2021 Vol. 20 No. 9 Previous Issue    Next Issue

    Crop Science
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Agricultural Economics and Management

      Cover illustration

    For Selected: Toggle Thumbnails
    Molecular characteristics and structure–activity relationships of food-derived bioactive peptides
    YANG Fu-jia, CHEN Xu, HUANG Mu-chen, YANG Qian, CAI Xi-xi, CHEN Xuan, DU Ming, HUANG Jian-lian, WANG Shao-yun
    2021, 20(9): 2313-2332.  DOI: 10.1016/S2095-3119(20)63463-3
    Abstract ( )   PDF in ScienceDirect  
    Peptides are functional active fragments of proteins which can provide nutrients needed for human growth and development, and they also have unique physiological activity characteristics relative to proteins.  Bioactive peptides contain a great deal of development potential.  More specifically, food-derived bioactive peptides have the advantages of a wide variety of sources, unique structures, high efficiency and safety, so they have broad development prospects.  This review provides an overview of the current advances regarding the preparation, functional characteristics, and structure–activity relationships of food-derived bioactive peptides.  Moreover, the prospects for the future development and application of food-derived bioactive peptides are discussed.  This review may provide a better understanding of food-derived bioactive peptides, and some constructive inspirations for further research and applications in the food industry.
    Crop Science
    Integrating the physical and genetic map of bread wheat facilitates the detection of chromosomal rearrangements
    ZHAO Lai-bin, XIE Die, HUANG Lei, ZHANG Shu-jie, LUO Jiang-tao, JIANG Bo, NING Shun-zong, ZHANG Lian-quan, YUAN Zhong-wei, WANG Ji-rui, ZHENG You-liang, LIU Deng-cai, HAO Ming
    2021, 20(9): 2333-2342.  DOI: 10.1016/S2095-3119(20)63289-0
    Abstract ( )   PDF in ScienceDirect  
    The bread wheat genome harbors a high content of repetitive DNA, which is amenable to detection and characterization using fluorescence in situ hybridization (FISH) karyotyping.  An integrated genetic map was derived from a recombinant inbred population bred from a cross between a synthetic hexaploid wheat and a commercial Chinese bread wheat cultivar, based on 28 variable FISH sites and >150 000 single nucleotide polymorphism (SNP) loci.  The majority (20/28) of the variable FISH sites were physically located within a chromosomal region consistent with the genetic location inferred from that of their co-segregating SNP loci.  The eight exceptions reflected the presence of either a translocation (1R/1B, 1A/7A) or a presumptive intra-chromosomal inversion (4A).  For eight out of the nine FISH sites detected on the Chinese Spring (CS) karyotype, there was a good match with the reference genome sequence, indicating that the most recent assembly has dealt well with the problem of placing tandem repeats.  The integrated genetic map produced for wheat is informative as to the location of blocks of tandemly repeated DNA and can aid in improving the quality of the genome sequence assembly in regions surrounding these blocks.
    Physiological response of flag leaf and yield formation of winter wheat under different spring restrictive irrigation regimes in the Haihe Plain, China
    LIU Xue-jing, YIN Bao-zhong, HU Zhao-hui, BAO Xiao-yuan, WANG Yan-dong, ZHEN Wen-chao
    2021, 20(9): 2343-2359.  DOI: 10.1016/S2095-3119(20)63352-4
    Abstract ( )   PDF in ScienceDirect  
    In order to identify the optimum period of spring water-restrictive irrigation for winter wheat (Triticum aestivum L.) in the Haihe Plain, China and elucidate its effects on flag leaf senescence and yield formation, field experiments were conducted at the Xinji Experimental Station of Hebei Agricultural University from 2016 to 2019 by using different irrigation regimes in spring, including the conventional regime involving two irrigation periods (control (CK), the 3-leaf unfolding stage and the anthesis stage) and a series of single, restrictive irrigation regimes (SRI) comprising irrigation at the 3-leaf unfolding stage (3LI), 4LI, 5LI, and 6LI.  There are five major findings: (1) The senescence (determined by the green leaf area, GLA) in the 4LI treatment occurred moderately earlier than that in CK, showed no significant difference with that in 5LI and 6LI, and occurred significantly later than that in 3LI.  (2) Compared with other SRI treatments, the GLA value and photosynthetic rate in 4LI were 14.82 and 20.1% higher, respectively.  Microstructural analysis of flag leaf also revealed that the mesophyll cells and chloroplasts were irregularly arranged under drought stress in 3LI and 6LI; however, drought stress had minimal negative effects on the microstructure in 4LI and 5LI.  (3) Postponed irrigation in spring could significantly increase superoxide dismutase (SOD) and catalase (CAT) activities in the early stage of grain filling; however, these activities would subsequently decrease.  Among the four SRI treatments, the overall enzyme activities were the highest in 4LI, and the combined malondialdehyde (MDA) content in flag leaves in 4LI and 5LI was 14.5% lower on average than that in 3LI and 6LI.  (4) The soluble sugar (SS) and proline (Pro) contents in 4LI were the highest among the four SRI treatments; however, they were lower than those in CK.  The abscisic acid (ABA) hormone content in 4LI and 5LI was lower than that in 3LI and 6LI, respectively, suggesting a smaller drought stress effect in 4LI and 5LI.  (5) In two growing seasons, there was a larger number of spikes per unit area in 4LI (i.e., 13.4% higher than that in 5LI and 6LI) and the 1 000-grain weight in 4LI was the highest among the four SRI treatments (i.e., 6.0% higher than that in the other three SRI treatments).  Therefore, a single restrictive irrigation regime at the 4-leaf unfolding stage is recommended to be effective in slowing down the senescence process of flag leaves and achieving high yield.
    Variation of carbon partitioning in newly expanded maize leaves and plant adaptive growth under extended darkness
    LIANG Xiao-gui, SHEN Si, GAO Zhen, ZHANG Li, ZHAO Xue, ZHOU Shun-li
    2021, 20(9): 2360-2371.  DOI: 10.1016/S2095-3119(20)63351-2
    Abstract ( )   PDF in ScienceDirect  
    Plants must maintain a balance between their carbon (C) supply and utilization during the day–night cycle for continuous growth since C starvation often causes irreversible damage to crop production.  It is not well known how C fixation and allocation in the leaves of crops such as maize adapt to sudden environmental changes.  Here, to quantify primary C fixation and partitioning in photosynthetic maize leaves under extended darkness and to relate these factors to plant growth, maize seedlings were subjected to extended darkness (ED) for three successive days at the 6th leaf fully expanded stage (V6).  ED reduced plant growth and leaf chlorophyll levels but not the rate of net CO2 exchange.  As a result of the reduction in photoassimilates, the accumulation of starch and total soluble carbohydrates (TSC) in mature leaves also decreased under ED.  However, the percentage of the daily C fixation reserved in mature leaves increased.  These transient C pools were largely composed of TSC and were mainly used for consumption by increased nocturnal respiration rather than for transport.  As the days went on, both the amount of C accumulated and the percentage of the daily fixed C that was reserved in leaves decreased, which could be largely accounted for by the attenuated starch synthesis in all treatments.  The activities of ADP-glucose pyrophosphorylase and soluble starch synthase decreased significantly over time.  Therefore, this study concluded that both starch and TSC are involved in the coordination of the C supply and plant growth under a sudden C shortage but that they may be involved in different ways.  While the ratio of reserved C to daily fixed C increased to maintain blade function under acute C starvation, both the amount and the proportion of C reserved in mature leaves decreased as plant growth continued in order to meet the growth demands of the plant.
    Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system
    CHEN Yuan, LIU Zhen-yu, HENG Li, Leila I. M. TAMBEL, ZHANG Xiang, CHEN Yuan, CHEN De-hua
    2021, 20(9): 2372-2381.  DOI: 10.1016/S2095-3119(20)63286-5
    Abstract ( )   PDF in ScienceDirect  
    Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction.  Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting.  The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride (MC) on temporal and spatial distributions of yield bolls, as well as yield and yield components.  During the 2013–2016 cotton growing seasons, the experiments were conducted on a short-season cotton cultivar CRRI50 at Yangzhou University, China.  Various combinations of plant density (12.0, 13.5 and 15.0 plants m–2) and MC dose (180, 270 and 360 g ha–1) were applied on cotton plants.  The combination of 13.5 plants m–2 and 270 g ha–1 MC resulted in the greatest boll number per unit area, the highest daily boll setting number and more than 90% of bolls positioned within 45–80 cm above the ground.  In conclusion, appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest, and thus overcome the labor-intensive problem in current transplanting cropping system. 
    Interactive effect of shade and PEG-induced osmotic stress on physiological responses of soybean seedlings
    Muhammad Ahsan ASGHAR, JIANG Heng-ke, SHUI Zhao-wei, CAO Xi-yu, HUANG Xi-yu, Shakeel IMRAN, Bushra AHMAD, ZHANG Hao, YANG Yue-ning, SHANG Jing, YANG Hui, YU Liang, LIU Chun-yan, YANG Wen-yu, SUN Xin, DU Jun-bo
    2021, 20(9): 2382-2394.  DOI: 10.1016/S2095-3119(20)63383-4
    Abstract ( )   PDF in ScienceDirect  
    Intensively farmed crops used to experience numerous environmental stresses.  Among these, shade and drought significantly influence the morpho-physiological and biochemical attributes of plants.  However, the interactive effect of shade and drought  on the growth and development of soybean under dense cropping systems has not been reported yet.  This study investigated the interactive effect of PEG-induced osmotic stress and shade on soybean seedlings.  The soybean cultivar viz., C-103 was subjected to PEG-induced osmotic stress from polyethylene glycol 6000 (PEG-6000) under shading and non-shading conditions.  PEG-induced osmotic stress significantly reduced the relative water contents, morphological parameters, carbohydrates and chlorophyll contents under both light environments.  A significant increase was observed in osmoprotectants, reactive oxygen species and antioxidant enzymes in soybean seedlings.  Henceforth, the findings revealed that, seedlings grown under non-shading conditions produced more malondialdehyde and hydrogen peroxide contents as compared to the shade-treated plants when subjected to PEG-induced osmotic stress.  Likewise, the shaded plants accumulated more sugars and proline than non-shaded ones under drought stress.  Moreover, it was found that non-shaded grown plants were more sensitive to PEG-induced osmotic stress than those exposed to shading conditions, which suggested that shade could boost the protective mechanisms against osmotic stress or at least would not exaggerate the adverse effects of PEG-induced osmotic stress in soybean seedlings.    
    Does heat accumulation alter crop phenology, fibre yield and fibre properties of sunnhemp (Crotalaria juncea L.) genotypes with changing seasons?
    Subrahmaniyan KASIRAJAN, Perumal VEERAMANI, ZHOU Wei-jun
    2021, 20(9): 2395-2409.  DOI: 10.1016/S2095-3119(20)63357-3
    Abstract ( )   PDF in ScienceDirect  
    Field experiments were carried out in split plot design during the dry and wet seasons for two years (two seasons each in 2016–2017 and 2017–2018) with two genotypes (SH4 and SUIN053), two plant geometry (30×15 cm and 45×15 cm main plots) and three levels of NPK (20 kg N ha–1, 40 kg P ha–1 and 40 kg K ha–1; 20 kg N ha–1, 60 kg P ha–1 and 60 kg K ha–1; 20 kg N ha–1, 80 kg P ha–1 and 80 kg K ha–1) with an objective to study the relationship between fibre yield of sunhmep and thermal indices.  The results indicated that the thermal units such as cumulative heat unit (CHU), photo thermal unit (PTU) and  helio thermal unit (HTU) were the highest during dry seasons, while relative temperature disparity (RTD) was the highest during wet seasons irrespective of the genotypes, plant geometry and fertilizer levels.  The combined analysis of variance showed that the suitability of sunnhemp genotypes for obtaining fibre and seed yields varied with season.  The results further indicated that sunnhemp grew during dry seasons with longer photoperiod and higher values of growing degree days (GDD), HTU and PTU resulted in a higher fibre yield, while a higher seed yield and relatively longer, finer and stronger fibres were obtained during wet seasons with higher RTD values.  Regression analysis indicated that CHU was positively related to fibre yield, while RTD was positively related to seed yield.   CHU beyond 2 000 °C d reduced seed yield and favoured fibre production.  In contrary to CHU, RTD values were positively related to seed yield and negatively related to fibre yield.   Similarly, HTU had an inverse relationship with fibre yield while PTU had a positive relationship with fibre yield.  The genotype SH4 produced a seed yield of 1 361 kg ha–1 during wet seasons, which was significantly higher than SUIN053, while a fibre yield of 990 kg ha–1 (significantly higher than that of SH4) was obtained for SUIN053 that required less CHU to attain the phenological events during dry seasons.  The per unit area yields of seed and fibre with the closer spacing (30 cm×15 cm)  by virtue of higher plant density were 17.0 and 14.9% higher than those with the spacing of 45 cm×15 cm, respectively.  Higher doses of P and K resulted in higher seed and fibre yields.
    Identification and expression analysis of the PbrMLO gene family in pear, and functional verification of PbrMLO23
    GUO Bing-bing, LI Jia-ming, LIU Xing, QIAO Xin, Musana Rwalinda FABRICE, WANG Peng, ZHANG Shao-ling, WU Ju-you
    2021, 20(9): 2410-2423.  DOI: 10.1016/S2095-3119(20)63558-4
    Abstract ( )   PDF in ScienceDirect  
    Mildew resistance locus O (MLO) is a plant-specific gene family that plays an important role in the growth and development of plants and their interactions with the environment.  However, the available information on this gene family in pear is limited.  Here, 24 PbrMLO genes were identified and divided into five subfamilies (I, II, III, IV and V).  Whole-genome duplication (WGD) and dispersed duplication contributed to the expansion of the PbrMLO family.  In addition, gene expression analysis revealed that PbrMLO genes were distributed in various pear tissues, suggesting their diverse functions.  We selected PbrMLO23 for further functional analysis.  Expression profile analysis by qRT-PCR showed that PbrMLO23 was highly expressed in pollen.  Subcellular localization analysis showed that PbrMLO23 was located on the plasma membrane.  When the expression level of PbrMLO23 was knocked down by using antisense oligonucleotides, pollen tube lengths increased, indicating that PbrMLO23 plays a functional role in inhibiting pollen tube growth.  In summary, these results provide evolutionary insight into PbrMLO and its functional characteristics and lay a foundation for further analysis of the functions of PbrMLO members in pear.
    Transcriptional profiles underlying the effects of salicylic acid on fruit ripening and senescence in pear (Pyrus pyrifolia Nakai)
    SHI Hai-yan, CAO Li-wen, XU Yue, YANG Xiong, LIU Shui-lin, LIANG Zhong-shuo, LI Guo-ce, YANG Yu-peng, ZHANG Yu-xing, CHEN Liang
    2021, 20(9): 2424-2437.  DOI: 10.1016/S2095-3119(20)63568-7
    Abstract ( )   PDF in ScienceDirect  
    Salicylic acid (SA) plays a pivotal role in delaying fruit ripening and senescence.  However, little is known about its underlying mechanism of action.  In this study, RNA sequencing was conducted to analyze and compare the transcriptome profiles of SA-treated and control pear fruits.  We found a total of 159 and 419 genes differentially expressed between the SA-treated and control pear fruits after 12 and 24 h of treatment, respectively.  Among these differentially expressed genes (DEGs), 125 genes were continuously differentially expressed at both treatment times, and they were identified as candidate genes that might be associated with SA-regulated fruit ripening and senescence.  Bioinformatics analysis results showed that 125 DEGs were mainly associated with plant hormone biosynthesis and metabolism, cell wall metabolism and modification, antioxidant systems, and senescence-associated transcription factors.  Additionally, the expression of several candidate DEGs in ripening and senescent pear fruits after SA treatments were further validated by quantitative real-time PCR (qRT-PCR).  This study provides valuable information and enhances the understanding of the comprehensive mechanisms of SA-meditated pear fruit ripening and senescence.
    Plant Protection
    Bioinformatic analysis and functional characterization of CFEM proteins in Setosphaeria turcica
    WANG Jian-xia, LONG Feng, ZHU Hang, ZHANG Yan, WU Jian-ying, SHEN Shen, DONG Jin-gao, HAO Zhi-min
    2021, 20(9): 2438-2449.  DOI: 10.1016/S2095-3119(20)63342-1
    Abstract ( )   PDF in ScienceDirect  
    Common in Fungal Extracellular Membrane (CFEM) domains are uniquely found in fungal extracellular membrane proteins which are important for pathogens.  This study identified 13 StCFEM proteins in the genome of Setosphaeria turcica, the hemibiotrophic fungus that causes northern corn leaf blight.  Sequence alignment and WebLogo analysis of their CFEM domains indicated that the amino acids were highly conserved and that, with the exception of StCFEM1, 2, 3, and 6, they contained eight cysteines.  Phylogenic analysis suggested that these 13 proteins (StCFEM1–13) could be divided into 2 clades based on the presence of the trans-membrane domain.  Six StCFEM proteins with a signal peptide and without a trans-membrane domain were considered as candidate effector proteins.  The CFEM domain in the candidate effector proteins could form a helical-basket structure homologous to Csa2 in Candida albicans.  Transcriptome analysis suggested that the 13 genes were expressed during fungal infection and a yeast secretion assay revealed that these candidate effectors were secreted proteins.  It was also found that StCFEM3, 4, and 5 couldn’t affect BAX/INF1-induced programmed cell death (PCD) in Nicotiana benthamiana and while StCFEM12 could suppress INF1-induced PCD, it showed no effect on BAX-induced PCD.  This study found that there were 13 members of the S. turcica CFEM protein family and that StCFEM12 was a candidate effector.  This study laid the foundation for illustrating the roles of CFEM proteins during the pathogenic processes of phytopathogens.
    Wheat straw biochar amendment suppresses tomato bacterial wilt caused by Ralstonia solanacearum: Potential effects of rhizosphere organic acids and amino acids
    TIAN Ji-hui, RAO Shuang, GAO Yang, LU Yang, CAI Kun-zheng
    2021, 20(9): 2450-2462.  DOI: 10.1016/S2095-3119(20)63455-4
    Abstract ( )   PDF in ScienceDirect  
    Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood.  This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth.  The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth.  The positive ‘biochar effect’ could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition.  Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum.  In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases.  Our findings highlight that biochar’s ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects’ in field conditions.
    Elimination of grapevine fleck virus and grapevine rupestris stem pitting-associated virus from Vitis vinifera 87-1 by ribavirin combined with thermotherapy
    HU Guo-jun, DONG Ya-feng, ZHANG Zun-ping, FAN Xu-dong, REN Fan
    2021, 20(9): 2463-2470.  DOI: 10.1016/S2095-3119(20)63336-6
    Abstract ( )   PDF in ScienceDirect  
    Vitis vinifera 87-1 plants infected by grapevine fleck virus (GFkV) and grapevine rupestris stem pitting-associated virus (GRSPaV) were used as the plant materials for virus elimination treatment.  This study evaluated the effects of ribavirin at different concentrations (15 and 25 μg mL–1; R15 and R25, respectively), thermotherapy (37°C; T), and the combination of ribavirin and thermotherapy (R15+T and R25+T) on eliminating viruses from grapevine plants in vitro.  Both R15 and R25 had phytotoxic effects and weakened plant growth.  Thermotherapy positively affected the growth of grapevine plants.  Plant height was significantly greater in T, R15+T, and R25+T than in CK, R15 and R25.  The proportion of dead plants after T, R15+T, and R25+T was 51.4, 11.4, and 8.6%, respectively.  The survival rates of regenerated plants after all treatments were >68.0%.  Ribavirin concentration and treatment time were related to the regeneration of shoot tips and elimination efficiencies of the two viruses.  The survival rates of plants after R15+T for 30, 40, and 50 days were 97.3, 90.7, and 74.4%, respectively.  The elimination rates of GRSPaV from plants in the three time quantum were 55.6, 84.6, and 93.8%, respectively.  The elimination rate of GFkV was 23.9% higher in R25 (35/44) than in R15 (25/45), and that of GRSPaV was 7.0% higher in R25 than in R15.  The combination of thermotherapy and chemotherapy was found to have a positive effect on the eradication of GFkV and GRSPaV, and R25+T for 50 days was able to completely eliminate the two viruses from in vitro grapevines.  
    Stability evaluation of reference genes for real-time quantitative PCR normalization in Spodoptera frugiperda (Lepidoptera: Noctuidae)
    SHU Ben-shui, YU Hai-kuo, DAI Jing-hua, XIE Zi-ge, QIAN Wan-qiang, LIN Jin-tian
    2021, 20(9): 2471-2482.  DOI: 10.1016/S2095-3119(20)63298-1
    Abstract ( )   PDF in ScienceDirect  
    Real-time quantitative PCR (qPCR) is a reliable and widely used technique for analyzing the expression profiles of target genes in different species, and reference genes with stable expressions have been introduced for the normalization of the data.  Therefore, stability evaluation should be considered as the initial step for qPCR experiments.  The fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a polyphagous pest that consumes many plant species and seriously threatens corn production around the world.  However, no studies thus far have examined the stability of reference genes in this pest.  In this study, the expression profiles of the eight candidate reference genes of Actin, elongation factor 1 alpha (EF1α), elongation factor 2 (EF2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribosomal protein L3 (RPL3), ribosomal protein L13 (RPL13), alpha-tubulin (α-TUB), and beta-1-tubulin (β-1-TUB) were obtained from S. frugiperda in different samples and the stability was evaluated by ΔCt, BestKeeper, geNorm, NormFinder, and RefFinder methods.  The results of pairwise variation (V) calculated by GeNorm indicated two reference genes could be selected for normalization.  Therefore, the combinations of the most stable reference genes for different experimental conditions of S. frugiperda were shown as follows: EF2 and RPL13 for developmental stages, RPL3 and β-1-TUB for larval tissue samples, EF2 and EF1α for the larval samples treated with different temperatures, RPL3 and EF1α for the larval samples under starvation stress, and RPL13 and EF1α for all the samples.  Our results lay the foundation for the normalization of qPCR analyses in S. frugiperda and could help guarantee the accuracy of subsequent research.
    Animal Science · Veterinary Medicine
    Identifying SNPs associated with birth weight and days to 100 kg traits in Yorkshire pigs based on genotyping-by-sequencing
    WU Ping-xian, ZHOU Jie, WANG Kai, CHEN De-juan, YANG Xi-di, LIU Yi-hui, JIANG An-an, SHEN Lin-yuan, JIN Long, XIAO Wei-hang, JIANG Yan-zhi, LI Ming-zhou, ZHU Li, ZENG Yang-shuang, XU Xu, QIU Xiao-tian, LI Xue-wei, TANG Guo-qing
    2021, 20(9): 2483-2490.  DOI: 10.1016/S2095-3119(20)63474-8
    Abstract ( )   PDF in ScienceDirect  
    Birth weight (BW) and days to 100 kg (D100) are important economic traits that are both affected by polygenes.  However, the genetic architecture of these quantitative traits is still elusive.  Genotyping-by-sequencing (GBS) data containing a large number of single nucleotide polymorphisms (SNPs) have become a powerful tool in genomic analysis.  To better understand their complex genetic structure, a total of 600 Yorkshire pigs were sequenced using GBS technology.  After quality control, 279 787 SNPs were generated for subsequent genome-wide association study (GWAS).  A total of 30 genome-wide SNPs (P<1.79E–07) were identified for D100.  Furthermore, a total of 22 and 2 suggestive SNPs (P<3.57E–06) were detected for D100 and BW, respectively.  Of these, one locus located on SSC12 (position: 46 226 512 bp) were evaluated to affect both BW and D100 in Yorkshire pigs, indicating the pleiotropism in different traits.  Considering the function of candidate genes, two genes, NSRP1 and DOCK7, were suggested as the most promising candidate genes involved in growth traits.  Thus, use of GBS is able to identify novel variants and potential candidate genes for BW and D100, and provide an opportunity for improving pig growth traits using genomic selection in pigs.
    Detection of arboviruses in Culicoides (Diptera: Ceratopogonidae) collected from animal farms in the border areas of Yunnan Province, China
    DI Di, LI Chen-xi, LI Zong-jie, WANG Xin, XIA Qi-qi, Mona SHARMA, LI Bei-bei, LIU Ke, SHAO Dong-hua, QIU Ya-feng, Soe-Soe WAI, YANG Shi-biao, WEI Jian-chao, MA Zhi-yong
    2021, 20(9): 2491-2501.  DOI: 10.1016/S2095-3119(21)63613-4
    Abstract ( )   PDF in ScienceDirect  
    Biting midges of the genus Culicoides (order Diptera, family Ceratopogonidae) are potential biological vectors for the transmission of certain arboviruses among humans, livestock, and wild animals.  This study collected a total of 405 Culicoides individuals from seven animal farms located in five counties in the border areas of Yunnan Province, China, and examined the Culicoides species composition and the major arboviruses carried by the Culicoides species.  The collected Culicoides were classified into seven species with variable abundances: Culicoides arakawae (5.43%, 22/405), Culicoides homotomus (1.23%, 5/405), Culicoides obsoletus (19.75%, 80/405), Culicoides orientalis (17.28%, 70/405), Culicoides oxystoma (29.38%, 119/405), Culicoides peregrinus (5.68%, 23/405), and Culicoides nipponensis (21.23%, 86/405).  Among the seven species, C. oxystoma and C. nipponensis were distributed in all the five counties with abundances of 13.33–44.87% and 10.00–46.83%, respectively, suggesting that these were the dominant species of Culicoides widespread on animal farms in the border areas.  PCR was used to detect major arboviruses in the collected Culicoides specimens, including bluetongue virus (BTV), Japanese encephalitis virus, Dengue virus, Zika virus, African swine fever virus, and African horse sickness virus.  Among the tested viruses, only BTV serotype 1 was tested positive in C. oxystoma specimens collected from a buffalo farm.  Culicoides oxystoma was the dominant species on animal farms in the sampled areas, but it has not previously been documented as positive for BTV in China.  The current results thus suggest that C. oxystoma could be an important vector for BTV transmission in these border areas, which, however, needs to be confirmed by further comprehensive experiments.  Overall, the present study provides the first profile of Culicoides species on animal farms in the China, Vietnam, and Myanmar border areas, establishes the prevalence of arboviruses carried by these Culicoides species, and suggests the vector potential of C. oxystoma species for the transmission of BTV. 
    Agro-ecosystem & Environment
    Peanut yield, nutrient uptake and nutrient requirements in different regions of China
    ZHAO Shi-cheng, LÜ Ji-long, XU Xin-peng, LIN Xiao-mao, Luiz Moro ROSSO, QIU Shao-jun, Ignacio CIAMPITTI, HE Ping
    2021, 20(9): 2502-2511.  DOI: 10.1016/S2095-3119(20)63253-1
    Abstract ( )   PDF in ScienceDirect  
    Nutrient balance is essential for attaining high yield and improving profits in agricultural farming systems, and crop nutrient uptake ratio and stoichiometry can indicate crop nutrient limitations in the field.  We collected a large amount of field data to study the variations in yield, nutrient uptake and nutrient stoichiometry of peanut (Arachis hypogaea L.) in Southeast China (SEC), North-central China (NCC), and Northeast China (NEC), during 1993 to 2018.  Peanut pod yield gradually increased from 1993 to 2018, with average yields of 4 148, 5 138, and 4 635 kg ha–1 in SEC, NCC, and NEC, respectively.  The nitrogen (N) internal efficiency (NIE, yield to N uptake ratio) was similar among the three regions, but phosphorus (P) IE (PIE, yield to P uptake ratio) changed from low to high among regions: NCC<SEC<NEC, while potassium (K) IE (KIE, yield to K uptake ratio) portrayed a different pattern of SEC<NCC<NEC.  Based on the nutrient IE, to produce 1 Mg of pod yield, the average N, P, and K requirements of the above-ground parts of peanut were roughly 47.2, 5.1, and 25.5 kg in SEC, 44.8, 5.7, and 20.6 kg in NCC, and 44.6, 4.4, and 14.7 kg in NEC, respectively.  The N/P ratio changed in the sequence NCC<SEC<NEC, and the N/K ratio was similar in NEC and NCC, but lower in SEC.  The N harvest index (HI) and KHI declined with increasing nutrient uptake across all regions under high nutrient uptake.  The low PIE and N/P ratios in NCC could be explained by the high P accumulation in stover, and high KIE and N/K ratios in NEC may be attributed to the low soil K supply.  The frontier analysis approach provides a practical framework and allows documentation of a decline in nutrient HI as nutrient uptake increases.  Lastly, this study reveals the limitation and surplus of nutrients of peanut in different regions of China.
    Changes in soil organic carbon pools following long-term fertilization under a rain-fed cropping system in the Loess Plateau, China
    WANG Ren-jie, SONG Jia-shan, FENG Yong-tao, ZHOU Jiang-xiang, XIE Jun-yu, Asif KHAN, CHE Zong-xian, ZHANG Shu-lan, YANG Xue-yun
    2021, 20(9): 2512-2525.  DOI: 10.1016/S2095-3119(20)63482-7
    Abstract ( )   PDF in ScienceDirect  
    Understanding the mechanism of soil organic carbon (SOC) sequestration is of paramount importance in sustaining crop productivity and mitigating climate change.  Long-term trials were employed to investigate the responses of total SOC and its pools, i.e., mineral-associated OC (MOC), particulate OC (POC, containing Light-POC and Heavy-POC), to fertilization regimes at Yangling (25-year), Tianshui (35-year) and Pingliang (37-year) under a rain-fed cropping system in the Loess Plateau.  The fertilization regimes in each trial included three treatments, i.e., control (no nutrient input, CK), chemical fertilizers (CF), and organic manure plus chemical fertilizers (MCF).  Relative to the CK, long-term fertilization appreciably increased SOC storage by 134, 89 and 129 kg ha–1 yr–1 under CF, and 418, 153 and 384 kg ha–1 yr–1 under MCF in plough layer soils (0–20 cm), respectively, at the Yangling, Tianshui and Pingliang sites.  The MOC pools accounted for 72, 67 and 64% of the total SOC at the above three sites with sequestration rates of 76, 57 and 83 kg ha–1 yr–1 under CF and 238, 118 and 156 kg ha–1 yr–1 under MCF, respectively.  Moreover, the MOC pool displayed a saturation behavior under MCF conditions.  The POC accordingly constituted 27, 33 and 36% of SOC, of which Light-POC accounted for 11, 17 and 22% and Heavy-POC for 17, 16 and 15% of SOC, respectively.  The sequestration rates of POC were 58, 32 and 46 kg ha–1 yr–1 under CF, and 181, 90 and 228 kg ha–1 yr–1 under MCF at the three respective sites, in which Light-POC explained 59, 81 and 72% of POC under CF, and 60, 40 and 69% of POC under MCF, with Heavy-POC accounting for the balance.  Compared with CK, the application of CF alone did not affect the proportions of MOC or total POC to SOC, whereas MCF application markedly reduced the proportion of MOC and increased the POC ratio, mainly in the Light-POC pool.  The distribution of SOC among different pools was closely related to the distribution and stability of aggregates.  The present study confirmed that organic manure amendment not only sequestered more SOC but also significantly altered the composition of SOC, thus improving SOC quality, which is possibly related to the SOC saturation level.
    Fate of low-molecular-weight organic phosphorus compounds in the P-rich and P-poor paddy soils
    LI Bao-zhen, Anna GUNINA, Mostafa ZHRAN, Davey L. JONES, Paul W. HILL, HU Ya-jun, GE Ti-da, WU Jin-shui
    2021, 20(9): 2526-2534.  DOI: 10.1016/S2095-3119(20)63310-X
    Abstract ( )   PDF in ScienceDirect  
    Continuous application of organic fertilizers can cause accumulation of organic phosphorus (P) in soil, especially in the low-molecular-weight organic phosphorus (LMWOP) forms.  This organic P pool represents a potentially important source of P for both plants and microorganisms.  To understand the effect of long-term fertilization (30 years) (P-rich soil) vs. fallowing (P-poor soil) on the bioavailability and fate of LMWOP in subtropical paddy soils, we determined the sorption and mineralization of 14C-labeled adenosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) in each soil.  The contents of carbon, nitrogen, and P in the P-rich soil were more than two times greater than those in the P-poor soil.  The mineralization rates of the LMWOP compounds were faster in the P-rich soil compared to the P-poor soil, and followed the order AMP>ADP>ATP.  Using sterilized soil, all forms of adenosine-P were strongly sorbed  to the solid phase and reached saturation in a short time, with the adsorbance increasing with the number of phosphate groups.  We concluded that the mineralization of LMWOP compounds was repressed slightly by sorption to the solid phase, but only in the short term.  Thus, LMWOP compounds serve as readily available sources of C for microorganisms, making P available for themselves as well as for the plants.  However, P accumulation and the progressive saturation of the P sorption sites in highly fertile soils may increase the potential risk of P runoff. 
    An entirely new approach based on remote sensing data to calculate the nitrogen nutrition index of winter wheat
    ZHAO Yu, WANG Jian-wen, CHEN Li-ping, FU Yuan-yuan, ZHU Hong-chun, FENG Hai-kuan, XU Xin-gang, LI Zhen-hai
    2021, 20(9): 2535-2551.  DOI: 10.1016/S2095-3119(20)63379-2
    Abstract ( )   PDF in ScienceDirect  
    The nitrogen nutrition index (NNI) is a reliable indicator for diagnosing crop nitrogen (N) status.  However, there is currently no specific vegetation index for the NNI inversion across multiple growth periods.  To overcome the limitations of the traditional direct NNI inversion method (NNIT1) of the vegetation index and traditional indirect NNI inversion method (NNIT2) by inverting intermediate variables including the aboveground dry biomass (AGB) and plant N concentration (PNC), this study proposed a new NNI remote sensing index (NNIRS).  A remote-sensing-based critical N dilution curve (Nc_RS) was set up directly from two vegetation indices and then used to calculate NNIRS.  Field data including AGB, PNC, and canopy hyperspectral data were collected over four growing seasons (2012–2013 (Exp.1), 2013–2014 (Exp. 2), 2014–2015 (Exp. 3), 2015–2016 (Exp. 4)) in Beijing, China.  All experimental datasets were cross-validated to each of the NNI models (NNIT1, NNIT2 and NNIRS).  The results showed that: (1) the NNIRS models were represented by the standardized leaf area index determining index (sLAIDI) and the red-edge chlorophyll index (CIred edge) in the form of NNIRS=CIred edge/(a×sLAIDIb), where “a” equals 2.06, 2.10, 2.08 and 2.02 and “b” equals 0.66, 0.73, 0.67 and 0.62 when the modeling set data came from Exp.1/2/4, Exp.1/2/3, Exp.1/3/4, and Exp.2/3/4, respectively; (2) the NNIRS models achieved better performance than the other two NNI revised methods, and the ranges of R2 and RMSE were 0.50–0.82 and 0.12–0.14, respectively; (3) when the remaining data were used for verification, the NNIRS models also showed good stability, with RMSE values of 0.09, 0.18, 0.13 and 0.10, respectively.  Therefore, it is concluded that the NNIRS method is promising for the remote assessment of crop N status.
    Agricultural Economics and Management
    Do credit constraints affect households’ economic vulnerability? Empirical evidence from rural China
    PENG Yan-ling, Yanjun REN, LI Hou-jian
    2021, 20(9): 2552-2568.  DOI: 10.1016/S2095-3119(20)63557-2
    Abstract ( )   PDF in ScienceDirect  
    Poverty alleviation is still one of the major challenges in developing countries, especially in transitional economy like China.  From the perspective of anti-poverty, this paper examines the impact of formal credit constraints (FCCs) and informal credit constraints (IFCCs) on economic vulnerability (EV) using the data from the China Household Income Project (CHIP) survey for 2013 (CHIPs 2013) of rural households.  The potential endogeneity problem of credit constraints (CCs) is addressed by applying the control function approach within an ordered probit model.  The results show that both FCCs and IFCCs have a robust positive and significant impact on the EV of rural households and that the impact of FCCs is greater than that of IFCCs.  To identify the potential mechanisms through which CCs affect EV, the seemingly unrelated regressions are used and the potential intercorrelation among these mechanisms is examined.  We find that the impact of CCs on EV is partly mediated by health, trust, per capita financial assets and per capita income, whereby health and per capita income contribute to most of the total indirect effect.  Thus, policies focus on supply-side and demand-side to improve credit accessibility could reduce rural households’ EV, especially through its positive effect on health and per capita income.
    Mental accounting and consumption of self-produced food
    HUANG Jia-qi, Gerrit ANTONIDES, Christian H. KUHLGATZ, NIE Feng-ying
    2021, 20(9): 2569-2580.  DOI: 10.1016/S2095-3119(20)63585-7
    Abstract ( )   PDF in ScienceDirect  
    This is an exploratory study on mental accounting and food budgeting of agricultural households, in which we assumed that agricultural households may have a mental account for consumption of their self-produced food.  Accordingly, they may reserve a certain quantity of self-produced food as a set budget for own consumption, implying that they may keep on consuming their own produce until they have consumed the quantity set for the mental budget.  By making the mental accounting assumption, we hypothesized that the consumption of self-produced food is independent of market price.  Also, we hypothesized that the consumption of self-produced food is increasing in the quantity of production if production is lower than the set budget, and independent of the quantity of production if production exceeds the set budget.  By applying a double-log demand model and using survey data from six poor rural counties in China, we tested these hypotheses for five food items, which are rice, flour, potatoes, pork, and eggs.  We found that the hypothesis of no significant effect of price holds for flour, potatoes, and pork if production is lower than the set budget, and for rice, pork, and eggs if production is higher than the set budget.  Production has a significant positive effect on consumption of self-produced food but with a much greater influence when production is lower than the set budget for all five food items.  These findings partly support our assumption of mental accounting of self-produced food.  Limitations, policy implications, and possible future studies are discussed.