湛江沿海五种石斑鱼线粒体DNA的RFLP分析

In this paper, genetic diversity of intraspecies, and genetic relationship of interspecies in Epinephelus spp. (E. merra, E. fario, E. awoara, E. akaara and E. septemfasciatus) were assessed by using mitochondrial DNA restriction fragment length polymorphisms (mtDNA RFLPs).The samples were collected from the coastal area of Zhanjiang,Guangdong province. MtDNA was extracted from the fresh liver tissue by applying a difference centrifugation procedures. Using 17 restriction enzymes with 5-or 6-bp recognition sites, the purified mtDNA was cleaved by single enzymes. These enzymes included BamH Ⅰ，Bgl Ⅰ，Bgl Ⅱ，Dra Ⅰ，EcoR Ⅰ，EcoR Ⅴ，Hind Ⅲ，Kpn Ⅰ，Mlu Ⅰ，Pst Ⅰ，Pvu Ⅱ，Sal Ⅰ，Sca Ⅰ，Sma Ⅰ，Sty Ⅰ，Xba Ⅰ and Xho Ⅰ. The phylogenetic analysis was done using the Neighbor joining(NJ) method and Unweighted pairgroup method with arithmetic mean(UPGMA) method. Genetic diversity indices such as haplotype diversity (h), average genetic distance between haplotypes (P) and nucleotide diversity (π) were calculated using Nei and Li's segment method to quantify the genetic diversity within species. There were 8, 5, 8, 5 and 2 haplotypes detected within E. merra, E. fario, E.awoara, E.akaara and E. septemfasciatus, respectively. The haplotype diversity (h) was 0.8943, 0.6186, 0.9242, 0.6927 and 0.1820,respectively. The average genetic distance between haplotypes (P) was 0.62%±0.31%, 0.64%±0.37%, 1.12%±0.55%,0.72%±0.42% and 0.45%, respectively. And the nucleotide diversity (π) was 0.22%, 0.13%, 0.46%, 0.17% and 0.04%, respectively. The wild groupers in the Zhanjiang Coastal Area exhibited a relative higher level of genetic diversity. The net genetic distance between species (P_net) was 0.0694（E. merra - E. fario）,0.1337（E. merra - E. awoara）,0.1090 E. merra -E. akaara）, 0.1286（E. merra - E. septemfasciatus）,0.1590（E. fario -E. awoara）,0.0825（E. fario -E. akaara）,0.1153（E. fario - E. septemfasciatus）,0.1131 E. awoara - E. akaara）,0.0724（E. awoara -E. septemfasciatus） and 0.1336（E. akaara - E. septemfasciatus）. Both NJ and UPGMA methods yielded an identical phylogenetic tree for the five species. The E. merra and E. fario first clustered together, then joined with E. akaara, and finally clustered with E. awoara and E. septemfasciatus.     

Comparison of conventional and molecular techniques to investigate the intestinal microflora of rainbow trout (Oncorhynchus mykiss)

The concept of the use of probiotic organisms or prebiotic compounds to modify the fish gut microflora is becoming a popular topic for investigation. A major flaw in many such studies is a failure to consider fully the nature of the established microflora, which is to be modified pre-, or probiotically. Since it is widely accepted that a large proportion of bacteria are non-culturable, the use of conventional bacteriological (culture) techniques alone to investigate fish intestinal microflora may be expected to bias results. We report a study designed to investigate the normal intestinal microflora of rainbow trout (Oncorhynchus mykiss) using both conventional bacteriological and molecular methods.Over an 18 month period, the intestinal microflora of a single population of laboratory-raised rainbow trout was investigated. Bacteria isolated using bacteriological techniques were identified using the BiOLOG system and 16S rRNA gene sequencing. Dominant bacteria consistently were Aeromonas sp. and Carnobacterium piscicola, demonstrating that the microflora is stable in fish kept in defined conditions. Restriction Fragment Length Polymorphism (RFLP) and 16S rRNA gene sequence analysis was used to investigate anaerobic and non-culturable bacteria. An obligate anaerobe, Clostridium gasigenes, was shown to be among the dominating intestinal microflora.     

Genotyping Cephalosporium gramineum and development of a marker for molecular diagnosis

This study investigated the genetic variation of 40 isolates of Cephalosporium gramineum, the causal agent of cephalosporium stripe disease of wheat, based on variations in internal transcribed spacers (ITS) and intergenic spacers (IGS) of rDNA. Of the isolates, 29 were from Japan and the rest from the USA and Europe. The ITS region was about 600 bp and almost identical among these isolates. In the IGS region (～5 kbp), restriction fragment length polymorphism analysis detected four genotypes among the 40 isolates. One representative isolate was selected from each of the four genotypes, and the IGS region was sequenced. Attempts to design a genotype‐specific marker based on the size of PCR products amplified with selected primers failed to differentiate among the four genotypes. Alternatively, a species‐specific primer set (CGIGS1 and CGIGS2) was developed that annealed within the conserved region, producing a DNA fragment of about 1·8 kbp. Tests of this primer set on a wide range of other fungi from 11 genera confirmed that it was specific to C. gramineum. This primer set could serve as an effective tool in the molecular diagnosis of C. gramineum and has the potential to assist in a better understanding of the host–pathogen interaction.     

普通野生稻和亚洲栽培稻核心种质遗传多样性的检测研究

以122份野生稻和75份栽培稻在44个RFLP位点的多态性为资料，采用逐步聚类法和分组随机法，按原始样本的50%、20%和10%，分别构建初级核心样本、次级核心样本和核心样本，用多态位点数(Np)、等位基因数(Na)、基因型数(Ng)及平均基因多样性(Hs)等参数，检测其遗传多样性。结果表明，初级核心样本的Np、Na和Ng分别达到原始样本的     

Mitochondrial DNA analysis reveals cytoplasmic variation within a single cultivar of perennial ryegrass (Lolium perenne L.)

Summary The extent of mitochondrial DNA restriction fragment length polymorphisms among individual plant samples of perennial ryegrass was determined. A total of 72 plants from three cultivars Yorktown II, S23 and Riikka were surveyed using three restriction enzymes (BamHI,EcoRI andHindIII) and three mitochondrial gene probes (coxI, coxIII andnad9). Polymorphisms were noted within each of the two cultivars Yorktown II and S23, whereas in Riikka no variation was detected. It seems most likely that the mitochondrial genome diversity within the same cultivar has resulted from non-homogeneous ancestor cytoplasms. The hybridization-based assay employed is simple to perform, gives unambiguous results, and may thus be used in mass screening of perennial ryegrass populations for breeding purpose.     

Verification of the parthenogenetic capability of unreduced eggs in an alfalfa mutant by a progeny test based on morphological and molecular markers

Apomixis involves the parthenogenetic development of apomeiotic eggs. It has the potential of cloning plants through seed, and thus furnishes a unique opportunity in breeding of allogamous sexual species, such as alfalfa, for developing superior cultivars with permanently fixed heterosis. Apomixis as a whole has not been detected in the genus Medicago, but components of apomixis have been reported. The formation of unreduced eggs through diplosporic meiosis was documented in a diploid mutant of M. saliva ssp. falcata (L.) Arcang., named PG-F9. Since in facultative apomictic species non-reductional meiosis and parthenogenesis could be tightly associated processes, a progeny test based on morphological trait and molecular marker evaluation was carried out to verify the occurrence of parthenogenesis in PG-F9. Morphological traits such as leaf shape, stipule form, stem pigmentation and flower colour were shown to be effective in the preliminary screening of progenies and most of the plants were classified as non-maternal (i.e. from sexual reproduction). Molecular investigations by means of random amplified polymorphic DNA (RAPD) fingerprint and heterozygous restriction fragment length polymorphism (RFLP) loci detection conducted on the progenies classified morphologically as maternal allowed two plants, molecularly similar but not identical to PG-F9, to be discovered. Owing to the high number of molecular markers conserved as in the mother plant, and because of the great discriminating efficiency of the primers and probes used, these progeny plants could most likely be generated through parthenogenesis of diplosporic eggs. In fact, the extraordinary preservation of maternal morphological traits and genomic loci over one generation may be explained only if apomictic reproductive events rarely took place in PG-F9.     

Molecular mapping of major genes and quantitative trait loci determining flowering time in response to photoperiod in barley

Two major genes (eam8 and eam10) and two quantitative trait loci (QTL) determining flowering time in barley were associated with restriction fragment length polymorphism markers. The loci eam8 and eam10 were found to map in regions of chromosomes 1HL and 3HL, respectively, already estimated from previous classical linkage analyses. While investigating doubled haploid lines of a spring habit barley mapping population, two QTL for flowering time were detected on chromosomes 1HL and 7HS, respectively, when the material was grown under long photoperiod conditions. When growing the same lines under short photoperiod, no QTL were discernible. Allelic and homoeologous relationships with flowering time loci described earlier in barley and other Triticeae species are discussed.     

现代生物技术在马铃薯晚疫病菌(Phytophthora in festans)研究中的应用

综述了同功酶、RFLP、PCR、RAPD、AFLP的基本原理及其在晚疫病菌研究中的应用。主要包括以下 6方面 :①绘制晚疫病菌的连锁图谱 ;②分析一个地区晚疫病菌的基因结构及其变化 ;③分析采自不同寄主的菌株基因结构的差异 ;④研究晚疫病菌的来源 ;⑤研究墨西哥以外地区A2交配型菌株的来源 ;⑥研究有性生殖的发生情况。同时还展望了现代生物技术在晚疫病菌研究中的发展方向 ,指出该研究领域国内与国外的差距及今后国内的研究方向     

香菇菌株限制性片段长度多态性

香菇菌株的ＤＮＡ片段通过隆转移到质粒载体Ｂｌｕｅｓｃｒｉｐｔ Ｍ１３－（ｐＢＳ）以获得部分基因文库。文库三个随机克隆和一个密环菌中１ＤＮＡ克隆被用作限制性片段长度多态性探针。其中三个探针可检测到多态性，提示了３２个野生和栽培香菇菌株的遗传分离。菌株间的相似性用平均链锁聚类方式（ＵＰＧＭＡ）聚类，相似性超过６０％的分为一组。２３个菌株被分成４组。９个菌株与其它菌株相似性均低于６０％而独立存在。从我们     

几个绵羊品种线粒体DNA限制性片断长度多态性比较研究

用ApaⅠ等15种识别6碱基的限制性内切酶研究了蒙古羊、乌珠穆沁羊、湖羊和小尾寒羊线粒体DNA的RFLP。结果表明，在所研究的个体中共检测到32个酶切位点，16种限制性态型，其中BglⅠ表现出多态，XhoⅠ无切点。16种限制性态型可归结为2种基因单倍型，即单倍型Ⅰ（BglⅠ－A）、单倍型Ⅱ（BglⅠ-B），单倍型Ⅰ为受试绵品种的基本单倍型。线粒体DNA多态度π值平均为0.0192%，表明受试绵羊品种线粒体DNA多态性比较贫乏。