1,721,000 research outputs found
Dall’origine delle specie coltivate alla confusione varietale in vite: attuali conoscenze e prospettive nell’era della post-genomica.
No full textCultivated grapevine, Vitis vinifera subsp. vinifera L., is one of the most widely grown fruit crops in the world. Sexual hybridization has been a major
driving force for its evolution and has generated thousands of varieties, whereas somatic mutations are the major source of intra-varietal grapevine diversity. Nowadays, more than 450 varieties are registered in Italy, and thousands of clones are recognized. All these grapes are proudly used to make some of the world’s finest wines, thanks not only to history, traditions, and excellent pedo-climatic conditions but also to a particularly heterogeneous collection of varieties, some of which have been growing here since the first half of the 19th century. However, in the past few decades the grapevine biodiversity has been eroded, due to the worldwide predominance of few successful cultivars and to cultivation restrictions for varieties not included in official grapevine lists. Therefore, there is a significant decrease of raw material for future selection and to address new breeding objectives. An efficient characterization system is important to define population structures, to avoid cases of synonymy (identical genotypes but different names) and homonymy (same names but different genotypes), and protect breeders’ rights. The oldest grape discrimination
techniques are based on phenological traits analysis carried out during all vegetative cycle. These techniques are elaborate and time-consuming. Characterization of grapevine has today been complemented by the use of DNA-based techniques, which enables more accurate identification and overcomes many of the limitations of phenotypic-based diversity analysis. Through the exploitation of molecular markers, many cases of synonymies/homonymies have been identified in the Italian collections. However, when molecular markers have been used to study clonal variation, consistent results have not always been obtained. The plethora of high-throughput technologies currently available provides promising
tools for the analysis of diversity within the varieties. Moreover, the anticipated improvements in NGS capacity will lead to further decrease the persample cost and increase the quality of the resulting genotype data. In this scenario, the objective of this paper is to review on varietal authentication methods with particular emphasis on those capable to distinguish clones within variety populations. After reporting the causes and consequences of genetic inter- and intra-varietal diversity, we will review the methodologies currently applied to unraveling them. We then provide information on the potential of post-genomic techniques as powerful tools to identify synonymous and homonymous cases and to distinguish clonal
populations
Strategie innovative di miglioramento genetico per l'utilizzazione di germoplasma selvatico di Solanum resistente a stress biotici.
No full text
Variation of DNA methylation and phenotypic traits following unilateral sexual polyploidization in Medicago
No full textSexual hybridization is an important
generator of biodiversity and a powerful breeding tool.
Hybridization can also overcome ploidy barriers when
it involves 2n gametes, as in the case of unilateral
sexual polyploidization (USP) that has been utilized in
several crops, among which alfalfa. This research was
aimed at gaining insights into the effects of USP on
genome methylation and on phenotypic traits in alfalfa,
an important forage species. The Methylation-Sensitive
Amplified Polymorphism technique was used to
estimate the cytosine methylation changes occurring
in a tetraploid (2n = 4x = 32) USP progeny from
crosses between a diploid Medicago sativa subsp.
falcata genotype that produces 2n eggs and a cultivated
tetraploid Medicago sativa subsp. sativa variety. De
novo methylation or demethylation in the USP progeny
were observed for 13% of the detected genomic sites,
indicating that methylation changes can be relevant.
USP plants showed larger surface area of the leaf epidermis cells than both parents, but this did not result
in larger leaf size or higher plant biomass. They
displayed significant higher ovule sterility than the
tetraploid parent, but normal fertility was observed in
crosses with unrelated male testers. We conclude that
hybridization and sexual polyploidization resulted in
novel variation in terms of remodeling of the methylation
landscape as well as changes in phenotypic traits
in alfalfa
Exploitation of incongruent Solanum species for introgression of late blight resistance into the cultivated potato.
No full textWhole-genome doubling affects pre-mirna expression in plants
Full text linkWhole-genome doubling (polyploidy) is common in angiosperms. Several studies have indicated that it is often associated with molecular, physiological, and phenotypic changes. Mounting evidence has pointed out that micro-RNAs (miRNAs) may have an important role in whole-genome doubling. However, an integrative approach that compares miRNA expression in polyploids is still lacking. Here, a re-analysis of already published RNAseq datasets was performed to identify microRNAs’ precursors (pre-miRNAs) in diploids (2x) and tetraploids (4x) of five species (Arabidopsis thaliana L., Morus alba L., Brassica rapa L., Isatis indigotica Fort., and Solanum commersonii Dun). We found 3568 pre-miRNAs, three of which (pre-miR414, pre-miR5538, and pre-miR5141) were abundant in all 2x, and were absent/low in their 4x counterparts. They are predicted to target more than one mRNA transcript, many belonging to transcription factors (TFs), DNA repair mechanisms, and related to stress. Sixteen pre-miRNAs were found in common in all 2x and 4x. Among them, pre-miRNA482, pre-miRNA2916, and pre-miRNA167 changed their expression after polyploidization, being induced or repressed in 4x plants. Based on our results, a common ploidy-dependent response was triggered in all species under investigation, which involves DNA repair, ATP-synthesis, terpenoid biosynthesis, and several stress-responsive transcripts. In addition, an ad hoc pre-miRNA expression analysis carried out solely on 2x vs. 4x samples of S. commersonii indicated that ploidy-dependent pre-miRNAs seem to actively regulate the nucleotide metabolism, probably to cope with the increased requirement for DNA building blocks caused by the augmented DNA content. Overall, the results outline the critical role of microRNA-mediated responses following autopolyploidization in plants
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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