甘蔗近年来作为制糖和生物乙醇的原料引起了越来越多的关注，提高它的产量对保证食糖安全和生物能源生产至关重要。属间远缘杂交是作物产生遗传变异的高效途径之一，尤其是高倍体作物甘蔗。斑茅因其具有许多优良的农艺性状，已被广泛研究用于改良甘蔗的抗旱性和其它抗逆性。然而，甘蔗属物种和斑茅间的亲缘关系以及甘蔗杂交后代中斑茅染色体的组成都仍不清晰。与先前利用叶绿体基因组DNA进行的遗传分析不同，本研究基于不同物种全基因组单核苷酸多态性明确了斑茅与甘蔗的亲缘关系比高粱更近。此外，利用热带种基因组设计的寡核苷酸染色体特异涂染探针能够清晰地识别斑茅的染色体。本研究首次建立的寡聚核苷酸基因组原位杂交体系，可用于检测甘蔗杂交后代中斑茅染色体的易位和单条染色体遗传。值得注意的是，我们还发现在BC₁子代中斑茅的染色体出现了n, 2n和超2n的遗传方式。这些遗传方式的不同可能是由于减数第一次分裂染色体加倍、减数第一次分裂和第二次分裂染色体加倍或减数第二次分裂时姐妹染色单体不分离所导致的。这些结果将为进一步选择斑茅染色体进行甘蔗遗传改良提供重要依据。

炭疽病是大豆最重要的病害之一，平头炭疽菌和胶孢炭疽菌是其最主要的病原菌。啶氧菌酯属于QoI类杀菌剂，常用于作物炭疽病的防治。然而，我国大豆平头炭疽菌和胶孢炭疽菌对啶氧菌酯的敏感性、抗性风险和抗性分子机制尚不清楚。本研究建立了大豆平头炭疽菌和胶孢炭疽菌对啶氧菌酯的敏感基线，采用室内药剂驯化的方法诱导抗性突变体，并测定抗性突变体的适合度和交互抗性，同时比较分析抗性突变体和敏感菌株的cyt b基因cDNA序列，进一步利用分子对接明确敏感菌株和突变体Cyt b蛋白与啶氧菌酯的结合力。结果表明：供试的128株平头炭疽菌和121株胶孢炭疽菌对啶氧菌酯的EC₅₀值频率分布呈连续单峰曲线，平均EC₅₀值分别为0.7740和1.1561 μg mL^-1，该平均EC₅₀值可作为相对敏感基线监测未来田间大豆平头炭疽菌和胶孢炭疽菌对啶氧菌酯的敏感性变化。分别筛选获得11株平头炭疽菌和6株胶孢炭疽菌的抗性突变体，其EC₅₀值分别为5.40–152.96 µg mL^-1、13.53–28.30 μg mL^-1。抗性突变体在分生孢子的产生、萌发和致病性方面表现出与亲本菌株相似或更高的生存适合度。啶氧菌酯与吡唑醚菌酯之间存在交互抗性，而与氟啶胺、苯醚甲环唑及丙环唑之间无交互抗性。平头炭疽菌7株高抗突变体（RF > 100）cyt b基因427位碱基由G突变为A，所编码的Cyt b蛋白143位由甘氨酸（G）突变为丝氨酸（S），4株中抗突变体（RF < 50）cyt b基因409位碱基由G突变为A，所编码的Cyt b蛋白137位由甘氨酸（G）突变为精氨酸（R）。分子对接验证发现G143S和G137R突变是平头炭疽菌对啶氧菌酯产生抗药性的主要机制。胶孢炭疽菌抗性突变体cyt b基因未发生突变。温室试验结果表明，啶氧菌酯不能有效地防治高抗突变体，对中抗突变体的防效也显著下降。总之，G143S和G137R是大豆平头炭疽菌对啶氧菌酯产生抗药性的主要机制，大豆平头炭疽菌和胶孢炭疽菌对啶氧菌酯的抗性风险为中至高等，生产中应对QoI类杀菌剂实施抗性监测，并采取有效的抗性管理策略。

干旱是造成冬小麦减产的最主要的自然灾害之一，然而气候变化背景下干旱发生的机制及其时空格局仍不明确。本研究基于华北平原1958-2015年气象站点的长时间序列气象数据，采用敏感性分析，M-K检测以及斜率估计等方法，分析了不同气象因素对冬小麦干旱风险的影响机制。结果表明，近60年来冬小麦生育期内气象因子发生了显著的变化，导致冬小麦面临着严重的干旱风险（生长季内水分亏缺量达到350 mm），尤其在拔节-抽穗和抽穗-成熟期这两个产量形成的关键时期面临的干旱威胁更加严重。冬小麦生育阶段的干旱风险和气象因子呈现较大的时空分异特征。尽管降水对于干旱风险格局起主导作用，但是在冬小麦生长的关键阶段，气温升高和相对湿度降低等气象因素的变化都将加剧其干旱风险。过去几十年中近90%的气象站点温度都呈明显的上升趋势，如果未来气温持续升高，冬小麦的水分亏缺和干旱风险将会进一步加剧。研究结果可为作物生产有效适应未来气候变化和保障区域粮食安全提供基础支撑。

High-performance liquid chromatography (HPLC) was employed to determine drug release rates based on emamectin benzoate concentrations in the medium.  Release kinetics equations were used to fit the drug release behavior.  The effects of particle size and release medium pH on the release rate were also investigated.  The indoor toxicity of emamectin benzoate-loaded polylactic acid microspheres on the diamondback moth larva (Plutella xylostella) was studied to explore drug sustained-release performance.  In acidic and neutral media, the drug release behavior of the microspheres was in accord with the first-order kinetics equation.  Increasing the spray dosage of emamectin benzoate-loaded polylactic acid microspheres initially resulted in an equivalent insecticidal efficacy with the conventional emamectin benzoate microemulsion.  However, the drug persistence period was four-fold longer than that observed using the conventional formulation.  The developed emamectin benzoate-loaded polylactic acid microspheres showed dramatic sustained-release performance.  A treatment threshold of greater than 35 mg mL^–1 was established for an efficient accumulated release concentration of emamectin benzoate-loaded microspheres.

    Obtaining transgenic plants is a common method for analyzing gene function. Unfortunately, stable genetic transformation is difficult to achieve, especially for plants (e.g., soybean), which are recalcitrant to genetic transformation. Transient expression systems, such as Arabidopsis protoplast, Nicotiana leaves, and onion bulb leaves are widely used for gene functional studies. A simple method for obtaining transgenic soybean callus tissues was reported recently. We extend this system with simplified culture conditions to gene functional studies, including promoter analysis, expression and subcellular localization of the target protein, and protein-protein interaction. We also evaluate the plasticity of this system with soybean varieties, different vector constructs, and various Agrobacterium strains. The results indicated that the callus transformation system is efficient and adaptable for gene functional investigation in soybean genotype-, vector-, and Agrobacterium strain-independent modes. We demonstrated an easy set-up and practical homologous strategy for soybean gene functional studies.

    Wheat and maize are increasingly used as alternative crops to sunflower monocultures that dominate the Hetao Irrigation District in China. Shifts from sunflower monocultures to alternate cropping systems may have significant effects on belowground microbial communities which control nutrient cycling and influence plant productivity. In this research, rhizosphere bacterial communities were compared among sunflower, wheat and maize cropping systems by 454 pyrosequencing. These cropping systems included 2 years wheat (cultivar Yongliang 4) and maize (cultivar Sidan 19) monoculture, more than 20 years sunflower (cultivar 5009) monoculture, and wheat-sunflower and maize-sunflower rotation. In addition, we investigated rhizosphere bacterial communities of healthy and diseased plants at maturity to determine the relationship between plant health and rotation effect. The results revealed taxonomic information about the overall bacterial community. And significant differences in bacterial community structure were detected among these cropping systems. Eight of the most abundant groups including Proteobacteria, Bacteroidetes, Acidobacteria, Gemmatimonadetes, Chloroflexi, Actinobacteria, Planctomycetes and Firmicutes accounted for more than 85% of the sequences in each treatment. The wheat-wheat rhizosphere had the highest proportion of Acidobacteria, Bacteroidetes and the lowest proportion of unclassified bacteria. Wheat-sunflower cropping system showed more abundant Acidobacteria than maize-sunflower and sunflower monoculture, exhibiting some influences of wheat on the succeeding crop. Maize-maize rhizosphere had the highest proportion of γ- Proteobacteria, Pseudomonadales and the lowest proportion of Acidobacteria. Sunflower rotation with wheat and maize could increase the relative abundance of the Acidobacteria while decrease the relative abundance of the unclassified phyla, as was similar with the health plants. This suggests some positive impacts of rotation with wheat and maize on the bacterial communities within a single field. These results demonstrate that different crop rotation systems can have significant effects on rhizosphere microbiomes that potentially alter plant productivities in agricultural systems.

      Annual ryegrass (Lolium multiflorum Lam.), a non-leguminous winter cover crop, has been adopted to absorb soil native N to minimize N loss from an intensive double rice cropping system in southern China, but a little is known about its effects on rice grain yield and rice N use efficiency. In this study, effects of ryegrass on double rice yield, N uptake and use efficiency were measured under different fertilizer N rates. A 3-year (2009–2011) field experiment arranged in a split-plot design was undertaken. Main plots were ryegrass (RG) as a winter cover crop and winter fallow (WF) without weed. Subplots were three N treatments for each rice season: 0 (N₀), 100 (N₁₀₀) and 200 kg N ha^–1 (N₂₀₀). In the 3-year experiment, RG reduced grain yield and plant N uptake for early rice (0.4–1.7 t ha^–1 for grain yield and 4.6–20.3 kg ha^–1 for N uptake) and double rice (0.6–2.0 t ha^–1 for grain yield and 6.3–27.0 kg ha^–1 for N uptake) when compared with WF among different N rates. Yield and N uptake decrease due to RG was smaller in N₁₀₀ and N₂₀₀ plots than in N₀ plots. The reduction in early rice grain yield in RG plots was associated with decrease number of panicles. Agronomic N use efficiency and fertilizer N recovery efficiency were higher in RG plots than winter fallow for early rice and double rice among different N rates and experimental years. RG tended to have little effect on grain yield, N uptake, agronomic N use efficiency, and fertilizer N recovery efficiency in the late rice season. These results suggest that ryegrass may reduce grain yield while it improves rice N use efficiency in a double rice cropping system.

The importance of soil organic carbon (SOC) sequestration in agricultural soils as climate-change-mitigating strategy has become an area of focus by the scientific community in relation to soil management. This study was conducted to determine the temporal effect of different tillage systems and residue management on distribution, storage and stratification of SOC, and the yield of rice under double rice (Oryza sativa L.) cropping system in the southern China. A tillage experiment was conducted in the southern China during 2005–2011, including plow tillage with residue removed (PT0), plow tillage with residue retention (PT), rotary tillage with residue retention (RT), and no-till with residue retention on the surface (NT). The soil samples were obtained at the harvesting of late rice in October of 2005, 2007 and 2011. Multiple-year residue return application significantly increased rice yields for the two rice-cropping systems; yields of early and late rice were higher under RT than those under other tillage systems in both years in 2011. Compared with PT0, SOC stocks were increased in soil under NT at 0–5, 5–10, 10–20, and 20–30 cm depths by 33.8, 4.1, 6.6, and 53.3%, respectively, in 2011. SOC stocks under RT were higher than these under other tillage treatments at 0–30 cm depth. SOC stocks in soil under PT were higher than those under PT0 in the 0–5 and 20–30 cm soil layers. Therefore, crop residues played an important role in SOC management, and improvement of soil quality. In the 0–20 cm layer, the stratification ratio (SR) of SOC followed the order NT>RT>PT>PT0; when the 0–30 cm layer was considered, NT also had the highest SR of SOC, but the SR of SOC under PT was higher than that under RT with a multiple-year tillage practice. Therefore, the notion that conservation tillage lead to higher SOC stocks and soil quality than plowed systems requires cautious scrutiny. Nevertheless, some benefits associated with RT system present a greater potential for its adoption in view of the multiple-year environmental sustainability under double rice cropping system in the southern China.

Excessive use of N fertilizer in intensive agriculture can increase crop yield and at the same time cause high carbon (C) emissions. This study was conducted to determine optimized N fertilizer application for high grain yield and lower C emissions in summer corn (Zea mays L.). A field experiment, including 0 (N0), 75 (N75), 150 (N150), 225 (N225), and 300 (N300) kg N ha–1 treatments, was carried out during 2010–2012 in the North China Plain (NCP). The results showed that grain yield, input energy, greenhouse gas (GHG) emissions, and carbon footprint (CF) were all increased with the increase of N rate, except net energy yield (NEY). The treatment of N225 had the highest grain yield (10 364.7 kg ha–1) and NEY (6.8%), but the CF (0.25) was lower than that of N300, which indicates that a rate of 225 kg N ha–1 can be optimal for summer corn in NCP. Comparing GHG emision compontents, N fertilizer (0–51.1%) was the highest and followed by electricity for irrigation (19.73–49.35%). We conclude that optimazing N fertilizer application rate and reducing electricity for irrigation are the two key measures to increase crop yield, improve energy efficiency and decrease GHG emissions in corn production.

Salinity is one of the major abiotic factors affecting the growth and productivity of crops in Hetao Irrigation District, China. In this study, the salinity tolerances of three local crops, wheat (Triticum aestinum L.), maize (Zea mays L.) and sunflower (Helianthus annuus L.), growing in 76 farm fields are evaluated with modified discount function. Salinity ecological zones appropriate for these local crops are characterized and a case study is presented for crop salinity ecological zoning. The results show that the yield reductions of wheat, maize and sunflower when grown in saline soils are attributed primarily to a reduction in spikelet number, 1 000-grain weight and seed number per head, respectively. Sunflower is the most tolerant crop among the three which had a salinity tolerance index (ST-index) of 12.24, followed by spring maize and spring wheat with ST-Indices of 9.00 and 7.43, respectively. According to the crop salinity tolerance results, the arable land in the Heping Village of this district was subdivided into four salinity ecological zones: the most suitable, suitable, sub-suitable and unsuitable zones. The area proportion of the most suitable zone for wheat, maize and sunflower within the Heping Village was 27.5, 46.5 and 77.5%, respectively. Most of the most suitable zone occurred in the western part of the village. The results of this study provide the scientific basis for optimizing the local major crop distribution and improving cultural practices management in Hetao Irrigation District.

Based on climate data from 254 meteorological stations, this study estimated the effects of climate change on rice planting boundaries and potential yields in the southern China during 1951-2010. The results indicated a significant northward shift and westward expansion of northern boundaries for rice planting in the southern China. Compared with the period of 1951-1980, the average temperature during rice growing season in the period of 1981-2010 increased by 0.4°C, and the northern planting boundaries for single rice cropping system (SRCS), early triple cropping rice system (ETCRS), medium triple cropping rice system (MTCRS), and late triple cropping rice system (LTCRS) moved northward by 10, 30, 52 and 66 km, respectively. In addition, compared with the period of 1951-1980, the suitable planting area for SRCS was reduced by 11% during the period of 1981-2010. However, the suitable planting areas for other rice cropping systems increased, with the increasing amplitude of 3, 8, and 10% for ETCRS, MTCRS and LTCRS, respectively. In general, the light and temperature potential productivity of rice decreased by 2.5%. Without considering the change of rice cultivars, the northern planting boundaries for different rice cropping systems showed a northward shift tendency. Climate change resulted in decrease of per unit area yield for SRCS and the annual average yields of ETCRS and LTCRS. Nevertheless, the overall rice production in the entire research area showed a decreasing trend even with the increasing trend of annual average yield for MTCRS.

Adequate freshwater supply has become an issue of increasing local and international concern. Reducing water use in agriculture, which is the largest water using sector of the economy, is both important and urgent. The aim of this paper was to quantify how recent cropping pattern changes have influenced water resources in the great Beijing metropolitan area, an expanding megacity which also includes rural counties. Crop production affects blue water use through water consumption and water pollution, the latter assessed here using a critical dilution method. From 1990 to 2010, the total blue water used by crop production declined due to a decrease in overall cropped area, initially in response to local government policies favouring urban development. However, the average blue water use per hectare increased from 2 112 m3 ha-1 yr-1 in 1990 to 2 764 m3 ha-1 yr-1 in 2003, largely as the result of a transition from cereal to vegetable crops, and in particular an increase in intensively managed plastic and glass covered vegetable production systems. Current policies aim to conserve agricultural land, in the interests of food security, and to stimulate cereal production systems with higher ecosystem services provision. As such, in 2010 the average blue water use was 2 425 m3 ha-1 yr-1. These results demonstrate that cropping pattern changes in peri-urban regions and rural communities surrounding the Beijing metropolitan area can have a substantial impact on water resources. They also highlight the tradeoffs between food production and urban and industrial water supply and the need for integrated policy development.

To establish a suitable and effective protocol of protein extraction for two-dimensional gel electrophoresis (2-DE) analysis in kenaf leaf tissues, three extraction methods (trichloroacetic acid/acetone, urea/thiourea, and phenol extraction methods) were applied to the extraction of kenaf leaf protein. The results were compared in regard to protein extraction efficiency, sodiumdodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and 2-DE gels. Furthermore, the 2-DE system was optimized for four aspects: the pH range of IPG (immobilized pH gradient) stripes, sampling methods, sample volumes, and concentration of polyacrylamide gels. The data presented showed that the phenol extraction method is the best method to perform 2-DE analysis of kenaf leaf protein. The protein extracted from phenol extraction method reached the purity of (26.40±0.859)%, showed (25.67±1.53) protein bands in one dimension SDS-PAGE gels, and (1 374±54.44) protein spots on 2-DE gels. The research also indicates that kenaf leaf protein spots were distributed mainly within the pH range of 4-8. More clear background with a better distribution effect and many protein spots could be obtained on 2-DE gels under the conditions of active rehydration loading, 24 cm IPG strips (linear pH gradient of 4-7), 1.4 mg samples, and 12% SDS-PAGE gels.