2009年在中国首次发现了柑橘褪绿矮缩病毒（CCDaV），该病毒在云南瑞丽造成柠檬大量发病、减产，损失严重。目前，CCDaV在中国其它柑橘种植省份的发生分布和流行趋势尚不清楚。为了系统掌握CCDaV在中国的发生分布及其分子特性，本研究于2017-2019年，从中国11个柑橘主要生产省份采集了1,772份柑橘样品，通过PCR检测发现，采自广西省、云南省和广东省的134份柑橘样品感染了CCDaV。其中感病品种分别为红宝石蜜柚（50.8%）、泰国青柚（24.0%）、尤力克柠檬（20.8%）、墨西哥莱檬（20.0%）、塔希提莱檬（18.2%）和三红蜜柚（3.2%）。在采集的甜橙、宽皮柑橘、杂柑、枳、葡萄柚和金柑等柑橘类型样品中均没有检测出CCDaV。与前期的研究结果相比，CCDaV在中国的发生区域正在逐步扩大，且感病品种的种类也在增加。此外，CCDaV在红宝石蜜柚、泰国青柚和三红蜜柚新梢上产生的症状较其在尤力克柠檬上更为严重，除产生典型的“V”型叶，叶片扭曲、畸形，黄化外，CCDaV在上述3种柚类品种上还能产生严重的脉明症状。本研究选取了17个CCDaV毒株与GenBank数据库中已知的15个CCDaV毒株进行全系列分析，结果显示CCDaV的序列保守性高，所有 32个CCDaV毒株的核苷酸相似性大约为99%-100%。系统发育树分析表明，CCDaV毒株间的亲缘关系与其采样地和寄主存在相关性。根据地理来源和寄主种类的差异，CCDaV毒株被划分成了4个不同的类群，其中中国和土耳其的CCDaV毒株属于不同的类群。此外，还首次证明中国的CCDaV毒株可能存在多个起源中心，且部分毒株可能来自泰国。本研究结果为明确CCDaV在中国的发生分布、流行规律，以及遗传演化提供了重要的理论依据。

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.

Seasonal soil freeze-thaw events may enhance soil nitrogen transformation and thus stimulate nitrous oxide (N₂O) emissions in cold regions.  However, the mechanisms of soil N₂O emission during the freeze-thaw cycling in the field remain unclear.  We evaluated N₂O emissions and soil biotic and abiotic factors in maize and paddy fields over 20 months in Northeast China, and the structural equation model (SEM) was used to determine which factors affected N₂O production during non-growing season.  Our results verified that the seasonal freeze-thaw cycles mitigated the available soil nitrogen and carbon limitation during spring thawing period, but simultaneously increased the gaseous N₂O-N losses at the annual time scale under field condition.  The N₂O-N cumulative losses during the non-growing season amounted to 0.71 and 0.55 kg N ha^–1 for the paddy and maize fields, respectively, and contributed to 66 and 18% of the annual total.  The highest emission rates (199.2–257.4 μg m^–2 h^–1) were observed during soil thawing for both fields, but we did not observe an emission peak during soil freezing in early winter.  Although the pulses of N₂O emission in spring were short-lived (18 d), it resulted in approximately 80% of the non-growing season N₂O-N loss.  The N₂O burst during the spring thawing was triggered by the combined impact of high soil moisture, flush available nitrogen and carbon, and rapid recovery of microbial biomass.  SEM analysis indicated that the soil moisture, available substrates including NH₄⁺ and dissolved organic carbon (DOC), and microbial biomass nitrogen (MBN) explained 32, 36, 16 and 51% of the N₂O flux variation, respectively, during the non-growing season.  Our results suggested that N₂O emission during the spring thawing make a vital contribution of the annual nitrogen budget, and the vast seasonally frozen and snow-covered croplands will have high potential to exert a positive feedback on climate change considering the sensitive response of nitrogen biogeochemical cycling to the freeze-thaw disturbance.   

Shortages and fluctuations in precipitation are influential limiting factors for the sustainable cultivation of rain-fed winter wheat on the Loess Plateau of China.  Plastic film mulching is one of the most effective water management practices to improve soil moisture, and may be useful in the Loess Plateau for increasing soil water storage.  A field experiment was conducted from July 2010 to June 2012 on the Loess Plateau to investigate the effects of mulching time and rates on soil water storage, evapotranspiration (ET), water use efficiency (WUE), and grain yield.  Six treatments were conducted: (1) early mulching (starting 30 days after harvest) with whole mulching (EW); (2) early mulching with half mulching (EH); (3) early mulching with no mulching (EN); (4) late mulching (starting 60 days after harvest) with whole mulching (LW); (5) late mulching with half mulching (LH); and (6) late mulching with no mulching (LN).  EW increased precipitation storage efficiency during the fallow periods of each season by 18.4 and 17.8%, respectively.  EW improved soil water storage from 60 days after harvest to the booting stage and also outperformed LN by 13.8 and 20.9% in each growing season.  EW also improved spike number per ha by 13.8 and 20.9% and grain yield by 11.7 and 17.4% during both years compared to LN.  However, EW decreased WUE compared with LN.  The overall results of this study demonstrated that EW could be a productive and efficient practice to improve wheat yield on the Loess Plateau of China.  

   Leaves play a key role in photosynthesis in rice plants. The premature senescence of such plants directly reduces the accumulation of photosynthetic products and also affects yield and grain quality significantly and negatively. A novel premature senescence mutant, mps1 (mid-late stage premature senescence 1), was identified from a mutant library consisting of ethyl methane sulfonate (EMS) induced descendants of Jinhui 10, an elite indica restorer line of rice. The mutant allele, mps1, caused no phenotypic differences from the wild type (WT), Jinhui 10, but drove the leaves to turn yellow when mutant plants grew to the tillering stage, and accelerated leaf senescence from the filling stage to final maturation. We characterized the agronomic traits, content of photosynthetic pigments and photosynthetic efficiency of mps1 and WT, and fine-mapped MPS1. The results showed that the MPS1-drove premature phenotype appeared initially on the leaf tips at the late tillering stage and extended to the middle of leaves during the maturing stage. Compared to the WT, significant differences were observed among traits of the number of grains per panicle (–31.7%) and effective number of grains per panicle (–38.5%) of mps1 individuals. Chlorophyll contents among the first leaf from the top (Top 1st), the second leaf from the top (Top 2nd) and the third leaf from the top (Top 3rd) of mps1 were significantly lower than those of WT (P<0.05), and the levels of photosynthetic efficiency from Top 1st to the forth leaf from the top (Top 4th) of mps1 were significantly lower than those of WT (P<0.01). Results from the genetic analysis indicated that the premature senescence of mps1 is controlled by a recessive nuclear gene, and this locus, MPS1 is located in a 37.4-kb physical interval between the markers Indel145 and Indel149 on chromosome 6. Genomic annotation suggested eight open reading frames (ORFs) within this physical region. All of these results will provide informative references for the further researches involving functional analyses and molecular mechanism exploring of MPS1 in rice.

The excessive nitrogen (N) fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency (NRE). Under an intensive rice system in the Ningxia irrigation region, China, environmental friendly N management practices are heavily needed to balance the amount of N input for optimum crop production while minimize the nitrogen loss. The objective of this study was to determine the influences of side-dressing (SD) technique in mechanical transplanting systems on the NRE, N leaching losses and rice yield in anthropogenic-alluvial soil during two rice growing seasons (2010-2011). Four fertilizer N treatments were established, including conventional urea rate (CU, 300 kg ha–1 yr–1); higher SD of controlled-release N fertilizer rate (SD1, 176 kg ha–1 yr–1); lower SD of controlled-release N fertilizer rate (SD2, 125 kg ha–1 yr–1); and control (CK, no N fertilizer). Field lysimeters were used to quantify drainage from undisturbed soil during six rice growing stages. Meanwhile, the temporal variations of total nitrigen (TN), NO3 –-N, and NH4 +-N concentrations in percolation water were examined. The results showed that SD1 substantially improved NRE and reduced N leaching losses while maintaining rice yields. Across two years, the averaged NRE under SD1 treatment increased by 25.5% as relative to CU, but yet the rice yield was similar between two treatments. On average, the nitrogen loss defined as TN, NH4 +-N, and NO3 –-N under the SD1 treatment reduced by 27.4, 37.2 and 24.1%, respectively, when compared with CU during the study periods. Although the SD2 treatment could further reduce N leaching loss to some extent, this technique would sharply decline rice yield, with the magnitude of as high as 21.0% relative to CU treatment. Additionally, the average NRE under SD2 was 11.2% lower than that under SD1 treatment. Overall, the present study concluded that the SD technique is an effective strategy to reduce N leaching and increase NRE, thus potentially mitigate local environmental threat. We propose SD1 as a novel alternative fertilizer technique under an irrigated rice-based system in Ningxia irrigation region when higher yields are under consideration.

A total of 479 bacterial strains were isolated from brine (Bohai, Qinhuangdao City, Hebei Province, China). Bioassay results indicated that 4 strains named Ha1, Ha17, Ha38, and Ha384 had herbicidal activity. And strain Ha1 had the highest effective herbicidal activity. As a result, this study aims to identify strain Ha1, characterize its physiological and biological activities, evaluate the herbicidal activity of its metabolites, and develop a ‘pesta’ formulation and assess its effectiveness on Digitaria sanguinalis. Ha1 was identified as Serratia marcescens based on 16S rDNA sequencing. This strain has a flagellum, a diameter of 0.5 to 0.8 μm, and a length of 0.9 to 2.0 μm. The indole test shows positive results, and the catalase enzyme exhibits strong positive reactions. Results further showed that the inhibitory concentration (IC50) of the crude extracts to D. sanguinalis radicula and coleoptile were 3.332 and 2.828 mg mL–1, respectively. Both the suppression of D. sanguinalis and the cell viability of the Ha1 formulation in ‘pesta’ were higher when stored at 4°C than at (25±2)°C. These results indicated that S. marcescens Ha1 can potentially be used as a biocontrol agent against D. sanguinalis.

Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) catalyses phosphoenolpyruvate (PEP) to yield oxaloacetate, which is involved in protein biosynthesis. Pyruvate kinase (PK; EC 2.7.1.40) catalyzes PEP to yield pyruvate, which is involved in fatty acid synthesis. In this study, five PEPC genes (AhPEPC1, AhPEPC2, AhPEPC3, AhPEPC4, and AhPEPC5) from peanut have been cloned. Using a quantitative real-time RT-PCR approach, the expression pattern of each gene was monitored during the seed development of four peanut varieties (E11, Hebeigaoyou, Naihan 1, and Huayu 26). It was found that these five genes shared similar expression behaviors over the developmental stages of E11 with high expression levels at 30 and 40 d after pegging (DAP); whereas these five genes showed irregular expression patterns during the seed development of Hebeigaoyou. In Naihan 1 and Huayu 26, the expression levels of the five genes remained relatively high in the first stage. The PEPC activity was monitored during the seed development of four peanut varieties and seed oil content was also characterized during whole period of seed development. The PEPC activity followed the oil accumulation pattern during the early stages of development but they showed a significantly negative correlation thereafter. These results suggested that PEPC may play an important role in lipid accumulation during the seed development of four peanut varieties tested.