杂交小麦应用是未来提高小麦产量的一种途径，当前部分杂交小麦品种株高的增加在一定程度上加大了其倒伏风险。本研究以两个抗倒伏性不同的杂交组合为试验材料，通过分析不同灌浆时期茎秆相关性状变化、基部第二节间转录组和代谢组数据及基部第二节间木质素合成积累等揭示其抗倒伏差异的形成机制。结果表明，抗倒伏杂交组合茎秆相关性状，如茎秆抗折力、穿刺强度、茎秆充实度及木质素含量（含G和S型单体）均显著高于倒伏敏感性组合。KEGG富集分析表明，灌浆后期差异代谢物和差异表达基因主要被显著富集到苯丙烷生物合成途径。本试验共鉴定了35个参与苯丙烷途径的关键调控基因，其中42%的基因在灌浆后期显著差异表达，且在显著差异表达基因中，超过80%的基因在抗倒伏组合中的表达显著高于其在倒伏敏感组合中的表达，而抗倒伏组合木质素合成途径中松柏醛、阿魏酸和松柏醇等中间代谢物显著低于倒伏敏感组合。综合分析表明，抗倒伏组合灌浆后期仍具有较高抗倒伏能力的关键在于其具有较高的木质素合成能力。本试验还通过对已审定杂交小麦和常规小麦品种的茎秆特征比较，提出了培育抗倒伏杂交小麦组合应关注的茎秆性状。

随着杂交小麦的应用面积逐渐增加，倒伏正在成为其获得高产的主要限制因素之一。然而，关于茎秆相关性状的配合力及其与抗倒伏杂种优势形成的研究较少。本研究，按照不完全双列杂交设计（NCII），以茎秆相关性状显著差异的3个不育系（母本）和8个恢复系（父本）为试验材料，配置24个杂交组合。对基部第二节间长度、基部第二节间抗折力等茎秆相关的8个性状开展主成分分析（PCA）、配合力分析及杂种优势分析。PCA结果表明，8个变量可被提取为两个主要因子，分别为正相关因子（因子1）和负相关因子（因子2），分别解释总变异的52.3％和33.2％。PCA和指标权重分析表明，因子1相关性状在抗倒伏优势形成中起主要作用，研究还表明，茎秆相关性状的遗传以加性效应为主。以恢复系R1，R4，R6及R7与不育系M3配置组合可获得具有较高抗倒伏能力的杂交组合，与其因子2相关性状具有较低的一般配合力效应（GCA），及因子1相关性状具有较高的GCA密切相关。杂种优势分析表明，因子1相关性状（除基部第二节间壁厚外）的GCA或特殊配合力效应（SCA）与抗倒伏杂种优势呈正相关关系。一般而言，抗倒伏杂种优势与不育系因子1相关性状GCA的相关系数显著高于其与恢复系的，此外，不育系因子1相关性状具有更高的方差值，表明，在配置杂交组合时应特别关注不育系因子1相关性状的选择。遗传分析表明，基部第二节间直径和重心高度的狭义遗传力明显低于其他性状（<60％），表明，在亲本选育时这两个性状适合在高世代进行选择。这些发现可为亲本选育和抗倒伏杂种优势的利用提供理论依据。

Because of the yield increase of 3.5–15% compared to conventional wheat, hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future.  In this study, we performed a principal component analysis (PCA) on two-line hybrids wheat and their parents using the grain weight (GW), the length of spike (LS), the kernel number of spike (KSN), and spike number (SPN) as variables.  The results showed that the variables could be classified into three main factors, the weight factor (factor 1), the quantity factor 1 (factor 2) and the quantity factor 2 (factor 3), which accounted for 37.1, 22.6 and 18.5%, respectively of the total variance in different agronomic variables, suggesting that the GW is an important indicator for evaluating hybrid combinations, and the grain weight of restorer line (RGW) could be used as a reference for parents selection.  The hybrid combination with a higher score in factor 1 direction and larger mid-parent heterosis (MPH) of the GW and its parents were used to carry out the analysis of grain filling, 1-aminocylopropane-1-carboxylicacid (ACC) and polyamine synthesis related genes.  The results suggested that the GW of superior grain was significantly higher than that of inferior grains in BS1453×JS1 (H) and its parents.  Both grain types showed a weight of H between BS1453 (M) and JS1(R), and a larger MPH, which may be caused by their differences in the active filling stage and the grain filling rate.  The ADP-glucose pyrophosphorylase (AGPase), granule bound starch synthase I (GBSSI), starch synthase III (SSS), and starch branching enzyme-I (SBE-I) expression levels of H were intermediated between M and R, which might be closely related to MPH formation of the GW.  Compared with R and H, the GW of M at maturity was the lowest.  The expression levels of spermidine synthase 2 (Spd2), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) had significantly positive correlations with the grain filling rate (r=0.77*, 0.51*, 0.59*), suggesting their major roles in the grain filling and heterosis formation.  These provide a theoretical basis for improving the GW of photo-thermo-sensitive male sterile lines (PTSMSL) by changing the endogenous polyamine synthesis in commercial applications.

    Porcine reproductive and respiratory syndrome virus (PRRSV) actively induces cell apoptosis both in vitro and in vivo, which can contribute critically to viral pathogenesis.  Previous studies have shown that the PRRSV nonstructural protein 4 (nsp4) is an important mediator of this process, but the underlying molecular details remain poorly understood.  In this study, we found that the PRRSV nsp4 interacted with the mitochondrial inner membrane protein cytochrome c1 (cyto.c1) and induced its proteolytic cleavage.  Interestingly, the cleaved N-terminal fragment of cyto.c1 was found to exert apoptotic activity, which could cause mitochondrial fragmentation, resulting in apoptotic cell death.  And RNA interference (RNAi) silencing experiments further confirmed the crucial role which cyto.c1 played in nsp4- and PRRSV-induced cell apoptosis.  Thus, our data provide an important piece of mechanistic clues for PRRSV-induced cell apoptosis and also elucidate a novel mechanism for the 3C-like proteases in this finding. 

    SWEETs (sugars will eventually be exported transporters) are a novel class of recently identified sugar transporters that play important roles in diverse physiological processes. However, only a few species of the plant SWEET gene family have been functionally identified. Up till now, there has been no systematic analysis of the SWEET gene family in Cucurbitaceae crops. Here, a genome-wide characterization of this family was conducted in cucumber (Cucumis sativus L.). A total of 17 CsSWEET genes were identified, which are not evenly distributed over the seven cucumber chromosomes. Cucumber SWEET protein sequences possess seven conserved domains and two putative serine phosphorylation sites. The phylogenetic tree of the SWEET genes in cucumber, Arabidopsis thaliana, and Oryza sativa was constructed, and all the SWEET genes were divided into four clades. In addition, a number of putative cis-elements were identified in the promoter regions of these CsSWEET genes: nine types involved in phytohormone responses and eight types involved in stress responses. Moreover, the transcript levels of CsSWEET genes were analyzed in various tissues using quantitative real-time polymerase chain reaction. A majority (70.58%) of the CsSWEET genes were confined to reproductive tissue development. Finally, 18 putative watermelon ClaSWEET genes and 18 melon CmSWEET genes were identified that showed a high degree of similarity with CsSWEET genes. The results from this study provided a basic understanding of the CsSWEET genes and may also facilitate future research to elucidate the function of SWEET genes in cucumber and other Cucurbitaceae crops.

In order to monitor plant chlorophyll content in real-time, a new vehicle-mounted detection system was developed to measure crop canopy spectral characteristics. It was designed to work as a wireless sensor network with one control unit and one measuring unit. The control unit included a personal digital assistant (PDA) device with a ZigBee wireless network coordinator. As the coordinator of the whole wireless network, the control unit was used to receive, display and store all the data sent from sensor nodes. The measuring unit consisted of several optical sensor nodes. All the sensor nodes were mounted on an on-board mechanical structure so that the measuring unit could collect the canopy spectral data while moving. Each sensor node contained four optical channels to measure the light radiation at the wavebands of 550, 650, 766, and 850 nm. The calibration tests verified a good performance in terms of the wireless transmission ability and the sensor measurement precision. Both stationary and moving field experiments were also conducted in a winter wheat experimental field. There was a high correlation between chlorophyll content and vegetation index, and several estimation models of the chlorophyll content were established. The highest R2 of the estimation models was 0.718. The results showed that the vehicle-mounted crop detection system has potential for field application.

The actions and interactions of acetochlor and As on the soil phosphatase activity were investigated after 1, 3, 6, 10, 15, 30 and 60 d of exposure under control conditions. The soils were exposed to various concentrations of acetochlor and As individually and simultaneously. The results showed that acetochlor, As only, and combined pollution all clearly inhibited soil phosphatase activity. The maximum inhibition ratios of soil phosphatase activity by acetochlor, As only and combined pollution were 36.44, 74.12 and 61.29%, respectively. Two kinetic models, ν=c/(1+bi) (model 1) and ν=c(1+ai)/(l+bi) (model 2), were used to describe the relationship between the concentrations of As and acetochlor and the activity of soil phosphatase. The semi-effect dose (ED50) values induced by As and acetochlor stress based on the inhibition of soil phosphatase were 18.1 and 33.11 mg kg-1, respectively, according to calculation by model 1. The interactive effect of acetochlor with As on soil phosphatase primarily consisted of significant antagonism effects at the higher concentrations tested. The step regression results show that the toxicity order was As (III)>acetochlor>As (III)×acetochlor throughout the incubation period.

In 2010, Chinese maize yields increased from 961.5 kg ha-1 in 1949 to 5 453.8 kg ha-1. This increase is the result of genetic improvements, an increase in nitrogen application, and refinement of planting densities. The objective of this study was to provide a theoretical basis for maize production research by analyzing the maize yield gain characteristics. Six varieties of maize were selected for the study; each selection is representative of a typical or commonly used maize variety from a specific decade, beginning from the 1950s and continuing through each decade into the 2000s. The selections and their corresponding decade were as follows: Baihe, 1950s; Jidan 101, 1960s; Zhongdan 2, 1970s; Yedan 13, 1980s; Zhengdan 958, 1990s; and Xianyu 335, 2000s. Each variety was planted under four different densities (37 500, 52 500, 67 500, and 82 500 plants ha-1) and four different nitrogen applications (0, 150, 225, and 300 kg ha-1) to study the effects on yield gain characteristics. The obtained results demonstrated that there was a maize yield increase of 123.19% between the 1950s variety and the 2000s variety. Modern Chinese maize varieties had a higher yield advantage. They also displayed the additional potential to acquire higher yield under increased planting densities and nitrogen applications. At the present cultivation levels (planting at 67 500 plants ha-1 with 225 kg ha-1 nitrogen application), the contribution types and corresponding yield increase percentages were as follows: genetic improvement, 45.37%; agronomic-management improvement, 30.94%; and genotype× agronomicmanagement interaction, 23.69%. At high-yielding cultivation levels (planting at 82 500 plants ha-1 with 300 kg ha-1 nitrogen application), the contribution types and corresponding yield increase percentages were as follows: genetic improvement, 31.30%; agronomic-management improvement, 36.23%; and genotype × agronomic-management interaction, 32.47%. The contribution of agronomic-management and genotype × agronomic-management interaction to yield increase would be larger with the corresponding management improvement. To further increase maize grain yield in China, researchers should further examine the effects of agronomic-management on maize yield and the adaptation of variety to agronomic-management.

Experiment was conducted at the Gongzhuling Experimental Station of Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Jilin Province, China, during 2009-2010. Six representative varieties of maize (Baihe in the 1950s, Jidan 101 in the 1960s, Zhongdan 2 in the 1970s, Yedan 13 in the 1980s, Zhengdan 958 in the 1990s, and Xianyu 335 in the 2000s) were each planted under two different densities (52 500 and 82 500 plants ha-1) and two different nitrogen application levels (150 and 300 kg ha-1). Root characteristics and distribution among soil layers were studied by the field root digging method. The results showed that root mass increased with the process of the growth and development of the plant, and it peaked at kernel filling stage, and decreased at maturity due to the root senesces. Root mass of different maize varieties from the 1950s to 1980s had a trend of increase, while it decreased for the modern varieties. Root length and root surface areas had the similar changing trend. The study suggested that early maize varieties may have root redundancy, and reducing root redundancy may be a direction for variety improvement for high yield. Root characteristics were affected by nitrogen application level and density; modern varieties were more suitable for higher fertilizer application level and density conditions. Root characteristics distribution among soil layers decreased by an exponent equation, but the regression coefficients of different varieties were different. Though the root length density (RLD) of every soil layer of different varieties also decreased by an exponent equation, there were large variations of RLD in every part of a layer.

The normalized difference vegetation index (NDVI) has proven to be typically employed to assess terrestrial vegetation conditions. However, one limitation of NDVI for drought monitoring is the apparent time lag between rainfall deficit and NDVI response. To better understand this relationship, time series NDVI (2000-2010) during the growing season in Sichuan Province and Chongqing City were analyzed. The vegetation condition index (VCI) was used to construct a new drought index, time-integrated vegetation condition index (TIVCI), and was then compared with meteorological drought indices-standardized precipitation index (SPI), a multiple-time scale meteorological-drought index based on precipitation, to examine the sensitivity on droughts. Our research findings indicate the followings: (1) farmland NDVI sensitivity to precipitation in study area has a time lag of 16-24 d, and it maximally responds to the temperature with a lag of about 16 d. (2) We applied the approach to Sichuan Province and Chongqing City for extreme drought monitoring in 2006 and 2003, and the results show that the monitoring results from TIVCI are closer to the published China agricultural statistical data than VCI. Compared to VCI, the best results from TIVCI3 were found with the relative errors of -4.5 and 6.36% in 2006 for drought affected area and drought disaster area respectively, and 5.11 and -5.95% in 2003. (3) Compared to VCI, TIVCI has better correlation with the SPI, which indicates the lag and cumulative effects of precipitation on vegetation. Our finding proved that TIVCI is an effective indicator of drought detection when the time lag effects between NDVI and climate factors are taken into consideration.