Markers associated with altitude and ecological factors in hexaploid Campeiostachys nutans (Griseb.) J. L. Yang,B. R. Baum et C. Yen and tetraploid Roegeneria nutans (Keng) Keng

The genetic basis of adaptation can be unraveled directly at the genome level, without regard to selectively advantageous genes or traits. Genetic variation and adaptation of polyploidy in the evolution of plants is becoming an area of intense interest. Whether hexaploid wheatgrass species has higher adaptability to altitude than tetraploid or not needs to be proofed by population genomic data. A fluorescence-based AFLP technique was used to investigate the allele share of hexaploid Campeiostachys nutans (Griseb.) J. L. Yang, B. R. Baum et C. Yen and tetraploid Roegeneria nutans (Keng) Keng as well as the genetic variation and natural selection in 22 natural populations and their association with ecological factors. Of all the AFLP bands, 84.29 % were found in common between two different ploidy wheatgrasses. In addition, we found that hexapoid C. nutans had 1.45 times the allelic frequency and more large-sized bands than tetraploid R. nutans. After genetic analyses, the next factor examined should be the effect of altitude on genetic variation. There were no significant inter-population genetic differentiations, suggesting that distance did not contribute to spatial isolation. Altitude and soil nutrient availability might play an important role in maintaining the genetic diversity. A certain percentage of positive selection loci were discovered in total genome allele. Hexaploid wheatgrass with higher ploidy numbers can show strong genetic adaptability to adverse high-altitude condition because of its complex genomic background with an additional H genome, which supports our hypothesis. Though this evolutionary process is believed to be the driving force behind sympatric speciation, we cannot forecast that hexaploid wheatgrass species will diversify into two species in the long term, but believe that diversification under local selection helps to increase the adaptability to the changes in altitude.     

Low genetic diversity in wild emmer (T. turgidum L. subsp. dicoccoides (Körn. ex Asch. et Graebn.) Thell.) from South-eastern Turkey revealed by Restriction Fragment Length Polymorphism

The present work was carried out to study genetic diversity among 17 populations of wild emmer wheat sampled from South-eastern Turkey, considered to be an important region for domestication of wheat. Eleven RFLP clones and 4 restriction enzymes combinations were used to probe the genomic DNA. A total of 151 polymorphic loci were obtained from the enzyme-probe combinations. The Genetic Distance (GD) values were from 0.019 (Gaziantep-3 and Sanliurfa-4) to 0.200 (Gaziantep-1 and K. Maras). Cluster analysis results showed that populations formed 2 clades within the dendrogram. Population Gaziantep-1 was unique and genetically most diverse from the remaining 16 populations. The results of average genetic distance (GD) among populations suggested that narrow genetic variability exist among 17 populations in the present study.     

Characterization of a flint maize (Zea mays L. convar. mays) Italian landrace: I. Morpho-phenological and agronomic traits

Maize (Zea mays L.) landraces have the highest genetic variation and adaptation to the natural and anthropological environment where they have evolved. Surveying both qualitative and quantitative morphological traits of existing landraces may be useful in maintaining their genetic diversity and preserving them from genetic erosion. Our research deals with the morpho-phenological and agronomic characterization of a flint maize landrace, named 'Nostrano di Storo', still grown in an inland hilly environment in the low valley of Chiese River in Trentino, North-Eastern Italy. The majority of plants from twenty field populations proved to belong, with few exceptions (NSt2, NSt9, NSt11), to a single population. It means that the plant material long grown in this area and maintained by local farmers through yearly selection forms a single landrace within which some populations (i.e. NSt1, NSt3, NSt4, NSt7, NSt10, NSt18, NSt19, NSt20) could be considered as most representative and taken as 'core'. This is supported by the fact that the genetic variability was much higher within than between field populations: half of the plant and ear traits investigated did not show any significant difference between populations whereas all traits but two showed highly significant differences within populations. Selection carried out over the years by each farmer according to his own criteria produced little genetic differentiation within the original population. Gene flow among farmer populations, most likely occurred through both pollen dispersion to neighboring cultivated fields and seed exchange among farmers, may help to explain the low genetic differentiation. This information is useful for both planning conservation and recognizing the landrace as a unique germplasm source of specific geographic origin.     

枣遗传图谱构建研究进展

枣遗传图谱是枣树分子辅助育种的重要工具之一。高质量的枣遗传图谱在遗传演化分析、QTLs基因定位等研究中发挥了重要作用。为开展图位克隆重要农艺性状基因、加快枣育种进程,本文简要概述了目前国内外枣遗传图谱的研究进展,包括设计亲本组合、真实子代鉴定、构建作图群体、遗传图谱构建和相关QTL定位研究等方面,进一步探讨前人研究存在的问题并提出相关解决措施,为开展筛选农艺状候选基因和枣分子辅助育种研究奠定了理论基础。     

Study of the genetic variability and similarity among and within Arachis villosulicarpa, A. pietrarellii and A. hypogaea through isoenzyme analysis

Arachis villosulicarpa is a perennial species cultivated for its soft and tasty seeds by indigenous inhabitants of the Mato Grosso State, Brazil. Besides A. hypogaea, this species is considered as the only species of Arachis which represents a valuable food source for human consumption. Due to the lack of knowledge concerning the genetic diversity of A. villosulicarpa, this study was conducted to evaluate the genetic variability of the accessions from the Germplasm Collection of CENARGEN/EMBRAPA (Brasília, DF, Brazil) and Instituto Agrono^mico (IAC, Campinas, SP, Brazil). In addition, the genetic similarity between A. villosulicarpa, the related wild species A. pietrarellii, and the cultivated peanut A. hypogaea cv. Tatu was evaluated. From the entire sample analyzed of A. villosulicarpa, the accession from Instituto Agrono^mico showed the highest indices of diversity for both enzymatic systems analyzed, pointing this accession as a promising source of genetic variabil ity that must be preserved in the Germplasm Bank. A high level of genetic similarity was observed between A. pietrarellii and A. villosulicarpa, supporting previous suggestions that A. pietrarellii could be the ancestral progenitor species of A. villosulicarpa or that both species originated from a common ancestor.     

Genetic diversity in Hordeum chilense Roem. et Schult. germplasm collection as determined by endosperm storage proteins

Hordeum chilense Roem. et Schult. shows interesting characteristics for breeding, such as disease or pest resistance and has high variability for endosperm storage proteins, valuable for the improvement of the breadmaking quality of both tritordeum and wheat. Knowledge of the genetic structure and the level of H. chilense genetic diversity within its distribution zone may be important to decide on breeding strategies as well as management procedures. The pattern of genetic variation within and among different regions of the distribution area of H. chilense, was analysed by endosperm storage proteins (gliadin and low-molecular- weight glutenin subunits). Several analyses were performed including AMOVA, direct correlation between phenotypic and geographic distance matrices and spatial genetics differentiation. Most genetic diversity was caused by differences among individuals within a population, although all the analyses performed suggest the existence of a low degree of differentiation within regions. Correlation values between phenotypic and geographic distances were low but significant. The spatial genetics analysis revealed that the average phenotypic distances of each of the spatial distance class were not lower (or higher) than that expected by chance. These results are explained by their neutral behaviour towards a selection of endosperm storage proteins and could be very useful in optimising future sample collecting strategies.     

The potential for genetic contamination vs. augmentation by native plants in urban gardens

Native plants in gardens can potentially aid conservation by contributing to genetic diversity and buffering small and otherwise isolated populations from extinction. However, gene flow from such plantings may threaten the genetic integrity of natural populations. We assessed the morphological and genetic diversity of garden plants in an urban population of Grevillea macleayana in south-eastern Australia. There were two main groups of garden plants: some similar to plants in nearby natural populations; others with unusual morphology. Multivariate analysis of morphological characters separated these groupings, which were confirmed by genetic analysis. Both groups produced seeds and flowering phenologies overlapped, indicating a potential for gene flow. Hand pollination showed that plants in each group could fertilize flowers of the other. Thus, these garden plants contributed to genetic variation in an urban/bushland metapopulation but there was potential for gene flow from the unusual plants. Unless carefully managed, garden plants may therefore cause disruption of the genetic integrity of nearby natural populations.     

Distribution and eco-geographic characterization of Carica papaya L. native to Mexico

Genetic Resources and Crop Evolution - Carica papaya L. is an important plant genetic resource that has a low level of genetic erosion. Knowing the distribution and eco-geography of native C....     

Studying the extent of genetic diversity among Gossypium arboreum L. genotypes/cultivars using DNA fingerprinting

Genetic diversity is an area of concern for sustaining crop yield. Information on genetic relatedness/diversity among Gossypium arboreum L. cultivars/genotypes is scanty. We have used random amplified polymorphic DNA (RAPD) analysis to assess the genetic divergence/relationship among 30 genotypes/cultivars of G. arboreum. Of 45 primers surveyed, 63% were polymorphic. Out of the total number of loci amplified, 36% were polymorphic. The calculated genetic similarity between the cultivars/genotypes was in the range of 47.05–98.73%. Two genotypes, HK-244 and Entry-17, were the most distantly related. The average genetic relatedness among all the genotypes was 80.46%. However, most of the cultivated varieties showed a close genetic relationship, indicating a narrow genetic base in comparison to the non-cultivated germplasm. The calculated coefficients were used to construct a dendrogram using the unweighted pair group of arithmetic means (UPGMA) algorithm, which grouped the genotypes/cultivars into two major and three smaller clusters. The study is the first comprehensive analysis of the genetic diversity of G. arboreum germplasm and identifies cultivars that will be useful in extending the genetic diversity of cultivated varieties and future genome mapping projects.     

Assessment of genetic diversity in cultivars and wild accessions of Luohanguo (<Emphasis Type="Italic">Siraitia grosvenorii</Emphasis> [Swingle] A. M. Lu et Z. Y. Zhang), a species with edible and medicinal sweet fruits endemic to southern China,using RAPD and AFLP markers

Genetic variation of wild populations and cultivars of Luohanguo (Siraitia grosvenorii), a plant species endemic to southern China, was assessed using random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers. Based on the results for 130 individuals from seven populations, a high level of genetic diversity of Luohanguo was observed at the species level. The percentage of polymorphic loci (P) was 89.4%, Nei’s gene diversity (H _e) was 0.239, and Shannon’s information index (H _o) was 0.373 based on the combined AFLP and RAPD data. There was a high degree of genetic differentiation, with 45.1% of the genetic variation attributed to differences between the populations. The genetic diversity of the Luohanguo cultivars is much lower than that of wild populations (P = 41.8%, H _e = 0.141, H _o = 0.211), and a distinct genetic differentiation is observed between the cultivars and wild accessions. The pool of genetic variation in the wild populations provides an excellent gene resource for Luohanguo breeding.     

Genetic variation of five species of Trifolium L. from south-west Turkey

Following a legume collection mission to south-west Turkey in 1996, five species of Trifolium were analysed for genetic variation within and between species in eleven morphological and flowering characters. The five species included two outcrossing species, T. michelianum and T. resupinatum, and three inbreeding species, T. clypeatum, T. glomeratum and T. tomentosum. The genetic diversity found was related to climate and edaphic factors. All five species showed significant amounts of genetic differentiation between sites and the species could be separated morphologically by principal components analysis and cluster analysis. The most significant source of genetic variation was found to be related to geographical distribution with those species which were widely distributed across south-west Turkey exhibiting much greater amounts of genetic variation between sites, than those which had a narrow distribution. The breeding system was found to be less important, but only the morphology of the outbreeding species showed any environmental clines in relation to climate. A multiple regression analysis was computed to estimate the effect of growing season on the days to flowering of each of the species.     

Genetic diversity in populations of wild diploid wheat Triticum urartu Tum. ex. Gandil. revealed by isozyme markers

Genetic variation and its distribution within and among 23 populations of Triticum urartu collected from Syria, Lebanon, Turkey, Armenia, and Iran was estimated using isozyme markers at eight polymorphic loci. The number of alleles per locus (A= 1.21), percentage polymorphic loci (P= 20.1%), and mean gene diversity (H_e= 0.024) were relatively low. In a population from Lebanon, a high number of alleles per locus (A= 2.13) and percentage polymorphic loci (P= 87.5%) was found. On average, genetic variation among populations (G_ST= 0.407) was smaller than within-population variation (0.593). However, different patterns of genetic structure were found among various geographic regions. Interpopulation variation was highest for the Iranian populations (0.89) followed by the Turkish populations (0.66). A reverse pattern was observed for the Syrian (0.11) and for the Lebanese (0.13) populations. The Armenian populations exhibited similar interpopulation and within-population variation. Principal component and cluster analyses resulted in distinct grouping of the geographically proximal populations, with the exception of the two Iranian populations. The Turkish populations were different from the neighboring Armenian populations compared to other countries. The populations from southern Syria and those from Lebanon also exhibited a high degree of genetic diversity. The two most heterozygous loci, Mdh-2 and Pgi-2, separated the populations along the first and second principal components, respectively. Most of the rare alleles were scattered sporadically throughout the geographic regions. Rare alleles with high frequencies were found in the Turkish and Armenian populations. These results indicated that different geographic regions require specific sampling procedures in order to capture the range of genetic variation observed in T. urartu populations.     

不同致病型水稻细条病菌的遗传多样性分析

采用引物BOX和ERIC对来自4省的35个细条病菌菌株进行Rep-PCR扩增,BOX引物扩增出14条指纹带,10种谱型,以致病型为单位计算遗传多样性值为0.63～1.00;ERIC引物扩增出19条指纹带,17种谱型,遗传多样性值为0.86～1;引物ERIC比BOX在遗传多样性方面有更好的分辨率;树状聚类图反映的遗传分簇差异,与菌株的致病型及其地理的来源之间没有相关性。     

Analysis of genetic diversity in Prunus sibirica L. in inner Mongolia using SCoT molecular markers

Genetic Resources and Crop Evolution - Population genetic diversity contributes to the protection and utilization of germplasm resources, especially via genetic breeding. In the present study,...     

江西野生毛花猕猴桃群体SSR遗传多样性研究

为分析江西野生毛花猕猴桃群体遗传多样性,以江西省境内的5个野生毛花猕猴桃雄性群体(72个个体)为试验材料,采用SSR分子标记技术,选取15对多态性引物,利用聚丙烯酰胺电泳对PCR产物进行检测。结果表明,15对SSR引物共检测到86个位点,多态性位点百分率为100.0%;观察到的平均等位基因数为5.733,有效等位基因数为3.002,Shannon信息指数为1.046。表观杂合度介于0.111~0.819之间,预期杂合度介于0.041~0.876之间,遗传分化系数为2.01,野生毛花猕猴桃雄性群体间存在较大的遗传分化。5个毛花猕猴桃雄性群体遗传距离范围为0.102~0.409,遗传相似度范围为0.665~0.903,群体间遗传距离与地理距离无相关性。群体的遗传多样性丰富度依次为庐山>井冈山>南源山>武功山>麻姑山,江西地区供试的野生毛花猕猴桃雄性群体在分子水平上具有丰富的多态性。本研究结果为毛花猕猴桃雄性品种选育、种质创新与利用提供了一定的理论基础。     

Test systems for assessing mutagenic potential of chemical substances.

The first report that certain chemicals have the potential of inducing heritable effects (mutation) appeared in the mid-1940's. Two decades passed before this and subsequent observations were translated into a concern that some of the chemicals to which we are exposed may constitute a hazard to man's genetic material and hence a threat to future generations of individuals. Such concern has led to the gradual evolution of the newest subdiscipline of toxicology, genetic toxicology. This subdiscipline is still young and faces many challenges in terms of developing sound toxicologic approaches for meeting specific evaluation needs in the interest of public health. This paper describes the current status of efforts in genetic toxicology and the types of steps which must be taken in order to begin to meet the needs and requirements of regulatory agencies.     

Genetic diversity in wild Tunisian populations of Mentha pulegium L. (Lamiaceae)

The allozyme variation of 15 Tunisian wild populations of Mentha pulegium L. threatened by human activities (clearing, hard-grazing, ploughing, traditional uses) was surveyed by the analysis of 14 isozyme loci using horizontal gel starch electrophoresis. The species exhibited a high level of genetic variation within populations (the mean Ap = 2.20, P = 72%, Ho = 0.349 and He = 0.229), which indicates a predominately outcrossing mating system and the recruitment of new genotypes via dispersal seeds. The genetic structure analysis of the populations using F statistics indicates no inbreeding, and showed an excess of heterozygosity for few loci. The moderate differentiation of populations (F_ST = 0.110) and the low rate of gene flow between them (Nm = 2.02) might been caused by recent isolation of the populations through biotope disturbances. The value of Nei's genetic identity varied from 0.839 to 0.999 reflecting a relatively low genetic divergence between populations. Cluster analysis using UPGMA method and Nei's genetic identity values, showed that populations geographically close didn't always cluster together. However, populations within the same bioclimatic stage generally subclustered together indicating that differentiation between bioclimatic regions occurred.     

Genetic variability in Turkmen populations of Pistacia vera L.

Seedlings of Pistacia vera L. developed from seeds of two separate populations in Turkmenistan, Kepele and Agachli, were evaluated for their growth potential and genetic polymorphism. Plant growth rate as well as random amplified polymorphic DNA (RAPD) analysis showed distinct differences between the two populations. In plant height growth rate, 17 Agachli accessions were 1.3 times higher on average than that of 10 accessions of Kepele (significant at p = 0.046) and 1.2 times higher for trunk diameter growth rate (p = 0.062). Cluster analysis divided most accessions into two main genetic groups according to their geographic origin. The Agachli group was further divided into two subgroups. One Kepele accession (K4), was genetically different from the rest and clustered on a separate outgroup. Two Agachli accessions (A12 and A17) were outside the two main populations clusters. Accessions K9 and K10 from Kepele were exceptional and were clustered in each of the two Agachli's subgroups, indicating a close genetic relationship between the two populations. In addition, high similarity values (0.58–1.00) and small genetic distances reflect plausible gene flow between Kepele and Agachli, which are 100 Km apart. Mantel test revealed significant relationship between the RAPD and the morphological traits matrices, pointing to the genetic basis for the measured differences in the growth rate. Growing the accessions on the same plot, under similar conditions enabled the evaluation of genotypic differences. The combination of morphological traits and molecular markers will further assist in preservation of genetic variability and cultivation of useful genotypes of P. vera L.     

Assessment of genetic diversity and genetic relationships among 29 populations of <Emphasis Type="Italic">Azadirachta indica</Emphasis> A. Juss. using RAPD markers

Randomly amplified polymorphic DNA (RAPD) analysis was employed to assess genetic divergence among 29 neem accessions collected from two agro-ecological regions of India (11 agro-climatic sub-zones), which cover three states, Punjab, Haryana and Rajasthan. Out of 24, 10-mer random primers used for studying genetic divergence, 14 were polymorphic, generating a total of 73 amplification products with an average of 5.21 products per polymorphic primer and estimated gene diversity of 0.49. Genetic relationships among accessions were evaluated by generating a similarity matrix based on Jaccard’s coefficient, ranging from 0.70 to 0.96. The phenetic dendrogram generated by UPGMA analysis grouped accessions into five clusters. RAPD performed within accessions (individual seedlings collected from the same mother plant) showed no variation indicating homogeneous population within accessions. Primers OPA-18, OPC-08 and OPI-03 were found most informative based on their resolving power. The degree of genetic variation detected among the 29 accessions with RAPD analysis suggests that RAPD can be used for studying genetic diversity in neem. The study also demonstrated that neem germplasm collected from northwestern plains of India shows no eco-geographical isolation based on sub-zones because accessions collected from different sub-regions are grouping together in the genetic tree.