1,721,009 research outputs found
New genetic achievements on gametophytic self-incompatibility of fruit trees
No full textSelf-incompatibility is a crucial aspect of the reproductive biology of many fruit species, and in view of its impact on fruit production it has been extensively studied by several research groups worldwide. Taking advantage of modern high-throughput technologies and multi-disciplinary approaches, recent studies provided interesting insights on many aspects related to this phenomenon, including the biochemical and cytological events underlying it, their genetic control, and the complex evolution of self-incompatibility genes in the Rosaceae. Hereby we discuss some of the most relevant results recently produced by the scientific community in this field, addressing theoretical and practical questions of fruit breeding and growing, and focusing on future research challenges
Use of semi-compatible crosses in breeding for apple scab resistance
No full textGametophytic self-incompatibility is generally considered a hurdle for breeding programs, as it reduces the number of possible cross combinations. The wide variety of S-haplotypes in apple (Malus × domestica) reduces the probability of fully incompatible crosses, while the occurrence of semi-compatible combinations is more frequent. The yield in such combinations does not vary much with respect to full compatibility, but noteworthy a single S-haplotype from the male parent (pollen donor) will be transmitted to the progeny. This aspect should be carefully taken into account in breeding programs when one or more genes of interest are placed in proximity to the S-locus, as the segregation of the paternal alleles in the progeny will skew from the expected 1:1 ratio, reducing the frequency of the allele linked to the rejected S-haplotype. Among the genes linked to the S-locus in the rosaceous fruit trees, one of the most important is the apple scab resistance gene Rvi5. This gene, introduced in Malus × domestica from M. micromalus and × M. atrosanguinea 804, was fine-mapped in two large segregating populations and proved to be placed in close proximity to the S-locus, on the bottom of chromosome 17. Therefore, knowledge of the S-genotype of parental cultivars can be exploited to plan semi-compatible crosses that dramatically increase the frequency of the resistance gene in the progeny, and to avoid those combinations that conversely would reduce it
La sterilità del ciliegio: gruppi di incompatibilità e varietà autofertili.
No full textIl ciliegio, come molte altre specie da frutto appartenenti alle Rosacee, possiede un meccanismo di auto-incompatibilità controllato dal locus S (“sterilità”). Questo meccanismo si è evoluto per promuovere la fecondazione incrociata impedendo l’auto-fecondazione; il fiore di una pianta non può quindi essere fecondato dal suo stesso polline o da polline prodotto da piante della stessa varietà. Una cultivar di ciliegio per essere produttiva richiede pertanto la consociazione con almeno un genotipo compatibile che ne assicuri un’efficiente impollinazione. In alternativa si può ricorrere a cultivar auto-compatibili, in cui una mutazione (spontanea o indotta) inattiva il sistema di riconoscimento polline-pistillo che porta all’incompatibilità, rendendo la varietà autofertile
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
Data mining for apple S-RNase alleles in resequencing datasets
No full textThe sequence of the apple (Malus × domestica Borkh.) genome was obtained from the cultivar ‘Golden Delicious’ and released in 2010; the availability of this draft reference genome opened up the possibility to explore the genetic variation within this species on a genome scale, using high-throughput strategies such as high-density SNP arrays or resequencing of different cultivars. However, while these techniques are immediately effective and highly informative on most genomic loci, the S-locus has some uncommon features, derived from its mechanism of inheritance and evolutionary dynamics, that require different approaches. The extremely high level of allelic polymorphism, the lack of co-linearity between different -haplotypes, the massive presence of transposable elements and the evidence of extensive gene duplication as one of the main forces driving its evolution, are factors that make the Slocus an unsuitable target for common genomic procedures, such as SNP-based high-throughput assays and alignment of resequencing data on the reference genome. The aim of this work was to define a strategy for obtaining information on the S-locus from the high-depth resequencing of 6X apple cultivars. We focused on the S-RNase gene and developed a strategy initially aimed at identifying the S-genotype of resequenced cultivars; the short sequence reads obtained from each cultivar were then used to check and to expand the available sequence data for each identified allele. Our preliminary results suggest that the huge amount of information that derives from resequencing cultivars can be of great help to resolve incomplete, fragmentary or inconsistent data in the current database of apple S-RNase alleles
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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