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Farmers' seed system is defined as a system in which seed selection, seed production, seed storage, seed management and seed diffusion are integrated with crop production. Formal seed system is the one that is run by formal privat...
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Farmers' seed system is defined as a system in which seed selection, seed production, seed storage, seed management and seed diffusion are integrated with crop production. Formal seed system is the one that is run by formal private and public seed companies. Farmers indicated that when they started sorghum farming the seed of farmers' varieties (FVs) they obtained was normally a gift from the parents and relatives. Thereafter own stock was the predominant seed source. However, for the improved varieties (IVs) purchasing was the common initial source. The current seed source is predominantly own stock. The farmers' seed system was dominantly dependent on the FVs. Consequently, the demand for IVs is very low. The weather conditions partly affect the seed-sourcing pattern. In a bad cropping season, farmers were forced to use seed sources other than own stock; namely, purchase gift, exchange and loan. Genetic diversity dictated the pattern of seed sources. High on-farm genetic diversity leads to more on-farm and less off-farm seed sourcing (more own stock than non-own stock). The most widely used non-cash based seed channels were gift and exchange. The role of formal seed system in seed supply is very limited. Over the last 20 years, the total amountof seed produced by Ethiopian Seed Enterprise (ESE) amounted to 16,740 tons, which is almost equivalent to two years' sorghum seed requirement. The low amount of seed produced and sold by the ESE is due to the low demand by farmers for IVs and lack of appropriate varieties for the intermediate and highland areas. Farmers' seed system has been found resilient, accommodative, adaptive and flexible. It has been always responsible for on-farm conservation, maintenance and selection of farmers' varieties.
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An Arabidopsis thaliana mutant was identified as having increases in 12 of 20 free proteogenic amino acids in seeds. Because these metabolites are produced from multiple, seemingly unrelated biosynthetic networks, it was not possi...
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An Arabidopsis thaliana mutant was identified as having increases in 12 of 20 free proteogenic amino acids in seeds. Because these metabolites are produced from multiple, seemingly unrelated biosynthetic networks, it was not possible to use a candidate gene approach to discover the enzyme defect responsible for this complex syndrome. Complementary metabolite profiling analyses revealed increased seed homomethionine and isovaleroyloxypropyl-glucosinolate, along with reduced 3-benzoyloxypropyl-glucosinolate. These data led to the discovery of impaired branched chain amino acid catabolic enzyme isovaleryl-CoA dehydrogenase (encoded by gene At3g45300 or atIVD) as the cause of this metabolic syndrome. These results indicate that catabolism plays an important role in regulating levels of branched chain amino acids in seeds. The diverse set of metabolites affected in the ivd1 mutants suggests the existence of a more complex network regulating seed amino acid accumulation than previously observed. This combined targeted and non-targeted metabolite profiling approach is broadly applicable to the characterization of metabolic mutants, human disease studies and crop germplasm.
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The efficiency of information diffusion on networks highly depends on both the network structure and the set of early spreaders. Moreover, in various realistic scenarios, to seed different nodes implies different costs, as in the ...
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The efficiency of information diffusion on networks highly depends on both the network structure and the set of early spreaders. Moreover, in various realistic scenarios, to seed different nodes implies different costs, as in the case of viral marketing, where costs often correlate with local network structure. The budgeted influence maximization (BIM) problem consists in determining a seed set whose diffusion maximizes the total number of influenced nodes, provided that the seeding cost is within a given budget. We investigate efficient seeding strategies for the BIM problem under the deterministic fixed threshold diffusion model. In particular, we introduce the concept of surrounding sets: relatively cheap seeds neighboring expensive, structurally-privileged nodes, which then become spreaders at lower costs. Numerical experiments with several real networks indicate our method outperforms strategies that seed nodes based on their influence/cost ratios. A key insight from our evaluation is that larger diffusion is generally attained from the surrounding sets that consider the two-hop neighborhood of influential nodes, as opposed to their immediate neighbors only. (C) 2019 Elsevier Inc. All rights reserved.
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Increasing yield and quality of seed storage compounds in a sustainable way is a key challenge for our societies. Genome-wide analyses conducted in both monocot and dicot angiosperms emphasized drastic transcriptional switches tha...
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Increasing yield and quality of seed storage compounds in a sustainable way is a key challenge for our societies. Genome-wide analyses conducted in both monocot and dicot angiosperms emphasized drastic transcriptional switches that occur during seed development. In Arabidopsis thaliana, a reference species, genetic and molecular analyses have demonstrated the key role of LAFL (LEC1, ABI3, FUSS, and LEC2) transcription factors (TFs), in controlling gene expression programs essential to accomplish seed maturation and the accumulation of storage compounds. Here, we summarize recent progress obtained in the characterization of these LAFL proteins, their regulation, partners and target genes. Moreover, we illustrate how these evolutionary conserved TFs can be used to engineer new crops with altered seed compositions and point out the current limitations. Last, we discuss about the interest of investigating further the environmental and epigenetic regulation of this network for the coming years. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
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The problem of finding optimal set of users for influencing others in the social network has been widely studied. Because it is NP-hard, some heuristics were proposed to find sub-optimal solutions. Still, one of the commonly used ...
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The problem of finding optimal set of users for influencing others in the social network has been widely studied. Because it is NP-hard, some heuristics were proposed to find sub-optimal solutions. Still, one of the commonly used assumption is the one that seeds are chosen on the static network, not the dynamic one. This static approach is in fact far from the real-world networks, where new nodes may appear and old ones dynamically disappear in course of time. The main purpose of this paper is to analyse how the results of one of the typical models for spread of influence - linear threshold - differ depending on the strategy of building the social network used later for choosing seeds. To show the impact of network creation strategy on the final number of influenced nodes - outcome of spread of influence, the results for three approaches were studied: one static and two temporal with different granularities, i.e. various number of time windows. Social networks for each time window encapsulated dynamic changes in the network structure. Calculation of various node structural measures like degree or betweenness respected these changes by means of forgetting mechanism - more recent data had greater influence on node measure values. These measures were, in turn, used for node ranking and their selection for seeding. All concepts were applied to experimental verification on five real datasets. The results revealed that temporal approach is always better than static and the higher granularity in the temporal social network while seeding, the more finally influenced nodes. Additionally, outdegree measure with exponential forgetting typically outperformed other time-dependent structural measures, if used for seed candidate ranking.
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Cinnamomum migao is an endangered evergreen woody plant species endemic to China. Its fruit is used as a traditional medicine by the Miao nationality of China and has a high commercial value. However, its seed germination rate is ...
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Cinnamomum migao is an endangered evergreen woody plant species endemic to China. Its fruit is used as a traditional medicine by the Miao nationality of China and has a high commercial value. However, its seed germination rate is extremely low under natural and artificial conditions. As the foundation of plant propagation, seed germination involves a series of physiological, cellular, and molecular changes; however, the molecular events and systematic changes occurring during C. migao seed germination remain unclear. In this study, combined with the changes in physiological indexes and transcription levels, we revealed the regulation characteristics of cell structures, storage substances, and antioxidant capacity during seed germination. Electron microscopy analysis revealed that abundant smooth and full oil bodies were present in the cotyledons of the seeds. With seed germination, oil bodies and other substances gradually degraded to supply energy; this was consistent with the content of storage substances. In parallel to electron microscopy and physiological analyses, transcriptome analysis showed that 80–90?% of differentially expressed genes (DEGs) appeared after seed imbibition, reflecting important development and physiological changes. The unigenes involved in material metabolism (glycerolipid metabolism, fatty acid degradation, and starch and sucrose metabolism) and energy supply pathways (pentose phosphate pathway, glycolysis pathway, pyruvate metabolism, tricarboxylic acid cycle, and oxidative phosphorylation) were differentially expressed in the four germination stages. Among these DEGs, a small number of genes in the energy supply pathway at the initial stage of germination maintained high level of expression to maintain seed vigor and germination ability. Genes involved in lipid metabolism were firstly activated at a large scale in the LK (seed coat fissure) stage, and then genes involved in carbohydrates (CHO) metabolism were activated, which had their own species specificity. Our study revealed the transcriptional levels of genes and the sequence of their corresponding metabolic pathways during seed germination. The changes in cell structure and physiological indexes also confirmed these events. Our findings provide a foundation for determining the molecular mechanisms underlying seed germination.
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Seed-size uniformity is an important grading factor in soya beans affecting value. Currently, it is determined by visual inspection. Image analysis-based seed-size measurements were used to predict size uniformity of soya bean sam...
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Seed-size uniformity is an important grading factor in soya beans affecting value. Currently, it is determined by visual inspection. Image analysis-based seed-size measurements were used to predict size uniformity of soya bean samples. Linear discriminant function models and artificial neural network classifiers were developed to classify samples in two uniformity classes (uniform or not uniform in size) using various size distribution parameters as measures of size uniformity. Both methods of classification performed equally well with an agreement in excess of 84% with the visual assessment of samples..
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Seed priming with gibberellic acid (GA3) could promote seed germination in tobacco; however, the molecular mechanism is poorly understood. In this study, the physiological development and transcriptional regulatory network of toba...
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Seed priming with gibberellic acid (GA3) could promote seed germination in tobacco; however, the molecular mechanism is poorly understood. In this study, the physiological development and transcriptional regulatory network of tobacco seeds primed with GA3 or water, and non-primed seeds were studied during seed germination. When compared with non-primed or hydro-primed seeds, tobacco seeds primed with 100 mg/L GA3 solution for 24 h showed increased germination speed and uniformity under low temperatures (10°C). GA1+3 levels and β-1,3-glucanase activity were significantly higher at the germination starting and pre-endosperm–rupture stages respectively. The transcriptome between the GA3-primed seeds and hydro-primed seeds was much similar than to that of the non-primed seeds. The transcripts for which their expression patterns were significantly up- or downregulated in both the GA3-primed and hydro-primed seeds relative to non-primed seeds were the focus of the study, 93.90% of which after priming and 83.89% of which during radicle expansion were regulated in the same manner, respectively. GA3 priming promoted seed germination that was associated with 67 differentially expressed transcripts after priming, 64 of which were associated with radicle expansion. Of these, ABA receptors PYL1 and PYL7, ABA biosynthesis genes ABA1, NCED6, NCED9, and AAO3, ABA negative signal regulators ABI2, AHG3, ABI3, ABI4, and ABI5, auxin response factor ARF10, ARF 16, and ARF17, and light receptors PHYB and negative signal regulators PIF1, and XERICO were induced by GA3 priming. This study, thus, preliminarily revealed the physiological and molecular mechanism of gibberellin-priming promoting seed germination.
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