不同地理种群麦长管蚜微卫星位点的遗传多态性

麦长管蚜是麦类作物的重要害虫之一，还是麦类黄矮病毒(Barley yellow dwarf virus，BYDV)的重要传播媒介。现已证明麦长管蚜是远距离迁飞性害虫。本研究通过微卫星标记技术检测了12个地理种群麦长管蚜的3个微卫星位点的遗传多态性，研究了不同地理种群间麦长管蚜基因型的遗传变异。研究结果不仅可以为研究麦蚜的成灾机理和适应机理提供分子遗传学证据，而且对于麦蚜的迁飞扩散、预测预报以及遗传控制也具有参考价值。     

华北地区转Cry1A+CpTI和Cry1A基因棉棉田害虫和天敌昆虫的群落结构*

2000～2001年采用背负式机动吸虫器取样法研究了转抗虫基因棉,双价(Cry1A十CpTI)转基因棉(SGK321)和Bt(Cry1A)棉(GK12),棉田的害虫和天敌群落结构。结果表明,从害虫群落组成上看,转抗虫基因棉田平均查得15科19种,从普通棉不施药和施药对照田平均分别查得14科17．5种和13．5科17．5种;转抗虫基因棉田的主要种类数量多于普通棉不施药和施药对照田,普通棉施药田主要优势种类为烟粉虱(Bemisia tabaci)和棉蚜(Aphis gossypii)2种;转抗虫基因棉田的绿盲蝽(Lygus lucorum)高于普通棉不施药和施药对照田,棉铃虫(Helicovcrpa armigera)是普通棉不施药对照田的常见种,转抗虫基因棉田则无。从天敌群落组成上来看,从转抗虫基因棉田共查得平均24．3科39.3种,从普通棉不施药和施药对照田平均分别查得24科43．5种和25科38种;微小花蝽、姬小蜂(Chrysonotomyia)和异须盲蝽(Cumpylomms diversicornis)为转基因棉和普通棉不施药对照的优势种,蜘蛛(Araneida)的优势度有所上升并成为丰盛种;而在普通棉施药处理田中,棉短瘤蚜茧蜂(Trioxys rietscheli)和龟纹瓢虫(Propylaea japonica)为优势种,寄生蚜虫跳小蜂(Aphidencyrtus shikokians)、棉短瘤蚜茧蜂(Trioxys rietschcli)和黄足蚜小蜂(Aphelinus flavipes)数量有所上升,成为丰盛种。相比而言,转抗虫基因棉田害虫和天敌的主要种类数量都明显多于普通棉施药田,表明转抗虫基因棉有利于保护棉田的生物多样性和棉田生态系统的管理。     

杀虫剂对苹果黄蚜与七星瓢虫的毒力及选择性研究

采用FAO推荐的点滴法,测定了15种常用杀虫剂对苹果黄蚜及其天敌七星瓢虫幼虫的毒力,比较了药剂在二者之间的毒力选择性。结果表明,供试杀虫剂中以吡虫啉对七星瓢虫幼虫和苹果黄蚜的选择性最高,其选择性比值(七里瓢虫LD50/苹果黄蚜LD50)为135．56,其次为氟氯氰菊酯、氯氰菊酯和马拉硫磷,其选择性比值分别为114．00、62．86和45．43。吡虫啉、氟氯氰菊酯、氯氰菊酯和马拉硫磷等选择性高的杀虫剂对苹果黄蚜相对毒力高,而对其天敌七星瓢虫相对安全,在协调苹果黄蚜的化学防治与生物防治策略中应选用对害虫毒力高,而对天敌相对安全的杀虫剂。     

异色瓢虫和多异瓢虫对两种色型豌豆蚜的捕食偏好研究

为了明确异色瓢虫和多异瓢虫对红色型和绿色型豌豆蚜的偏好性及对种群的控制作用,本文将异色瓢虫捕食豌豆蚜的总密度设置为90头?皿?1、120头?皿?1、150头?皿?1,多异瓢虫捕食豌豆蚜的总密度设置为42头?皿?1、60头?皿?1、78头?皿?1,分别进行了异色瓢虫和多异瓢虫对2种色型豌豆蚜的选择捕食作用研究。结果显示:当2种色型豌豆蚜共存时,异色瓢虫雌成虫对红色型豌豆蚜在低密度(90头?皿?1)和中密度(120头?皿?1)时均不表现喜(偏)好性,而在高密度(150头?皿?1)时表现正喜(偏)好性,对绿色型豌豆蚜在各密度条件下均不表现喜(偏)好性;对2种色型豌豆蚜的转换效应因总猎物密度的不同而表现不同,即红色型豌豆蚜在低密度(90头?皿?1)时无转换行为,在中密度(120头?皿?1)和高密度(150头?皿?1)时均表现负转换效应,而绿色型豌豆蚜则在各个密度条件下均不表现转换效应。多异瓢虫雌成虫对2种色型豌豆蚜在各密度下均不表现明显的喜(偏)好性;对2种色型豌豆蚜的转换效应因总猎物密度的不同而有所不同,即在低密度(42头?皿?1)时对2种色型豌豆蚜均不表现转换效应,在中高密度(60头?皿?1和78头?皿?1)时,对2种色型豌豆蚜均表现为负转换效应。由此可知,多异瓢虫对2种色型豌豆蚜无明显的选择偏好;异色瓢虫在红绿色型种群数量较低时,对2种色型没有明显的选择偏好作用,但当红色型和绿色型种群数量较高时,异色瓢虫对红色型豌豆蚜具有一定的偏好性,可能影响2种色型豌豆蚜虫种群动态变化。说明优势天敌瓢虫是引起2种色型豌豆蚜种群数量变化的因素之一。     

不同类型棉田昆虫群落结构研究

运用群落生态学原理和方法,于2007年6月26日至8月20日系统调查了平作春棉田和夏棉田主要害虫的种群数量动态,并利用相对丰富度、优势度指数、优势集中性指数、多样性指数和均匀度分析了其群落结构和时间动态.结果表明:两类棉田昆虫群落组成较为丰富,由10目35科48种组成.其中春棉田昆虫群落为9目30科39种,夏棉田昆虫群落为10目30科43种;优势种是棉蚜(Aphis gossypii Glover.)、烟粉虱(Bemisia tabaci Gennadius)和朱砂叶螨[Tetranychus cinnarinus(J(Bois)].在6月底至7月上旬春棉田优势种主要有朱砂叶螨,7月初数量达最多;两类棉田在7月中旬以后优势种均为棉蚜,7月底至8月中旬优势种均为烟粉虱.两类棉田昆虫群落的总个体数变化较大,但春棉田中昆虫群落和害虫亚群落总个体数始终高于夏棉田;春棉田害虫的相对丰富度较大,而夏棉田天敌的相对丰富度较大;两类棉田以寄生性天敌群落相似系数最高(0.949 4),植食性害虫群落最低(0.439 4);春棉田昆虫群落多样性指数最高为1.895 3,夏棉田昆虫群落多样性指数最高为2.095 1,均匀度的变化趋势与多样性指数变化基本一致,而优势集中性指数的变化趋势与多样性指数和均匀度的变化正好相反,优势集中性指数越大,多样性指数和均匀度越小.     

石榴园5种主要食叶类害虫与其捕食性天敌之间的关系

为统筹利用自然天敌和通过化学措施全年综合防治石榴园害虫,对石榴园害虫及其天敌进行了系统调查,明确了江淮丘陵区石榴园主要食叶类害虫为棉蚜、小绿叶蝉、黄刺蛾、扁刺蛾和小袋蛾。采用灰色关联度分析法、生态位分析法和空间格局聚集强度指数分析法分析了主要害虫与其捕食性天敌在数、时、空方面的关系,综合排序得出:棉蚜的主要捕食性天敌是异色瓢虫、中华草蛉和八斑球腹蛛,小绿叶蝉的主要捕食性天敌是粽管巢蛛、三突花蟹蛛和草间小黑蛛,黄刺蛾的主要捕食性天敌是粽管巢蛛、锥腹肖蛸和八斑球腹蛛,扁刺蛾的主要捕食性天敌是锥腹肖蛸、八斑球腹蛛和粽管巢蛛,小袋蛾的主要捕食性天敌是三突花蟹蛛、粽管巢蛛和异色瓢虫。棉蚜种群的聚集均数λ值大于2,其聚集是本身原因引起的;而小绿叶蝉、黄刺蛾、扁刺蛾和小袋蛾及其捕食性天敌的λ值小于2,其聚集是环境中某些因子引起的。     

淮北棉田害虫与捕食性天敌群落动态变化研究

对淮北棉田害虫和捕食性天敌群落动态变化进行了研究。田间系统调查共发现害虫35种,捕食性天敌24种;害虫优势种为棉蚜、烟粉虱、棉叶螨、棉盲蝽;捕食性天敌优势种主要为四点亮腹蛛、龟纹瓢虫、T-纹豹蛛、草间小黑蛛、八斑球腹蛛、华姬猎蝽、小花蝽、青翅隐翅虫。该区棉田害虫与捕食性天敌在棉株上的分布特点为:四点亮腹蛛、T-纹豹蛛、草间小黑蛛、八斑球腹蛛、小花蝽、青翅隐翅虫为下部>中部>上部;烟粉虱、棉盲蝽为上部>中部>下部;华姬猎蝽7月30日前为上部>下部>中部,8月9日后为下部>上部>中部;棉蚜在6月20日前为上部>下部>中部,在6月30日后为下部>上部>中部;棉叶螨前期主要分布在下部,后期向上转移;龟纹瓢虫在7月10日前为上部>中部>下部,7月20日之后为下部>上部>中部。群落均匀度在棉花生长发育前期较低,中期逐渐上升,后期又逐渐下降;集中度的变化趋势与均匀度相反;多样性在棉花生育中期最高。以物种为单位和以功能团为单位的群落多样性指数和均匀度指数呈高度正相关,相关系数(r)为0.9904。     

南宁市十字花科蔬菜害虫天敌群落结构分析

南宁市十字花科蔬菜害虫天敌群落物种有70种(类)，隶属7目26科。主要有青翅隐翅虫(Paederus fuseipes)，长足虻(Dolichopodidae)、小菜蛾绒茧蜂(Cotesta plutellae)、八斑鞘蛛(Coleoserma octumaculalum)、食虫沟瘤蛛(Ummeliata insecticeps)、浅斑近微蛛(Eperigone fredeorum)和肖蛸(Tetragnatha)。蜘蛛的种类和数量皆为无公害和常规栽培两类菜地天敌之最。群落的多样性和均匀度偏低，优势种突出。文中揭示了两类菜地天敌群落的相似性及其结构特点和时间动态。认为占两类菜地节肢动物群落物种的53．44％和占个体数量的24．96％的菜地害虫天敌资源，是值得进一步研究和保护利用的自然生物控制因素。     

不同管理模式对花椒园节肢动物群落结构及稳定性的影响

为探讨有利于花椒园节肢动物群落结构的管理模式,2012年对云南省昭通市3种常见管理模式(粗放、免耕、精细)下花椒园节肢动物群落的组成和结构进行了系统调查。采用群落特征指数和主成分分析法对节肢动物群落特征、季节性变化及稳定性进行了研究。结果表明,调查区花椒园节肢动物群落由2纲9目97科318种组成,其中害虫主要种类为大青叶蝉(Tettigoniella viridis)、小绿叶蝉(Empoasca flavescens)、棉蚜(Aphis gossypii)和小长蝽(Nysius ercae),天敌主要种类为大灰食蚜蝇(Metasyrphus corolla)、斑食蚜蝇(Melanostoma scalare)、环腹瘿蜂属一种(Frigates sp.)和翠绿巨胸小蜂(Perilampus prasinus)。3种模式下,粗放模式丰富度(21.985 7)最高,但植食性类群亚群落个体比例(36.13%)也最高。免耕模式的多样性指数(3.649 1)、均匀性指数(0.694 3)和稳定性指数Ss/Si(0.074 7)、Nn/Np(0.557 2)、Sd/Sp(0.545 5)、Nd/Np(1.467 8)均高于其他两种模式。精细模式的优势度最高(0.193 1)、群落特征指数全年波动较大,受到外界干扰强烈。免耕模式下天敌对主要害虫的跟随作用较好且害虫爆发高峰期的虫口数量(最高81头)皆低于同时期粗放模式(最高189头)与精细模式(最高123头)。主成分分析表明粗放模式与精细模式下主导群落变化的主要因素为害虫,而免耕模式下天敌起到了主导作用,其对害虫的调控效果较好。因此综合考虑生态经济效益,免耕模式为有利于当地花椒种植的管理模式。     

柑橘粉虱与主要捕食性天敌之间的空间关系研究

聚集强度指数用来判别天敌和害虫的空间分布及其关系,但抽样样方的大小影响聚集强度指数的大小。为了分析在不同大小聚块条件下,天敌对柑橘粉虱空间上跟随关系的密切程度、聚集原因和聚集范围,为评价柑橘粉虱的天敌优势种提供科学依据,用聚块样方方差分析法、灰色关联度分析法、空间聚集强度指数法、种群聚集均数法和ρ指数法对安徽省潜山县茶园不同大小聚块条件下的柑橘粉虱及其11种主要天敌中的6种天敌进行分析。柑橘粉虱与其6种天敌的关联度分析结果表明,与柑橘粉虱空间上跟随关系密切的天敌是草间小黑蛛(0.848 6)、八点球腹蛛(0.840 6)和龟纹瓢虫(0.805 5),与柑橘粉虱空间上跟随关系较不密切的天敌是红点唇瓢虫(0.764 2)。在聚块内包含有1、2、4、8个基本样方时,随着聚块内基本样方数的增多,聚集分布格局的扩散系数不断增大,均匀和随机格局的扩散系数C值不断减小。聚块基本样方数为2、4、6、8、16和32时与为1时之间的柑橘粉虱及其天敌的空间分布聚集程度差异均不显著。柑橘粉虱的种群聚集均数λ多数大于2,其聚集是本身原因引起的;天敌和柑橘粉虱在种群聚集均数为正值时,随着聚块中基本样方数的增加,种群聚集均数不断增大。用柑橘粉虱不同大小聚块的ρ指数判断个体群聚集时的最小范围是聚块中有1个基本样方,即本文的1.7 m2,为该虫抽样时确定样方大小提供科学依据。     

江淮丘陵和黄河故道不同施肥处理葡萄园葡萄十星叶甲Oides decempunctata与其天敌的关系

在运用葡萄丰产栽培措施的同时,为合理保护和利用自然天敌进行葡萄十星叶甲的综合防治,对安徽省萧县和肥东县喷施钕肥、镧肥、醋肥和清水的葡萄园葡萄十星叶甲及其主要天敌进行系统调查,并用灰色系统分析法和生态位分析法对两者之间在数量、时间和空间格局等方面的关系进行分析。经综合排序,萧县十星叶甲主要天敌喷水处理区为龟纹瓢虫、草间小黑蛛和拟环纹狼蛛,喷醋处理区为拟环纹狼蛛、龟纹瓢虫和异色瓢虫,喷钕处理区为草间小黑蛛、异色瓢虫和龟纹瓢虫,喷镧处理区为龟纹瓢虫、异色瓢虫和草间小黑蛛。肥东县十星叶甲主要天敌喷水处理区为草间小黑蛛、八斑球腹蛛和拟环纹狼蛛,喷醋处理区为拟环纹狼蛛、草间小黑蛛和龟纹瓢虫,喷钕处理区为草间小黑蛛、拟环纹狼蛛和八斑球腹蛛,喷镧处理区为八斑球腹蛛、草间小黑蛛和拟环纹狼蛛。萧县和肥东县两地间各处理的十星叶甲主要天敌的种类和位次差异明显。喷水区两地相同的两种主要天敌是草间小黑蛛和拟环纹狼蛛,喷醋区两地相同的两种主要天敌是拟环纹狼蛛和龟纹瓢虫,喷钕区和喷镧区两地相同的主要天敌都是草间小黑蛛。     

生境和施肥对棉田节肢动物群落结构的影响

采用不同的生境和施肥组合方法,研究生境复杂性和施肥对棉田节肢动物群落结构的影响,以期为棉田害虫生态防治提供理论依据。生境复杂性设棉田未覆盖稻草(A1)与覆盖稻草(A2)2种方式,施肥设复合肥90 kg(N).hm 2(B1)、复合肥90 kg(N).hm 2添加沼肥90 kg(N).hm 2(B2)、复合肥90 kg(N).hm 2添加尿素90 kg(N).hm 2(B3)3种方式。每个小区采取平行线跳跃法抽取10株棉花,每周一次调查每株棉花上和植株周围0.25 m2地表部分所有节肢动物种类数量和个体数量。结果表明,蜘蛛类(Araneae)个体数[A2(391.1±70.1)头.10株1,A1(226.8±29.3)头.10株1]、优势种天敌星豹蛛(Pardosa astrigera)个体数[A2(171.7±13.3)头.10株1,A1(59.3±9.8)头.10株1]、蜘蛛类优势集中性(A20.527±0.089,A10.258±0.049)、害虫类多样性(A21.459±0.067,A11.245±0.249)覆草生境极显著高于未覆草生境。害虫类均匀度(A20.635±0.040,A10.588±0.100)覆草生境显著高于未覆草生境。害虫类个体数[A2(772.4±206.9)头.10株1,A1(1 156.4±243.7)头.10株1]]、目标害虫棉大卷叶螟(Syleptahn derogate)个体数[A2(320.8±80.6)头.10株1,A1(659.5±254.8)头.10株1]、害虫类优势集中性(A20.311±0.029,A10.400±0.107)、蜘蛛类多样性(A20.997±0.169,A11.584±0.138)、蜘蛛类均匀度(A20.536±0.073,A10.803±0.052)覆草生境极显著低于未覆草生境。施肥方式极显著影响了害虫类个体数[B1(1 015.3±344.1)头.10株1,B2(714.0±152.2)头.10株1,B3(1 164.0±168.9)头.10株1]、棉大卷叶螟个体数[B1(552.0±253.8)头.10株1,B2(280.6±63.7)头.10株1,B3(638.0±256.0)头.10株1]、害虫类优势集中性(B10.370±0.055,B20.282±0.022,B30.414±0.111)、害虫类多样性(B11.324±0.228,B21.511±0.066,B31.222±0.200)、蜘蛛类多样性(B11.167±0.374,B21.418±0.373,B31.286±0.262)、害虫类均匀度(B10.600±0.039,B20.683±0.043,B30.550±0.081);显著影响了蜘蛛类优势集中性(B10.457±0.175,B20.353±0.167,B30.368±0.123)、蜘蛛类均匀度(B10.613±0.160,B20.701±0.130,B30.695±0.168)、捕食性昆虫类多样性(B11.190±0.153,B21.496±0.179,B31.474±0.125)。生境与施肥对害虫类个体数、棉大卷叶螟数个体数、害虫类优势集中性、害虫类多样性、害虫类均匀度的交互作用极显著,生境与施肥对蜘蛛物种数的交互作用显著。棉田覆草改善优势种天敌星豹蛛的生存环境,显著提高对棉大卷叶螟的控制效果;复合肥添加沼肥不利于棉大卷叶螟种群数量的增长。     

干旱与Cd双重胁迫对土壤-小麦-蚜虫系统Cd转移规律影响的研究

为探究干旱和重金属双重胁迫对土壤-小麦-蚜虫系统内Cd转移规律的影响,为小麦蚜虫的生态调节提供理论依据,本研究以麦长管蚜[Sitobionavenae(Fabricius)]为研究对象,用原子吸收分光光度法分别测定不同土壤Cd含量(100 mg?kg-1、200 mg?kg-1)及不同程度干旱胁迫(无胁迫、中度胁迫、重度胁迫)处理下小麦根茎叶及蚜虫体内的Cd含量。结果表明:土壤Cd含量及干旱单一胁迫均对小麦及蚜虫体内的Cd含量造成了显著影响(P0.05)。两者交互作用对小麦根部及叶部的Cd含量影响显著,而对小麦茎部及蚜虫体内Cd含量影响不显著。在相同胁迫条件下, Cd在小麦中的积累分布为根茎叶。随着干旱胁迫程度增大,小麦根部Cd含量及土壤-根转移系数降低,茎部Cd含量及根-茎转移系数升高,麦长管蚜Cd含量在土壤Cd含量100mg?kg-1下高于土壤Cd含量200 mg?kg-1;中度干旱胁迫增加了麦长管蚜体内Cd累积量,而重度干旱胁迫则降低了其体内Cd累积量。叶-蚜虫的Cd转移系数明显大于土壤-根、根-茎和茎-叶转移系数且大于1,说明Cd在麦长管蚜体内产生了生物富集作用。综上所述,干旱胁迫促进了Cd从土壤向小麦茎部转移和根部Cd累积,但抑制了Cd从根部到茎部转移和茎部Cd累积;中度干旱胁迫促进了麦长管蚜体内Cd的积累,而重度干旱胁迫抑制了麦长管蚜体内Cd的积累。     

Perennial Wild Relatives of Chickpea as Potential Sources of Resistance to Helicoverpa armigera

The legume pod borer, Helicoverpa armigera (Hübn.), is one of the major constraints to chickpea production, and host plant resistance is an important component for the management of this pest. The levels of resistance in the cultivated chickpea are low to moderate, and therefore, we evaluated 17 accessions of perennial Cicer along with three cultivated chickpea genotypes for resistance to H. armigera. There was a significant reduction in both leaf feeding and larval weights when the larvae were fed on the leaves of Cicer microphyllum Benth. accessions ICC 17146, ICC 17236, ICC 17240, and ICC 17248. Relative resistance index based on leaf feeding, larval survival, and larval weight indicated that C. microphyllum accessions ICC 17146, ICC 17236, ICC 17234, ICC 17240, ICC 17243, and ICC 17248 were highly resistant to H. armigera. Under natural infestation, accessions belonging to C. microphyllum, C. canariense Santos Guerra et Lewis, and C. macracanthum M. Pop suffered a damage rating of <2.0 compared to 4.0 in C. judaicum Boiss. accession ICC 17148 (annual species) and 8.5–9.0 in the cultivated chickpeas (1 = <10% leaf area damaged, and, 9 = >80% leaf area damaged). There was considerable diversity in the accessions belonging to perennial wild species of chickpea, and these can be exploited to increase the levels and diversify the basis of resistance to H. armigera in the cultivated chickpea.     

Scavenging and active predation in generalist predators: A mesocosm study employing DNA-based gut content analysis

Scavenging presumably is common among invertebrate generalist predators, however, only few studies have specifically dealt with the consumption of dead prey. Here consumption of dead and living prey within a guild of generalist predators was investigated using mesocosm experiments and DNA-based gut content analysis. A community of predators including carabids, staphylinids and spiders was released into 0.2 m² mesocosms, planted with wheat and infested with grain aphids Sitobion avenae. At predator release, freshly killed bird cherry-oat aphids, Rhopalosiphum padi, were provided as carrion prey at the soil surface. Two days after predator release, predators were collected and their gut content screened for DNA of both aphid species using multiplex PCR. Comparing detection frequencies of DNA from living and dead prey, we found that all predators frequently consumed dead aphids, except for the lycosid spider Trochosa ruricola which exclusively fed on S. avenae. In contrast, in the tetragnathid spider Pachygnatha degeeri, supposed to feed mainly on living prey, detection rates of R. padi DNA were high. Our findings support previous assumptions that many generalist predators are facultative scavengers. This needs to be considered for the interpretation of field-derived data using approaches of gut content analyses as well as when assessing predators’ pest control potential.     

Denaturing gradient gel electrophoresis analysis of gut bacterial community for the Japanese earthworms

The gut bacterial community structure for Pheretima hilgendorfi and P. heteropoda (Family Megascolecidae), and Allolobophora japonica (Family Lumbricidae) collected from agricultural grasslands in Japan was analyzed by denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S rRNA gene fragments (PCR-DGGE) and compared with those in the surrounding soils. Denaturing gradient gel electrophoresis (DGGE) profiles indicated that each earthworm species had their own specific bacterial communities, and multidimentional scaling analysis grouped the DGGE profiles into three groups: gut samples from P. hilgendorfi and P. heteropoda, gut samples from A. japonica and samples from the surrounding soils. Nine dominant bands were identified by their direct sequencing and cloning. Major three bands from P. hilgendorfi and P. heteropoda were closely related to Bacillus species belonging to the phylum Firmicutes. Major four and two bands from A. japonica were closely related to the phyla Proteobacteria and Bacteroidetes, respectively.     

Assessment of changes in soil organic matter after invasion by exotic plant species

Invasive exotic plants can modify soil organic matter (SOM) dynamics and other soil properties. We evaluated changes in particulate organic matter (POM) and carbon (C) mineralisation in adjacent plots invaded by Solidago gigantea, Prunus serotina, Heracleum mantegazzianum and Fallopia japonica, and non-invaded control plots on different soils in Belgium. Litter decomposition of S. gigantea and P. serotina was compared to that of the native species Epilobium hirsutum, Betula pendula and Fagus sylvatica. Disregarding the differences in site characteristics (soil texture, parental material and plant species), we argued that the invasion by S. gigantea and P. serotina enhance SOM dynamics by increasing C mineralisation in 2 out of 3 sites invaded by S. gigantea and in 1 out of 3 sites invaded by P. serotina; C in coarse POM (cPOM, 4,000–250 μm) and fine POM (fPOM, 250–50 μm) in 1 site invaded by S. gigantea and C content in total POM (tPOM, 4,000–50 μm) and the organo-mineral fraction (OMF, 0–50 μm) in 1 site invaded by P. serotina. H. mantegazzianum and F. japonica slowed down SOM dynamics by reducing C mineralisation in three out of four sites; C and nitrogen (N) of fPOM in the invaded compared with the non-invaded plots at one site invaded by H. mantegazzianum. However, N content of cPOM (4,000–250 μm) was higher in the invaded sites by F. japonica compared with the non-invaded plots. Our results indicated that the effects of invasion by exotic plant species were not species-specific but site-specific.     

Genetic diversity and phylogeny of pink-pigmented facultative methylotrophic bacteria isolated from the phyllosphere of tropical crop plants

Genetic diversity of pink-pigmented facultative methylotrophic bacteria belonging to the genus, Methylobacterium, was assessed using 16S ribosomal RNA (rRNA) gene sequencing, amplified ribosomal DNA restriction analysis (ARDRA), and differential carbon-substrate utilization profile in the phyllosphere of cotton, maize, sunflower, soybean, and mentha plants. Methylobacterium populi, Methylobacterium thiocyanatum, Methylobacterium suomiense, M. aminovorans, and Methylobacterium fujisawaense were identified to colonize the phyllosphere of these crop plants. Among these, M. populi found to be the dominating species followed by M. aminovorans. The diversity indices like Shannon index of diversity, Pielou index of evenness, and Margalef index of richness calculated based on combined data of ARDRA, 16S rRNA gene sequence, and differential carbon-substrate utilization revealed that sunflower leaves showed richest methylobacterial diversity, followed by soybean, while cotton and mentha leaves recorded the lowest diversity. The outcome of this study indicates that diversity of Methylobacterium in phyllosphere depends upon the host plant species colonized.