2019 Vol. 18 No. 6 Previous Issue    Next Issue

    Special Focus: Molecular tools and mechanisms of rice-Xanthomonas oryzae interactions
    Crop Science
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Agricultural Economics and Management

      Cover illustration

    For Selected: Toggle Thumbnails
    Special Focus: Molecular tools and mechanisms of rice-Xanthomonas oryzae interactions
    Editorial- Molecular tools and mechanisms of rice-Xanthomonas oryzae interactions
    CHEN Gong-you
    2019, 18(6): 1177-1177.  DOI: 10.1016/S2095-3119(19)62721-8
    Abstract ( )   PDF in ScienceDirect  
    Bacterial leaf blight (BLB) and bacterial leaf streak (BLS), caused by Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, lead to severe loss in yields and quality in most rice-growing areas around the world. As the staple crop and the model plant for biology research, characterizing the diseases of rice has great significance. It is crucial to elucidate the interaction between the pathogens and rice as well as the mechanisms of pathogenesis and resistance. The special topic of the three papers is the pathogenicity of plant pathogenic bacteria and host resistance to pathogens. 

    Transcription activator-like effectors (TALEs) secreted into plant cell through the type III secretion system (T3SS) are important virulence factors of the pathogens. TALEs’ function depends on the direct interaction between its TFB domain and host plant basal transcription factor IIA gamma subunit (TFIIAγ). 

    The first article from Tian et al. (2019) investigated the key domain and residues of plant TFIIAγ and core residues of TALE TFB domain that are indispensable for TFIIAγ-TALEs interaction in the process of TALE-carrying Xanthomonas invasion plants, which provides theoretical guidance for the subsequent cultivation of disease-resistant rice varieties. 

    The elucidation of molecular mechanism underlying induction of T3SS gene expression is a very important step to lift the veil on global virulence regulation network in Xoo. Thus, in the second paper, Xu et al. (2019) constructed an effective T3SS protein expression vector pH3-flag based on the backbone of almost widely used vector in the pathogens. The experimental results suggested that the expression system will work as a useful molecular tool in understanding some virulence genes expression and regulation in Xoo and other Xanthomonas spp. 

    β-Glucosidase responds to various biotic and abiotic stresses, but its function in disease resistance remains unclear. The third article from Li et al. (2019) mentioned that OsBGLU19 and OsBGLU23, encoding β-glucosidases, mediate rice resistance to BLS. They confirmed that β- glucosidase is involved in the interaction between rice and Xanthomonas

    The findings of the papers above highlight our understanding through several novel perspectives, as well as the operational system, on the interaction between plants and pathogenic Xanthomonas for our goals of plant resistance breeding.
    The key residues of OsTFIIAγ5/Xa5 protein captured by the arginine-rich TFB domain of TALEs compromising rice susceptibility and bacterial pathogenicity
    TIAN Jing-jing, HUI Shu-gang, SHI Ya-rui, YUAN Meng
    2019, 18(6): 1178-1188.  DOI: 10.1016/S2095-3119(18)62108-2
    Abstract ( )   PDF in ScienceDirect  
    Xanthomonas bacteria secrete transcription activator-like effector (TALE) proteins into host cells to activate plant disease susceptibility genes to cause disease, and the process is dependent on interaction between bacteria TFB domain of TALEs and host plant basal transcription factor IIA gamma subunit (TFIIAγ). The key domain or residues of plant TFIIAγ and core residues of bacteria TFB domain that are indispensable for TFIIAγ-TALEs interaction in the process of TALE-carrying Xanthomonas invasion plants are unknown. Here, we showed that the third α-helix domain of OsTFIIAγ5/Xa5, especially the 38th, 39th, 40th and 42th residues were key sites for capturing by TALEs of Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial blight disease. The latter segment of Xoo TFB domain harboring seventy-two amino acid residues was vital for TALE specific binding with host plant OsTFIIAγ5/Xa5. Substitution of some residues in this core region of TFB domain completely compromised capacity of TALEs capturing rice OsTFIIAγ5/Xa5. The rich and conserved arginine residues in this core region of TFB domain were responsible for TALE-dependent plant susceptibility gene activation and virulence of Xoo. These results provide a potential strategy for improving resistance to TALE-carrying pathogens in plants by site-specific modification of key residues of host plant TFIIAγ. 
    An improved protein expression system for T3SS genes regulation analysis in Xanthomonas oryzae pv. oryzae
    XU Jin-bo, ZHANG Cui-ping, WUNIERBIEKE Mei-li, YANG Xiao-fei, LI Yi-lang, CHEN Xiao-bin, CHEN Gong-you, ZOU Li-fang
    2019, 18(6): 1189-1198.  DOI: 10.1016/S2095-3119(19)62606-7
    Abstract ( )   PDF in ScienceDirect  
    Xanthomonas oryzea pv. oryzae (Xoo) is the causal agent of bacterial blight of rice, which is a significant threat to many of rice-growing regions. The type III secretion system (T3SS) is an essential virulence factor in Xoo. Expression of the T3SS is often induced in the host environment or in hrp-inducing medium but is repressed in nutrient-rich medium. The elucidation of molecular mechanism underlying induction of T3SS genes expression is a very important step to lift the veil on global virulence regulation network in Xoo. Thus, an efficient and reliable genetic tool system is required for detection of the T3SS proteins. In this study, we constructed a protein expression vector pH3-flag based on the backbone of pHM1, a most widely used vector in Xoo strains, especially a model strain PXO99A. This vector contains a synthesized MCS-FLAG cassette that consists of a multiple cloning site (MCS), containing a modified pUC18 polylinker, and Flag as a C-terminal tag. The cassette is flanked by transcriptional terminators to eliminate interference of external transcription enabling detection of accurate protein expression. We evaluated the potential of this expression vector as T3SS proteins detection system and demonstrated it is applicable in the study of T3SS genes expression regulation in Xoo. This improved expression system could be very effectively used as a molecular tool in understanding some virulence genes expression and regulation in Xoo and other Xanthomonas spp.
    OsBGLU19 and OsBGLU23 regulate disease resistance to bacterial leaf streak in rice
    LI Bei-bei, LIU Ying-gao, WU Tao, WANG Ji-peng, XIE Gui-rong, CHU Zhao-hui, DING Xin-hua
    2019, 18(6): 1199-1210.  DOI: 10.1016/S2095-3119(18)62117-3
    Abstract ( )   PDF in ScienceDirect  
    β-Glucosidase belongs to the glycoside hydrolase I family, which is widely present in multiple species and responds to various biotic and abiotic stresses. In rice, whether β-glucosidase is involved in the interaction between plants and microorganisms is not clear. In this study, we found that the expression of several genes encoding β-glucosidases, including OsBGLU19 and OsBGLU23, were upregulated after inoculation with Xanthomonas oryzae pv. oryzicola (Xoc) and downregulated after inoculation with X. oryzae pv. oryzae (Xoo). The respective insertion mutants of OsBGLU19 and OsBGLU23, bglu19 and bglu23, were more susceptible to Xoc infection. The expression of OsAOS2, a key gene in the jasmonic acid signal pathway, was dramatically downregulated after inoculation with Xoc in the bglu19 and bglu23 mutants. Simultaneously, the expression of downstream disease resistance-related genes, such as OsPR1a, OsPR5 and a key transcription factors OsWRKY72 were obviously downregulated. The resistance mediated by OsBGLU19 and OsBGLU23 to bacterial leaf streak is related to disease resistance-related genes above mentioned.
    Crop Science
    Integrating transcriptomic and proteomic analyses of photoperiodsensitive in near isogenic maize line under long-day conditions
    SONG Xiao-heng, TIAN Lei, WANG Shun-xi, ZHOU Jin-long, ZHANG Jun, CHEN Zan, WU Liu-ji, KU Li-xia, CHEN Yan-hui
    2019, 18(6): 1211-1221.  DOI: 10.1016/S2095-3119(18)62040-4
    Abstract ( )   PDF in ScienceDirect  
    As a short-day plant species, maize requires an optimal photoperiod for inducing reproductive growth. However, there is a lack of information regarding photoperiod-induced changes in maize mRNA and protein levels. In this study, a photoperiod-insensitive maize inbred line and its near isogenic photoperiod-sensitive line were used. By integrating RNAbased transcriptomic and iTRAQ LC-MS/MS-based proteomic approaches, we generated a comprehensive inventory of the transcripts and proteins with altered abundances in response to a long photoperiod (LP) during growth stage transitions. We detected 22 000 transcripts in RNA-sequence runs and 5 259 proteins from an iTRAQ-based analysis. A weak correlation between mRNA- and protein-level changes was observed, suggesting the LP-induced transition between maize growth stages is largely regulated post-transcriptionally. Differentially expressed genes influenced by LP conditions were associated with several regulatory processes in both maize inbred lines, especially phosphate ion transport and the circadian rhythm. Additionally, 31 transcripts and six proteins related to photoperiodic flowering in maize were identified by comparing transcriptomic and proteomic data. This transcriptomic and proteomic analysis represents the first comprehensive and comparative study of gene/protein-level changes occurring in photoperiod-sensitive and -insensitive maize inbred lines
    Genetic dissection of hexanol content in soybean seed through genome-wide association analysis
    XIA Ning, YAN Wen-bing, WANG Xiao-qi, SHAO Yu-peng, YANG Ming-ming, WANG Zhi-kun, ZHAN Yu-hang, TENG Wei-li, HAN Ying-peng, SHI Yan-guo
    2019, 18(6): 1222-1229.  DOI: 10.1016/S2095-3119(19)62674-2
    Abstract ( )   PDF in ScienceDirect  
    Hexanol is a major compound contributing to the off-flavors (the bean-like odor) of soybean derived soymilk. The most effective way to reduce the off-flavors of soymilk is the screening and utilization of soybean cultivars with improved hexanol content. However, no genome-wide genetic analysis for this particular trait has been conducted to date. The objective of the present study was to dissect the genetic basis of hexanol content in soybean seed through genome-wide association analysis (GWAS). A total of 105 soybean accessions were analyzed for hexanol content in a three-year experiments and genotyped by sequencing using the specific locus amplified fragment sequencing (SLAF-seq) approach. A total of 25 724 single nucleotide polymorphisms (SNPs) were obtained with minor allele frequencies (MAF)>5%. GWAS showed that 25 quantitative trait nucleotides (QTNs) were significantly associated with the hexanol concentration in soybean seed. These identified QTNs distributed on different genomic regions of the 15 chromosomes. A total of 91 genes were predicted as candidate genes underlying the seed hexanol level and six candidates were predicted possibly underlying the seed hexanol by gene based association. In this study, GWAS has been proven to be an effective way to dissect the genetic basis of the hexanol concentration in multiple genetic backgrounds. The identified beneficial alleles and candidate genes might be valuable for the improvement of marker-assisted breeding efficiency for low hexanol level and help to explore possible molecular mechanisms underlying hexanol content in soybean seed.
    Leaf chlorophyll content retrieval of wheat by simulated RapidEye, Sentinel-2 and EnMAP data
    CUI Bei, ZHAO Qian-jun, HUANG Wen-jiang, SONG Xiao-yu, YE Hui-chun, ZHOU Xian-feng
    2019, 18(6): 1230-1245.  DOI: 10.1016/S2095-3119(18)62093-3
    Abstract ( )   PDF in ScienceDirect  
    Leaf chlorophyll content (LCC) is an important physiological indicator of the actual health status of individual plants. An accurate estimation of LCC can therefore provide valuable information for precision field management. Red-edge information from hyperspectral data has been widely used to estimate crop LCC. However, after the advent of red-edge bands in satellite imagery, no systematic evaluation of the performance of satellite data has been conducted. Toward this end, we analyze herein the performance of winter wheat LCC retrieval of currant and forthcoming satellites (RapidEye, Sentinel-2 and EnMAP) and their new red-edge bands by using partial least squares regression (PLSR) and a vegetation-indexbased approach. These satellite spectral data were obtained by resampling ground-measured hyperspectral data under various field conditions and according to specific spectral response functions and spectral resolution. The results showed: 1) This study confirmed that RapidEye, Sentinel-2 and EnMAP data are suitable for winter wheat LCC retrieval. For the PLSR approach, Sentinel-2 data provided more accurate estimates of LCC (R2=0.755, 0.844, 0.805 for 2002, 2010, and 2002+2010) than do RapidEye data (R2=0.689, 0.710, 0.707 for 2002, 2010, and 2002+2010) and EnMAP data (R2=0.735, 0.867, 0.771 for 2002, 2010, and 2002+2010). For index-based approaches, the MERIS terrestrial chlorophyll index, which is a vegetation index with two red-edge bands, was the most sensitive and robust index for LCC for both the Sentinel-2 and EnMAP data (R2≥0.628), and the indices (NDRE1, SRRE1 and CIRE1) with a single red-edge band were the most sensitive and robust indices for the RapidEye data (R2≥0.420); 2) According to the analysis of the effect of the wavelength and number of used red-edge spectral bands on LCC retrieval, the short-wavelength red-edge bands (from 699 to 734 nm) provided more accurate predictions when using the PLSR approach, whereas the long-wavelength red-edge bands (740 to 783 nm) gave more accurate predictions when using the vegetation indice (VI) approach. In addition, the prediction accuracy of RapidEye, Sentinel-2 and EnMAP data was improved gradually because of more number of red-edge bands and higher spectral resolution; VI regression models that contain a single or multiple red-edge bands provided more accurate predictions of LCC than those without red-edge bands, but for normalized difference vegetation index (NDVI)-, simple ratio (SR)- and chlorophyll index (CI)-like index, two red-edge bands index didn’t significantly improve the predictive accuracy of LCC than those indices with a single red-edge band. Although satellite data with higher spectral resolution and a greater number of red-edge bands marginally improve the accuracy of estimates of crop LCC, the level of this improvement remains insufficient because of higher spectral resolution, which results in a worse signal-to-noise ratio. The results of this study are helpful to accurately monitor LCC of winter wheat in large-area and provide some valuable advice for design of red-edge spectral bands of satellite sensor in future.
    Effect of low-nitrogen stress on photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with different lownitrogen tolerances
    WU Ya-wei, LI Qiang, JIN Rong, CHEN Wei, LIU Xiao-lin, KONG Fan-lei, KE Yong-pei, SHI Hai-chun, YUAN Ji-chao
    2019, 18(6): 1246-1256.  DOI: 10.1016/S2095-3119(18)62030-1
    Abstract ( )   PDF in ScienceDirect  
    Nitrogen (N) is a critical element for plant growth and productivity that influences photosynthesis and chlorophyll fluorescence. We investigated the effect of low-N stress on leaf photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with difference in tolerance to low N levels. The low-N tolerant cultivar ZH311 and low-N sensitive cultivar XY508 were used as the test materials. A field experiment (with three N levels: N0, 0 kg ha–1; N1, 150 kg ha–1; N2, 300 kg ha–1) in Jiyanyang, Sichuan Province, China, and a hydroponic experiment (with two N levels: CK, 4 mmol L–1; LN, 0.04 mmol L–1) in Chengdu, Sichuan Province, China were conducted. Low-N stress significantly decreased chlorophyll content and rapid light response curves of the maximum fluorescence under light (Fm´), fluorescence instable state (Fs), non-photochemical quenching (qN), the maximum efficiency of PSII photochemistry under dark-adaption (Fv/Fm), potential activity of PSII (Fv/Fo), and actual photochemical efficiency of PSII (ΦPSII) of leaves. Further, it increased the chlorophyll (Chl) a/Chl b values and so on. The light compensation point of ZH311 decreased, while that of XY508 increased. The degree of variation of these indices in low-N tolerant cultivars was lower than that in low-N sensitive cultivars, especially at the seedling stage. Maize could increase Chl a/Chl b, apparent quantum yield and light saturation point to adapt to N stress. Compared to low-N sensitive cultivars, low-N tolerant cultivars maintained a higher net photosynthetic rate and electron transport rate to maintain stronger PSII activity, which further promoted the ability to harvest and transfer light. This might be a photosynthetic mechanism by which low-N tolerant cultivar adapt to low-N stress.
    Stability analysis of different cotton genotypes under normal and water-deficit conditions
    Muhammad Riaz, Jehanzeb Farooq, Saghir Ahmed, Muhammad Amin, Waqas Shafqat Chattha, Maria Ayoub, Riaz Ahmed Kainth
    2019, 18(6): 1257-1265.  DOI: 10.1016/S2095-3119(18)62041-6
    Abstract ( )   PDF in ScienceDirect  
    Cotton plant observes significant reduction in seed cotton yield when subjected to water stress. To find out genotypes having better drought tolerance, seven genotypes of Gossypium hirsutum L. were tested under two moisture levels, i.e., normal and water deficit stress conditions at five locations of Punjab, Pakistan (Faisalabad, Sahiwal, Vehari, Rahim Yar Khan, and Bahawalpur) in 2013 and 2014. Genotype×environment interaction (GEI) was studied using the genotype main effects and genotype by environment interaction (GGE) biplot and additive main effect and multiplicative interaction analysis. The genotypes G3 (7001/11) and G6 (FH-942) were stable under normal condition, while under drought condition, the stable genotype was G5 (FH-326) when analysed using additive main effects and multiplicative interaction (AMMI) biplot scheme. While GGE biplot analysis on the basis of best performance revealed that under normal condition the genotypes, G1 (L-13/10) and G2 (FH-2056/10), carrying the common position in biplot. Whereas, under water deficit stress condition, G5 was the best adaptive genotype at all five locations. In the same way, ranking of genotypes showed that the G5 was the ideal genotype under both conditions. So, it is concluded that the genotype G5 (FH-326) was found best for water deficit stress condition and can be cultivated under water scarce areas of Punjab.
    The role of AtGPDHc2 in regulating cellular redox homeostasis of Arabidopsis under salt stress
    ZHAO Ying, LIU Meng, WANG Feng, DING Dong, ZHAO Chang-jiang, HE Lin, LI Zuo-tong, XU Jing-yu
    2019, 18(6): 1266-1279.  DOI: 10.1016/S2095-3119(18)62082-9
    Abstract ( )   PDF in ScienceDirect  
    Plants glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the formation of glycerol-3-phosphate, and plays an essential role in glycerolipid metabolism and stress responses. In the present study, the knock-out mutants of cytosolic GPDH (AtGPDHc2) and wild-type Arabidopsis plants were treated with 0, 50, 100, and 150 mmol L–1 NaCl to reveal the effects of AtGPDHc2 deficiency on salinity stress responses. The fluctuation in redox status, reactive oxygen species (ROS) and antioxidant enzymes as well as the transcripts of genes involved in the relevant processes were measured. In the presence of 100 and 150 mmol L–1 NaCl treatments, AtGPDHc2-deficient plants exhibited a pronounced reduction in germination rate, fresh weight, root length, and overall biomass. Furthermore, loss of AtGPDHc2 resulted in a significant perturbation in cellular redox state (NADH/NAD+ and AsA/DHA) and consequent elevation of ROS and thiobarbituric acid-reactive substances (TBARS) content. The elevated ROS level triggered substantial increases in ROS-scavenging enzymes activities, and the up-regulated transcripts of the genes (CSD1, sAPX and PER33) encoding the antioxidant enzymes were also observed. In addition, the transcript levels of COX15, AOX1A and GLDH in gpdhc2 mutants decreased in comparison to wild-type plants, which demonstrated that the deficiency of AtGPDHc2 might also has impact on mitochondrial respiration under salt stress. Together, this work provides some new evidences on illustrating the roles of AtGPDHc2 playing in response to salinity stress by regulating cellular redox homeostasis, ROS metabolism and mitochondrial respiration.
    Physiological and transcriptomic analyses of roots from Malus sieversii under drought stress
    GENG Da-li, LU Li-yuan, YAN Ming-jia, SHEN Xiao-xia, JIANG Li-juan, LI Hai-yan, WANG Li-ping, YAN Yan, XU Ji-di, LI Cui-ying, YU Jian-tao, MA Feng-wang, GUAN Qing-mei
    2019, 18(6): 1280-1294.  DOI: 10.1016/S2095-3119(19)62571-2
    Abstract ( )   PDF in ScienceDirect  
    Water deficit is one of the main limiting factors for apple growth and production.  Root architecture plays an important role in drought tolerance of plants.  However, little is known about the molecular basis of root system in apple trees under drought.  In this study, we compared root morphology of two widely used rootstocks of apple (R3 and Malus sieversii) under drought.  Our results suggested that M. sieversii is more tolerant to drought than R3, since M. sieversii had a higher ratio of root to shoot as well as root hydraulic conductivity under long-term drought conditions.  We then performed whole-genome transcriptomic analysis to figure out the molecular basis of root responses in M. sieversii under drought.  It was found that genes involved in transcription regulation, signaling or biosynthesis of hormones, and oxidative stress were differentially expressed under drought.  Consistent with the gene expression profile, roots of M. sieversii had higher activities of peroxidase (POD) and superoxide dismutase (SOD) under drought, as well as higher content of abscisic acid (ABA) and lower content of auxin.  Taken together, our results revealed the physiological and transcriptomic analyses of M. sieversii roots in response to drought. 
    Effect of exogenous GA3 on flowering quality, endogenous hormones, and hormone- and flowering-associated gene expression in forcingcultured tree peony (Paeonia suffruticosa)
    GUAN Yan-ren, XUE Jing-qi, XUE Yu-qian, YANG Ruo-wen, WANG Shun-li, ZHANG Xiu-xin
    2019, 18(6): 1295-1311.  DOI: 10.1016/S2095-3119(18)62131-8
    Abstract ( )   PDF in ScienceDirect  
    Gibberellins (GAs) promote flowering in the forcing-cultured tree peony (Paeonia suffruticosa), however, the mechanism of regulating flowering is not fully understood.  In this study, exogenous GA3 was applied to five-year-old Luoyang Hong plants to explore responses in terms of endogenous hormones, flowering quality, and the hormone- and flowering-associated gene expression.  Exogenous GA3 application significantly promoted flower bud development and new branch growth, as well as improved flowering quality.  Exogenous GA3 application also stimulated the synthesis of endogenous GA3 and indole-3-acetic acid (IAA) but reduced abscisic acid (ABA) levels.  To further elucidate the regulatory mechanism, eight genes for GA biosynthesis and signaling, including PsCPS, PsKS, PsGA3ox, PsGA2ox, PsGID1b, PsGID1c, PsDELLA, and PsGID2 were cloned for the first time, and sequence analysis was also performed.  The results suggested that all the cloned genes have conserved structure as each homologous gene reported in the other species.   Phylogenetic trees constructed by the each cloned gene showed that the phylogenetic evolutionary relationship of P. suffruticosa was closely related to Vitis vinifera.  The expression patterns of the above genes, and genes for ABA and IAA biosynthetic and signaling, and the flowering time were also investigated.  Most of the above genes showed higher expression in the control buds than those in the GA3 treated buds at six developmental stages, whereas the expression levels of PsSOC1 and PsSPL9 were up-regulated by GA3 treatment.  The results also showed that the GA-biosynthetic and signaling pathways are conserved in tree peony, and the PsCPS, PsGA3ox, PsGA2ox, PsGID1, PsDELLA, and PsGID2 genes are necessary for feedback regulation of GAs.  Furthermore, hormone changes promoted PsSOC1 and PsSPL9 expression, and repressed PsSVP expression, which contributed to the improvement flowering quality in tree peony of forcing culture. 
    Genetic diversity and population structure analysis of Capsicum germplasm accessions
    GU Xiao-zhen, CAO Ya-cong, ZHANG Zheng-hai, ZHANG Bao-xi, ZHAO Hong, ZHANG Xiao-min, WANG Hai-ping, LI Xi-xiang, WANG Li-hao
    2019, 18(6): 1312-1320.  DOI: 10.1016/S2095-3119(18)62132-X
    Abstract ( )   PDF in ScienceDirect  
    Genetic diversity plays an essential role in plant breeding and utilization.  Pepper is an important vegetable and spice crop worldwide.  The genetic diversity of 1 904 accessions of pepper conserved at the National Mid-term Genebank for Vegetables, Beijing, China was analyzed based on 29 simple sequence repeat (SSR) markers, which were evenly distributed over 12 pepper chromosomes.  The pepper accessions were divided into two groups in a genetic structure analysis, and the two groups showed obvious differences in fruit type and geographical distribution.  We finally selected 248 accessions capturing 75.6% of the SSR alleles as the core collection for further research.  Insights into the genetic structure of pepper provide the basis for population-level gene mining and genetic improvement.
    Animal Science · Veterinary Medicine
    Effect of relative humidity at chronic temperature on growth performance, glucose consumption, and mitochondrial ATP production of broilers
    ZHOU ying, ZHANG Min-hong, FENG Jing-hai, DIAO Hua-jie
    2019, 18(6): 1321-1328.  DOI: 10.1016/S2095-3119(19)62584-0
    Abstract ( )   PDF in ScienceDirect  
    An experiment was conducted to investigate the effect of relative humidity (RH) at chronic temperature on growth performance, glucose consumption, and mitochondrial adenosine triphosphate (ATP) production of broilers.  A total of 180 28-day-old Arbor Acres broilers (half males and half females) were randomly allocated to three treatments, each containing six replicates of 10 birds per treatment, using a completely randomized design.  Birds were reared at 35, 60 or 85% RH at 32°C for 15 days (temperature increased by 3°C every 3 days from 20 to 32°C within 15 days: 20–23–26–29–32°C).  RH affected (P<0.05) average daily feed intake (ADFI), average daily gain (ADG), average daily water consumption (ADWC), blood glucose concentrations, muscle glycogen levels, avian uncoupling protein (av UCP) mRNA expression, and cytochrome c oxidase (CCO) activity in liver of broilers at 42 days of age.  The 85% RH decreased (P<0.05) ADFI, ADG and ADWC; 35% RH decreased (P<0.02) ADG.  Both 85 and 35% RH increased (P<0.01) blood glucose and decreased (P<0.05) muscle glycogen.  Both 85 and 35% RH increased (P<0.05) av UCP mRNA expression.  35% RH decreased (P<0.05) CCO activity.  In conclusion, both high and low RH inceased glucose consumption and reduced mitochondrial ATP poduction, leading to a decline in growth rate.
    Generation of pigs with a Belgian Blue mutation in MSTN using CRISPR/ Cpf1-assisted ssODN-mediated homologous recombination
    ZOU Yun-long, LI Zhi-yuan, ZOU Yun-jing, HAO Hai-yang, HU Jia-xiang, LI Ning, LI Qiu-yan
    2019, 18(6): 1329-1336.  DOI: 10.1016/S2095-3119(19)62694-8
    Abstract ( )   PDF in ScienceDirect  
    CRISPR/Cpf1 has emerged recently as an effective tool for genome editing in many organisms, but its use in pigs to generate precise genetic modifications has seldom been described.  Myostatin (MSTN) is a well-characterized negative regulator of muscle development, and natural mutations in this gene cause a double-muscled phenotype in many species.  However, to the best of our knowledge, no naturally occurring mutation in MSTN has been found in pigs.  In addition, no living pig models with sophisticated modifications orthologous to natural mutations in MSTN have yet been reported.  In this study, we exploited the CRISPR/Cpf1 system to introduce a predefined modification orthologous to the natural MSTN mutation found in Belgian Blue cattle (thus known as the Belgian Blue mutation).  Our research demonstrated that the cutting efficiency of CRISPR/Cpf1 was 12.3% in mixed porcine fetal fibroblasts in drug free medium, and 41.7% in clonal colonies obtained using G418 selection.  Then, the Cpf1-sgRNA vector, ssODN template, and a self-excision cassette were co-transfected into porcine fetal fibroblasts.  After G418 selection, 8 clonal colonies were examined and 5 with genetic modification were found.  Of these 5, 2 harbored the precise 11-bp deletion.  Using 1 heterozygous clonal colony, 2 cloned Duroc piglets were successfully generated, which was heterozygous for the Belgian Blue mutation.  In summary, our results demonstrate that CRISPR/Cpf1 system can be used efficiently to generate double-stranded breaks, and also to mediate homologous recombination to introduce precise genomic modifications in pigs.
    Agro-ecosystem & Environment
    Residue management induced changes in soil organic carbon and total nitrogen under different tillage practices in the North China Plain
    PU Chao, KAN Zheng-rong, LIU Peng, MA Shou-tian, QI Jian-ying, ZHAO Xin, ZHANG Hai-lin
    2019, 18(6): 1337-1347.  DOI: 10.1016/S2095-3119(18)62079-9
    Abstract ( )   PDF in ScienceDirect  
    Crop residue retention has been considered a practicable strategy to improve soil organic carbon (SOC) and total nitrogen (TN), but the effectiveness of residue retention might be different under varied tillage practices.  To evaluate the effects of residue management on the distribution and stocks of SOC and TN under different tillage practices, a bifactorial experiment with three levels for tillage practices (no-tillage, rotary tillage, and conventional tillage) and two levels for residue managements (residue retention and residue removal) was conducted in the North China Plain (NCP).  Results showed that after a short experimental duration (3–4 years), concentrations of SOC and TN in the 0–10 cm layer were higher under no-tillage than under conventional tillage, no matter whether crop residues were retained or not.  Residue retention increased SOC and TN concentrations in the upper layers of soil to some degree for all tillage practices, as compared with residue removal, with the greatest increment of SOC concentration occurred in the 0–10 cm layer under rotary tillage, but in the 10–30 cm layer under conventional tillage.  The stocks of SOC in the 0–50 cm depth increased from 49.89 Mg ha–1 with residue removal to 53.03 Mg ha–1 with residue retention.  However, no-tillage did not increase SOC stock to a depth of 50 cm relative to conventional tillage, and increased only by 5.35% as compared with rotary tillage.  Thus, residue retention may contribute more towards SOC sequestration than no-tillage.  Furthermore, the combination between residue retention and no-tillage has the greatest advantage in enhancing SOC and TN in the NCP region.
    Comparison of carbon sequestration efficiency in soil aggregates between upland and paddy soils in a red soil region of China
    LIU Kai-lou, HUANG Jing, LI Da-ming, YU Xi-chu, YE Hui-cai, HU Hui-wen, HU Zhi-hua, HUANG Qing-hai, ZHANG Hui-min
    2019, 18(6): 1348-1359.  DOI: 10.1016/S2095-3119(18)62076-3
    Abstract ( )   PDF in ScienceDirect  
    There is limited information on carbon sequestration efficiency (CSE) of soil aggregates in upland and paddy soils under long-term fertilization regimes.  In a red soil region of southern China, an upland soil experiment started in 1986 and a paddy soil experiment commenced in 1981.  These experiments were conducted using different fertilization treatments.  After 30 years, soil organic carbon (SOC) content and stock of different aggregate components were analyzed.  The results showed that the SOC contents and stocks in upland soil were lower than in paddy soil.  In both upland and paddy soils, the SOC contents and stocks of all aggregate components in NPKM (combined treatment with chemical nitrogen (N), phosphorus (P), potassium (K) fertilizers and manure) were the highest among all treatments.  Compared with CK (no fertilizer), SOC content of all aggregate components in NPKM was increased by 13.21–63.11% and 19.13–73.33% in upland and paddy soils, respectively.  Meanwhile, the change rates in SOC stock of all aggregate components in upland soil were lower than in paddy soil, although the change rate of SOC stock of all aggregate components in NPKM was higher than in other treatments.  Furthermore, a linear equation could fit the relationships between carbon (C) input and change rate of SOC stock (P<0.05).  Results indicated that the sum of CSE from all aggregate components in upland soil (16.02%) was higher than that of paddy soil (15.12%) in the same climatic condition and from the same parent material.  However, the CSEs from all aggregates were higher than that of bulk soil, although the result from bulk soil also showed that the CSE of upland soil was higher than that of paddy soil.
    Effects of salinity on the soil microbial community and soil fertility
    ZHANG Wen-wen, WANG Chong, XUE Rui, WANG Li-jie
    2019, 18(6): 1360-1368.  DOI: 10.1016/S2095-3119(18)62077-5
    Abstract ( )   PDF in ScienceDirect  
    Saline area is an important reserve resource of arable land, however, the effects of soil microorganisms on the soil fertility in saline coastal ecosystems remain poorly understood.  The salinity effects on soil microorganisms, nutrient availabilities and their relationships were studied in soils along a salinity gradient.  A total of 80 soil samples were collected from 16 sites at four salinity levels (non-saline soil, salt content<1 g kg–1; low salinity soil, salt content=1–2 g kg–1; middle salinity soil, salt content=2–4 g kg–1; high salinity soil, salt content>4 g kg–1).  The results showed that the salinity increased soil pH and exchangeable Na percent, but decreased soil organic matter, soil exchangeable K, and soil microbial biomass.  Both the abundance and community composition of soil bacteria and fungi were significantly different between the non-saline and the saline soils.  The predominant genera of soil bacteria (Planctomyces and Archangium, positive for carbon fixation) and fungi (Hydropisphaera, efficient in lignin degradation) changed with the increasing soil salinity and the decreasing soil organic matter.  In summary, soil salinity changed the abundances of soil bacterial, fungal, and arbuscular mycorrhizal communities and, subsequently, affected their function in saline coastal ecosystems.
    Foliar application of micronutrients enhances crop stand, yield and the biofortification essential for human health of different wheat cultivars
    Muhammad Zahir Aziz, Muhammad Yaseen, Tanveer Abbas, Muhammad Naveed, Adnan Mustafa, Yasir Hamid, Qudsia Saeed, XU Ming-gang
    2019, 18(6): 1369-1378.  DOI: 10.1016/S2095-3119(18)62095-7
    Abstract ( )  
    Globally about half of the world’s population is under micronutrient malnutrition due to poor quality food intake.  To overcome this problem, fortification and biofortification techniques are often used.  Biofortification is considered a better option than fortification due to the easy control of nutrient deficiencies present in daily food.  This field experiment was conducted to evaluate the effects of foliar application of a micronutrient mixture (MNM) consisting of zinc (Zn), iron (Fe), copper (Cu), manganese (Mn) and boron (B) on yield and flour quality of wheat.  The results show the effectiveness of foliar feeding for growth and yield parameters, in addition to the enriching of wheat grains with Zn, Cu, Fe, Mn and B.  Compared to the control without foliar feeding, foliar application on wheat crop increased tillering ability, spike length, grain yield and the contents of Zn, Cu, Mn, Fe and B by 21, 47, 22, 22 and 25% in wheat flour, respectively.  Therefore, foliar feeding of micronutrients could be an effective approach to enrich wheat grains with essential nutrients for correcting malnutrition.
    The impacts of climate change on wheat yield in the Huang-Huai- Hai Plain of China using DSSAT-CERES-Wheat model under different climate scenarios
    QU Chun-hong, LI Xiang-xiang, JU Hui, LIU Qin
    2019, 18(6): 1379-1391.  DOI: 10.1016/S2095-3119(19)62585-2
    Abstract ( )   PDF in ScienceDirect  
    Climate change has been documented as a major threat to current agricultural strategies.  Progress in understanding the impact of climate change on crop yield is essential for agricultural climate adaptation, especially for the Huang-Huai-Hai Plain (3H Plain) of China which is an area known to be vulnerable to global warming.  In this study, the impacts of climate change on winter wheat (Triticum aestivum L.) yield between the baseline period (1981–2010) and two Representative Concentration Pathways (RCP8.5 and RCP4.5) were simulated for the short-term (2010–2039), the medium-term (2040–2069) and the long-term (2070–2099) in the 3H Plain, by considering the relative contributions of changes in temperature, solar radiation and precipitation using the DSSAT-CERES-Wheat model.  Results indicated that the maximum and minimum temperatures (TMAX and TMIN), solar radiation (SRAD), and precipitation (PREP) during the winter wheat season increased under these two RCPs.  Yield analysis found that wheat yield increased with the increase in SRAD, PREP and CO2 concentration, but decreased with an increase in temperature.  Increasing precipitation contributes the most to the total impact, increasing wheat yield by 9.53, 6.62 and 23.73% for the three terms of future climate under RCP4.5 scenario, and 11.74, 16.38 and 27.78% for the three terms of future climate under RCP8.5 scenario.  However, as increases in temperature bring higher evapotranspiration, which further aggravated water deficits, the supposed negative effect of increasing thermal resources decreased wheat yield by 1.92, 4.08 and 5.24% for the three terms of future climate under RCP4.5 scenario, and 3.64, 5.87 and 5.81% for the three terms of future climate under RCP8.5 scenario with clearly larger decreases in RCP8.5.  Counterintuitively, the impacts in southern sub-regions were positive, but they were all negative in the remaining sub-regions.  Our analysis demonstrated that in the 3H Plain, which is a part of the mid-high latitude region, the effects of increasing thermal resources were counteracted by the aggravated water deficits caused by the increase in temperature.
    Agricultural Economics and Management
    Is the feminization of labor harmful to agricultural production? The decision-making and production control perspective
    LIU Jia-cheng, XU Zhi-gang, ZHENG Qiu-fen, Lillian Hua
    2019, 18(6): 1392-1401.  DOI: 10.1016/S2095-3119(19)62649-3
    Abstract ( )   PDF in ScienceDirect  
    Even today, academics continue to debate the effect of feminization of agricultural labor force on agricultural output.  By considering the dimensions of participation in decision-making and production, this study divides the various agricultural production models into three types: (i) the traditional model of decisions made either jointly by men and women or by men alone while both genders participate in production, (ii) complete feminization of agricultural decision-making and the production labor force, and (iii) feminization of the agricultural production labor force only.  This study investigates the effects of combining or separating decision-making and production in regard to agricultural development in the context of feminization of the agricultural labor force.  Using follow-up data collected from 2004–2008 by the Ministry of Agriculture of China, we built a comprehensive panel data model to test our hypotheses.  Our research shows that in comparison to traditional agricultural households and fully feminized agricultural labor forces, partially feminized production resulted in lower grain yield and technological advancement.  The feminization of agricultural labor does not necessarily have a negative impact on agricultural output, especially since heavy manual labor is being increasingly replaced by agricultural machinery and outsourcing of tasks.  The degree of feminization of the decision-making and production processes should be an important consideration when evaluating the purported negative effects of the feminization of agricultural labor. 
    Do farmers care about climate change? Evidence from five major grain producing areas of China
    SONG Chun-xiao, LIU Rui-feng, Les Oxley, MA Heng-yun
    2019, 18(6): 1402-1414.  DOI: 10.1016/S2095-3119(19)62687-0
    Abstract ( )   PDF in ScienceDirect  
    Using a logistic model, this paper empirically investigated farmers’ perception of climate change and its determinants based on a field survey of 1 350 rural households across five major grain producing provinces in China.  The results show: i) There is an apparent difference in perception levels for long-term temperature and precipitation changes.  Specifically, 57.4% of farmers perceived the long-term temperature change correctly, but only 29.7% of farmers perceived the long-term precipitation change correctly; ii) The factors influencing the farmers’ perceptions are almost completely different between precipitation and temperature, the former are mostly agriculture related, while latter are mostly non-agriculture related, except for farm size; and iii) Farmers are not expected to pay more attention to long-term precipitation changes over the crop growing seasons, because less than 30% of farmers can correctly perceive long-term precipitation change.  Therefore, to improve the accuracy of farmers’ perceptions of climate change, the government is recommended to: i) enhance education and training programs; ii) speed up land transfer and expand household land farm size; iii) develop farmer cooperative organizations; iv) invest more in agricultural infrastructure, specifically in major grain producing regions; and v) improve the agricultural environment and increase farming income.
    A rapid approach for isolating a single fungal spore from rice blast diseased leaves
    FEI Li-wang, LU Wen-bo, XU Xiao-zhou, YAN Feng-cheng, ZHANG Li-wei, LIU Jin-tao, BAI Yuan-jun, LI Zhen-yu, ZHAO Wen-sheng, YANG Jun, PENG You-liang
    2019, 18(6): 1415-1418.  DOI: 10.1016/S2095-3119(19)62581-5
    Abstract ( )   PDF in ScienceDirect  
    Single spore isolation is a fundamental approach in plant pathology and mycology to isolate and identify plant fungal pathogens from diseased samples.  However, routine single spore isolation procedure is time-consuming and has a high risk of contamination by other microorganisms.  In this study, we developed a rapid approach for isolating a single spore of the fungal pathogen, Pyricularia oryzae, from rice blast diseased leaves in the paddy field with low potential of contamination.  First, rice blast leaves with single lesions were selected in the paddy field, and a single lesion was cut out and pressed and dragged gently across the surface of water agar.  Next, a germinated single spore with a barely visible piece of agar was cut out of water agar with a dissecting needle under a stereomicroscope at approximately 120-fold magnification.  Last, the germinated single spore with water agar was transferred onto oatmeal tomato agar for growth and preservation.  Based on our experience, a skilled technician or student can successfully isolate single spore from over 150 independent diseased samples with nearly no contaminations in a single working day.  This approach is also suitable for isolating single spore from other fungal disease samples that produce abundant aerial conidia.