E. Glen Price

Bio: E. Glen Price is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Gene pool. The author has an hindex of 1, co-authored 1 publications receiving 470 citations.

Comparative evolution of cereals.

Abstract: First, we shall introduce the materials with which we are dealing, and this requires some understanding of formal names and botanical classification. The taxonomy of cultivated plants has long been in a state of confusion. The same array of variation is treated in radically different ways by different taxonomists (see Jirasek, 1966; Jeffrey, 1968). Classifications are cluttered with Latin names that have little or no biological meaning, and some individual taxa are given ranks ranging from variety to genus depending on who is doing the classifying. Inept classifications have probably caused more difficulty in understanding the origin and evolution of cultivated plants than any other factor. We shall use the gene pool classification suggested by Harlan and de Wet (1971) in order to treat the several cereals on a uniform basis. In this system the total array of variation within maximum genetic reach is partitioned into primary, secondary, and tertiary gene pools. The primary gene pool includes all those races that can be crossed with the crop, yielding reasonably fertile hybrids in which the chromosomes pair well and in whose offspring genetic segregation is reasonably normal. The primary gene pool corresponds to the widely accepted concept of the biological species. The secondary gene pool includes all those species that can be crossed with the crop but with restricted gene flow. Genes can be transferred from the secondary to the primary gene pool, but one must struggle with those barriers that separate biological species such as sterility, poor chromosome pairing, lethal or weak hybrids, or poorly adapted hybrid derivatives and so on. The tertiary gene pool includes all those species that can be crossed with the crop, but the hybrids lead essentially nowhere. The hybrids are lethal, completely sterile, or anomalous. If any gene transfer is possible at all, it must be through radical manipulation of some sort such as embryo culture, tissue culture, use of complex hybrid bridges and so on (see Harlan and de Wet, 1971). Polyploid series in cultivated plants pose some special problems. As a general rule, we have suggested (Harlan and de Wet, 1971) that each level be treated as a separate gene pool. The barriers between ploidy levels are not necessarily strong, however, and morphological differences are sometimes minimal and difficult to describe. Each series is different and appropriate treatments must be worked out crop by crop. Separate gene pools for ploidy levels in potato or sugarcane may not be appropriate at all. In the cereals considered here, the only problem of separation by ploidy level occurs in oats where A vena strigosa and A. barbata races are difficult to distinguish morphologically. Our gene pool classification is not intended to be a formal taxonomic system but rather a simple device to bring a genetic focus to bear on the taxonomies already available. The conventional epithets can be used without undue confusion pro-

Molecular Systematics of Plants

Abstract: Preface. Part I: Molecules and genomes in plant systematics. Chloroplast DNA and the study of plant phylogeny: present status and future prospects - M T Clegg and G Zurawski Use of chloroplast DNA rearrangements in reconstructing plant phylogeny - S R Downie and J D Palmer Mitochondrial DNA in plant systematics: applications and limitations - J D Palmer Ribosomal RNA as a phylogenetic tool in plant systematics - R K Hamby and E A Zimmer Evolution of the NOR and 5S DNA loci in the Triticeae - R Appels and B Baum Part II: Molecular approaches to plant evolution Intraspecific chloroplast DNA variation: systematic and phylogenetic implications - D E Soltis, P S Soltis and B G Milligan Molecular data and polyploid evolution in plants - P S Soltis, J J Doyle and D E Soltis Molecular systematics and crop evolution - J Deobley Part III: Model studies of phylogenetic relationships Contributions of molecular data to polyploid evolution in plants - P S Soltis, J J Doyle and D E Soltis Molecular systematics and crop evolution - J Deobley Contributions of molecular data to papilionoid legume systematics - J J Doyle, M Levin and A Bruneau Chloroplast DNA variation in the asteraceae: phylogenetic and evolutionary implications - R K Jansen, H J Michaels, R S Wallace, K-J Kim, S C Keeley, L E Watson and J D Palmer Chloroplast DNA restriction site variation and the evolution of the annual habit in North American Coreopsis (Asteraceae) - D J Crawford, J D Palmer and M Kobayashi Molecular systematics of onagraceae: examples from Clarkia and Fuschia - K J Systema and J E Smith Floral morphology and chromosome number in the subtribe oncidiinae (Orchidaceae): evolutionary insights from a phylogenetic analysis of the chloroplast DNA restriction site variation - M W Chase and J D Palmer Part IV: Theoretical perspectives The suitability of molecular and morphological evidence in reconstructing plant phylogeny -M J Donaghue and M J Sanderson Character-site weighting for restriction site data in phylogenetic reconstruction, with an example from chloroplast DNA - V A Albert, B D Mishler and M W Chase Polymorphism, hybridization and variable evolutionary rate in molecular phylogenies - K Ritland and J E Eckenwalder Index.

The nature of selection during plant domestication

Abstract: Plant domestication is an outstanding example of plant–animal co-evolution and is a far richer model for studying evolution than is generally appreciated. There have been numerous studies to identify genes associated with domestication, and archaeological work has provided a clear understanding of the dynamics of human cultivation practices during the Neolithic period. Together, these have provided a better understanding of the selective pressures that accompany crop domestication, and they demonstrate that a synthesis from the twin vantage points of genetics and archaeology can expand our understanding of the nature of evolutionary selection that accompanies domestication.

Contrasting patterns in crop domestication and domestication rates: recent archaeobotanical insights from the Old World

Abstract: † Background Archaeobotany, the study of plant remains from sites of ancient human activity, provides data for studying the initial evolution of domesticated plants. An important background to this is defining the domestication syndrome, those traits by which domesticated plants differ from wild relatives. These traits include features that have been selected under the conditions of cultivation. From archaeological remains the easiest traits to study are seed size and in cereal crops the loss of natural seed dispersal. † Scope The rate at which these features evolved and the ordering in which they evolved can now be documented for a few crops of Asia and Africa. This paper explores this in einkorn wheat (Triticum monococcum) and barley (Hordeum vulgare) from the Near East, rice (Oryza sativa )f rom China, mung (Vigna radiata )a nd urd (Vigna mungo) beans from India, and pearl millet (Pennisetum glaucum) from west Africa. Brief reference is made to similar data on lentils (Lens culinaris), peas (Pisum sativum), soybean (Glycine max) and adzuki bean (Vigna angularis). Available quantitative data from archaeological finds are compiled to explore changes with domestication. The disjunction in cereals between seed size increase and dispersal is explored, and rates at which these features evolved are estimated from archaeobotanical data. Contrasts between crops, especially between cereals and pulses, are examined. † Conclusions These data suggest that in domesticated grasses, changes in grain size and shape evolved prior to non-shattering ears or panicles. Initial grain size increases may have evolved during the first centuries of cultivation, within perhaps 500‐1000 years. Non-shattering infructescences were much slower, becoming fixed about 1000‐2000 years later. This suggests a need to reconsider the role of sickle harvesting in domestication. Pulses, by contrast, do not show evidence for seed size increase in relation to the earliest cultivation, and seed size increase may be delayed by 2000‐4000 years. This implies that conditions that were sufficient to select for larger seed size in Poaceae were not sufficient in Fabaceae. It is proposed that animal-drawn ploughs (or ards) provided the selection pressure for larger seeds in legumes. This implies different thresholds of selective pressure, for example in relation to differing seed ontogenetics and underlying genetic architecture in these families. Pearl millet (Pennisetum glaucum) may show some similarities to the pulses in terms of a lag-time before truly largergrained forms evolved.