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Effects of crop evolution under domestication and narrowing genetic bases of crop species
Get PDFCrop improvement is very crucial to satisfy the world demand in the presence of different challenges like climate change, reducing arable land and increasing population growth. Crop improvement program is continuously striving to increase crop yield, enhance crop quality and improve crop tolerance to biotic and abiotic stresses. Domestication has a great role in increasing agricultural productivity through selecting suitable crop plants to human beings like high yielding varieties with resistance to biotic and abiotic stresses, improved nutritional quality, big seed and fruit size, non-shattering, reduction of seed dispersal mechanisms, a more compact growth habit, early matured crop plants. Domesticated food crops are derived from a phylogenetically diverse assemblage of wild ancestors through artificial selection for different traits. Plant breeding and domestication of crop plants have a profound impact on the genetic diversity through selecting the desirable crops by neglecting other crop plants with undesirable traits. Domestication of crop plants shifted from hunter-gatherer to agricultural societies which leaded the rise of modern civilization. The amount or quantum of genetic diversity available in a breeding population is referred to as genetic base of that population. In other words, genetic base represents spectrum of genetic variability in a plant breeding population. Depending upon the amount of genetic diversity present in a plant breeding population, genetic base is of two types, viz. broad genetic base and narrow genetic base. Plant populations that are composed of several pure lines, inbred lines or heterozygotes and homozygotes are said to have broad genetic base. Examples of such populations are mass selected varieties, multiline varieties, synthetics, composites and land races. Such genotypes have wider adaptation to environmental changes. Those plant populations that have been developed from single homozygote or heterozygote are-said to have narrow genetic base. Examples of such populations are pure line variety, varieties developed by backcross, pedigree method bulk method, and single seed decent method, clonal variety and hybrids between two inbred lines or pure lines. Genetic loss is directly connected with the reduction of genetic diversity including the loss of individual genes and as well as the loss of particular combinations of genes such as those manifested in locally adapted landraces. Eventually, genetic erosion is the depletion in population variation because of inbreeding and genetic drift which is largely causes the endangerment of small isolated populations. Narrowing of genetic diversity might result the complete loss of crop plants. </p
Phenotypic variability analysis of key sorghum (Sorghum bicolor (L) moench) genotypes under dry lowland areas
No full textSorghum is a climate-resilient food security and nutrition crop, which has been produced as a staple food in the semi-arid tropical regions of the world. However, moisture stress is increasingly affecting sorghum performance, especially at the flowering stage when water availability is critical for grain filling, thus reducing the sorghum grain yield. Therefore, the experiment was conducted to identify the best-adapted superior sorghum genotypes and quantify genetic variability, heritability and genetic advance as percent of mean for yield and yield components of sorghum genotypes. An alpha lattice experimental design with two replications was used to assess 42 sorghum genotypes in total at Mieso and Kobo. The combined analyses of variance revealed the presence of substantial genetic variation among sorghum genotypes for yield and agronomic traits. Among the traits with high genotypic coefficients of variation and heritability observed for plant height, panicle width and panicle yield were linked with higher values of genetic advance as a percentage of the mean. This result indicates that additive gene action governs the variability of these traits. High heritability and genetic advancement percentages were obtained for plant height (95.63 and 45.39 %, respectively), 1000-seed weight (77.98 and 23.86 %, respectively), panicle exertion (74.87 and 51.88 %, respectively), and panicle yield (65.43 and 37.32 %, respectively). The maximum grain yield was obtained from genotype 4x14 (6.32 tha-1), followed by genotypes 8x15 (5.92 tha-1), 1x15 (5.88 tha-1), 13x14 (5.78 tha-1) and 6x15 (5.57 tha-1), with an average value of 5.00 tha-1, which was greater than the mean value of the check (ESH-4) (4.77 tha-1). In general, this study revealed wider genetic variability in the tested genotypes for different traits under moisture stress conditions. The selection and hybridization on these genotypes for a desired traits with high (H2) coupled with higher GCV and GAM will be effective to develop and select high yielding, stable and early sorghum genotypes. The results of this investigation would help determine the most pertinent genetic material and plan the subsequent breeding program to encourage efforts for varietal improvement. The most promising and potential genotypes that could be used commercially were identified by the study following an in-depth investigation of their superiority and yield stability over time across different parts of the country
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Genetic mapping in crop plants
Get PDFThe genetic map is the chromosome linear linkage map that uses the chromosome recombination and exchange rate as the relative length and genetic markers as the main body. Genetic-map construction is a critically important tool for further genomic studies, as well as for genetic breeding of economically important species. Linkage maps are estimates of the distance between two genetic loci, based on the frequency of recombination. A genetic linkage map with high density and resolution is a critical and indispensable tool in a wide range of genetic and genomic researches. Highly saturated genetic linkage maps are extremely helpful to breeders and are an essential prerequisite for many biological applications such as the identification of marker-trait associations, mapping Quantitative Trait Loci (QTL), candidate gene identification, development of molecular markers for Marker-Assisted Selection (MAS) and comparative genetic studies. Molecular markers are the basis for high-resolution genetic linkage map construction and Quantitative Trait Loci (QTL) fine-mapping, which provide powerful tools for genetic analyses of economic traits. With the rapid development of the biotechnology, dominant DNA markers were gradually replaced by co-dominant markers in genetic mapping including Single Nucleotide Polymorphisms (SNPs) and microsatellites (SSRs). The research area of Association Mapping (AM) is currently receiving major attention for genetic studies of quantitative traits in all major crops. With the development of molecular marker technology in the 1980s, the fate of plant breeding has changed. Different types of molecular markers have been developed and advancement in sequencing technologies has geared crop improvement. Genetic mapping uses the Mendelian principles of segregation and recombination to determine the relative proximity of DNA markers along the chromosomes of an organism. The progress made in molecular plant breeding, genetics, genomic selection and genome editing has contributed to a more comprehensive understanding of molecular markers and provided deeper insights into the diversity available for crops and greatly complemented breeding stratagems. Genetic markers are important developments in the field of plant breeding. The genetic marker is a gene or DNA sequence with a known chromosome location controlling a particular gene or trait. Genetic markers are closely related with the target gene and they act as sign or flags.</p
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Climate-Smart Agriculture: Effect of Climate Change on Food Security and Its Mitigation Strategies
No full textGlobal climate change has a detrimental effect on agricultural production, leading to food insecurity. It is the primary factor limiting crop productivity in arid and semi-arid tropical regions. The increasing challenges posed by climate change necessitate innovative approaches to sustain global food security. This review examines climate-smart agriculture (CSA) as a viable solution to address these challenges. CSA integrates sustainable farming practices that enhance productivity, promote resilience to climate impacts, reduce greenhouse gas emissions, and improve the adaptive capacities of agricultural systems. The review highlights key strategies within CSA, including the adoption of improved crop varieties, efficient water management, and agroecological techniques. It also discusses the socioeconomic implications of CSA, emphasizing the importance of stakeholder engagement and policy support for successful implementation. Relevant information was gathered using key terms such as CSA, climate change, adaptation, mitigation, and food security from databases like Scopus, Web of Science, and Google Scholar. The review underscores the potential of CSA to ensure food security in a changing climate while contributing to environmental sustainability. There is a pressing need to strengthen government policies and international cooperation to fund climate-smart agricultural initiatives. This includes promoting knowledge-sharing and providing financial incentives for farmers who adopt sustainable practices. Additionally, it is essential to encourage farmers to diversify crops and integrate livestock and agroecological practices to reduce risks associated with climate variability
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