欢迎访问作物学报,今天是

作物学报 ›› 2018, Vol. 44 ›› Issue (10): 1539-1547.doi: 10.3724/SP.J.1006.2018.01539

• 耕作栽培·生理生化 • 上一篇    下一篇

不同种植方式大豆根际土壤细菌多样性分析

王芳1,陈井生2,刘大伟3   

  1. 1齐齐哈尔大学生命科学与农林学院 / 抗性基因工程与寒地生物多样性保护黑龙江省重点实验室, 黑龙江齐齐哈尔 161006
    2黑龙江省农科院大庆分院, 黑龙江大庆 163316
    3东北农业大学农学院, 黑龙江哈尔滨 150030
  • 收稿日期:2018-02-05 接受日期:2018-07-20 出版日期:2018-10-10 网络出版日期:2018-07-31
  • 基金资助:
    本研究由黑龙江省省属高等学校基本科研业务费科研项目(2012K-M21)

Bacterial Diversity of Soybean Rhizosphere Soil under Different Cropping Patterns

Fang WANG1,Jing-Sheng CHEN2,Da-Wei LIU3   

  1. 1 College of Life Sciences and Agroforestry, Heilongjiang Provincial Key Laboratory of Resistance Gene Engineering and Protection of Biodiversity in Cold Areas, Qiqihar University, Qiqihar 161006, Heilongjiang, China
    2 Daqing Branch of Heilongjiang Academy of Agricultural Sciences, Daqing 163316, Heilongjiang, China
    3 Agronomy College, Northeast Agricultural University, Harbin 150030, Heilongjiang, China
  • Received:2018-02-05 Accepted:2018-07-20 Published:2018-10-10 Published online:2018-07-31
  • Supported by:
    This study was supported by the Heilongjiang Provincial Higher-education Basic Scientific Research Project(2012K-M21)

摘要:

利用Illumina MiSeq第二代高通量测序平台, 对黑龙江省不同地区轮作及连作大豆根际土壤细菌16S rDNA基因组测序, 初步分析在不同种植方式下受大豆胞囊线虫侵染的大豆根际土壤细菌群落结构的变化。从6个土壤样本中共获得25 419个OTUs, 鉴定到细菌的47个门, 147个纲, 709个属。变形菌门、放线菌门、酸杆菌门、芽单胞菌门、浮霉菌门是供试土壤细菌的优势菌门, 占所有细菌群落总数90%以上。连作4年总OTUs及丰富度最高, 连作20年最低。不同轮作方式土壤细菌丰富度差异不显著(P > 0.05), 短期连作与长期连作细菌丰富度及多样性差异显著(P < 0.05)。不同轮作方式下放线菌门相对丰度低于连作方式, 芽单胞菌门和拟杆菌门相对丰度高于同地区连作方式。土壤功能细菌根瘤菌(Bradyrhizobium)、链霉菌属(Streptomyces)、芽孢杆菌属(Bacillus)、溶杆菌属(Lysobacter)、土微菌属(Pedomicrobium)的相对丰度在不同年限连作下高于轮作。长期连作土壤优势细菌丰度与轮作土壤相似性更高。

关键词: 大豆, 轮作, 连作, 细菌多样性, Illumina MiSeq 测序

Abstract:

To study bacterial community structure of soybean rhizosphere soil in rotation and continuous cropping, 16S rDNA gene were sequenced of soil samples infected soybean cyst nematode from Heilongjiang Province two regions by the second generation of high-throughput sequencing Illumina MiSeq platform. A total of 25 419 OTUs were obtained from six soil samples and classified into 47 phylum, 147 class, and 709 genera. Proteobacteria, Actinobacteria, Acidobacteria, Gemmatimonadetes, Planctomycetes were dominant bacteria, accounting for more than 90% of all soil bacterial communities. The total OTUs and richness were the highest in four years continuous cropping and the lowest in twenty years continuous cropping. The difference of bacteria abundance in different rotational cropping years was not obvious (P > 0.05), but abundance and adversity were significant in continuous cropping (P < 0.05). The relative abundance of Actinobacteria in different rotations was lower than that in continuous cropping, and the relative abundance of Gemmatimonadetes and Bacteroidetes was higher than that in the same area. The relative abundance of soil functional bacteria Bradyrhizobium, Streptomyces, Bacillus, Lysobacter, and Pedomicrobium were higher in different continuous cropping years than those in rotations. Predominant bacterial abundance in long term continuous cropping was more similar with that in rotational cropping.

Key words: soybean, rotation, continuous cropping, bacterial diversity, Illumina MiSeq sequencing

图1

相似度为97%水平下各样品稀释性曲线 RR: 感病品种-大麻-抗病品种; RS: 感病品种-大麻-感病品种; RQ: 玉米-谷子-感病品种; C4: 连作4年; C10: 连作10年; C20: 连作20年。"

图2

6个土壤样品丰度分布曲线 RR: 感病品种-大麻-抗病品种; RS: 感病品种-大麻-感病品种; RQ: 玉米-谷子-感病品种; C4: 连作4年; C10: 连作10年;C20: 连作20年。"

表1

不同轮作下大豆根际土壤细菌序列统计及多样性指数"

样品
Sample
有效序列数量
Effective
sequence-number
OTUs数量
OTUs number (97%)
Chao指数
Chao index
Shannon指数
Shannon index
感病品种-大麻-抗病品种(大庆) RR (Daqing) 39530 4243 5247.7 a 10.45 a
感病品种-大麻-感病品种(大庆) RS (Daqing) 37614 4140 5122.7 a 10.57 a
玉米-谷子-感病品种(齐齐哈尔) RQ (Qiqihar) 54387 4229 4972.7 a 10.20 b

表2

不同连作下大豆根际土壤细菌序列统计及多样性指数"

样品
Sample
有效序列数量
Effective
sequence-number
OTUs数量
OTUs number (97%)
Chao指数
Chao index
Shannon指数
Shannon index
连作4年(大庆) C4 (Daqing) 67271 4928 5659.6 a 10.47 a
连作10年(大庆) C10 (Daqing) 69356 4173 4583.8 b 10.23 b
连作20年(齐齐哈尔) C20 (Qiqihar ) 52387 3706 4147.0 b 10.09 c

图3

各样品在门水平的群落相对丰度"

图4

各样品在纲水平的群落相对丰度"

图5

样品聚类分析热图"

图6

6个土壤样品群落主成分分析"

[1] 宋杰 . 连作土壤寄生真菌多样性及对大豆胞囊线虫抑制作用. 东北农业大学博士学位论文, 黑龙江哈尔滨, 2016
Song J . Diversity and Suppressive Effect of Parasitic Fungi on Soybean Cyst Nematode in Soybean Monoculture Soil. PhD Dissertation of Northeast Agricultural University, Harbin, China, 2016 ( in Chinese with English abstract)
[2] 许艳丽, 刁琢, 李春杰, 潘凤娟, 战丽莉, 田中艳, 张思佳, 胡新 . 品种混种方式对大豆胞囊线虫控制作用. 土壤与作物, 2012,1:70-78
Xu Y L, Diao Z, Li C J, Pan F J, Zhan L L, Tian Z Y, Zhang S J, Hu X . Soybean cultivar mixtures for managing soybean cyst nematode. Soils Crops, 2012,1:70-78 (in Chinese with English abstract)
[3] 陈立杰, 朱艳, 刘彬, 段玉玺 . 连作和轮作大豆对大豆胞囊线虫群体数量及土壤线虫群落结构的影响. 植物保护学报, 2007,34:347-352
doi: 10.3321/j.issn:0577-7518.2007.04.003
Chen L J, Zhu Y, Liu B, Duan Y X . Influence of continuous cropping and rotation on soybean cyst nematode and soil nematode community structure. Acta Phytophy Sin, 2007,34:347-352 (in Chinese with English abstract)
doi: 10.3321/j.issn:0577-7518.2007.04.003
[4] 王进闯, 王敬国 . 大豆连作土壤线虫群落结构的影响. 植物营养与肥料学报, 2015,21:1022-1031
Wang J C, Wang J G . Effects of continuous soybean monoculture on soil nematode community. J Plant Nutr Fert, 2015,21:1022-1031 (in Chinese with English abstract)
[5] 靳学慧, 辛惠普, 郑雯, 台莲梅, 张亚玲, 闫凤云 . 长期轮作和连作对土壤中大豆胞囊线虫数量的影响. 中国油料作物学报, 2006,28:189-193
doi: 10.3321/j.issn:1007-9084.2006.02.017
Jin X H, Xin H P, Zheng W, Tai L M, Zhang Y L, Yan F Y . Effect of long-term rotational and continuous cropping on soybean cyst nematode number. Chin J Oil Crop Sci, 2006,28:189-193
doi: 10.3321/j.issn:1007-9084.2006.02.017
[6] Hamid M I, Hussain M, Wu Y P, Zhang X L, Xiang M C, Liu X Z . Successive soybean-monoculture cropping assembles rhizosphere microbial communites for the soil suppression of soybean cyst nematode. FEMS Microbiol Ecol, 2017,93, doi: 10.1093/femsec/fiw222
[7] Weller D M, Raaijmakers J M, Gardener B B, Thomashow L S . Microbial populations responsible for specific soil suppressiveness to plant pathogens. Annu Rev Phytopathol, 2002,40:309-348
doi: 10.1146/annurev.phyto.40.030402.110010
[8] Mendes R, Kruijt M, de Bruijn I, Dekkers E, Menno van der V M, Schneider J H M, Piceno Y M, DeSantis T Z, Andersen G L, Bakker P A H M, Raaijmakers J M . Deciphering the rhizosphere microbiome for disease-suppressive bacteria. Science, 2011,332:1097-1100
doi: 10.1126/science.1203980 pmid: 21551032
[9] 周岚, 杨永, 王占海, 陈阜, 曾昭海 . 玉米-大豆轮作及氮肥施用对土壤细菌群落结构的影响. 作物学报. 2013,39:2016-2022
doi: 10.3724/SP.J.1006.2013.02016
Zhou L, Yang Y, Wang Z H, Chen F, Zeng Z H . Influence of maize-soybean rotation and N fertilizer on bacterial community. Acta Agron Sin, 2013,39:2016-2022 (in Chinese with English abstract)
doi: 10.3724/SP.J.1006.2013.02016
[10] 于镇华, 王艳红, 燕楠, 李彦生, 谢志煌, 金剑 . CO2浓度升高对不同大豆品种根际微生物丰度的影响. 土壤与作物. 2017, ( 6):9-16
Yu Z H, Wang Y H, Yan N, Li Y S, Xie Z H, Jin J . Effects of elevated CO2 on the abundance of rhizosphere bacteria, fungi and denitrification bacteria in different soybean cultivars. Soils Crops, 2017, ( 6):9-16 (in Chinese with English abstract)
[11] Souza R H, Babujia L C, Silva P A, de Fátima Guimarães M, Arias C A, Hungria M . Impact of the ahas transgene and of herbicides associated with the soybean crop on soil microbial communities. Transgenic Res, 2013,22:877-892
doi: 10.1007/s11248-013-9691-x
[12] Lee Y H, Kim H . Response of soil microbial communities to different farming systems for upland soybean cultivation. J Korean Soc Appl Biol Chem, 2011,54, 423-433
doi: 10.3839/jksabc
[13] Granada C, da Costa P B, Lisboa B B, Vargas L K, Passaglia L M P . Comparison among bacterial communities present in arenized and adjacent areas subjected to different soil management regimes. Plant Soil, 2013,373:339-358
doi: 10.1007/s11104-013-1796-8
[14] Zhou J, Davey M E, Figueras J B, Rivkina E, Gilichinsky D, Tiedje J M . Phylogenetic diversity of a bacteria community determined from Siberian tundra soil DNA. Microbiology, 1997,143:3913-3919
doi: 10.1023/A:1006853600205 pmid: 9421915
[15] Zhu Y B, Tian J Q, Shi F Y, Su L, Liu K K, Xiang M C . Rhizosphere bacterial communities associated with healthy and Heterodera glycines-infected soybean roots. Eur J Soil Biol, 2013,58:32-37
[16] 朱琳, 曾椿淋, 李雨青, 俞冰倩, 高凤, 魏巍, 徐艳丽 . 基于高通量测序的大豆连作土壤细菌群落多样性分析. 大豆科学, 2017,36:419-424
Zhu L, Zeng C L, Li Y Q, Yu B Q, Gao F, Wei W, Xu Y L . The characteristic of bacterial community diversity in soybean field with continuous cropping based on the high-throughput sequencing. Soybean Sci, 2017,36:419-424 (in Chinese with English abstract)
[17] 周燕 . 间作及接种根瘤菌对大豆种植土壤细菌群落结构的影响. 广西大学硕士学位论文, 广西南宁, 2014
doi: 10.7666/d.Y2887846
Zhou Y . Effects of Intercropping and Inoculating Rhizobias on Soybean Soil Bacterial Community Structure. MS Thesis of Guangxi University, Nanning, Guangxi, China, 2014 ( in Chinese with English abstract)
doi: 10.7666/d.Y2887846
[18] 朱英波, 史凤玉, 张瑞敬, 武云鹏 . 黑龙江大豆轮作和连作土壤细菌群落多样性比较. 植物保护学报, 2014,41:403-409
Zhu Y B, Shi Y F, Zhang R J, Wu Y P . Comparison of bacterial diversity in rotational and continuous soybean cropping soils in Heilongjiang. Acta Phytophy Sin, 2014,41:403-409 (in Chinese with English abstract)
[19] Li X G, Ding C F, Zhang T L, Wang X X . Fungal pathogen accumulation at the expense of plant-beneficial fungi as a consequence of consecutive peanut monoculturing. Soil Biol Biochem, 2014,72:11-18
doi: 10.1016/j.soilbio.2014.01.019
[20] Wang G M, Stribley D P, Tinker P B, Walker C . Effects of pH on arbuscular mycorrhiza: I. Field observations on the long-term liming experiments at Rothamsted and Woburn. New Phytol, 1993,124:465-472
doi: 10.1111/nph.1993.124.issue-3
[21] 陈雪丽 . 黑土区连作大豆根际微生物群落特征研究. 中国科学院大学博士学位论文, 北京, 2015
Chen X L . Characterization of Microorganism Community in the Rhizosphere of Continuous Cropping Soybean in Black Soil. PhD Dissertation of University of Chinese Academy of Sciences, Beijing, China, 2015 ( in Chinese with English abstract)
[22] 王晋莉 . 大豆连作条件下的根际细菌与氨氧化微生物群落特征及其影响因素. 中国农业大学博士学位论文, 北京, 2014
Wang J L . Rhizospheric Bacterial and Ammonia-oxidizer Communities under Continuous Monoculture of Soybean Crop. PhD Dissertation of China Agricultural University, Beijing, China, 2014 ( in Chinese with English abstract)
[23] 魏巍 . 大豆长期连作土壤对根腐病病原微生物的抑制作用. 中国科学院博士学位论文, 北京, 2012
Wei W . The Suppressiveness Caused by Long-tern Continuous Cropping of Soybean on the Root Rot and Pathogens. PhD Dissertation of Chinese Academy of Sciences, Beijing, China, 2012 ( in Chinese with English abstract)
[24] 顾美英, 徐万里, 茆军, 梁智, 张志东, 房世杰 . 连作对新疆绿洲棉田土壤微生物数量及酶活性的影响. 干旱地区农业研究, 2009,27(1):1-5
Gu M Y, Xu W L, Mao J, Liang Z, Zhang Z D, Fang S J . Effects of cotton continuous cropping on the amount of soil microbes and enzyme activities in Xinjiang. Agric Res Arid Areas, 2009,27(1):1-5 (in Chinese with English abstract)
[25] Sanguin H, Sarniguet A, Gazengel K, Moënne-Loccoz Y, Grundmann G L . Rhizosphere bacterial communities associated with disease suppressiveness stages of take-all decline in wheat monoculture. New Phytol, 2009,184:694-707
doi: 10.1111/nph.2009.184.issue-3
[26] Schreiner K, Hagn A, Kyselková M, Moënne-Loccoz Y, Welzl G, Munch J C, Schloter M . Comparison of barley succession and take-all disease as environmental factors shaping the rhizobacterial community during take-all decline. Appl Environ Microbiol, 2010,76:4703-4712
doi: 10.1128/AEM.00481-10
[27] Chen S Y, Dickson D W. Biological control of plant parasitic nematodes. In: Manzanilla-Lopez R H, Marban-Mendoza N, eds. Practical Plant Nematology. Jalisco, Mexico: Colegio de Postgraduados and Mundi-Prensa, Biblioteca Basica de Agricultura, 2012. pp 761-811(in English)
[28] 王闯进 . 大豆连作对根际土壤生物群落的影响. 中国农业大学博士学位论文, 北京, 2014
Wang C J . The Impact of Continuous Soybean Monoculture on Soil Communities in the Rhizosphere. PhD Dissertation of China Agricultural University, Beijing, China, 2014 ( in Chinese with English abstract)
[29] Zhu Y B, Tian J Q, Shi F Y, Tian J Q, Liu J B, Chen S Y, Xiang M C, Liu X Z . Effect of soybean monoculture on the bacterial communities associated with cyst of Heterodera glycines. J Nematol, 2013,45:228-235
[30] Chen J, Moore W H, Yuen G Y, Kobayashi D , Caswell-Chen E P. Influence of Lysobacter enzymogenes strain C3 on nematodes. J Nematol, 2006,38:233-239
[31] Lee Y S, Nguyen X H, Moon J H . Ovicidal activity of lactic acid produced by Lysobacter capsici YS1215 on eggs of root-knot nematode, Meloidogyne incognita. J Microbiol Biotechnol, 2014,24:1510-1515
[32] Orcutt B N, Sylvan J B, Knab N J, Edwards K J . Microbial ecology of the dark ocean above, at, and below the seafloor. Microbiol Mol Biol Rev, 2011,75:361-422
doi: 10.1128/MMBR.00039-10 pmid: 3122624
[33] 殷继忠, 李亮, 接伟光, 蔡柏岩 . 连作对大豆根际土壤细菌菌群结构的影响. 生物技术通报, 2018,34(1):1-6
Yin J Z, Li L, Jie W G, Cai B Y . Effects of continuous cropping on bacterial flora structure in soybean rhizosphere soil. Biotechnol Bull, 2018,34(1):1-6 (in Chinese with English abstract)
[34] 谷岩, 邱强, 王振民, 陈喜凤, 吴春胜 . 连作大豆根际微生物群落结构及土壤酶活性. 中国农业科学, 2012,45:3955-3964
Gu Y, Qiu Q, Wang Z M, Chen X F, Wu C S . Effects of soybean continuous cropping on microbial and soil enzymes in soybean rhizosphere. Sci Agric Sin, 2012,45:3955-3964 (in Chinese with English abstract)
[35] 顾美英, 徐万里, 茆军, 张志东, 唐光木, 葛春辉 . 新疆绿洲农田不同连作年限棉花根际土壤微生物群落多样性. 生态学报, 2012,32:3031-3040
Gu M Y, Xu W L, Mao J, Zhang Z D, Tang G M, Ge C H . Microbial community diversity of rhizosphere soil in continuous cotton cropping system in Xinjiang. Acta Ecol Sin, 2012,32:3031-3040 (in Chinese with English abstract)
[36] 刘素慧, 刘世琦, 张自坤, 尉辉, 齐建建, 段吉峰 . 大蒜连作对其根际土壤微生物和酶活性的影响. 中国农业科学, 2010,43:1000-1006
Liu S H, Liu S Q, Zhang Z K, Wei H, Qi J J, Duan J F . Influence of garlic continuous cropping on rhizosphere soil microorganisms and enzyme activities. Sci Agric Sin, 2010,43:1000-1006 (in Chinese with English abstract)
[37] 陈慧, 郝慧荣, 熊君, 齐晓辉, 张重义, 林文雄 . 地黄连作对根际微生物区系及土壤酶活性的影响. 应用生态学报, 2007,18:2755-2759
Chen H, Hao H R, Xiong J, Qi X H, Zhang Z Y, Lin W X . Effects of successive cropping Rehmannia glutinosa on rhizosphere soil microbial flora and enzyme activities. Chin J Appl Ecol, 2007,18:2755-2759 (in Chinese with English abstract)
[38] 林茂兹, 王海斌, 林辉锋 . 太子参连作对根际土壤微生物的影响. 生态学杂志, 2012,31:106-111
Lin M Z, Wang H B, Lin H F . Effects of Pseudostellariae heterophylla continuous cropping on rhizosphere soil microorganisms. Chin J Ecol, 2012,31:106-111 (in Chinese with English abstract)
[39] 刘金波, 许艳丽 . 我国连作大豆土壤微生物研究现状. 中国油料作物学报, 2008,30:132-136
Liu J B, Xu Y L . Current research of soil microbial of successive soybean cropping in China. Chin J Oil Crop Sci, 2008,30:132-136 (in Chinese with English abstract)
[1] 陈玲玲, 李战, 刘亭萱, 谷勇哲, 宋健, 王俊, 邱丽娟. 基于783份大豆种质资源的叶柄夹角全基因组关联分析[J]. 作物学报, 2022, 48(6): 1333-1345.
[2] 杨欢, 周颖, 陈平, 杜青, 郑本川, 蒲甜, 温晶, 杨文钰, 雍太文. 玉米-豆科作物带状间套作对养分吸收利用及产量优势的影响[J]. 作物学报, 2022, 48(6): 1476-1487.
[3] 王炫栋, 杨孙玉悦, 高润杰, 余俊杰, 郑丹沛, 倪峰, 蒋冬花. 拮抗大豆斑疹病菌放线菌菌株的筛选和促生作用及防效研究[J]. 作物学报, 2022, 48(6): 1546-1557.
[4] 于春淼, 张勇, 王好让, 杨兴勇, 董全中, 薛红, 张明明, 李微微, 王磊, 胡凯凤, 谷勇哲, 邱丽娟. 栽培大豆×半野生大豆高密度遗传图谱构建及株高QTL定位[J]. 作物学报, 2022, 48(5): 1091-1102.
[5] 李阿立, 冯雅楠, 李萍, 张东升, 宗毓铮, 林文, 郝兴宇. 大豆叶片响应CO2浓度升高、干旱及其交互作用的转录组分析[J]. 作物学报, 2022, 48(5): 1103-1118.
[6] 彭西红, 陈平, 杜青, 杨雪丽, 任俊波, 郑本川, 罗凯, 谢琛, 雷鹿, 雍太文, 杨文钰. 减量施氮对带状套作大豆土壤通气环境及结瘤固氮的影响[J]. 作物学报, 2022, 48(5): 1199-1209.
[7] 王好让, 张勇, 于春淼, 董全中, 李微微, 胡凯凤, 张明明, 薛红, 杨梦平, 宋继玲, 王磊, 杨兴勇, 邱丽娟. 大豆突变体ygl2黄绿叶基因的精细定位[J]. 作物学报, 2022, 48(4): 791-800.
[8] 李瑞东, 尹阳阳, 宋雯雯, 武婷婷, 孙石, 韩天富, 徐彩龙, 吴存祥, 胡水秀. 增密对不同分枝类型大豆品种同化物积累和产量的影响[J]. 作物学报, 2022, 48(4): 942-951.
[9] 王吕, 崔月贞, 吴玉红, 郝兴顺, 张春辉, 王俊义, 刘怡欣, 李小刚, 秦宇航. 绿肥稻秆协同还田下氮肥减量的增产和培肥短期效应[J]. 作物学报, 2022, 48(4): 952-961.
[10] 杜浩, 程玉汉, 李泰, 侯智红, 黎永力, 南海洋, 董利东, 刘宝辉, 程群. 利用Ln位点进行分子设计提高大豆单荚粒数[J]. 作物学报, 2022, 48(3): 565-571.
[11] 周悦, 赵志华, 张宏宁, 孔佑宾. 大豆紫色酸性磷酸酶基因GmPAP14启动子克隆与功能分析[J]. 作物学报, 2022, 48(3): 590-596.
[12] 王娟, 张彦威, 焦铸锦, 刘盼盼, 常玮. 利用PyBSASeq算法挖掘大豆百粒重相关位点与候选基因[J]. 作物学报, 2022, 48(3): 635-643.
[13] 谭雪莲, 郭天文, 胡新元, 张平良, 曾骏, 刘晓伟. 黄土高原旱作区马铃薯连作根际土壤微生物群落变化特征[J]. 作物学报, 2022, 48(3): 682-694.
[14] 董衍坤, 黄定全, 高震, 陈栩. 大豆PIN-Like (PILS)基因家族的鉴定、表达分析及在根瘤共生固氮过程中的功能[J]. 作物学报, 2022, 48(2): 353-366.
[15] 张国伟, 李凯, 李思嘉, 王晓婧, 杨长琴, 刘瑞显. 减库对大豆叶片碳代谢的影响[J]. 作物学报, 2022, 48(2): 529-537.
Viewed
Full text


Abstract

Cited

  Shared   
  Discussed   
No Suggested Reading articles found!