土壤调理剂中添加硅和有机肥可抑制重金属离子从土壤向作物的转移，但目前并不清楚硅和有机肥如何通过影响土壤性质和微生态环境进而减少水稻的镉积累。本研究通过两地田间实验分析了含硅和有机肥的L型土壤调理剂对细菌和真菌群落多样性、土壤pH、有机质及有效硅含量的影响。结果表明，随着土壤调理剂中硅和有机肥含量的增加，两个试验点的水稻产量分别增加了16.8%~25.8%和6.8%~13.1%, 稻米Cd含量显著降低了8.2%~21.1%和10.8%~40.6%。土壤微生物组学分析证明与镉吸附、螯合相关的Firmicutes和Actinobacteriota细菌和与大分子物质降解有关的Basidiomycota真菌种群丰度的增加，有利于抑制土壤中镉的活性（土壤ESC-Cd降低了14.4%~14.8%和18.1%~20.6%），这与施用土壤调理剂引起有机质和有效硅含量增加有关。总之，L型土壤调理剂中的有机质和硅可通过调节土壤中镉钝化优势菌群，降低土壤镉有效性，最终减少稻米镉积累。

株型和叶色是棉花纤维产量的重要影响因素。本研究基于遗传分析、茎秆石蜡切片和植物激素处理方法，发现棉花矮红株突变体（DR）是一个赤霉素敏感型突变体，由一个单显性基因位点突变引起，将其命名为GhDR。通过BSA-seq结合靶向测序基因型检测（GBTS）方法将控制突变性状基因定位在A09 染色体约197 kb的候选区间内，包含 25 个注释基因。基于候选基因的注释信息，及其在突变体和正常植株之间的序列和表达差异，GH_A09G2280基因被认为是控制矮红突变体表型的最佳候选基因。在DR突变体GhDR/GH_A09G2280基因编码区发现了一个2 bp的缺失，导致GhDR基因产生移码突变，蛋白翻译提前终止。GhDR是拟南芥AtBBX24的同源基因，编码B-box锌指蛋白。移码缺失导致GhDR 的C末端缺失了核定位结构域和VP结构域，并改变了其亚细胞定位结果。比较转录组分析表明，在DR突变体中，参与赤霉素生物合成和信号转导的关键基因下调表达，而与赤霉素降解和花青素生物合成相关基因上调表达。本研究初步揭示了GhDR基因同时调控棉花株型和花青素积累的潜在分子机制。

柑橘黄化斑驳相关病毒（Citrus yellow mottle-associated virus，CiYMaV）属马铃薯X病毒属（Potexvirus）、印度柑橘病毒亚属（Mandarivirus），最早于2018年在巴基斯坦被发现，目前该病毒在巴基斯坦多地柑橘产区有发生。本研究首先借助植物双元表达载体pCass4-RZ构建了3个CiYMaV的全长cDNA克隆（pCiYMaV-FL-1、pCiYMaV-FL-18和pCiYMaV-FL-22），随后通过农杆菌真空浸润接种强德勒柚（Citrus grandis）验证其侵染活性。结果表明，在接种40-60天，3个克隆均引起严重的叶脉黄化、叶片斑驳和植株矮化的症状。直接组织点免疫（direct tissue blot immunoassay，DTBIA）和反转录聚合酶链式反应（reverse transcription polymerase chain reaction，RT-PCR）的检测结果表明3个克隆的侵染率为94.7-100%。尽管3个克隆引发的症状相似，pCiYMaV-FL-22在接种60天时，其在植株内的RNA和蛋白积累水平最高。因此，选择pCiYMaV-FL-22将其接种到7种柑橘和3种草本寄主上，结果表明pCiYMaV-FL-22能成功侵染7种柑橘寄主，并且在5个柑橘品种上引起明显症状。通过透射电镜，在接种pCiYMaV-FL-22的柑橘植株组织中观察到长线型、弯曲的病毒颗粒。综上所述，本研究构建了CiYMaV的全长感染性cDNA克隆，完成了该病毒的柯赫氏法则验证，为进一步研究该病毒侵染的分子机制和开发能应用于柑橘上的病毒载体奠定了基础。

本研究以感染黄龙病菌亚洲种（‘Candidatus Liberibacter asiaticus’, CLas）的长叶橙（Citrus sinensis Osbeck）为材料，建立CLas侵染长叶橙的茎段培养方法，利用PCR和荧光定量PCR检测分析腋芽离体再生嫩梢中CLas的增殖情况。在此基础上，取CLas侵染长叶橙枝条进行表面消毒处理，切取腋芽嫁接于柑橘试管砧木，进行试管培养，利用PCR和荧光定量PCR检测腋芽再生嫩梢中CLas的增殖规律；采用直接组织印迹免疫法（Direct tissue blot immune assay，DTBIA）对试管苗中CLas的分布进行检测。培养基中添加适合浓度的激素可促进感病柑橘茎段离体培养的萌芽，萌芽率最高的培养基为MS+6-BA 1.0 mg·L^-1+GA 0.2 mg·L^-1+IAA 0.2 mg·L^-1。茎段萌芽30 d时，嫩梢病原PCR检测的阳性率达75%，其CLas浓度平均为温室条件下培养茎段原叶片中脉的28.2倍，最高为484.2倍。试管嫁接苗萌芽10、15、20、25、30和40 d时，嫩梢CLas PCR检测的阳性率分别为10%、15%、15%、20%、55%和70%，CLas浓度分别为7.5×10⁴ 、2.2×10⁶ 、1.4×10⁷、2.2×10⁷ 、1.2×10⁸和1.4×10⁸ cells μg^-1 DNA；萌芽30和40 d的试管苗中CLas浓度超过10⁸的比例分别达30%和40%。DTBIA检测结果显示，试管苗中黄龙病菌的分布比温室保存的感病柑橘中均匀。CLas侵染柑橘试管苗的主要症状为嫩梢枯死、停止生长、叶黄和落叶。感病试管苗的死亡率在萌芽40 d后会急剧升高，60 d时死亡率达82.0%。CLas在通过腋芽嫁接的柑橘试管苗中能快速增殖，该方法的建立为深入开展柑橘黄龙病病原生物学、病原-寄主互作及抗菌药物快速筛选等研究奠定一定基础。本研究建立了一种快速增殖和高浓度富集柑橘黄龙病菌的培养方法。

Citrus Huanglongbing (HLB, yellow shoot disease) is one of the most serious citrus diseases worldwide.  To better improve the detection sensitivity, a droplet digital PCR (ddPCR) assay was developed for the rapid detection of ‘Candidatus Liberibacter asiaticus’ (Las), the putative causal agent of HLB.  The detection of sensitivity comparison using positive plasmid indicated that ddPCR was superior to quantitative PCR (qPCR) for detecting and quantifying Las at low concentrations.  The Las detection of 40 field samples also showed that six of 13 asymptomatic samples (46.15%) with high C_t value (>35) were positive by ddPCR.  This methodology showed great potential for early HLB infection diagnosis.

Received  26 June, 2017    Accepted  17 October, 2017
© 2018 CAAS. Publishing services by Elsevier B.V.  All rights reserved.
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Streptomyces rubrogriseus HDZ-9-47, isolated from eggs of Meloidogyne spp., was evaluated as a potential biocontrol agent of Meloidogyne incognita under in vitro and protective field.  Microscopic observations showed that HDZ-9-47 parasitized eggs of M. incognita within 7 days.  In vitro, the culture filtrate of HDZ-9-47 caused 97.0% mortality of second-stage juveniles (J2s) of M. incognita and inhibited more than 50% egg hatching.  In the field, compared with the control, the root-knot index and J2s density in the treatment of drench the broth contained 10¹² HDZ-9-47 spores were respectively reduced by 51.1 and 80.7% at 90 days post transplantation, which were better than that in other application doses and methods.  In addition, reduction rates of root-knot index and J2s density of the treatment of combined application of HDZ-9-47 with biofumigation was 87.1 and 91.0%, respectively, better than either of HDZ-9-47 or biofumigation used alone or fosthiazate treatment.  And tomato yield also increased by 16.1%.  Together, our results suggest that HDZ-9-47 could be an effective biocontrol agent of M. incognita, and that application of HDZ-9-47 combined with cabbage residue biofumigation was a promising and sustainable option for M. incognita control.

To identity the potential pathogen associated with the yellow vein clearing symptom on lemon trees, the profiles of virus-derived small interfering RNAs from citrus samples were obtained and analyzed by deep sequencing method in this study.  Twenty-seven contigs almost cover the full length genome of Citrus yellow vein clearing virus (CYVCV) isolate YN were obtained using the small RNA deep sequencing technology.  Analysis showed that this isolate CQ shared the highest nucleotide identity with isolate Y1 (JX040635) and YN (KP313242), both of which belong to the genus Mandarivirus in the family Alphaflexiviridae.  Mapping analysis of viral-derived siRNA (vsiRNA) profiles revealed an uneven distribution pattern of their generations along both positive and negative genome strands, and 22- and 21-nt vsiRNAs ranked the majority.  BLAST against viroids and other viral databases confirmed that this sample was single-infected only by CYVCV, which indicated that CYVCV was the exact causal agent for the yellow clearing symptom occurring on lemon.  This is the first CYVCV isolate detected in Chongqing and the second in China.  This result could provide a molecular basis for the investigation of citrus viral diseases to protect citrus health in this region. 

Two miniature inverted-repeat transposable elements (MITEs), MCLas-A and MCLas-B, were recently identified from ‘Candidatus Liberibacter asiaticus’ known to be associated with citrus Huanglongbing (HLB, yellow shoot disease). MCLas-A was suggested as an active MITE because of its mobility. The immediate upstream gene of the two MITEs was predicted to be a putative transposase. The goal of this study is to analyze the sequence variation in the upstream putative transposase of MITEs and explore the possible correlation between sequence variation of transposase gene and MITE activity. PCR and sequence analysis showed that 12 sequence types were found in six major amplicon types from 43 representative ‘Ca. L. asiaticus’ isolates from China, the United States and Brazil. Out of the 12 sequence types, three (T4, T5-2, T6) were reported for the first time. Recombination events were found in the two unique sequence types (T5-2 and T6) which were detected in all Brazilian isolates. Notably, no sequence variation or recombination events were detected in the upstream putative transposase gene of MCLas-A, suggesting the conservation of the transposase gene might be closely related with the MITE activity. Phylogenetic analysis demonstrated two well supported clades including five subclades were identified, clearly reflecting the geographical origins of isolates, especially that of Ruili isolates, São Paulo isolates and a few Florida isolates.

The problem of associating the agricultural market names on web sites with their locations is essential for geographical analysis of the agricultural products. In this paper, an algorithm which employs the administrative ontology and the statistics from the search results were proposed. The experiments with 100 market names collected from web sites were conducted. The experimental results demonstrate that the algorithm proposed obtains satisfactory performance in resolving the problem above, thus the effectiveness of the method is verified.

In recent years, with the rapid development of information science, ontology becomes a popular research topic in the fields of knowledge engineering and information management. The reason for ontology being so popular is in large part due to what they promise: a shared and common understanding of some domain that can be communicated across people and computers. In the field of agriculture, FAO has started up the Agricultural Ontology Service (AOS) study project since 2001, AOS aims at providing knowledge service by agricultural domain ontology, it is the new seedtime for agricultural information service. However, establishing the ontology necessitates a great deal of expert assistance; manually setting it up would entail a lot of time, not to mention that there are only a handful of experts available. For this reason, using automatic technology to construct the ontology is a subject worth pursuing. A semi-automatic construction method for agricultural professional ontology from web resources is presented in this paper. For semi-structured web pages, the method automatically extracted and stored structured data through a program, built pattern mapping between relational database and ontology through human-computer interaction, and automatically generated a preliminary ontology, finally completed checking and refining by domain experts. The method provided a viable approach for ontology construction based on network resources in the actual work.

Insecticidal activities of the petroleum ether-, chloroform-, ethyl acetate-, and water-soluble fractions of the methanolicextract of Ficus sarmentosa var. henryi were assayed against Musca domestica adults. The chloroform- and ethyl acetatesolublefractions were the most active with 92.6 and 88.9% mortalities (24 h after treatment) respectively. Therefore, thetwo fractions were combined and four compounds, isolated from the fractions by activity-guided fractionation, wereelucidated as 7-hydroxycoumarin, apigenin, eriodictyol, and quercetin by spectroscopic method and displayed excellentinsecticidal activities against adults of M. domestica and 4th instar larva of Aedes albopictus. Among those, 7-hydroxycoumarin showed the strongest insecticidal activities with lethal concentrations (LC50) values of 72.13 μg g-1sugar and 4.87 μg mL-1 (48 h after treatment) against the test insects respectively. The cytoxicities of these compounds onBTI-Tn-5B1-4 cell were also investigated for the insecticidal mechanism and found that quercetin represented superiorinhibitory activity with MTT assay and reactive oxygen species (ROS) against BTI-Tn-5B1-4 cell, but slightly weaker thanthat of the positive control (azadirachtin) and significantly greater than the negative control (DMSO only). Meanwhile,eriodictyol demonstrated the strongest effect on the mitochondrial membrane potentials (MMP). In conclusion, based ontheir comparative toxicities to commercial insecticides and their cytotoxic effects, some of the compounds from theF. sarmentosa have potential as botanical insecticides.

The whole-plant morphology, leaf ultrastructure, photosynthesis as well as enzyme activities of two tomato cultivars (Meifen-2 and Hongsheng) to differential light availabilities (450-500 μmol m-2 s-1, 75-100 μmol m-2 s-1) were examined in controlled environment. The results showed that the plant biomass and root/shoot ratio decreased and the specific leaf area increased significantly under the low light condition. There was a significant increase in malondialdehyde (MDA) concentration, superoxide dismutase (SOD) and peroxidase (POD) activities and decrease in soluble sugar and protein contents in LL-grown plants. For both cultivars, downregulation of photosynthesis and electron transport components were observed in LL-grown plants, the inhibition of the photosynthesis under the LL condition could be partially explained by the decrease of stomata density and by the changes of chloroplast.