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2018 Vol. 17 No. 04 Previous Issue    Next Issue

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Commentary
Review
Crop Science
Horticulture
Plant Protection
Animal Science · Veterinary Medicine
Agricultural Economics and Management


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Duck hepatitis B virus (DHBV) shares many basic characteristics with hepatitis B virus (HBV) and is an attractive model for vaccine development. In this study, DHBV DNA vaccines were designed to express envelope and capsid fusion proteins to enhance the breadth of immune response in ducks. Attenuated Salmonella typhimurium (SL7207) was used as a carrier and adjuvant to boost the magnitude of immune response. The results of this study enriched our knowledge of the antigenicity of envelope and capsid fusion proteins in ducks and demonstrated the value of using attenuated S. typhimurium (SL7207) to deliver DHBV vaccines. In the future, it is worth further exploring DNA vaccines expressing multiple antigen genes delivered by attenuated S. typhimurium, as well as the therapeutic benefits when applied to the duck model of DHBV infection. See pages 928–939 by Liu et al. in details. The photo showed here were ducklings inoculated with DHBV DHA vaccines delivered by attenuated S. typhimurium which was provided by Liu Siyang and Prof. Jia Renyong from the Avian Disease Research Center, Sichuan Agricultural University, China.


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Commentary

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Challenges to increasing the soil carbon pool of agro-ecosystems in China LIN Er-da, GUO Li-ping, JU Hui 2018, 17(04): 723-725.  DOI: 10.1016/S2095-3119(17)61744-1 Abstract ( )   PDF (648KB) ( )       Climate change will place agro-ecological systems and food security at serious risk. At the 21st Conference of the Parties (COP21) in Paris in December of 2015, parties to the United Nations Framework Convention on Climate Change (UNFCCC) reached a historic agreement (Paris Agreement) to combat climate change and to accelerate and intensify the actions and investments needed for a sustainable low carbon future. An initiative named the “4‰ initiative: Soils for food security and climate” was proposed by the French Minister of Agriculture, and this initiative was launched officially at the COP21 and adopted by many global organizations. The aim of this initiative was to increase carbon sequestration in soil to mitigate fossil fuel combustion emissions of greenhouse gasses. The present study found that China has high CO2 emissions but a low soil carbon pool, and indicates that 4‰ increments of the soil carbon pool will not be sufficient to offset national CO2 emissions. The current soil carbon sequestration rate would also not reach the mean level requested by the initiative. Therefore, China faces big challenges to achieve this initiative. An integrated use of straw technology may be used more widely to improve carbon sequestration, and other opportunities include improved fertilizer use efficiency and greenhouse gas mitigation through the waste management project under construction in China. This paper suggests that China may put forward the biomass treatment centered high yield and fertilizer-carbon sequestration project to enhance resilience of agro-ecosystems to climate change.

Review

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Mechanisms and molecular approaches for heat tolerance in rice (Oryza sativa L.) under climate change scenario Syed Adeel Zafar, Amjad Hameed, Muhammad Amjad Nawaz, MA Wei, Mehmood Ali Noor, Muzammil Hussain, Mehboob-ur-Rahman 2018, 17(04): 726-738.  DOI: 10.1016/S2095-3119(17)61718-0 Abstract ( )   PDF (3850KB) ( )   Rice, a staple cereal crop in many parts of the world, has been confronted with multiple environmental stresses including high temperature, negatively impacts the booting as well as anthesis growth stages.  The situation is further complicated by the changing climatic conditions, resulting in gradual escalation of temperature as well as changing the rainfall pattern and frequency, thus raising a concern of food security worldwide.  The situation can be combat by developing rice varieties with excellent genetics with improved morpho-physiological, biochemical, and molecular mechanisms, together can minimize the adverse effects of heat stress.  Here, several strategies (encompassing genetic and genomic, and mechanisms involved) for mitigating the impact of high temperature on rice have been discussed.  Finally, the utilization of genomic knowledge in augmenting the conventional breeding approaches have been comprehensively elaborated to develop heat tolerant germplasm.

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Research progress on plant tolerance to soil salinity and alkalinity in sorghum HUANG Rui-dong 2018, 17(04): 739-746.  DOI: 10.1016/S2095-3119(17)61728-3 Abstract ( )   PDF in ScienceDirect   Sorghum is an important source of food, feed and raw material for brewing, and is expected to be a promising bioenergy crop.  Sorghum is well known for its strong resistance to abiotic stress and wide adaptability, and salt tolerance is one of its main characteristics.  Increasing sorghum planting acreage on saline-alkalien land is one way to effectively use this kind of marginal soil.  In this paper, domestic and overseas research on plant tolerance to soil salinity and alkalinity in sorghum, including salt-tolerant genetics and breeding, physiology, cultivation, and identification of tolerant germplasms, are reviewed.  Suggestions for further studies on salinity and alkalinity tolerance in sorghum are given, and the prospects for sorghum production in saline-alkalien land are discussed.

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Maize-soybean strip intercropping: Achieved a balance between high productivity and sustainability DU Jun-bo, HAN Tian-fu, GAI Jun-yi, YONG Tai-wen, SUN Xin, WANG Xiao-chun, YANG Feng, LIU Jiang, SHU Kai, LIU Wei-guo, YANG Wen-yu 2018, 17(04): 747-754.  DOI: 10.1016/S2095-3119(17)61789-1 Abstract ( )   PDF in ScienceDirect   Intercropping is one of the most vital practice to improve land utilization rate in China that has limited arable land resource. However, the traditional intercropping systems have many disadvantages including illogical field lay-out of crops, low economic value, and labor deficiency, which cannot balance the crop production and agricultural sustainability. In view of this, we developed a novel soybean strip intercropping model using maize as the partner, the regular maize-soybean strip intercropping mainly popularized in northern China and maize-soybean relay-strip intercropping principally extended in southwestern China. Compared to the traditional maize-soybean intercropping systems, the main innovation of field lay-out style in our present intercropping systems is that the distance of two adjacent maize rows are shrunk as a narrow strip, and a strip called wide strip between two adjacent narrow strips is expanded reserving for the growth of two or three rows of soybean plants.  The distance between outer rows of maize and soybean strips are expanded enough for light use efficiency improvement and tractors working in the soybean strips.  Importantly, optimal cultivar screening and increase of plant density achieved a high yield of both the two crops in the intercropping systems and increased land equivalent ratio as high as 2.2.  Annually alternative rotation of the adjacent maize- and soybean-strips increased the grain yield of next seasonal maize, improved the absorption of nitrogen, phosphorus, and potasium of maize, while prevented the continuous cropping obstacles.  Extra soybean production was obtained without affecting maize yield in our strip intercropping systems, which balanced the high crop production and agricultural sustainability.

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The transformation of agriculture in China: Looking back and looking forward JIAO Xiao-qiang, Nyamdavaa Mongol, ZHANG Fu-suo 2018, 17(04): 755-764.  DOI: 10.1016/S2095-3119(17)61774-X Abstract ( )   PDF (835KB) ( )   China’s grain yield increased from 1 t ha–1 in 1961 to 6 t ha–1 in 2015, while successfully feeding not only its large population but also supplying agricultural products all over the world.  These achievements were greatly supported by modern technology and distinct governmental policy.  However, China’s grain production has been causing a number of problems mainly related to declining natural resources and a lack of environmental protection.  Due to the growing population and changing dietary requirements, increasing food production must be achieved by increasing resource use efficiency while minimizing environmental costs.  We propose two novel development pathways that can potentially sustain agricultural crop production in the next few decades: (i) enhancing nutrient use efficiency with zero increase in chemical fertilizer input until 2020 and (ii) concurrently increasing grain yield and nutrient use efficiency for sustainable intensification with integrated nutrient management after 2020.  This paper provides a perspective on further agricultural developments and challenges, and useful knowledge of our valuable experiences for other developing countries.

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Overview on current criteria for heavy metals and its hint for the revision of soil environmental quality standards in China CHEN Shi-bao, WANG Meng, LI Shan-shan, ZHAO Zhong-qiu, E Wen-di 2018, 17(04): 765-774.  DOI: 10.1016/S2095-3119(17)61892-6 Abstract ( )   PDF in ScienceDirect   Following rapid social and economic development over the past several decades, soil pollution by heavy metals (HMs) has been both serious and widespread in China.  The Soil Environmental Quality Standards (SEQSs) in China (GB 15618-1995) have been introduced to encourage and enforce sustainable soil HM management.  However, in recent years, HM contents in soils have frequently been found to exceed their associated standard values, while the crops growing on them might still meet regulatory standards, and vice versa.  There is thus growing awareness that GB 15618-1995 does not effectively regulate current soil HM pollution, as it has encountered bottlenecks, and disappointing outcomes caused by poor execution along with deficiencies and gaps in the policies.  However, due to the deficiency of scientific research about relationships between soil HM concentrations and their ecological or human health effects, the development of SEQSs in China is still greatly restricted.  This paper discusses international SEQSs of HMs as well their development in China over time, then examines current Chinese SEQSs to demonstrate their potential regulatory deficiencies by referring to international SEQSs.  The corresponding legislative policies are described, and scientific information or responses are outlined for maintaining soil environmental quality.  China’s experience has shown that policy and science can be linked to work in tandem to better understand and manage soil quality issues.

Crop Science

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Genetic characteristics of a wheat founder parent and a widely planted cultivar derived from the same cross CHANG Li-fang, LI Hui-hui, WU Xiao-yang, LU Yu-qing, ZHANG Jin-peng, YANG Xin-ming, LI Xiu-quan, LIU Wei-hua, LI Li-hui 2018, 17(04): 775-785.  DOI: 10.1016/S2095-3119(17)61710-6 Abstract ( )   PDF in ScienceDirect   Founder parents have contributed significantly to the improvement of wheat breeding and production.  In order to investigate the genetic characteristics of founder parents and widely planted cultivars, Mazhamai (M), Biyumai (B) and six sibling lines (BM1–6) derived from the cross M×B were phenotyped for eight yield-related traits over multiple years and locations and genotyped using the the wheat 90K single nucleotide polymorphism (SNP) assay.  BM4 has been used as a founder parent, and BM1 has been widely planted, whereas BM2, 3, 5, and 6 have not been used extensively for breeding or planting in China.  Phenotypic comparisons revealed that BM4 and BM1 displayed a better overall performance than the other sibling lines.  BM1 showed higher thousand-grain weight than BM4, whereas BM4 exhibited lower coefficient of variation for most of the yield-related traits across different years and locations, indicating that BM4 was widely adaptable and more stable in different environments.  SNP analysis revealed that BM4 and BM1 inherited similar proportions of the M genome but are dissimilar to BM2, 3, 5, and 6.  Both BM1 and BM4 have specific alleles that differ from the other BM lines, and most of these alleles are concentrated in specific chromosomal regions that are found to associate with favorable QTLs, these SNPs and their surrounding regions may carry the genetic determinants important for the superior performance of the two lines.  But BM4 has more genetic diversity than BM1 with more specific alleles and pleiotropic regions, indicating that the genome of BM4 may be more complex than the other sibling lines and has more favorable gene resources.  Our results provide valuable information that can be used to select elite parents for wheat and self-pollinating crop breeding.

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Evaluation of a new method for quantification of heat tolerance in different wheat cultivars LI Qiang, WANG Zheng-rui, LI Ding, WEI Jian-wei, QIAO Wen-chen, MENG Xiang-hai, SUN Shu-luan, LI Hui-min, ZHAO Ming-hui, CHEN Xiu-min, ZHAO Feng-wu 2018, 17(04): 786-795.  DOI: 10.1016/S2095-3119(17)61716-7 Abstract ( )   PDF in ScienceDirect   Heat stress seriously affects wheat production in many regions of the world.  At present, heat tolerance research remains one of the least understood fields in wheat genetics and breeding and there is a lack of effective methods to quantify heat stress and heat tolerance in different wheat cultivars.  The objective of this study was to use various wheat cultivars to evaluate stress intensity (δ) and a new method for quantification of heat tolerance and compare this technique with three other currently utilized methods.  This new parameter for heat tolerance quantification is referred to as the heat tolerance index (HTI) and is an indicator of both yield potential and yield stability.  Heat treatments were applied in a controlled setting when anthesis had been reached for 80% of the wheat.  The stress intensity evaluation indicated heat shock was the main factor associated with kernel weight reduction while grain yield reduction was mainly associated with chronic high temperature.  The methods evaluation showed that a temperature difference of 5°C from natural temperatures was a suitable heat treatment to compare to the untreated controls.  HTI was positively correlated with yield under heat stress (r=0.8657, δ2010=0.15, in 2009–2010; r=0.8418, δ2011=0.20, in 2010–2011; P<0.01), and negatively correlated with yield reduction rate (r=–0.8344, in 2009–2010; r=–0.7158, in 2010–2011; P<0.01).  The results of this study validated the use of HTI and temperature difference control for quantifying wheat heat tolerance that included the yield potential and the stability of different wheat cultivars under heat stress.  Additionally, 10 wheat cultivars showed high HTI and should be further tested for their heat confirming characteristics for use in wheat heat tolerance breeding.

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Comparative proteomics analysis of maize (Zea mays) leaves infected by small brown planthopper (Laodelphax striatellus) ZHAO Mei-ai, LEI Zhen, PEI Yu-he, SHAO Xiao-yu, GUO Xin-mei, SONG Xi-yun? 2018, 17(04): 796-805.  DOI: 10.1016/S2095-3119(17)61824-0 Abstract ( )   PDF in ScienceDirect   Maize rough dwarf disease (MRDD) is a viral disease caused by brown planthopper infestation, and leads to great yield loss, especially in China.  Comparative proteomics was performed using maize inbred line Zheng 58 and LN 287.  MRDD pathogen was detected as rice black-streaked dwarf virus (RBSDV) by quantitative real time PCR (qRT-PCR) in Shandong Province, China.  The modified trichloroacetic acid (TCA)/acetone method was used for soluble protein extraction from leaves.  Two-dimensional electrophoresis (2-DE) analysis was performed on 24-cm long, pH 4-7 linear immobilized pH gradient (IPG) strips, and gels were stained with silver and coomassie brilliant blue.  We identified 944 proteins expressed in RBSDV infected maize leaves by proteomics approaches.  Among these, 44 protein spots that revealed a 1.5-fold difference in intensity were identified  by mass spectrometry between mock-inoculated and RBSDV infected samples.  Among these, 17 and 26 spots were up-regulated, and 27 and 18 spots were down-regulated in the virus infected samples of Zheng 58 and LN 287, respectively.  Differential protein spots were analyzed by mass spectrometry identification, which could be divided into six categories.  Furthermore, the expression of stress-related proteins was detected and confirmed by qRT-PCR.  This study lays the foundation for further investigations, enabling the enhancement of MRDD resistance in maize.

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Comparison of agronomic performance between inter-sub-specific hybrid and inbred japonica rice under different mechanical transplanting methods HU Ya-jie, WU Pei, ZHANG Hong-cheng, DAI Qi-gen, HUO Zhong-yang, XU Ke, GAO Hui, WEI Hai-yan, GUO Bao-wei, CUI Pei-yuan 2018, 17(04): 806-816.  DOI: 10.1016/S2095-3119(17)61819-7 Abstract ( )   PDF in ScienceDirect   Mechanical transplanting has been applied to rice cultivation to save labor costs and ease labor shortages in Asian countries, especially in China.  However, little information is available related to the characteristics of agronomic performance when comparing inter-sub-specific hybrid rice (IHR) and inbred japonica rice (IJR) under mechanical transplanting method.  In 2013 and 2014, field experiments were conducted using IHR (Yongyou 2640) and IJR (Wuyunjing 24) under two cultivation patterns, that is, pot seedlings mechanically transplanted (PS) and carpet seedlings mechanically transplanted (CS).  Grain yield, yield components, leaf area index (LAI), leaf area duration (LAD), aboveground biomass, crop growth rate (CGR), nitrogen (N) uptake, and N accumulation were investigated.  When compared with CS, PS displayed significantly increased grain yield for both varieties because the larger sink size allowed higher N accumulation from panicle initiation to maturity.  Moreover, total aboveground biomass under PS increased significantly compared with that under CS; that is, higher photosynthetic productivity resulted from a greater LAI and higher LAD during the grain filling stage.  Higher N absorption capacity in the middle and late growth periods resulted in significantly enhanced total N uptake under PS.  When compared with IJR for both treatments, IHR generated 75.2% more grain yield.  However, the characteristics creating high yield of IHR were different from those of IJR.  Greater aboveground biomass production as well as higher N uptake and accumulation created higher grain yield in IHR than in IJR.  These results suggest higher yield could be achieved using PS with IHR, attributing to exploit both yield superiority and productive potential.

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Response of yield increase for dryland winter wheat to tillage practice during summer fallow and sowing method in the Loess Plateau of China LI Hui, XUE Jian-fu, GAO Zhi-qiang, XUE Nai-wen, YANG Zhen-ping 2018, 17(04): 817-825.  DOI: 10.1016/S2095-3119(17)61806-9 Abstract ( )   PDF in ScienceDirect   Soil moisture is the most critical limiting factor impacting yields of dryland winter wheat (Triticum aestivum L.) and it is strongly affected by tillage practice and sowing methods.  This study was to assess the link between sowing method and tillage practice during summer fallow and their subsequent effect on soil moisture and grain yield.  Furthermore, we sought to identify a more appropriate farming management practice for winter wheat production in Loess Plateau region of China.  The experiment was conducted from 2011 to 2013, using a two-factor split plot design, including subsoiling (SS) or no tillage (NT) during summer fallow for main plots, and conventional drill sowing (DS) or plastic film drill sowing (FM) for sub-plots.  Results showed that the maximum soil water storage (SWS) was under SS×FM treatment with values of 649.1 mm (2011–2012) and 499.4 mm (2012–2013).  The SWS during the 2011–2012 growing season were 149.7 mm higher than that in the 2012–2013 growing season.  And adoption of SS×FM significantly increased precipitation use efficiency (PUE) and water use efficiency (WUE) compared to other treatments for both seasons.  Moreover, adoption of SS×FM significantly increased yield by 13.1, 14.4, 47.3% and 25.9, 39.1, 35.7% than other three treatments during the two growing seasons, respectively.  In summary, combining subsoiling during summer fallow with plastic film drill sowing (SS×FM) increased SWS at sowing and effectively improved WUE, thus representing a feasible technology to improve grain yield of dryland winter wheat in the Loess Plateau of China.

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Enzymatic activity and chlorophyll fluorescence imaging of maize seedlings (Zea mays L.) after exposure to low doses of chlorsulfuron and cadmium ZHAO Li-juan, XIE Jing-fang, ZHANG Hong, WANG Zhen-tao, JIANG Hong-jin, GAO Shao-long 2018, 17(04): 826-836.  DOI: 10.1016/S2095-3119(17)61717-9 Abstract ( )   PDF in ScienceDirect   The aim of this research was to study the influence of chlorsulfuron residue and cadmium on the enzymatic activity and photosynthetic apparatus of maize (Zea mays L.) plants.  Chlorsulfuron and cadmium at 0.001 and 5.0 mg kg–1, respectively, were mixed and applied to soil prior to planting.  The levels of chlorsulfuron- and cadmium-induced stress to plants were estimated by growth, chlorophyll content, lipid peroxide content, enzyme activities, and major fluorescence parameters of chlorophyll (revealed by the fluorescence imaging system FluorCam).  Chlorsulfuron negatively affected the chlorophyll content, photochemical efficiency of photosystem II in the dark-adapted state, the maximum efficiency of photosystem II, photochemical quenching coefficient, and steady-state fluorescence decline ratio in the leaves of maize seedlings.  However, cadmium did not produce noticeable changes.  Plants that were exposed to both chlorsulfuron and cadmium showed an obvious increase in the steady-state fluorescence decline ratio.  These results implied that the seedlings possessed more resistance to cadmium than to chlorsulfuron and their resistance to chlorsulfuron toxicity was enhanced by the presence of cadmium.  The results also suggested that chlorophyll fluorescence imaging reveals overall alterations within the leaves but may not reflect small-scale effects on tissues, as numeric values of specific parameters are averages of the data collected from the whole leaf.

Horticulture

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The positive function of selenium supplementation on reducing nitrate accumulation in hydroponic lettuce (Lactuca sativa L.) LEI Bo, BIAN Zhong-hua, YANG Qi-chang, WANG Jun, CHENG Rui-feng, LI Kun, LIU Wen-ke, ZHANG Yi, FANG Hui, TONG Yun-xin 2018, 17(04): 837-846.  DOI: 10.1016/S2095-3119(17)61759-3 Abstract ( )   PDF in ScienceDirect   High nitrate (NO3−) in vegetables, especially in leaf vegetables poses threaten to human health.  Selenium (Se) is an important element for maintaining human health, and exogenous Se application during vegetable and crop production is an effective way to prevent Se deficiency in human bodies.  Exogenous Se shows positive function on plant growth and nutrition uptake under abiotic and/or biotic stresses.  However, the influence of exogenous Se on NO3− accumulation in hydroponic vegetables is still not clear.  In the present study, hydroponic lettuce plants were subjected to six different concentrations (0, 0.1, 0.5, 5, 10 and 50 µmol L–1) of Se as Na2SeO3.  The effects of Se on NO3− content, plant growth, and photosynthetic capacity of lettuce (Lactuca sativa L.) were investigated.  The results showed that exogenous Se positively decreased NO3− content and this effect was concentration-dependent.  The lowest NO3− content was obtained under 0.5 µmol L–1 Se treatment.  The application of Se enhanced photosynthetic capacity by increasing the photosynthesis rate (Pn), stomatal conductance (Cs) and the transpiration efficiency (Tr) of lettuce.  The transportation and assimilation of NO3− and activities of nitrogen metabolism enzymes in lettuce were also analysed.  The NO3− efflux in the lettuce roots was markedly increased, but the efflux of NO3− from the root to the shoot was decreased after treated with exogenous Se.  Moreover, Se application stimulated NO3− assimilation by enhancing nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase enzyme (GOGAT) activities.  These results provide direct evidence that exogenous Se shows positive function on decreasing NO3− accumulation via regulating the transport and enhancing activities of nitrogen metabolism enzyme in lettuce.  We suggested that 0.5 µmol L–1 Se can be used to reduce NO3− content and increase hydroponic lettuce yield.

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Structure and expression analysis of the sucrose synthase gene family in apple TONG Xiao-lei, WANG Zheng-yang, MA Bai-quan, ZHANG Chun-xia, ZHU Ling-cheng, MA Feng-wang, LI Ming-jun 2018, 17(04): 847-856.  DOI: 10.1016/S2095-3119(17)61755-6 Abstract ( )   PDF in ScienceDirect   Sucrose synthases (SUS) are a family of enzymes that play pivotal roles in carbon partitioning, sink strength and plant development.  A total of 11 SUS genes have been identified in the genome of Malus domestica (MdSUSs), and phylogenetic analysis revealed that the MdSUS genes were divided into three groups, named as SUS I, SUS II and SUS III, respectively.  The SUS I and SUS III groups included four homologs each, whereas the SUS II group contained three homologs.  SUS genes in the same group showed similar structural characteristics, such as exon number, size and length distribution.  After assessing four different tissues, MdSUS1s and MdSUS2.1 showed the highest expression in fruit, whereas MdSUS2.2/2.3 and MdSUS3s exhibit the highest expression in shoot tips.  Most MdSUSs showed decreased expression during fruit development, similar to SUS enzyme activity, but both MdSUS2.1 and MdSUS1.4 displayed opposite expression profiles.  These results suggest that different MdSUS genes might play distinct roles in the sink-source sugar cycle and sugar utilization in apple sink tissues.

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Physiological mechanisms of resistance to cold stress associated with 10 elite apple rootstocks WANG Yan-xiu, HU Ya, CHEN Bai-hong, ZHU Yan-fang, Mohammed Mujitaba Dawuda, Sofkova Svetla 2018, 17(04): 857-866.  DOI: 10.1016/S2095-3119(17)61760-X Abstract ( )   PDF in ScienceDirect   A study was conducted in attempting to identify the cold-resistant apple rootstocks and to establish a comprehensive evaluation system.  In this study, 10 elite apple dwarfing rootstocks (GM256, JM7, M26, M7, SC1, SH1, SH38, SH6, M9, and T337) were employed for the experiment and the following parameters were investigated under different low temperature stress conditions (0, –15, –20, –25, –30, and –35°C): the changes of the relative electrical conductivity (REC), anthocyanin content, protein content, soluble sugar content, soluble starch content, proline content, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity of the dormant branches.  The inflection temperature that could represent the plant tissue semi-lethal temperature (LT50) was obtained by the measurements of REC.  The LT50 was used to evaluate eight other indices.  The results showed that there was no significant correlation between LT50 and POD activity as well as between the soluble sugar, protein and proline contents at 0 and –15°C.  Soluble starch content at 0 and –15°C and anthocyanin content at –15–(–30)°C were significantly but negatively correlated to the LT50 and the MDA content at 0–(–20)°C was significantly positively correlated to the LT50.  Statistical analysis based on principal component analysis and LT50 showed that cold resistant apple rootstocks in the decreasing order from high to low as GM256, SH6, SH38, SH1, SC1, M26, M7, JM7, T337, and M9.

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Comparative analysis of flower-meristem-identity gene APETALA2 (AP2) codon in different plant species WU Yan-qing, LI Zhi-yuan, ZHAO Da-qiu, TAO Jun 2018, 17(04): 867-877.  DOI: 10.1016/S2095-3119(17)61732-5 Abstract ( )   PDF in ScienceDirect   The flower-meristem-identity gene APETALA2 (AP2), one of class-A genes, is involved in the establishment of the floral meristem and the forming of sepals and petals.  Codon usage bias (CUB) identifies differences among species, meanwhile dynamic analysis of base composition can identify the molecular mechanisms and evolutionary relationships of a specific gene.  In this study, eight coding sequences (CDS) of AP2 gene were selected from different plant species using the GenBank database.  Their nucleotide composition (GC content), genetic index, relative synonymous codon usage (RSCU) and relative codon usage bias (RCUB) were calculated with R Software to compare codon bias and base composition dynamics of AP2 gene codon usage patterns in different plant species.  The results showed that the usage of AP2 gene codons from different plant species were influened by GC bias, especially GC3s.  Overall, base composition analysis indicated that the usage frequency of codon AT in the gene coding sequence was higher than GC among AP2 gene CDS from different plant species.  Furthermore, most AP2 gene CDSs ended with AT; AGA, GCU and UGU had relatively high RSCU values as the most dominant codon; the usage characteristic of the AP2 gene codon in Malus domestica was similar to that of Vitis vinifera; Paeonia lactiflora was similar to Paeonia suffruticosa and Solanum lycopersicum was similar to Petunia×hybrida.  There was a moderate preference in the usage of AP2 gene codon among different plant species from relatively low frequency of optimal codon (Fop) values and high effective number of codons (ENC) value.  This study has revealed the usage characteristics of the AP2 gene codon from the comparision of AP2 gene codon preference and base dynamics in different plant species and provide a platform for further study towards transgenic engineering and codon optimization.

Plant Protection

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Rediscovery and analysis of Phytophthora carbohydrate esterase (CE) genes revealing their evolutionary diversity QIAN Kun, LI Deng-hui, LIN Run-mao , SHI Qian-qian, MAO Zhen-chuan, YANG Yu-hong, FENG Dong-xin, XIE Bing-yan 2018, 17(04): 878-891.  DOI: 10.1016/S2095-3119(17)61867-7 Abstract ( )   PDF (916KB) ( )   A continuous co-evolutionary arms-race between pathogens and their host plants promotes the development of pathogenic factors by microbes, including carbohydrate esterase (CE) genes to overcome the barriers in plant cell walls.  Identification of CEs is essential to facilitate their functional and evolutionary investigations; however, current methods may have a limit in detecting some conserved domains, and ignore evolutionary relationships of CEs, as well as do not distinguish CEs from proteases.  Here, candidate CEs were annotated using conserved functional domains, and orthologous gene detection and phylogenetic relationships were used to identify new CEs in 16 oomycete genomes, excluding genes with protease domains.  In our method, 41 new putative CEs were discovered comparing to current methods, including three CE4, 14 CE5, eight CE12, five CE13, and 11 CE14.  We found that significantly more CEs were identified in Phytophthora than in Hyaloperonospora and Pythium, especially CE8, CE12, and CE13 that are putatively involved in pectin degradation.  The abundance of these CEs in Phytophthora may be due to a high frequency of multiple-copy genes, supporting by the phylogenetic distribution of CE13 genes, which showed five units of Phytophthora CE13 gene clusters each displaying a species tree like topology, but without any gene from Hyaloperonospora or Pythium species.  Additionally, diverse proteins associated with products of CE13 genes were identified in Phytophthora strains.  Our analyses provide a highly effective method for CE discovery, complementing current methods, and have the potential to advance our understanding of function and evolution of CEs.

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Streptomyces sp. RP1A-12 mediated control of peanut stem rot caused by Sclerotium rolfsii Simi Jacob, Ramgopal Rao Sajjalaguddam, Hari Kishan Sudini 2018, 17(04): 892-900.  DOI: 10.1016/S2095-3119(17)61816-1 Abstract ( )   PDF in ScienceDirect   Sclerotium rolfsii Sacc. is a destructive soilborne fungal pathogen with a wide host range that includes peanuts.  Biological control offers an interesting alternative to fungicides for sustainable management of soilborne diseases.  The current investigation is aimed at evaluating one potential biocontrol agent Streptomyces sp. RP1A-12 for growth promotion and the management of peanut stem rot disease caused by S. rolfsii under field conditions.  Preliminary studies conducted under in vitro and the greenhouse conditions showed promising results against the stem rot pathogen.  Further in vitro and pot experiments conducted to assess Streptomyces sp. RP1A-12 for its growth promoting abilities using whole organisms have shown an increase in seed germination, root and shoot length.  Other parameters like nodule number and plant biomass were also significantly increased over control treatments indicating that the test bioagent possesses growth promoting abilities along with disease suppression capabilities.  Subsequently field studies were carried out for two consecutive rainy seasons.  The bioagent was applied as whole organism and partially purified crude metabolites.  Results indicate the bioagent reduced stem rot disease incidence by 64–67% and 22–49% respectively in two field trials conducted with notable increase in yield.  Partially purified Streptomyces sp. RP1A-12 metabolites exhibited an even greater effect in reducing the incidence and severity of stem rot compared to the pathogen inoculated control.

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Regionalization of wheat powdery mildew oversummering in China based on digital elevation ZOU Ya-fei, QIAO Hong-bo, CAO Xue-ren, Liu Wei, FAN Jie-ru, SONG Yu-li, WANG Bao-tong, ZHOU Yi-lin 2018, 17(04): 901-910.  DOI: 10.1016/S2095-3119(17)61851-3 Abstract ( )   PDF in ScienceDirect   Blumeria graminis f. sp. tritici, the pathogen that causes wheat powdery mildew, is one of the most important diseases affecting wheat production in China, and the oversummering is the key stage of wheat powdery mildew epidemic.  The more oversummering regionalization of wheat powdery mildew has played an important role in disease prediction, prevention and control.  In this study, we analyzed the correlation between oversummering data of wheat powdery mildew and the meteorological factors over the past years, and determined that temperature was the key meteorological factor influencing oversummering of wheat powdery mildew.  The average temperature at which wheat powdery mildew growth was terminated (26.2°C) was used as the threshold temperature to regionalize the oversummering range of wheat powdery mildew.  This regionalization was done using the GIS ordinary kriging method combined with the Digital Elevation model (DEM) of China.  The results showed that annual probability of oversummering region based on Model 26.2 were consistent with the actual survey of the more summer wheat powdery mildew.  Wheat powdery mildew oversummering regions in China mainly cover mountainous or high-altitude areas, and these regions form a narrow north-south oversummering zone.  Oversummering regions of wheat powdery mildew is mainly concentrated in the high-altitude wheat growing areas, including northern and southern Yunnan, northwestern Guizhou, northern and southern Sichuan, northern and southern Chongqing, eastern and southern Gansu, southeastern Ningxia, northern and southern Shaanxi, central Shanxi, western Hubei, western Henan, northern and western Hebei, western Liaoning, eastern Tibet, eastern Qinghai, western Xinjiang and other regions of China.

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Sub-lethal effects of Beauveria bassiana (Balsamo) on field populations of the potato tuberworm Phthorimaea operculella Zeller in China YUAN Hui-guo, WU Sheng-yong, LEI Zhong-ren,?Silvia I. Rondon, GAO Yu-lin 2018, 17(04): 911-918.  DOI: 10.1016/S2095-3119(17)61898-7 Abstract ( )   PDF in ScienceDirect   The potato tuberworm Phthorimaea operculella Zeller, is one of the most important potato pests worldwide including China.  Several reports indicate that P. operculella could be controlled biologically by the use of beneficial fungus such as Beauveria bassiana (Bals.-Criv) Vuill.  However, limited information is available under growing conditions in China.  Thus, this study evaluated the sub-lethal effects of B. bassiana on the offspring of P. operculella by the age-stage, two-sex life table.  First instar larva of P. operculella were treated with 1×107 conidia mL–1 of the fungus, and several biological parameters were evaluated.  The fecundity, duration of the egg stage, all larval stages, pre-adult stage, and total pre-oviposition period, were significantly shorter than the control treatment.  Offspring of treated parents, presented a net reproductive rate and mean generation time of 17.43 per day and 24.98 days, respectively, compared to 65.79 per day and 26.51 days for the untreated ones.  This study provides basic information to help understanding the potential long-term effects of entomopathogenic fungi on P. operculella.

Animal Science · Veterinary Medicine

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Effects of conditioners (single-layer, double-layer and retention-conditioner) on the growth performance, meat quality and intestinal morphology of growing and finishing pigs DUAN Hai-tao, LI Jun-guo, XUE Min, YANG Jie, DONG Ying-chao, LIANG Ke-hong, QIN Yu-chang 2018, 17(04): 919-927.  DOI: 10.1016/S2095-3119(17)61782-9 Abstract ( )   PDF in ScienceDirect   This experiment was conducted to investigate the effects of feed conditioners (single-layer, double-layer and retention-conditioner) on the growth performance, meat quality and intestinal morphology of pigs throughout the growing to finishing phase.  A total of 96 growing pigs ((28.70±3.20) kg) were selected and randomized into three treatment groups with four replicates per group.  Eight pigs were used per replicate for the 17-week feeding trial.  The grower diet was given at 0 to 6 weeks and a finisher diet was given at 6 to 17 weeks.  The treatments were as follows: SC diet (control; single-layer conditioning), DC diet (double-layer conditioning), and RC diet (retention-conditioning).  Starch gelatinization was significantly higher (P<0.05) in the RC treatment than in the SC treatment, however, there was no significant difference in the starch gelatinization between the DC group and the RC group.  In the growing phase, the feed to gain index (F:G) was significantly lower (P<0.05) in the RC group than in the SC and DC groups.  Between growing and finishing, the F:G was the lowest (P<0.05) in the SC group compared to the RC or DC group.  Drip loss, a measurement of meat quality, was significantly lower (P<0.05) in longissimus dorsi tissue collected from pigs fed the RC diet than in tissues collected from pigs fed the SC diet.  The intestinal quality of the duodenum and jejunum tissues showed a significant increase (P<0.05) in the crypt depth and villus height in the RC group compared to the SC- or DC-treated pigs.  These results demonstrated that the retention-conditioner treatment decreased the F:G in growing pigs, improved intestinal morphology and enhanced the meat quality in the finishing pigs.  However, the retention-conditioner treatment had a negative impact on growth performance in the finishing pigs.

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Immunogenicity and protective efficacy of DHBV DNA vaccines expressing envelope and capsid fusion proteins in ducks delivered by attenuated Salmonella typhimurium LIU Si-yang, JIA Ren-yong, LI Qing-qing, FENG Dai-shen, SHEN Hao-yue, YANG Cui, WANG Ming-shu, ZHU De-kang, CHEN Shun, LIU Ma-feng, ZHAO Xin-xin, YIN Zhong-qiong, JING Bo, CHENG An-chun 2018, 17(04): 928-939.  DOI: 10.1016/S2095-3119(17)61829-X Abstract ( )   PDF in ScienceDirect   Duck hepatitis B virus (DHBV) shares many basic characteristics with hepatitis B virus (HBV) and is an attractive model for vaccine development.  In this study, DHBV DNA vaccines were designed to express envelope and capsid fusion proteins to enhance the breadth of immune response in ducks.  Attenuated Salmonella typhimurium (SL7207) was used as a carrier and adjuvant to boost the magnitude of immune response.  Based on this strategy, novel DNA vaccines (SL7207-pVAX1-LC and SL7207-pVAX1-SC) were generated.  Growth kinetics, genetic stabilities and relative transcription levels of the L, S and C genes introduced by these vaccine strains were measured before inoculation to guarantee safety and efficacy.  The relative transcript levels of the CD4 and CD8 T genes and the antibody levels (IgY) in ducks receiving the vaccines were higher than those in single gene delivered groups.  Additionally, the copy number of covalently closed circular DNA in hepatocytes after DHBV challenge also provided evidence that our fusion vaccines could enhance the protective efficiency against DHBV infection in ducks.

Agricultural Economics and Management

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Estimating the average treatment effect of adopting stress tolerant variety on rice yield in China ZHOU Jie-hong, TANG Li-qun, Xiaohua Yu 2018, 17(04): 940-948.  DOI: 10.1016/S2095-3119(17)61848-3 Abstract ( )   PDF (824KB) ( )   Climate extremes, characterized by droughts and floods, have become one of the major constraints to sustainable improvement of rice productivity.  Variety choice, considered as one of the main adaptation measures, could help farmers reduce yield loss resulting from these extremes.  Based on a three-year panel survey of 1 080 Chinese rice farms in major rice producing provinces, we assume Hicksian neutral technology and employ an IV regression to estimate the average treatment effect (ATE) on rice yield for adopting stress tolerant variety, and find that farmers who adopted the stress tolerant variety on average increased rice yield by 15.5% in comparison to the non-adopters.

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Climate change and Chinese farmers: Perceptions and determinants of adaptive strategies ZHAI Shi-yan, SONG Gen-xin, QIN Yao-chen, YE Xin-yue, Leipnik Mark 2018, 17(04): 949-963.  DOI: 10.1016/S2095-3119(17)61753-2 Abstract ( )   PDF in ScienceDirect   Farmers’ perceptions, beliefs, adaptive strategies, and barriers regarding climate change are critical to promoting sustainable ecosystems and societal stability.  This paper is based on an extensive survey of 1 500 farmers and their households in Henan Province in China during 2013–2014.  Henan is the largest agricultural province in China with over 51 million farmers.  The survey results showed that approximately 57% of the respondents perceived the direct impact of climate change during the past 10 years, with 70.3% believing that climate change posed a risk to their livelihood.  Not surprisingly, most farmers reported that they have adopted new measures to mitigate the negative impacts of climate change.  The main barriers hindering farmers’ adopting adaptation measures were lack of funds and timely information.  A multinomial logit model revealed that land ownership, knowledge of crop variety and the causes of climate change, as well as the belief of climate change, were all positively related to the likelihood of employing adaptive strategies.  Moreover, the percentage of households engaging in agriculture activity, and years of engaging in farming were both negatively correlated with famer’s likelihood of adopting adaptation strategies.  More importantly, farmers with high incomes were less likely to adopt adaptive strategies and more willing to engage in other business activities.  In conclusion, it is important to communicate climate change related information and government policies in rural areas, promote farmer associations and other educational outreach efforts to assist Chinese farmers to deal with climate change.