library have been deposited with the GenBank under the accession numbers GT067016-GT067085. As an important result in this study, 7 genes related to anther development were isolated. Results from semi-quantitative RT-PCR showed 6 genes were expressed only in disk florets of fertile plants compared with that of male sterile plants. These ESTs obtained provide important clues for further isolation and identification of fertility-related genes in Z. elegans.

PHYSIOLOGY & BIOCHEMISTRY · TILLAGE · CULTIVATION

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A Novel Approach to the Water Uptake Dynamics in Roots of Maize, Wheat and Barley Under Salt Stress BU Qing-mei, BIAN Dian-xia, LIU Lin-de , ZHU Jian-jun 2012, 12(4): 576-584.  DOI: 10.1016/S1671-2927(00)8577 Abstract ( )   PDF in ScienceDirect   The water uptake dynamics in maize, wheat, and barley under salt stress were investigated with a xylem pressure probe. The average xylem pressure responses to salt stress in the three plants were 36, 93, and 89% of the osmotic stresses for maize, wheat, and barley, respectively, which are significantly smaller than the magnitude of the osmotic stresses being applied. In order to explain the thermodynamic discrepancies among the water potential changes in the root xylem of the three plants, a novel approach, tentatively named the “symplastic flow dilution model” was proposed in this paper. The model was presented in an attempt to give answers to the problem of how the roots under salt stress could absorb water when the water potential of the xylem sap is considerably higher than that of the solution in the root ambient. According to the model, the salt solution in the microenvironment of the endodermis of a root was diluted to some extent by the efflux from cells so the central stele of the root is not exposed to the same solution bathing the root with the same salt concentration. In contrast, we also presented another approach, the “reflection coefficient progression approach”, which was less likely to be true because it requires a considerable amount of solute to be transported into the root xylem when the salt stress is severe.

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The Dynamics of Changes in Starch and Lipid Droplets and Sub-Cellular Localization of β-Amylase During the Growth of Lily Bulbs WU Sha-sha, WU Jin-di, JIAO Xue-hui, ZHANG Qi-xiang, , LV Ying-min 2012, 12(4): 585-592.  DOI: 10.1016/S1671-2927(00)8578 Abstract ( )   PDF in ScienceDirect   The ultra-structure of mother and outer daughter scales of Lilium Oriental hybrid Sorbonne were studied using transmission electron microscope to examine the sub-cellular localization of starch and lipid droplets during growth and development from shoot emergence to senescence. The contents of starch granules and lipid droplets in the cell of the mother scales decreased significantly from shoot emergence to anthesis, indicating that these scales served as a source for growth and development. After flowering, the number of starch granules and lipid droplets increased dramatically, and finally the cells were filled with the above molecules indicating that the bulb becomes a major sink during bulb enlargement. Ultrastructure observation also showed that symplastic pathway is the main pathway in cells in the exchange and transportation of material during bulb development. The activity of β-amylase, one of the key enzymes catalyzing starch breakdown, showed a similar trend. The enzyme sub-cellular localization via immune-gold electron-microscopy showed that β- amylase was predominantly located together with starch granules, while the gold particles were scarcely found in other sub-cellular compartments. The result suggested that this enzyme is compartmented together with its functional substrate supporting its function in catalyzing starch breakdown in living plant cells.

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Modeling the Potential Geographic Distribution of Black Pepper (Piper nigrum) in Asia Using GIS Tools HAO Chao-yun, FAN Rui, Milton Cezar Ribeiro, TAN Le-he, WU Hua-song, YANG Jian-feng, ZHENG Wei-quan , YU Huan 2012, 12(4): 593-599.  DOI: 10.1016/S1671-2927(00)8579 Abstract ( )   PDF in ScienceDirect   Known as the “king of spices”, black pepper (Piper nigrum), a perennial crop of the tropics, is economically the most important and the most widely used spice crop in the world. To understand its suitable bioclimatic distribution, maximum entropy based on ecological niche modeling was used to model the bioclimatic niches of the species in its Asian range. Based on known occurrences, bioclimatic areas with higher probabilities are mainly located in the eastern and western coasts of the Indian Peninsula, the east of Sumatra Island, some areas in the Malay Archipelago, and the southeast coastal areas of China. Some undocumented places were also predicted as suitable areas. According to the jackknife procedure, the minimum temperature of the coldest month, the mean monthly temperature range, and the precipitation of the wettest month were identified as highly effective factors in the distribution of black pepper and could possibly account for the crop’s distribution pattern. Such climatic requirements inhibited this species from dispersing and gaining a larger geographical range.

PLANT PROTECTION

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Xoryp_08180 of Xanthomonas oryzae pv. oryzicola, Encoding a Hypothetical Protein, is Regulated by HrpG and HrpX and Required for Full Virulence in Rice SHEN Yi-ping, ZOU Li-fang, LI Yu-rong, ZOU Hua-song, LIU Xi-ling , CHEN Gong-you 2012, 12(4): 600-610.  DOI: 10.1016/S1671-2927(00)8580 Abstract ( )   PDF in ScienceDirect   Xanthomonas oryzae pv. oryzicola (Xoc) causes a destructive bacterial leaf streak disease in rice. Some of the gene products annotated as hypothetical proteins in the genome of Xoc may contribute to its virulence in rice. A mutant, Mxoc1679, screened from our previous Tn5-tagged mutant library for Xoc strain RS105, showed reduced virulence in rice. In this mutant, a gene named as Xoryp_08180 was disrupted by Tn5 insertion. Xoryp_08180 encodes a 1 306-aa hypothetical protein which is highly conserved in Xanthomonas spp. Non-polar mutation of Xoryp_08180 in RS105 strain led to a significant reduction in bacterial virulence and growth in rice, a delayed hypersensitive response (HR) in non-host tobacco, and a decrease in extracellular protease activity. The deficiencies above were restored to wild-type level in the complementary strain by expressing Xoryp_08180 in trans. In addition, the expression of Xoryp_08180 was repressed in hrpG and hrpX mutants in planta but not in a nutrient-rich condition. These results suggested that Xoryp_08180 is a virulence factor required for extracellular protease production, HR induction and full virulence of Xoc.

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The Effect of Wheat Mixtures on the Powdery Mildew Disease and Some Yield Components LI Ning, JIA Shao-feng, WANG Xiu-na, DUAN Xia-yu, ZHOU Yi-lin, WANG Zong-hua , LU Guodong 2012, 12(4): 611-620.  DOI: 10.1016/S1671-2927(00)8581 Abstract ( )   PDF in ScienceDirect   Mixtures composed of five wheat cultivars, Jingshuang 16, Jing 411, Jingdong 8, Lunxuan 987, and Baofeng 104, with different levels of resistance against powdery mildew were tested for their potential containment of the disease development in the field and for the influence on grain yield and the content of crude protein in the years 2007 and 2010. The plots were inoculated artificially with mixed isolates collected in the fields and propagated in the greenhouse and the disease was scored in 7 d interval during the two growing seasons. It was indicated that certain combinations, e.g., Jingdong 8: Lunxuan 987, Jingdong 8:Baofeng 104, and Jing 411:Jingdong 8:Baofeng 104, showed positive efficacy on the mildew. The cultivar combinations tested in 2007 showed increase of grain yield, while most of the combinations tested in 2010 did not show the increase. The differences of the increases or decreases were not statistically significant except combinations Jing 411:Jingdong 8:Baofeng104, Jingshuang16:Jingdong8:Lunxuang 987 and Jingshuang 16:Jingdong 8:Lunxuan 987: Baofeng 104, which showed the decrease of the grain yield. The mixtures did not show influence on the content of crude protein in grain. More cultivar combinations need to be tested.

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The Efficiency of Southern rice black-streaked dwarf virus Transmission by the Vector Sogatella furcifera to Different Host Plant Species LI You-zhi, CAO Yang, ZHOU Qian, GUO Hai-ming , OU Gao-cai 2012, 12(4): 621-627.  DOI: 10.1016/S1671-2927(00)8582 Abstract ( )   PDF in ScienceDirect   Southern rice black-streaked dwarf disease is a new rice disease that severely affects rice production in South China. To understand transmission capacity of the vector Sogatella furcifera to Southern rice black-streaked dwarf virus (SRBSDV) among different host plant species, potential host plants of SRBSDV collected from the diseased rice field and/or adjacent to the field in Hunan Province, China, were determined by RT-PCR, and the transmission rates of SRBSDV by S. furcifera among different host plant species were investigated. The results showed that host plants of SRBSDV in the rice fields were five of family Gramineae (Oryza sativa, Echinochloa crusgalli, Zea mays, Paspalum distichum, Alopecurus aequali) and two of family Cyperaceae (Juncellus serotinus and Cyperus difformis). S. furcifera could not transmit SRBSDV between gramineous plants and cyperaceous plants, and could not transmit SRBSDV between the gramineous plants, J. serotinus and C. difformis as well. However, SRBSDV could be transmitted by S. furcifera within gramineous plants. S. furcifera could transmit SRBSDV between interspecies among three species plants (O. sativa, E. crusgalli and Z. mays), and between P. distichum and A. aequali. At 15, 20, 25, 30, and 35°C, both macropterous and brachypterous adult of S. furcifera could transmit SRBSDV from the plants (e.g., E. crusgalli, Z. mays and O. sativa) infected with SRBSDV to rice seedlings. The transmission rates were first increased and then decreased with the increase of temperature. Macropterous adults transmitted SRBSDV from the viruliferous E. crusgalli, Z. may and rice plants to the healthy rice seedlings, and the infected rates of rice seedlings were 26.2, 18.8 and 23.7% at 15°C, 56.6, 64.6 and 53.6% at 25°C, and was 11.2, 10.2 and 7.3% at 35°C, respectively. Transmission capacity of brachypterous adults was significantly higher than that of macropterous adults at 15, 20 and 25°C (P<0.05), while transmission capacity of brachypterous adults was relatively lower compared with that of macropterous ones at 35°C. These results offer evidence on the transmission of SRBSDV via the vector S. furcifer among different host plants, which can be helpful to control Southern rice black-streaked dwarf disease by the appropriate cultural measures in South China.

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A Fragment of Cadherin-Like Protein Enhances Bacillus thuringiensis Cry1B and Cry1C Toxicity to Spodoptera exigua (Lepidoptera: Noctuidae) LU Qiong, ZHANG Yong-jun, CAO Guang-chun, ZHANG Li-li, LIANG Ge-mei, LU Yan-hui, WU Kong-ming, GAO Xi-wu , GUO Yu-yuan 2012, 12(4): 628-638.  DOI: 10.1016/S1671-2927(00)8583 Abstract ( )   PDF in ScienceDirect   Cry toxins produced by Bacillus thuringiensis (Bt) are effective biological insecticides against certain insect species. In this study, bioassay results indicated that Cry1B and Cry1C were toxic to Spodoptera exigua. We also identified a cadherin-like gene in S. exigua that could enhance the toxicity of Cry1B and Cry1C. The cadherin-like gene identified from the larvae midgut tissue was cloned by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The full-length cDNA of the gene consisted of 5 220 bp encoding 1 740 amino acid with a predicted molecular mass of 196 kD. BLAST search analysis showed that the predicted amino acid sequence had a high sequence identity to the published sequences of cadherin-like proteins from other Lepidoptera insects. Spatial expression of the cadherin-like gene detected by qRT-PCR analysis revealed that the cadherin-like gene was mainly present in the gut of 4th instar larvae and during different life stages. The results suggested that the commercial development of this synergist has the potential to enhance Cry1B and Cry1C toxicity against Lepidoptera insects.

ANIMAL SCIENCE · VETERINARY SCIENCE

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Effect of Beak Trimming Stress on the Apoptosis and Its Related Protein Expression of Chicken Spleen SUN Gui-rong, LI Yan, KANG Xiang-tao, TIAN Ya-dong, ZHANG Hu , LI Kui 2012, 12(4): 639-645.  DOI: 10.1016/S1671-2927(00)8584 Abstract ( )   PDF in ScienceDirect   Beak trimming was a part of routine husbandry for poultry industry, which was the most efficient and economic way to reduce the incidence of cannibalism. However, the controversy about young chicken trimming still exits and it was drawing more concern recently along with the popular of animal behavior and welfare theory. To evaluate the influence of beak trimming on young chicken spleen development and find the key regulators of the spleen development, in this study, the electron microscope technique, flow cytometry and immunohistochemical techniques were used to investigate the effects of beak trimming stress on the spleen development. The result of electronic microscope showed that significant stress response could be found in chicken spleen cells after beak trimming. Cell volume became larger, chromatin of cell nuclear agglutinated conglobation, cytoplasm formed more vacuole, and mitochondria emerged vacuolization phenomenon in splenic lymphocyte after beak trimming. From the flow cytometry, the lymphocyte of spleen in the control group and experimental group were mainly in G1 phase, and the remaining small amount was in S and M phases. Of interest, the number of the lymphocyte which are in G1 phase within immune organ in the experimental group were more than that in the control group, but the number of cells in S and M phases were less than that in the control group. And beak trimming decreased the lymphocytes proliferation index of spleen. Inmmuohistochemical result showed that the beak trimming stress did not affect the expression sites of two apoptosis-related genes, Bcl-2 and Bax, in the spleen. But the expression level of Bcl-2 decreased while Bax increased in chicken immune organs after beak trimming. Furthermore, the beak trimming increased spleen cell apoptosis with a time-dependant style. Our findings may make a contribution to the active precaution of stress response.

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Baicalin Induces IFN-α/β and IFN-γ Expressions in Cultured Mouse Pulmonary Microvascular Endothelial Cells HU Ge, XUE Jiu-zhou, LIU Jing, ZHANG Tao, DONG Hong, DUAN Hui-qin, YANG Zuo-jun, RENXiao-ming , MU Xiang 2012, 12(4): 646-654.  DOI: 10.1016/S1671-2927(00)8585 Abstract ( )   PDF in ScienceDirect   We studied the effect of baicalin, an extract from Radix Scutellariae (a traditional Chinese medicine) in inducing mouse pulmonary microvascular endothelial cells (MPMVECs) to produce interferons (IFNs). MPMVECs were cultured in vitro in the presence of different concentrations of baicalin (10, 20, and 30 μg mL-1), and the cells and the culture media were harvested at various time intervals. The proteins and mRNA levels (relative to β-actin) of IFN-α/β and IFN-γ were analyzed by RT-PCR and enzyme-linked immunosorbent assay (ELISA). It was observed that baicalin substantially up-regulated the expression of IFN-α/β and IFN-γ. In all baicalin-treated groups, the relative levels of IFN-α/β and IFN-γ mRNAs peaked after 12 h of culturing, and IFN-α/β and IFN-γ proteins peaked after 24 h of culturing. These results suggest that baicalin can effectively induce the expression of IFNs in pulmonary microvascular endothelial cells, and thus potentially act as an antiviral compound. This study may provide background information for developing new antiviral drugs based on baicalin.

AGRICULTURAL ENVIRONMENT, ECOLOGY AND ENERGY

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Effects of Long-Term Winter Planted Green Manure on Physical Properties of Reddish Paddy Soil Under a Double-Rice Cropping System YANG Zeng-ping, XU Ming-gang, ZHENG Sheng-xian, NIE Jun, GAO Ju-sheng, LIAO Yu-lin , XIE Jian 2012, 12(4): 655-664.  DOI: 10.1016/S1671-2927(00)8586 Abstract ( )   PDF in ScienceDirect   Soil physical properties are important indicators of the potential for agricultural production. Our objective was to evaluate the effects of long-term inputs of green manures on physical properties of a reddish paddy soil (Fe-Typic Hapli-Stagnic Anthrosols) under a double cropping system. The common cropping pattern before the study was early-late rice-fallow (winter). The field treatments included rice-rice-fallow (R-R-WF), rice-rice-rape (R-R-RP), rice-rice-Chinese milk vetch (RR- MV), and rice-rice-ryegrass (R-R-RG). The rape, Chinese milk vetch and ryegrass were all incorporated as green manures 15 d before early rice transplanting during the following year. The soil bulk density in all green manure treatments was significantly reduced compared with the winter fallow treatment. Soil porosity with green manure applications was significantly higher than that under the winter fallow. The green manure treatments had higher 0.25-5 mm water stable aggregates and aggregates stabilities in the plow layer (0-15 cm depth) compared with the fallow treatment. The mean weight diameter (MWD) and normalized mean weight diameter (NMWD) of aggregates in the green manure treatment were larger than that with the winter fallow. Soil given green manure retained both a higher water holding capacity in the plow layer soil, and a larger volume of moisture at all matric potentials (-10, -33 and -100 kPa). We conclude that the management of double-rice fields in southern central China should be encouraged to use green manures along with chemical fertilizers to increase SOC content, improve soil physical properties and soil fertility.

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CH4 Concentrations and Emissions from Three Rivers in the Chaohu Lake Watershed in Southeast China YANG Li-biao, LI Xin-yan, YAN Wei-jin, MA Pei , WANG Jia-ning 2012, 12(4): 665-673.  DOI: 10.1016/S1671-2927(00)8587 Abstract ( )   PDF in ScienceDirect   This study was conducted at three rivers of the Chaohu Lake watershed during the summer season of 2008, aiming to investigate the diurnal variations of dissolved CH4 concentrations and emissions, as well as the dynamics of CH4 accumulation emission rates over consecutive 72 h. The results showed that CH4 concentrations in the Fengle, Hangbu, and Nanfei rivers ranged from 56.33-124.79, 160.82-341.03, and 213.49-716.81 nmol L-1, respectively, over a daily cycle; while the saturation of CH4 ranged from 188.72-418.07, 538.74-1 142.46, and 715.23-2 401.38%, respectively, which indicated that surface waters were in all cases oversaturated with respect to the atmosphere. An obvious diurnal variation pattern of the dissolved CH4 concentrations demonstrated a higher value during daytime but a lower value for night time. Additionally, the highest dissolved CH4 concentrations were detected in the Nanfei River which received substantial urban wastewater discharges. CH4 emissions measured with floating chambers ranged from 5.82-15.46, 5.77-8.41, and 13.51-49.25 mg C m-2 h-1 for the Fengle, Hangbu, and Nanfei rivers, respectively, over a daily cycle. Significantly higher CH4 emissions were also observed from the Nanfei River. The accumulative CH4 emissions for each river increased with time, while a decline trend on the accumulation rates was investigated over the consecutive 72 h.

AGRICULTURAL ECONOMICS AND MANAGEMENT

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Using Quantile Regression Approach to Analyze Price Movements of Agricultural Products in China LI Gan-qiong, XU Shi-wei, LI Zhe-min, SUN Yi-guo , DONG Xiao-xia 2012, 12(4): 674-683.  DOI: 10.1016/S1671-2927(00)8588 Abstract ( )   PDF in ScienceDirect   This paper studies how the price movements of pork, chicken and egg respond to those of related cost factors in short terms in Chinese market. We employ a linear quantile approach not only to explore potential data heteroscedasticity but also to generate confidence bands for the purpose of price stability study. We then evaluate our models by comparing the prediction intervals generated from the quantile regression models with in-sample and out-of-sample forecasts. Using monthly data from January 2000 to October 2010, we observed these findings: (i) the price changes of cost factors asymmetrically and unequally influence those of the livestock across different quantiles; (ii) the performance of our models is robust and consistent for both in-sample and out-of-sample forecasts; (iii) the confidence intervals generated from 0.05th and 0.95th quantile regression models are good methods to forecast livestock price fluctuation.

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Honey Safety Standards and Its Impacts on China's Honey Export WEI Guo-xue, HUANG Ji-kun , YANG Jun 2012, 12(4): 684-693.  DOI: 10.1016/S1671-2927(00)8589 Abstract ( )   PDF in ScienceDirect   Food safety standard draws increasing concerns on agricultural trade throughout the world. This paper aims to assess the impact of maximum residual limit standard (MRL) of chloromycetin on honey exporting from China. To achieve this objective, the paper discusses the trends of China’s honey production and export practices, analyzes changes on MRL of chloromycetin adopted by major importing countries, and use a gravity model to estimate the impact of MRL of chloromycetin on China’s honey export. The results show that despite the rapid growth of China’s honey production, honey export has declined significantly since 2000. The major reason of declining honey export was mainly due to the more stringent food safety standards indicated by MRL of chloromycetin imposed by importing countries on their honey imports.