Some microbiological aspects of bauxite mineralization and beneficiation

A microbial survey of Jamnagar bauxite mines in Gujarat, India, revealed the indigenous presence of a variety of autotrophic and heterotrophic bacteria and fungi associated with the ore body and water ponds in the vicinity. Among these, bacteria belonging to the genera Thiobacillus, Bacillus and Pseudomonas are implicated in the weathering of aluminosilicates; the precipitation of iron oxyhydroxides; the dissolution and conversion of alkaline metal species; and the formation of alumina, silica and calcite minerals. Fungi belonging to the genus Cladosporium can reduce ferric iron and dissolve alumina silicates. Biogenesis thus plays a significant role in bauxite mineralization. Various types of bacteria and fungi, such as Bacillus polymyxa, Bacillus coagulans and Aspergillus niger, were found to be efficient in significant calcium solubilization and partial iron removal from bauxite ore. Probable mechanisms in the biobeneficiation process are analyzed. Biobeneficiation is shown to be an effective technique for the removal of iron and calcium from bauxite ores for use in refractories and ceramics.

Electrochemical processing of ocean manganese nodules with microbial enhancement to recover valuable metals

In this paper, electroleaching and electrobioleaching of ocean manganese nodules are discussed along with the role of galvanic interactions in bioleaching. Polarization studies using a manganese nodule slurry electrode system indicated that the maximum dissolution of iron and manganese due to electrochemical reduction occurred at negative DC potentials of -600 and -1,400 mV(SCE). Electroleaching and electrobioleaching of ocean manganese nodules in the presence of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans at the above negative applied DC potentials resulted insignificant dissolution of copper, nickel and cobalt in 1 M H2SO4 and in sulfuric acid solution at pH 0.5 and 2.0. Mechanisms involved in electrobioleaching of ocean manganese nodules are discussed. Galvanic leaching of ocean manganese nodules in the presence of externally added pyrite and pyrolusite for enhancement of dissolution was also studied. Various electrochemical and biochemical parameters were optimized, and the electroleaching and galvanic processes thus developed are shown to yield almost complete dissolution of all metal values. This electrobioleaching process developed in the laboratory may be cost effective, energy efficient and environmentally friendly.

Assessment of genetic diversity and identification of core collection in sandalwood germplasm using RAPDS

Sandalwood is an economically important aromatic tree belonging to the family Santalaceae. The trees are used mainly for their fragrant heartwood and oil that have immense potential for foreign exchange. Very little information is available on the genetic diversity in this species. Hence studies were initiated and genetic diversity estimated using RAPD markers in 51 genotypes of Santalum album procured from different geographcial regions of India and three exotic lines of S. spicatum from Australia. Eleven selected Operon primers (10mer) generated a total of 156 consistent and unambiguous amplification products ranging from 200bp to 4kb. Rare and genotype specific bands were identified which could be effectively used to distinguish the genotypes. Genetic relationships within the genotypes were evaluated by generating a dissimilarity matrix based on Ward's method (Squared Euclidean distance). The phenetic dendrogram and the Principal Component Analysis generated, separated the 51 Indian genotypes from the three Australian lines. The cluster analysis indicated that sandalwood germplasm within India constitutes a broad genetic base with values of genetic dissimilarity ranging from 15 to 91 %. A core collection of 21 selected individuals revealed the same diversity of the entire population. The results show that RAPD analysis is an efficient marker technology for estimating genetic diversity and relatedness, thereby enabling the formulation of appropriate strategies for conservation, germplasm management, and selection of diverse parents for sandalwood improvement programmes.

An Improved molecular tool for distinguishing monoecious and dioedious Hydrilla

Two biotypes of hydrilla [Hydrilla verticillata(L.f.) Royle] occur in the United States, a dioecious type centered in the southeast and a monoecious type in the central Atlantic and northeastern states. Ecosystem managers need tools to distinguish the types as the ranges of each type expand and begin to overlap. A molecular tool using the randomly amplified polymorphic DNA (RAPD) procedure is available but its use is limited by a need for reference samples. We describe an alternative molecular tool which uses “universal primers” to sequence the trnL intron and trnL-F intergenic spacer of the chloroplast genome. This sequence yields three differences between the biotypes (two gaps and one single nucleotide polymorphism). A primer has been designed which ends in a gap that shows up only in the dioecious plant. A polymerase chain reaction (PCR) using this primer produces a product for the monoecious but not the dioecious plant.

Produção in vitro e criopreservação de raízes de Cleome rosea Vahl (Capparaceae)

Cleome rosea é uma espécie nativa, de porte herbáceo, ocorrente em restingas brasileiras. Estudos recentes têm revelado o potencial medicinal da espécie para importantes propriedades farmacológicas, como por exemplo, as atividades anti-inflamatória, antigenotóxica, antiviral e antibacteriana. Porém, nos últimos anos, C. rosea não tem sido encontrada em várias regiões de seu ambiente natural, devido, principalmente, às ações antrópicas. Dessa forma, torna-se relevante o desenvolvimento de métodos de conservação que permitam o estudo e exploração das propriedades medicinais da espécie. O cultivo in vitro de raízes representa uma forma eficiente para produção de biomassa, devido ao rápido crescimento, produção estável de metabólitos, além de representar uma potencial fonte de explantes para a propagação em massa de diferentes espécies. O presente trabalho teve como objetivo a produção in vitro de culturas de raízes de C. rosea, associada à criopreservação, como forma de manutenção em longo prazo das culturas, monitorada através da análise de estabilidade genética. As culturas estabelecidas a partir de explantes radiculares de plantas propagadas in vitro de C. rosea demonstraram excelente capacidade de multiplicação de raízes em meio de cultura suplementado com o fitorregulador ANA, com manutenção dessa capacidade ao longo de sucessivas subculturas. Associado a esses resultados, o estabelecimento de protocolos de criopreservação pelo método de vitrificação resultou em elevados valores de frequência de recuperação do material após congelamento em nitrogênio líquido com as soluções de vitrificação PVS2 e PVS3. Os estudos de monitoramento da estabilidade genética, pela técnica de marcadores moleculares RAPD, revelaram a presença de polimorfismos significativos em uma das três culturas iniciadas a partir de raízes de C. rosea criopreservadas. Esses resultados demonstram as possibilidades de produção de raízes de C. rosea e conservação em longo prazo através da criopreservação, iniciando estudos inéditos para a espécie.

Genetic identification of four Malaysian mackerel species off Coast of Peninsular Malaysia based on molecular marker

Random Amplified Polymorphic DNA (RAPD) markers and cytochrome b (Cyt-b) gene sequences were utilized to fingerprint and construct phylogenetic relationships among four species of mackerel commonly found in the Straits of Malacca namely Rastrelliger kanagurta, R. brachysoma, Decapterus maruadsi and D. russelli. The UPGMA dendogram and genetic distance clearly showed that the individuals clustered into their own genus and species except for the Decapterus. These results were also supported by partial mtDNA cytochrome b gene sequences (279 bp) which found monotypic sequence for all Decapterus studied. Cytochrome b sequence phylogeny generated through Neighbor Joining (NJ) method was congruent with RAPD data. Results showed clear discrimination between both genera with average nucleotide divergence about 25.43%. This marker also demonstrated R. brachysoma and R. kanagurta as distinct species separated with average nucleotide divergence about 2.76%. However, based on BLAST analysis, this study indicated that the fish initially identified as D. maruadsi was actually D. russelli. The results highlighted the importance of genetic analysis for taxonomic validation, in addition to morphological traits.

Perfil genético de Enteroccocus faecalis isolados de infecção endodôntica primária no Brasil comparados a isolados orais e não-orais do Reino Unido e do Japão

Enterococcus faecalis (E. faecalis), conhecidamente patógeno oportunista, tem sido frequentemente associado a infecções sistêmicas graves. É também encontrado na cavidade oral, com destaque em infecção endodôntica refratária. O objetivo deste estudo foi avaliar características moleculares de E. faecalis isolados de infecção endodôntica primária no Brasil e comparar com isolados orais e não orais de pacientes do Reino Unido e do Japão, assim como E. faecalis resistentes à vancomicina. O presente estudo também investigou o relacionamento entre E. faecalis de diferentes origens (oral e não oral) e de diferentes áreas geográficas para obter uma melhor compreensão do envolvimento dos diferentes reservatórios no surgimento e propagação de clones virulentos, aqueles que possuem genes que conferem infectividade e virulência, assim como resistência aos antibióticos. Para tal, foram estudados E. faecalis isolados em infecções endodônticas no Brasil (n = 20) e orais no Reino Unido (n = 10), e em infecções não orais no Japão (n = 9). Além disso, 20 E. faecalis isolados ambientais do Hospital Universitário de Gales (Cardiff, Reino Unido), classificados como Enterococcus resistentes à vancomicina (VRE) também foram examinados. A Concentração Inibitória Mínima (CIM) dos isolados do Brasil foi obtida pelo método de diluição em agar de acordo com as recomendações do Clinical and Laboratory Standards Institute (CLSI). Reação em cadeia da polimerase (inglês - PCR) foi a técnica empregada para detectar os genes de virulência e aqueles associados à resistência aos antibióticos, enquanto Reação de Amplificação Aleatória de DNA Polimórfico (inglês - RAPD-PCR) foi escolhida para a tipagem molecular. Dentre os genes de virulência examinados, o gene que codifica a gelatinase gelE foi o mais prevalente entre os isolados (77-100%). Entre isolados orais, foram detectados os genes agg de substâncias de agregação, esp de proteína de evasão imune, cylB de citolisina, genes de resistência à tetraciclina tetM e tetL e à eritromicina ermB com diferentes prevalências. Os isolados clínicos hospitalares do Japão apresentaram perfil genético similar aos isolados orais, mas com maior prevalência de ermB e cylB. Todas as amostras de VRE foram positivas para os genes gelE, esp, agg, vanA, ermB e tetM, 95% foram positivos para cylB e 17% positivo para tetL. Todas as amostras foram negativas para ermA, asa373, vanB, vanC1 e vanC2/3. RAPD-PCR revelou agrupamento de VRE em comparação com outros isolados. Neste estudo, os isolados de E. faecalis de infecções orais apresentaram genes de resistência à tetraciclina, um antimicrobiano frequentemente usado no tratamento local de infecções dentárias, abrindo um debate muito importante sobre o papel e a eficácia desta droga para infecções orais. Claramente, são necessários mais estudos nesta área principalmente em relação à expressão de fatores de virulência entre isolados endodônticos para melhor nortear as estratégias de tratamento. As pressões externas no microambiente dos canais radiculares podem ser responsáveis pela seleção de espécies mais resistentes e virulentas. Por fim, embora isolados orais apresentem genes de virulência fundamentais para a patogenicidade, estes foram detectados em menor incidência em comparação com os isolados não-orais e VRE.

The review of recent advances in fish genetics and biotechnology

Great advances have been, and are being made in our knowledge of the genetics and molecular biology (including genomics, proteomics and structural biology). Global molecular profiling technologies such as microassays using DNA or oligonucleotide chip, and protein and lipid chips are being developed. The application of such biotechnological advances are inevitable in aquaculture in the areas of improvement of aquaculture stocks where many molecular markers such as RFLPs, AFLDs and RAPD are now available for genome analysis, finger printing and genetic linkage mapping. Transgenic technology has been developed in a number of fish species and research is being pursed to produce transgenic fish carrying genes that encode antimicrobial peptides such as lysozyme thereby achieving disease resistance in fish. Also it is a short cut to achieving genetic change for fast growth and other desirable traits like early sexual maturity, temperature tolerance and feed conversion efficiency. KEYWORDS: Fish genetics, transgenesis, monoploidy, diploidy, polyploidy,gynogenesis, androgenesis, cryopreservation.

葡萄属植物系统学研究

葡萄属（Vitis.L.）植物隶属于葡萄科(Vitaceae)，主要分布于北温带，最南可以分布到南美洲的委内瑞拉和亚洲的越南以及印度北部。本文通过对该属分类研究历史的回顾，认为该属存在的问题主要表现在如下几个方面： 1）葡萄属自1753 年由Carl Linne创立以来，虽经planchon于1887年做了修订，但属的范围仍需进一步界定;2）在Planchon之后的100多年中未见有一全面的分类学修订工作，出现在该属的800多个名称需要考证;3）对一些广布种的变异认识不足，导致了大量可疑种。针对这些问题本文进行了如下几个方面的工作： l、形态学：通过大量的野外工作和标本观察，对该属植物的主要性状做了分析，讨论了这些性状状态在葡萄属中的变异规律及演化趋势，将灌木状习性、退化的卷须以及不裂的叶片视为进化的性状。 2、细胞学：利用前人对葡萄属(Vitis.L.)染色体数目的统计及一些杂交实验分析的结果，结合形态学等方面的特征分析，认为在葡萄科，染色体基数X=10为原始的，而x=19则为衍生的。葡萄属的染色体基数xl9(2n=38)，多倍体较少见;麝香葡萄属[Muscadinia (Planch.) Sma11]的染色体基数为x=10 (2n=20)．与蛇葡萄属、酸蔹藤属和爬山虎属的一致。葡萄属和麝香葡萄属间的杂种是不育的。 3、孢粉学：对葡萄属32种5变种及麝香葡萄属[Muscadinia (Planch.) Sma11]1种的花粉外壁做扫描电镜观察，结果发现花粉外壁雕纹在这两属间和葡萄属内变异较小，对区分属以及属下种上类群意义不大，但对种的鉴别有重要的价值。 4、植物化学：前人对植物化学的工作表明，植物的一些次生代谢产物如类黄酮化合物在葡萄科各类群中的分布规律较好地反映了各类群间的关系。这些结果较好地支持了Planchon对葡萄属范围的界定。 5、山葡萄复合体(V.amurensis complex)包括山葡萄(V.amurensis Rupr.)、燕山葡萄(V.amuresis Rupr. var. dissecta Skvorts.=var.yanshanensisD．Z．Lu et H．P．Liang)、百花山葡萄(V.baihuashanensis M．S．Kang et D．Z．Lu)、复叶葡萄(V.piasezkii Maxim.)、少毛复叶葡萄[V. piasezkii Maxux1．var. pagnuccii (Planch.) Rehd.]共3个种和2个变种，广泛分布于中国北方，形态变异较大。本文对该复合体做了形态分析，并用RAPD (Random Amplified Polymorphic DNAs)分子标记方法分析了这几个类群的关系。综合这些结果，归并了燕山葡萄和百花山葡萄。 在上述工作的基础上，我们得出了如下的结论： l、葡萄属在葡萄科中是一个进化的类群。整理后的葡萄属包括8系62种、l亚种和15变种，其中有2个新系、1个新组合系、2个新变种、1个新组合种和l3个新异名。 2、本文赞同SmaU在1903年作出的分类学处理，把麝香葡萄作为一个独立的属，比葡萄属原始但与葡萄属有着最近的亲缘关系。 3、依据形态特征和APD分析结果把山葡萄复合体的3个种2变种归并为2种l变种，即山葡萄、复叶葡萄和少毛复叶葡萄，认为分子标记技术在分析属内近缘种闻关系上很有价值。 4、葡萄属具有东亚和北美2个现代分布中心，该属可能起源于北美的东部，在晚白垩纪经白令陆桥散布至欧亚大陆。

稻属的分子系统学研究

稻属（Oryza L）属于禾本科的稻族，主要分布于世界的热带和亚热带地区。一般认为稻属包括20个左右的野生种和2个栽培种，我国有4-5种。迄今为止，对于稻属中种的数目和划分;稻属中所包括的种类是否为一单系类群;各基因组之闻的关系和起源以及稻属的起源等等，学术界仍然存有争议。本文评述了稻属分子系统学研究的进展，研究中存在的问题以及对未来稻属系统学研究的展望。针对稻属的分子系统学研究中所存在的问题，运用核糖体DNA转录间隔区序列测定、随机扩增多态性DNA（RAD）和SSR-anchoredPCR等分子生物学的手段对稻属中全部23个种的来自中国和世界不同地区的材料开展了分子系统学的研究。所得主要结果如下： 1．对产于中国的三种野生稻和栽培稻的二个亚种的核糖体DNA第一转录间隔区进行了序列测定。 DNA序列分别用PAUP程序进行分支分析和用MEGA程序中的UPGMA和Neighbor-joining进行聚类分析，结果表明核糖体DNA转录间隔区序列适合于进行稻属的分子系统学研究。 2．用荧光自动测序法和人工同位素测序法测定了稻属23个种和4个外类群的转录间隔区的序列。所有的DNA序列用Clustal V程序排阵后，再用PAUP程序进行分支分析。结果表明： A．稻属中的23个种组成四个主要分支，分别相当于Vaughan(1989)的四个种复合体。 B．所有AA基因组的种都在一个分支中。除了O.meridionalis与其它种的关系相对较远外，AA基因组种间有一定程度的分化，但不大。 C．尽管BB、BBCC、CC、CCDD和EE基因组的种都在一个分支中，但它们之间的分化是较为明显的。O.australiensis与该分支中的其它种的关系相对较远。以上两个分支的关系较为密切，它们组成一个自然类群，是稻属的核心部分。 D．O.ridleyi与O.longiglumis非常近缘，它们组成一个分支。 E．O.meyeriana与O．granulata有非常密切的关系。O.brachyantha与O.meyeriana近缘，而与AA基因组的关系较远。O,schlechter/与Leersia hexandra近缘，而与稻属中其它种的关系较远。作为外类群的Porteresia coarctata与稻属的a brachyantha非常近缘，这有可能说明将它作稻属中的一员的观点是正确的。 3．用RAPD和ISSR技术对稻属23介种的36份材料以及Porteresia coar ctata和Leersia hexandra各1份材料进行PCR扩增。16个10-mer RAPD随机引物共扩增出368个多态条带，5个锚定SSR引物共扩增出1 16个多态条带。RAPD和ISSR扩增出的多态条带合在同一数据矩阵中，用NTSYS-pc程序进行聚类分析。得出的结果与ITS序列分支分析的结果相似。 A.从表征图上亦可区分出四个群。所有的AA基因组的种聚在一起，O.nivara与O.rufipogon的关系密切，两个种的界限不清楚，所以认为它们是一个种：O.rufipogon.。 B.分布于中国的O.officinalis与O.minuta非常近缘，而菲律宾的四倍体O.officinalis则与同是基因组的O.eichingeri和O.rhizomatis关系密切。EE基因组的O.australiensis与Officinalis群保持一种松散的联系。 C。具FF基因组的O.brachyantha与O.schlechteri近缘，它们与Porteresiacoarctata和Leersia hexandra关系的密切程度要大于它们与稻属其它种的关系。 D。最后讨论了RAPD和ISSR用予植物属内的系统发育研究存在的问题。本研究结果说明RAPD和ISSR适合于进行属内近缘种亲缘关系的研究。

银杉的遗传多样性及系统位置的研究一兼论松科的分子系统学

银杉属Cathaya是我国著名植物学家陈焕镛和匡可任建立的松科单型属，该属是否成立及该属在松科中的系统位置至今仍众说不一。银杉Cathazyaargyro phylla是银杉属的唯一幸存种，被誉为第三纪的活化石，并被列为我国一级保护的濒危植物，也是世界植物红皮书所列少数几种濒危裸子植物之一，保护区虽已设立数个，但该物种的濒危原因仍为未解之谜。本文针对上述问题开展了松科植物的分子系统学研究，探讨了银杉属的系统位置及松科的属间关系，并通过遗传多样性的研究探讨了银杉的濒危机制及保护策略。 1．松科的分子系统学研究 为选取合适的分子标记，本文先探讨了ITS-1在松科等裸子植物中的系统学价值。对1 6种裸子植物（其中含松科10属12种）的ITS-1的扩增结果如下：ITS-1在裸子植物属闻存在极大的长度变异(约600-2600bp)，因而不适用于属级以上的系统学研究;在同属种中，ITs-1的长度虽较一致，但与被子植物的ITS-1相比，裸子植物的ITS-1太长(如在松属中超过2600bp)，难以进行大规模研究。银杉属ITS-1的扩增产物中，一个片段的长度与松属ITS-1的长度相当，另一个片段的长度与云杉属ITS-l的长度相当，这三属间的关系值得进一步研究。此外，在松科植物ITS-1的研究中必须注意真菌“污染”这一问题。 由于ITS不适用于裸子植物属间关系的研究，因而本文运用rbcL-accD基因片段及trnK基因的PCR-RFLP分析探讨银杉属的系统位置及松科的属间关系。rbcL和trnK虽然都是叶绿体基因，但位于trnK内含子区的natK基因与rbcL基因在所受的选择压及进化速率上相差甚远，通过这两个基因研究结果的比较有助于评价系统树的可靠性。此外，考虑到松科的10个属中有9个属的rbcL基因序列已被测定，我们补测了银杉属的rbcL基因序列，进而对松科10个属的rbcL基因序列进行了全面分析。PCR -RFLP分析及rbcL基因的序列分析结果如下： A. PCR扩增的松科rbcL-accD基因片段均长约2550bp，属间没有明显的长度变异，1 8种限制性内切酶的单酶切及7种组合双酶切共获得86个酶切位点，其中54个为变异位点。PAUP和MEGA软件分析均表明：银杉属、松属、黄杉属和落叶松属构成一个单系群，且银杉属与松属的关系似乎近于它与另外二属的关系，但这一结果来得到bootstrap分析的较强支持;黄杉属近缘于落叶松属;冷杉属近缘于油杉属。 B．PCR扩增出的松科trnK基因均长约2557bp，在属间也没有明显的长度变异。16种限制性内切酶的单酶切及7种组合双酶切共获得92个酶切位点，其中68个为变异位点。变异位点中的35个具有系统发育信息，其中28个位于matK基因上。分布于整个trnK基因上的informative位点和仅分布于matK基因上的informative位点分别用于PAUP(version 3.1.1)分析，且PAUP分析中分别用Wagner简约法和Dollo筒约法构建系统树。总体看来，Wager简约树和Dono简约树的结构基本一致（Cedrus的位置除外）：Abies、Keteleeria、Tsuga和Pseudolarix分为一支，且这一支在所有的简约树中均得到分辨;Pseudotsuga近缘于Larix,而Abkes相对近缘于Keteleeria; Cathaya与Ables-Keteleeria-Pseudolarix-Tsuga这一支的关系较远，它与松科的其它属聚在一起，但b∞tstrap分析也不支持它与任何一个属有很近的关 系，说明Cathaya是比较孤立的一个属。Cedrus的位置较特殊，在Wagner简约树中它位于松属以外的其它8个属的基部（因松属为外类群），而在Dollo筒约树中它位于Al}ies-Kete~eer uz-Pseudo/zr/x- Tsuga达一支的基部，并且它与这一支的关系得到了bootstrap分析的较强支持。 C．银杉的rbeL基因长1425bp，其序列与松科其它9个属的rbcL基因序列均有较大差异，从遗传距离(Mega软件中的P-distance)上看，银杉属作为一个属是无可非议的。PAUp和Mega软件分析均表现：Abies、Keteleeria、Pseudolter和Tsuga分为一支，且Cathaya与这一支的关系较远;Pseuaiotsuga近缘于Larix,且这二属间的关系得到了bootstrap分析的强烈支持;Abies近缘于Keteleeria，Pseudolarix近缘于Tsuga，且这两支也得到了bootstrap分析的较强支持;Cathaya与Pinus聚为一支，但支持强度不高。Cetirus的位置与trnK基因的PCR-RFLP分析结果极为相似。 根据rbcL-accD基因片段及trnK基因的PCR-RFLP分析以及rbcL基因的序列分析可以得出如下结论：<1> Cathaya作为一个属不仅是成立的，而且是一个较为孤立的属，将它置于其它任何属内都是不正确的，该属与Abies-Keteleer ia-Pseudolarx-Tsuga这一支的关系较远，相对而言Cathaya与Pinus的关系可能稍近一些。<2>松科主要分为两大支：一支含Abies、KeteZeera、Pseudolarx和Tsuga，该支中Abies近缘于KetelaeriaPseudolarix近缘于Tsuga;另一支含Pseudotsuga、Larix、Cathaya、Pinus和Picete，该支中Pseudotsuga明显近缘于Larix;Cedrus可能更近于Abies-Keteleeria-Pseudolarix-Tsuga这一支。 2．银杉的遗传多样性研究 本研究运用随机扩增多态DNA(RAPD)方法对银杉的1 1 3个个体（分别采自现存全部4个居群：金佛山、花坪、大瑶山和八西山)进行了遗传多样性检测。21个1O-mer的寡核苷酸引物共检测11个位点，其中42个位点是多态的，占37%，这一多态位点百分率仅为裸子植物多态位点百分率平均值的一半左右，说明银杉的遗传多样性水平很低。对多态位点的分析发现银杉屠群内发生了十分严重的遗传漂变，因而导致屠群间的强烈分化。AMOVA分析表明：银杉的遗传变异中，34.7%的变异存在于居群闻，这一数值是裸子植物GST平均值(6。8%)的5倍多;在金佛山屠群中，17%的遗传变异存在于亚居群间，这一数值也是裸子植物GsT平均值的两倍多。银杉的这一居群遗传结构与其它裸子植物的居群遗传结构截然不同。此外，我们提出了度量遗传多样性水平的分化指数概念及其计算方法，并发现遗传多样性水平的高低与生境的复杂程度有一定的相关性。 银杉的遗传多样性水平很低，其适应幅必然很窄，且由于严重的遗传漂变导致居群间的强烈分化，使基因流受阻，进而产生严重的近交，近交又使银杉的适应能力进一步下降，并使极为有限的遗传多样性进一步丧失，这种恶性循环会导致银杉濒危程度的加剧，甚至绝灭。 鉴于银杉独特的居群遗传结构，即有相当大一部分遗传变异存在于居群之间，取样保护时，不仅要在每个居群中取足够多的个体，而且要在尽可能多的居群中取样。就原地保护而言，由于每个居群和亚居群都有独特的基因型，因而都具有保护价值。另外，人工加强居群间的基因流（如人工授粉）对提高银杉各居群的适应能力肯定是有益的。

中国普通野生稻（Oryza rufipogon Griff.）群体遗传学及保护策略的研究

普通野生稻的基因资源对水稻的育种已经起过并将继续起至关重要的作用。所以，研究和保存其遗传多样性具有重要的意义。首先对普通野生稻在我国的分布现状作了较为全面的野外调查。采集了69个群体，近2000个个体的硅胶干燥叶片。研究了从硅胶干燥的小量叶片中高效率、高质量制备DNA的方法。并用此方法制备了44个代表群体，1168个个体的总DNA，建立了中国普通野生稻的总DNA库。随机选取19个引物对29个群体、651个个体的总DNA进行了RAPD扩增。统计出群体和地区内的多态性片段百分比（PPB），RAPDistance和WINAMOVA程序联用分析遗传变异在地区间、地区内群体间和群体内的组成。广西濠江流域5个野生群体的分析结果表明了中下游群体的PPB值显著高于中上游群体。从而从分子水平上证实了水流对无性繁殖体的传播影响了沿江分布群体的遗传多样性和遗传结构。6个现有原位保护群体的分析结果说明了5个群体值得进一步原位保护，而另一个群体适合异位保护。中国境内29个群体的统计分析揭示出群体间的遗传多样性差异很大（PPB值从23.29%到46.18%）。广东具有的PPB值最高（79.12%），其次是海南（77.11%）和广西（68.67%）。因而，华南是我国普通野生稻的遗传多样性中心。18个群体AMOVA分析结果均表明了遗传变异主要存在于群体内，但群体间业已有较大的遗传分化。从175个随机引物中筛选出9个引物，成功地鉴定出5个群体的克隆多样性和克隆结构。这二者与群体的生态环境，特别是水分状况密切相关。也同时受人类干扰强度的影响。而与群体所处的纬度没有明显的相关性。 根据以上结果，普通野生稻原位保护的策略是选取分布在不同地理区域、遗传多样性水平高的群体。分布在广东、海南和广西的6个群体，具有很高的遗传多样性，建议加以原位保护。此外，孤岛状隔离在我国普通野生稻分布区边缘的3个小群体也应立即进行原位保护。此外，原位保护的群体应给予适度的干扰以维系较高的克隆多样性和遗传多样性。在进行遗传多样性研究和异位保护时，每群体的取样个体数应不少于25株，相邻取样个体间的距离应大于12米。