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203 results on '"Niedz, Randall P."'

41. The effects of nitrogen and potassium nutrition on the growth of nonembryogenic and embryogenic tissue of sweet orange (Citrus sinensis (L.) Osbeck)

Author

Evens Terence J and Niedz Randall P

Subjects
Botany, QK1-989
Abstract

Abstract Background Mineral nutrients are one of the most basic components of plant tissue culture media. Nitrogen in the form of NH4+ and NO3- is the dominant mineral nutrient in most plant tissue culture formulations, with effects dependent on both the proportion and the amount of NH4+ and NO3-. The effects of nitrogen nutrition on the growth of nonembryogenic and embryogenic cell lines of sweet orange (C. sinensis (L.) Osbeck cv. 'Valencia'), tissues routinely used in citrus horticultural and plant improvement research, was explored using an experimental approach free of ion confounding that included a 2-component mixture (NH4+:K+) and a quantitative factor [NO3-] crossed by the mixture, thereby providing ion-specific estimates of proportional and amount effects. Results First, the linear mixture component, though only a comparison of the design space vertices, was highly significant for both tissue types and showed that NH4+ was required by both tissues. Second, the NH4+ * K+ mixture term was highly significant for both tissue types, revealing that NH4+ and K+ exhibit strong synergistic blending and showed that growth was substantially greater at certain blends of these two ions. Third, though the interaction between the NH4+:K+ mixture and NO3- amount on fresh weight accumulation for both tissue types was significant, it was substantially less than the main effect of the NH4+:K+ mixture. Fourth, a region of the design space was identified where fresh weight growth was increased 198% and 67% over the MS medium controls for nonembryogenic and embryogenic tissues. Conclusion By designing a mineral nutrient experiment free of ion confounding, a direct estimation of ion-specific proportional and amount effects on plant tissue growth is possible. When the ions themselves are the independent factors and/or mixture components, the resulting design space can be systematically explored to identify regions where the response(s) is substantially improved over current media formulations. In addition, because the response is over a defined experimental region, a specific medium formulation is more accurately interpreted as a coordinate in the specified design geometry.

Published
2008
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46. Reticulated origin of domesticated emmer wheat supports a dynamic model for the emergence of agriculture in the fertile crescent

Author

Niedz, Randall P., Civan, Peter, Ivaničová, Zuzana, Brown, Terence A., Brown, Terence A., and University of Manchester [Manchester]

Subjects
0106 biological sciences, DNA, Plant, Retroelements, Range (biology), Evolution, [SDV]Life Sciences [q-bio], Population, lcsh:Medicine, Biology, Rna multigene family, Aflp analysis, Polymerase Chain Reaction, 01 natural sciences, Gene flow, Common wheat, 03 medical and health sciences, Phylogenetic networks, Phylogenetics, Botany, Wild wheats, lcsh:Science, Domestication, education, Triticum, ComputingMilieux_MISCELLANEOUS, 030304 developmental biology, 2. Zero hunger, 0303 health sciences, education.field_of_study, Multidisciplinary, Phylogenetic tree, Tetraploid wheats, lcsh:R, Agriculture, Models, Theoretical, 15. Life on land, Near-east, Phylogeography, Fixation (population genetics), Evolutionary biology, Triticum-dicoccoides, Hybridization, Genetic, lcsh:Q, Research Article, 010606 plant biology & botany
Abstract

We used supernetworks with datasets of nuclear gene sequences and novel markers detecting retrotransposon insertions in ribosomal DNA loci to reassess the evolutionary relationships among tetraploid wheats. We show that domesticated emmer has a reticulated genetic ancestry, sharing phylogenetic signals with wild populations from all parts of the wild range. The extent of the genetic reticulation cannot be explained by post-domestication gene flow between cultivated emmer and wild plants, and the phylogenetic relationships among tetraploid wheats are incompatible with simple linear descent of the domesticates from a single wild population. A more parsimonious explanation of the data is that domesticated emmer originates from a hybridized population of different wild lineages. The observed diversity and reticulation patterns indicate that wild emmer evolved in the southern Levant, and that the wild emmer populations in south-eastern Turkey and the Zagros Mountains are relatively recent reticulate descendants of a subset of the Levantine wild populations. Based on our results we propose a new model for the emergence of domesticated emmer. During a pre-domestication period, diverse wild populations were collected from a large area west of the Euphrates and cultivated in mixed stands. Within these cultivated stands, hybridization gave rise to lineages displaying reticulated genealogical relationships with their ancestral populations. Gradual movement of early farmers out of the Levant introduced the pre-domesticated reticulated lineages to the northern and eastern parts of the Fertile Crescent, giving rise to the local wild populations but also facilitating fixation of domestication traits. Our model is consistent with the protracted and dispersed transition to agriculture indicated by the archaeobotanical evidence, and also with previous genetic data affiliating domesticated emmer with the wild populations in southeast Turkey. Unlike other protracted models, we assume that humans played an intuitive role throughout the process. Natural Environment Research Council [NE/E015948/1]; Slovak Research and Development Agency [APVV-0661-10, APVV-0197-10] info:eu-repo/semantics/publishedVersion

Published
2013

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