Journal of Integrative Agriculture

Problems, challenges and future of plant disease management: from an ecological point of view

HE Dun-chun, ZHAN Jia-sui, XIE Lian-hui

2016, 15(4): 705-715. DOI: 10.1016/S2095-3119(15)61300-4

Abstract ( ) PDF in ScienceDirect

Plant disease management faces ever-growing challenges due to: (i) increasing demands for total, safe and diverse foods to support the booming global population and its improving living standards; (ii) reducing production potential in agriculture due to competition for land in fertile areas and exhaustion of marginal arable lands; (iii) deteriorating ecology of agro-ecosystems and depletion of natural resources; and (iv) increased risk of disease epidemics resulting from agricultural intensification and monocultures. Future plant disease management should aim to strengthen food security for a stable society while simultaneously safeguarding the health of associated ecosystems and reducing dependency on natural resources. To achieve these multiple functionalities, sustainable plant disease management should place emphases on rational adaptation of resistance, avoidance, elimination and remediation strategies individually and collectively, guided by traits of specific host-pathogen associations using evolutionary ecology principles to create environmental (biotic and abiotic) conditions favorable for host growth and development while adverse to pathogen reproduction and evolution.

Towards sustainable intensification of apple production in China—Yield gaps and nutrient use efficiency in apple farming systems

WANG Na, Joost Wolf, ZHANG Fu-suo

2016, 15(4): 716-725. DOI: 10.1016/S2095-3119(15)61099-1

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China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits. However, the annual productivity of China’s apple is significantly lower than that of other dominant apple producing countries. In addition, apple production is based on excessive application of chemical fertilizers and the nutrient use efficiency (especially nitrogen) is therefore low and the nutrient emissions to the environment are high. Apple production in China is considerably contributes to farmers’ incomes and is important as export product. There is an urgent need to enhance apple productivity and improve nutrient use efficiencies in intensive apple production systems in the country. These can be attained by improved understanding of production potential, yield gaps, nutrient use and best management in apple orchards. To the end, priorities in research on apple production systems and required political support are described which may lead to more sustainable and environmental-friendly intensification of apple production in China.

Western blot detection of PMI protein in transgenic rice

RONG Rui-juan, WU Peng-cheng, LAN Jin-ping, WEI Han-fu, WEI Jian, CHEN Hao, SHI Jia-nan, HAO Yu-jie, LIU Li-juan, DOU Shi-juan, LI Li-yun, WU Lin, LIU Si-qi, YIN Chang-cheng, LIU Guo-zhen

2016, 15(4): 726-734. DOI: 10.1016/S2095-3119(15)61053-X

Abstract ( ) PDF in ScienceDirect

Phosphomannose isomerase (PMI) encoding gene manA is a desirable selective marker in transgenic research. Understanding of its expression patterns in transgenic plant and establishing highly sensitive detection method based on immunoassay have great impacts on the application of PMI. In this study, PMI-specific monoclonal antibodies were generated using recombinant protein as immunogen, and could be used in Western blot to detect as little as 0.5 ng His-tagged PMI protein or rice expressed PMI protein in sample accounted for 0.4% of single rice grain (about 0.08 mg). PMI protein driven by CaMV-35S promoter was detected in dozens of tested tissues, including root, stem, leaf, panicle, and seed at all developmental stages during rice growing, and PMI protein accounted for about 0.036% of total protein in the leaves at seedling stage. The established method potentially can be used to monitor PMI protein in rice grains.

Mapping of three QTLs for seed setting and analysis on the candidate gene for qSS-1 in rice (Oryza sativa L.)

Elsheikh Y M Ahmed, ZHANG Yan-pei, YU Jian-ping, Rashid M A Rehman, ZHANG Zhan-ying, ZHANG Hong-liang, LI Jin-jie, LI Zi-chao

2016, 15(4): 735-743. DOI: 10.1016/S2095-3119(15)61299-0

Abstract ( ) PDF in ScienceDirect

The lower seed setting is one of the major hindrances which face grain yield in rice. One of the main reasons to cause low spikelet fertility (seed setting) is male sterility or pollen abortion. Notably, pollen abortion has been frequently observed in advanced progenies of rice. In the present study, 149 BC₂F₆individuals with significant segregation in spikelet fertility were generated from the cross between N040212 (indica) and Nipponbare (japonica) and used for primary gene mapping. Three QTLs, qSS-1, qSS-7 and qSS-9 at chromosomes 1, 7 and 9, respectively, were found to be associated with seed setting. The recombinant analysis and the physical mapping information from publicly available resources exhibited that the qSS-1, qSS-7 and qSS-9 loci were mapped to an interval of 188, 701 and 3 741 kb, respectively. The seed setting responsible for QTL qSS-1 was further fine mapped to 93.5 kb by using BC₂F₇ population of 1 849 individuals. There are 16 possible putative genes in this 93.5 kb region. Pollen vitality tests and artificial pollination indicated that the male gamete has abnormal pollen while the female gamete was normal. These data showed that low seed setting rate relative to qSS-1 may be caused by abnormal pollen grains. These results will be useful for cloning, functional analysis of the target gene governing spikelet fertility (seed setting) and understanding the genetic bases of pollen sterility.

Gene and protein expression profiling analysis of young spike development in large spike wheat germplasms

CHEN Dan, ZHANG Jin-peng, LIU Wei-hua, WU Xiao-yang, YANG Xin-ming, LI Xiu-quan, LU Yu-qing, LI Li-hui

2016, 15(4): 744-754. DOI: 10.1016/S2095-3119(15)61179-0

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The wheat grain number per spike (GNPS) is a major yield-limiting factor in wheat-breeding programs. Germplasms with a high GNPS are therefore valuable for increasing wheat yield potential. To investigate the molecular characteristics of young spike development in large-spike wheat germplasms with high GNPS, we performed gene and protein expression profiling analysis with three high-GNPS wheat lines (Pubing 3228, Pubing 3504 and 4844-12) and one low-GNPS control variety (Fukuho). The phenotypic data for the spikes in two growth seasons showed that the GNPS of the three large-spike wheat lines were significantly higher than that of the Fukuho control line. The Affymetrix wheat chip and isobaric tags for relative and absolute quantitation-tandam mass spectrometry (iTRAQ-MS/MS) technology were employed for gene and protein expression profiling analyses of young spike development, respectively, at the floret primordia differentiation stage. A total of 598 differentially expressed transcripts (270 up-regulated and 328 down-regulated) and 280 proteins (122 up- regulated and 158 down-regulated) were identified in the three high-GNPS lines compared with the control line. We found that the expression of some floral development-related genes, including Wknox1b, the AP2 domain protein kinase and the transcription factor HUA2, were up-regulated in the high-GNPS lines. The expression of the SHEPHERD (SHD) gene was up-regulated at both the transcript and protein levels. Overall, these results suggest that multiple regulatory pathways, including the CLAVATA pathway and the meristem-maintaining KNOX protein pathway, take part in the development of the high-GNPS phenotype in our wheat germplasms.

A novel constitutive promoter and its downstream 5´ UTR derived from cotton (Gossypium spp.) drive high-level gene expression in stem and leaf tissues

SUN Bao, SUN Guo-qing, MENG Zhi-gang, ZHANG Rui, GUO San-dui

2016, 15(4): 755-762. DOI: 10.1016/S2095-3119(15)61054-1

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The development of genetically modified crops requires new promoters and regulatory regions to achieve high gene expression and/or tissue-specific expression patterns in plants. To obtain promoter sequences of plants with new properties, we analyzed the expression traits of the cotton (Gossypium hirsutum) translation elongation factor 1A gene family. The results showed that the GhEF1A8 gene is highly expressed in different organs of cotton plants, and showed much higher transcript levels in stems and leaves. Its promoter (GhEF1A1.7) and the 5´ untranslated region (5´ UTR), comprising a regulatory region named PGhEF1A8, were isolated from cotton and studied in stably transformed tobacco plants. The regulatory region sequences were fused to the β-glucuronidase (GUS) reporter gene to characterize its expression pattern in tobacco. Histochemical and fluorometric GUS activity assays demonstrated that PGhEF1A8 could direct GUS gene expression in all tissues and organs in transgenic tobacco, including leaves, stems, flowers, and roots. The level of GUS activity in the leaves and stems was significantly higher than in cauliflower mosaic virus (CaMV) 35S promoter::GUS plants, but as same as CaMV 35S promoter::GUS plants in flower and root tissues. GUS expression levels decreased 2–10-fold when the 5´ UTR was absent from PGhEF1A8. Deletion analysis of the PGhEF1A8 sequence showed that the region −647 to −323 might possess negative elements that repress transgene expression in tobacco plants. The results suggested that the GhEF1A8 regulation region may represent a practical choice to direct high-level constitutive expression of transgenes and could be a valuable new tool in plant genetic engineering.

Isolation and molecular characterization of the FLOWERING LOCUS C gene promoter sequence in radish (Raphanus sativus L.)

XU Yuan-yuan, WANG Jing, NIE Shan-shan, HUANG Dan-qiong, WANG Yan, XU Liang, WANG Rong-hua, LUO Xiao-bo, LIU Li-wang

2016, 15(4): 763-774. DOI: 10.1016/S2095-3119(15)61295-3

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Both bolting and flowering times influence taproot and seed production in radish. FLOWERING LOCUS C (FLC) plays a key role in plant flowering by functioning as a repressor. Two genomic DNA sequences, a 3 046-bp from an early- and a 2 959-bp from a late-bolting radish line were isolated and named as RsFLC1 and RsFLC2, respectively, for they share approximately 87.03% sequence identity to the FLC cDNA sequences. The genomic DNA sequences, 1 466-bp and 1 744-bp, flanking the 5´-regions of RsFLC1 and RsFLC2, respectively, were characterized. Since both of them harbor the basic promoter elements, the TATA box and CAAT box, they were designated as PRsFLC1 and PRsFLC2. The transcription start site (TSS) was identified at 424 and 336 bp upstream of the start codon in PRsFLC1 and PRsFLC2, respectively. cis-regulatory elements including CGTCA (MeJA-responsive) and ABRE (abscisic acid-responsive) motifs were found in both promoters, while some cis-regulatory elements including TCA element and GARE-motif were present only in PRsFLC1. These sequence differences lead to the diversity of promoter core elements, which could partially result in the difference of bolting and flowering time in radish line NauDY13 (early-bolting) and Naulu127 (late-bolting). Furthermore, to investigate the activity of these promoters, a series of 5´-deletion fragment-GUS fusions were constructed and transformed into tobacco. GUS activity was detected in PRsFLC1-(1 to 4)-GUS-PS1aG-3 and PRsFLC2-(1 to 4)-GUS-PS1aG-3 transgenic tobacco leaf discs, and this activity progressively decreased from PRsFLC-1-GUS-PS1aG-3 to PRsFLC-5-GUS-PS1aG-3. Deletion analysis indicated that the cis-regulatory elements located at –395 bp to +1 bp may be critical for specifying RsFLC gene transcription.

Cloning and characterization of CaGID1s and CaGAI in Capsicum annuum L.

CAO Ya-cong, ZHANG Zheng-hai, WANG Li-hao, SUI Xiao-lei, ZHANG Zhen-xian, ZHANG Bao-xi

2016, 15(4): 775-784. DOI: 10.1016/S2095-3119(15)61275-8

Abstract ( ) PDF in ScienceDirect

Fruit set and development are affected by many phytohormones, including gibberellin. Little is known regarding molecular mechanism underlying gibberellin mediated fruit set and development especially in Capsicum. Three gibberellin receptors, CaGID1b.1, CaGID1b.2 and CaGID1c, and a DELLA protein, CaGAI, have been identified in Capsicum annuum L. During the fruit development, the expression level of CaGID1c was low, and the expression fold change is mild. However, CaGID1b.1 and CaGID1b.2 were relatively higher and more acute, which indicates that CaGID1b.1 and CaGID1b.2 may play an important role in fruit pericarp, placenta and seed. Ectopic expressions of CaGID1b.1, CaGID1b.2 and CaGID1c in Arabidopsis double mutant gid1a gid1c increased plant height, among which CaGID1b.2 had the most significant effect; CaGAI reduced plant height in double mutant rga-24/gai-t6, having a similar function to AtGID1 and AtGAI in stem elongation. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays indicated that CaGID1b.1 and CaGID1b.2 interact with CaGAI in a GA-dependent manner, while CaGID1c interacts with CaGAI in a GA-independent manner. Our study reveals the key elements during gibberellin signaling in Capsicum and supports the critical importance of gibberellin for Capsicum fruit set and development.

Response of root morphology, physiology and endogenous hormones in maize (Zea mays L.) to potassium deficiency

ZHAO Xin-hua, YU Hai-qiu, WEN Jing, WANG Xiao-guang, DU Qi, WANG Jing, WANG Qiao

2016, 15(4): 785-794. DOI: 10.1016/S1671-2927(00)10445

Abstract ( ) PDF in ScienceDirect

Potassium (K) deficiency is one of the major abiotic stresses which has drastically influenced maize growth and yield around the world. However, the physiological mechanism of K deficiency tolerance is not yet fully understood. To identify the differences of root morphology, physiology and endogenous hormones at different growing stages, two maize inbred lines 90-21-3 (tolerance to K deficiency) and D937 (sensitive to K deficiency) were cultivated in the long-term K fertilizer experimental pool under high potassium (+K) and low potassium (–K) treatments. The results indicated that the root length, volume and surface area of 90-21-3 were significantly higher than those of D937 under –K treatment at different growing stages. It was noteworthy that the lateral roots of 90-21-3 were dramatically higher than those of D937 at tasselling and flowering stage under –K treatment. Meanwhile, the values of superoxide dismutase (SOD) and oxidizing force of 90-21-3 were apparently higher than those of D937, whereas malondialdehyde (MDA) content of D937 was obviously increased. Compared with +K treatment, the indole-3-acetic acid (IAA) content of 90-21-3 was largely increased under –K treatment, whereas it was sharply decreased in D937. On the contrary, abscisic acid (ABA) content of 90-21-3 was slightly increased, but that of D937 was significantly increased. The zeatin riboside (ZR) content of 90-21-3 was significantly decreased, while that of D937 was relatively increased. These results indicated that the endogenous hormones were stimulated in 90-21-3 to adjust lateral root development and to maintain the physiology function thereby alleviating K deficiency.

Intercropping of rice varieties increases the efficiency of blast control through reduced disease occurrence and variability

HAN Guang-yu, LANG Jie, SUN Yan, WANG Yun-yue, ZHU You-yong, LU Bao-rong

2016, 15(4): 795-802. DOI: 10.1016/S2095-3119(15)61055-3

Abstract ( ) PDF in ScienceDirect

Creating a crop-heterogeneous system by intraspecific mixtures of different rice varieties can substantially reduce blast diseases. Such variety mixtures provide an ecological approach for effective disease control, maintaining high yields with the minimum fungicide applications. Whether such an approach is universally applicable for random rice variety combinations and what is the variation pattern of the diseases under intercropping still remains unclear. We conducted two-year large-scale field experiments involving 47 rice varieties/lines and 98 variety-combinations to compare the occurrence of rice blast in monoculture and intercropping plots at multiple sites. In the experiments, the plant height of the selected traditional varieties was about 30 cm taller, and their life cycle was 10 days longer, than that of the improved rice varieties. The monoculture included either traditional or modern rice varieties grown in separate plots. The intercropping included both traditional and modern rice varieties planted together in the same plots. Results from the field experiments under natural disease conditions demonstrated significant reduction for rice blast disease in intercropping plots, compared with that in monoculture plots. For traditional varieties, the average blast incidence reduced from ~26% in monoculture to ~10% in intercropping, and the disease severity reduced from ~17 in monoculture to ~5 in intercropping. For modern varieties, the average blast incidence reduced from ~19% in monoculture to ~10% in intercropping, and the severity from ~10 in monoculture to ~4 in intercropping. Traditional rice varieties (~72%) had a much greater increase in the efficiency of disease control than modern varieties (~60%). In addition, substantially lower values of variance in the blast incidence and severity was detected among the variety combinations in intercropping plots than in monoculture plots. Based on these results, we conclude that the intercropping or mixture of rice varieties greatly reduces the occurrence and variation of rice blast disease in particular variety combinations, which makes the intercropping system more stable and consistent for disease suppression on a large scale of rice cultivation.

Physiological changes and expression characteristics of ZIP family genes under zinc deficiency in navel orange (Citrus sinensis)

XING Fei, FU Xing-zheng, WANG Nan-qi, XI Jian-long, HUANG Yi, ZHOU Wei, LING Li-li, PENG Liang-zhi

2016, 15(4): 803-811. DOI: 10.1016/S2095-3119(15)61276-X

Abstract ( ) PDF in ScienceDirect

Zinc (Zn) deficiency is widespread among citrus plants, but information about the mechanisms for Zn deficiency response in these plants is scarce. In the present study, different navel orange (Citrus sinensis (L.) Osbeck) leaves with various yellowing levels were sampled in our experimental orchard, and upon estimation of nutrient contents, Zn deficiencies were diagnosed as mild, moderate, and severe. Further analysis of chlorophyll content, photosynthetic characteristics, antioxidant enzyme activities, and expression levels of Zn/Iron-regulated transporter-like protein (ZIP) family genes were conducted in the sampled Zn-deficient leaves. The results showed that chlorophyll contents and net photosynthetic rate (P_n) seemed to decrease with reduced Zn contents. In addition, comparison of severe Zn-deficient and normal leaves revealed that activities of peroxidase (POD) and catalase (CAT) increased significantly, whereas that of Zn-containing enzymes such as Cu/Zn superoxide dismutase (Cu/Zn-SOD) significantly reduced with decreasing Zn contents. As expected, expression of the ZIP family genes, ZIP1, ZIP3, and ZIP4, was induced by Zn deficiencies. These results deepen our understanding of Zn deficiency in citrus plants as well as provide useful preliminary information for further research.

Functional identification of phenazine biosynthesis genes in plant pathogenic bacteria Pseudomonas syringae pv. tomato and Xanthomonas oryzae pv. oryzae

LI Wen, XU You-ping, Jean-Pierre Munyampundu, XU Xin, QI Xian-fei, GU Yuan, CAI Xin-zhong

2016, 15(4): 812-821. DOI: 10.1016/S2095-3119(15)61176-5

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Phenazines are secondary metabolites with broad spectrum antibiotic activity and thus show high potential in biological control of pathogens. In this study, we identified phenazine biosynthesis (phz) genes in two genome-completed plant pathogenic bacteria Pseudomonas syringae pv. tomato (Pst) DC3000 and Xanthomonas oryzae pv. oryzae (Xoo) PXO99^A. Unlike the phz genes in typical phenazine-producing pseudomonads, phz homologs in Pst DC3000 and Xoo PXO99^A consisted of phzC/D/E/F/G and phzC/E1/E2/F/G, respectively, and the both were not organized into an operon. Detection experiments demonstrated that phenazine-1-carboxylic acid (PCA) of Pst DC3000 accumulated to 13.4 μg L^–1, while that of Xoo PXO99^A was almost undetectable. Moreover, Pst DC3000 was resistant to 1 mg mL^–1 PCA, while Xoo PXO99^Awas sensitive to 50 μg mL^–1 PCA. Furthermore, mutation of phzF blocked the PCA production and significantly reduced the pathogenicity of Pst DC3000 in tomato, while the complementary strains restored these phenotypes. These results revealed that Pst DC3000 produces low level of and is resistant to phenazines and thus is unable to be biologically controlled by phenazines. Additionally, phz-mediated PCA production is required for full pathogenicity of Pst DC3000. To our knowledge, this is the first report of PCA production and its function in pathogenicity of a plant pathogenic P. syringae strain.

Comparative genomics provide a rapid detection of Fusarium oxysporum f. sp. conglutinans

LING Jian, ZHANG Ji-xiang, ZENG Feng, CAO Yue-xia, XIE Bing-yan, YANG Yu-hong

2016, 15(4): 822-831. DOI: 10.1016/S2095-3119(15)61237-0

Abstract ( ) PDF in ScienceDirect

Fusarium oxysporum f. sp. conglutinans (Foc) is the causal agent of Fusarium wilt disease of Brassica oleracea. A rapid, accurate, and reliable method to detect and identify plant pathogens is vitally important to integrated disease management. In this study, using a comparative genome analysis among Fusarium oxysporum (Fo), we developed a Foc-specific primer set (Focs-1/Focs-2) and established a multiplex-PCR assay. In the assay, the Focs-1/Focs-2 and universal primers for Fusarium species (W106R/F106S) could be used to detect Foc isolates in a single PCR reaction. With the optimized PCR parameters, the multiplex-PCR assay showed a high specificity for detecting Foc and was very sensitive to detect as little as 100 pg of pure Foc genomic DNA or 1 000 spores in 1 g of twice-autoclaved soil. We also demonstrated that Foc isolates were easily detected from infected plant tissues, as well as from natural field soils, using the multiplex-PCR assay. To our knowledge, this is a first report on detection Fo by comparative genomic method.

Isolation, identification, derivatization and phytotoxic activity of secondary metabolites produced by Cladosporium oxysporum DH14, a locust-associated fungus

LU Yi-hui, LI Shuai, SHAO Ming-wei, XIAO Xiao-hui, KONG Li-chun, JIANG Dong-hua, ZHANG Ying-lao

2016, 15(4): 832-839. DOI: 10.1016/S2095-3119(15)61145-5

Abstract ( ) PDF in ScienceDirect

Three main phytotoxic compounds including lunatoic acid A (1), 5Z-7-oxozeaenol (2) and zeaenol (3) were isolated from the fermentation broth of Cladosporium oxysporum DH14, a fungus residing in the locust (Oxya chinensis ) gut. Two additional derivative compounds, compound 1a and 1b, were synthesized by methylation and chlorination of compound 1, respectively. The structures of such compounds were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those previously reported in the literature. Compounds 1–3 exhibited significantly phytotoxic activities against the radicle growth of Amaranthus retroflexus L. with the 50% inhibitory concentrations (IC₅₀ values) of 4.51, 4.80 and 8.16 μg mL^–1, respectively, which is comparable to that positive control 2,4-dichlorophenoxyacetic acid (IC₅₀=1.95 μg mL^–1). Furthermore, the compound 1 showed selective phytotoxic activity with the inhibition rate of less than 22% against the crops of Brassica rapa L., Sorghum durra, Brassica campestris L., Capsicum annucm and Raphanus sativus L. under the concentration of 100 μg mL^–1. Both derivatives of compound 1 had moderate phytotoxic activity against the radicle growth of A. retroflexus L. The findings of our present study suggest that these compounds provide new promising candidates for the potential management strategies of weeds.

Transcriptome datasets supply basic gene information for RNAi pest management and gene functional studies in Nephotettix cincticeps (Uhler)

CHEN Tai-yu, HOU Ji-xiang, LIN Yong-jun

2016, 15(4): 840-847. DOI: 10.1016/S2095-3119(15)61133-9

Abstract ( ) PDF in ScienceDirect

RNA interference (RNAi) technology has the potential to be used in pest management in crop production. Here, the transcriptome of Nephotettix cincticeps (Uhler) was deeply sequenced to investigate the systematic RNAi mechanism and candidate genes for dsRNA feeding. In our datasets, a total of 81 225 transcripts were obtained with the length from 150 bp to about 4.2 kb. Almost all the genes related to the RNAi core pathway were proved to be present in N. cincticeps transcriptome. Two transcripts that respectively encode a systemic interference defective (SID) were identified in our database, indicating that the systematic RNAi pathway can function effectively in N. cincticeps. Our datasets not only supply basic gene information for the studies of gene expression and functions in N. cincticeps, such as the control genes for gene expression analysis, but also provide candidate genes for RNAi pest management, such as the genes that encode P450 monooxygenase, V-ATPase and chitin synthase.

Heritabilities and genetic and phenotypic correlations of litter uniformity and litter size in Large White sows

ZHANG Tian, WANG Li-gang, SHI Hui-bi, YAN Hua, ZHANG Long-chao, LIU Xin, PU Lei, LIANG Jing, ZHANG Yue-bo, ZHAO Ke-bin, WANG Li-xian

2016, 15(4): 848-854. DOI: 10.1016/S2095-3119(15)61155-8

Abstract ( ) PDF in ScienceDirect

Litter uniformity, which is usually represented by within-litter weight coefficient of variation at birth (CVB), could influence litter performance of sows and the profitability of pig enterprises. The objective of this study was to characterize CVB and its effect on other reproductive traits in Large White sows. Genetic parameters and genetic correlation of the reproductive traits, including CVB, within-litter weight coefficient of variation at three weeks (CVT), total number born (TNB), number born alive (NBA), number born dead (NBD), gestation length (GL), piglet mortality at birth (M₀), piglet mortality at three weeks (M₃), total litter weight at birth (TLW0), and total litter weight at three weeks (TLW₃) were estimated for 2 032 Large White litters. The effects of parity and classified litter size on CVB, CVT, TNB, NBA, NBD, GL, M₀, M₃, TLW₀, and TLW₃ were also estimated. The heritabilities of these reproductive traits ranged from 0.06 to 0.17, with the lowest heritability for CVB and the highest heritability for TLW0. Phenotypic and genetic correlations between these reproductive traits were low to highly positive and negative (ranging from −0.03 to 0.93, and −0.53 to 0.93, respectively). The genetic correlations between TNB and CVB, and between M₀ and CVB were 0.32 and 0.29, respectively. In addition, CVB was significantly influenced by parity and litter size class (P<0.05). All the results suggest that piglet uniformity should be maintained in pig production practices and pig breeding programs.

Screening and characterization of a novel ruminal cellulase gene (Umcel-1) from a metagenomic library of gayal (Bos frontalis)

LI Bi-feng, ZHU Ya-xin, GU Zhao-bing, CHEN Yuan, LENG Jing, GOU Xiao, FENG Li, LI Qing, XI Dong-mei, MAO Hua-ming, YANG Shu-Li

2016, 15(4): 855-861. DOI: 10.1016/S2095-3119(15)61144-3

Abstract ( ) PDF in ScienceDirect

Gayal is a rare semi-wild bovine species found in the Indo-China. They can graze grasses, including bamboo leaves, as well as reeds and other plant species, and grow to higher mature live weights than Yunnan Yellow cattle maintained in similar harsh environments. The aim of this study was to identify specific cellulase in the gayal rumen. A metagenomic fosmid library was constructed using genomic DNA isolated from the ruminal contents of four adult gayals. This library contained 38 400 clones with an average insert size of 35.5 kb. The Umcel-1 gene was isolated from this library. Investigation of the cellulase activity of 24 random clones led to the identification of the Umcel-1 gene, which exhibited the most potent cellulase activity. Sequencing the Umcel-1 gene revealed that it contained an open reading frame of 942 base pairs that encoded a product of 313 amino acids. The putative gene Umcel-1 product belonged to the glycosyl hydrolase family 5 and showed the highest homology to the cellulase (GenBank accession no. YP_004310852.1) from Clostridium lentocellum DSM 5427, with 44% identity and 62% similarity. The Umcel-1 gene was heterologously expressed in Escherichia coli BL21, and recombinant Umcel-1 was purified. The activity of purified recombinant Umcel-1 was assessed, and the results revealed that it hydrolyzed carboxymethyl cellulose with optimal activity at pH 5.5 and 45°C. To our knowledge, this study provides the first evidence for a cellulase produced by bacteria in gayal rumen.

High gene flows promote close genetic relationship among fine-wool sheep populations (Ovis aries) in China

HAN Ji-long, YANG Min, GUO Ting-ting, LIU Jian-bin, NIU Chun-e, YUAN Chao, YUE Yao-jing, YANG Bo-hui

2016, 15(4): 862-871. DOI: 10.1016/S2095-3119(15)61104-2

Abstract ( ) PDF in ScienceDirect

The aim of our present study was to construct genetic structure and relationships among Chinese fine-wool sheep breeds. 46 individuals from 25 breeds or strains were genotyped based on the Illumina Ovine 50K SNP array. Meanwhile, genetic variations among 482 individuals from 9 populations were genotyped with 10 microsatellites. In this study, we found high genetic polymorphisms for the microsatellites, while 7 loci in the Chinese superfine Merino strain (Xinjiang types) (CMS) and 5 loci in Gansu alpine superfine-wool sheep strain (GSS) groups were found deviated from Hardy-Weinberg equilibrium (HWE). Genetic drift F_ST=0.019 (P<0.001) and high gene flows were detected in all the 7 fine-wool sheep populations. Phylogenetic analysis showed fine-wool sheep populations were clustered in a group independent from the Chinese indigenous breeds such that the 7 fine-wool sheep clustered distinct from Liangshan semifine-wool sheep (LS) and Hu sheep (HY) reflected by different population differentiation analyses. Overall, our findings suggested that all fine-wool sheep populations have close genetic relationship, which is consistent with their breeding progress. These populations, therefore, can be regarded as open-breeding populations with high levels of gene flows. Furthermore, the two superfine-wool strains, viz., CMS and GSS, might be formed by strong artificial selection and with frequent introduction of Australian Merino. Our results can assist in breeding of superfine-wool sheep and provide guidance for the cultivation of new fine-wool sheep breeds with different breeding objectives.

Growth performance and rumen microorganism differ between segregated weaning lambs and grazing lambs

JI Shou-kun, JIANG Cheng-gang, LI Rui, DIAO Qi-yu, TU Yan, ZHANG Nai-feng, SI Bing-wen

2016, 15(4): 872-878. DOI: 10.1016/S2095-3119(15)61267-9

Abstract ( ) PDF in ScienceDirect

Two feeding patterns of the segregated weaning or grazing in the pasture are carried out worldwide in animal production. To investigate the difference of growth performance and rumen microorganism population related to methane metabolism in the two feeding patterns, three groups of lambs (70 in total) were used: Weaning at 21 days old and being subjected to high-concentration diets (3WK group with 20 lambs), weaning at 35 days old and being subjected to high-concentration diets (5WK group with 20 lambs), or grazing at pasture with the nursing mother (Grazing group with 30 lambs). The growth performance, pH value of rumen content, and the rumen microbes were investigated during weaning period and fattening period with approximately 3 months. Our results showed that lambs in 3WK and 5WK groups demonstrated a better growth performance than the lambs in Grazing group, but no significant difference was observed in the pH value between the three groups (P>0.05). The total rumen bacterial population of the Grazing lambs was significantly lower than that of 3WK lambs (P<0.05) and 5WK lambs (P<0.05); however, the population of methanogens was 4.2- and 2.7-fold lower in the 3wk (P<0.05) and 5wk (P<0.05) lambs compared with Grazing lambs, respectively; protozoa were also 3.5- and 3.4-fold lower in the 3WK (P<0.05) and 5WK (P<0.05) lambs, respectively. The results revealed that segregated weaning lambs may have better growth performance, and reduce methane-producing microbes.

Soil properties and corn (Zea mays L.) production under manure application combined with deep tillage management in solonetzic soils of Songnen Plain, Northeast China

MENG Qing-feng, LI Da-wei, ZHANG Juan, ZHOU Lian-ren, MA Xian-fa, WANG Hong-yan, WANG Guang-cheng

2016, 15(4): 879-890. DOI: 10.1016/S2095-3119(15)61196-0

Abstract ( ) PDF in ScienceDirect

Poor soil structure and nutrients, excessive exchangeable Na⁺, high pH as well as low enzyme activities are common in the solonetz, and significantly restrict corn (Zea mays L.) production. Cattle manure application combined with deep tillage is an important management practice that can affect soil physico-chemical properties and enzyme activities as well as corn yield in the solonetz. Field experiments were carried out in a randomized complete block design comprising four treatments: Corn with conventional tillage was used as a control, and corn with manure application combined with deep tillage as well as film mulching and aluminium sulfate were used as the experimental treatments, respectively. The relationship between corn yield and measured soil properties was determined using stepwise regression analysis. Manure application combined with deep tillage management was more effective than conventional tillage for increasing corn yield and for improving soil properties in the solonetz. The highest corn yield was obtained in the treatments with manure application+deep tillage+plastic film mulching (11 472 and 12 228 kg ha^–1), and increased by 38 and 43% comparing with the control treatment (8 343 and 8 552 kg ha^–1) both in the 2013 and 2014 experiments, respectively. Using factor analysis, three factors were obtained, which represented soil fertility status, soil saline-alkaline properties and soil structural properties both in the 2013 and 2014 experiments, respectively. Manure and deep tillage management resulted in two distinct groups of soil properties: (1) soils with manure application combined with deep tillage and (2) soils with conventional tillage. Stepwise regression analysis showed that corn yield was significantly and positively correlated to urease and available P, as well as negatively correlated to pH, electrical conductivity (EC), exchange sodium percentage (ESP), and bulk density (ρ_b). We concluded that ρb was dominant factor for corn yield on the basis of discriminant coefficient. Manure application combined with deep tillage management resulted in an increase in corn yield mainly owing to improved soil structural properties, followed by decreased soil saline-alkaline obstacle as well as increased urease activity and available P. This result is likely that the improvement in soil organic matter (SOM) from manure application greatly and positively contributed to better soil physico-chemical properties and enzyme activities, especially decrease in ρ_b. Suggestion for corn production should be improvement in soil structural properties firstly. This could cause decrease in ρ_b that key factor which limited the corn production in the solonetz.

Estimating distribution of water uptake with depth of winter wheat by hydrogen and oxygen stable isotopes under different irrigation depths

GUO Fei, MA Juan-juan, ZHENG Li-jian, SUN Xi-huan, GUO Xiang-hong, ZHANG Xue-lan

2016, 15(4): 891-906. DOI: 10.1016/S2095-3119(15)61258-8

Abstract ( ) PDF in ScienceDirect

Crop root system plays an important role in the water cycle of the soil-plant-atmosphere continuum. In this study, combined isotope techniques, root length density and root cell activity analysis were used to investigate the root water uptake mechanisms of winter wheat (Triticum aestivum L.) under different irrigation depths in the North China Plain. Both direct inference approach and multisource linear mixing model were applied to estimate the distribution of water uptake with depth in six growing stages. Results showed that winter wheat under land surface irrigation treatment (T_s) mainly absorbed water from 10–20 cm soil layers in the wintering and green stages (66.9 and 72.0%, respectively); 0–20 cm (57.0%) in the jointing stage; 0–40 (15.3%) and 80–180 cm (58.1%) in the heading stage; 60–80 (13.2%) and 180–220 cm (35.5%) in the filling stage; and 0–40 (46.8%) and 80–100 cm (31.0%) in the ripening stage. Winter wheat under whole soil layers irrigation treatment (Tw) absorbed more water from deep soil layer than T_s in heading, filling and ripening stages. Moreover, root cell activity and root length density of winter wheat under T_w were significantly greater than that of T_s in the three stages. We concluded that distribution of water uptake with depth was affected by the availability of water sources, the root length density and root cell activity. Implementation of the whole soil layers irrigation method can affect root system distribution and thereby increase water use from deeper soil and enhance water use efficiency.

Nutrient uptake requirements with increasing grain yield for rice in China

CHE Sheng-guo, ZHAO Bing-qiang, LI Yan-ting, YUAN Liang, LIN Zhi-an, HU Shu-wen, SHEN Bing

2016, 15(4): 907-917. DOI: 10.1016/S2095-3119(15)61143-1

Abstract ( ) PDF in ScienceDirect

Improved estimates of nutrient requirements for rice (Oryza sativa L.) in China are essential to optimize fertilization regulation for increasing grain yields and reducing the potential of environmental negative influences, especially under high-yielding intensive systems. A database involving rice grain yields, nutrient concentrations and accumulations collected from on-field station experiments in the literatures published from 2000 to 2013 in China was developed to understand the relationships between grain yields and plant nutrient uptakes, and to quantify nutrient requirements for different yield levels. Considering all data sets, rice grain yield ranged from 1.4 to 15.2 t ha^–1 with the mean value of 7.84 t ha^–1, and ca. 10.4% of yield observations were higher than the yield barrier level of 10 t ha^–1. N requirement to produce one ton grain was 21.10 kg for the yield range <4.0 t ha^–1 with a high variation of 45.8%. Except of the yield range <4.0 t ha^–1, the values of N requirement, firstly increased from 18.78 kg for yield range 4.0–5.5 t ha^–1 to 20.62 kg for yield range 7.0–8.5 t ha^–1, then decreased slightly to 19.67 and 19.17 kg for the yield range 8.5–10 and >10 t ha^–1, respectively. Phosphorus (P) and potassium (K) requirements showed increasing trends, from 3.51 and 19.87 kg per t grain for <4.0 t ha^–1 yield range to 4.10 and 21.70 kg for >10.0 t ha^–1 range. In conclusion, nutrient requirement varied with increasement of grain yield, and N, P and K presented various response trends, increasing, declining or stagnating, which would be of great benefit for improving fertilizer strategies.

Effects of land use change on the spatiotemporal variability of soil organic carbon in an urban-rural ecotone of Beijing, China

YE Hui-chun, HUANG Yuan-fang, CHEN Peng-fei, HUANG Wen-jiang, ZHANG Shi-wen, HUANG Shan-yu, HOU Sen

2016, 15(4): 918-928. DOI: 10.1016/S2095-3119(15)61066-8

Abstract ( ) PDF in ScienceDirect

Understanding the effects of land use changes on the spatiotemporal variation of soil organic carbon (SOC) can provide guidance for low carbon and sustainable agriculture. In this paper, based on the large-scale datasets of soil surveys in 1982 and 2009 for Pinggu District — an urban-rural ecotone of Beijing, China, the effects of land use and land use changes on both temporal variation and spatial variation of SOC were analyzed. Results showed that from 1982 to 2009 in Pinggu District, the following land use change mainly occurred: Grain cropland converted to orchard or vegetable land, and grassland converted to forestland. The SOC content decreased in region where the land use type changed to grain cropland (e.g., vegetable land to grain cropland decreased by 0.7 g kg^–1; orchard to grain cropland decreased by 0.2 g kg^–1). In contrast, the SOC content increased in region where the land use type changed to either orchard (excluding forestland) or forestland (e.g., grain cropland to orchard and forestland increased by 2.7 and 2.4 g kg^–1, respectively; grassland to orchard and forestland increased by 4.8 and 4.9 g kg^–1, respectively). The organic carbon accumulation capacity per unit mass of the soil increased in the following order: grain cropland soil

Effects of two efflux pump inhibitors on the drug susceptibility of Riemerella anatipestifer isolates from China

LI Ya-fei, JIANG Hong-xia, XIANG Rong, SUN Na, ZHANG Ya-nan, ZHAO Li-qing, GU Peng, WANG Li-qiao, ZENG Zhen-ling

2016, 15(4): 929-933. DOI: 10.1016/S2095-3119(15)61031-0

Abstract ( ) PDF in ScienceDirect

The objective of this study was to verify the supposition that efflux might be involved in the drug resistance of Riemerella anatipestifer isolates. Two broad-spectrum efflux pump inhibitors, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and Phe-Arg-β-naphthylamide (PAβN), on the contribution of minimum inhibitory concentrations of amikacin, streptomycin, chloramphenicol, tetracycline, ceftriaxone, ceftazidime, nalidixic acid, levofloxacin, enrofloxacin, as well as ciprofloxacin against 69 clinical R. anatipestifer isolates were investigated. We first reported that the two efflux pump inhibitors could restore the antimicrobial susceptibility of R. anatipestifer isolates. It is suggested that active efflux system is possible to be linked with the development of resistance in R. anatipestifer isolates.

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