Isozyme polymorphisms in natural populations of Avena fatua and A. barbata
About: This article is published in Heredity.The article was published on 1970-08-01 and is currently open access. It has received 106 citations till now. The article focuses on the topics: Avena fatua.
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TL;DR: A comparison of genetic similarity matrices revealed that, if the comparison involved both cultivated and wild soybean accessions, estimates based on RFLPs, RAPD, AFLPs and SSRs are highly correlated, indicating congruence between these assays.
Abstract: The utility of RFLP (restriction fragment length polymorphism), RAPD (random-amplified polymorphic DNA), AFLP (amplified fragment length polymorphism) and SSR (simple sequence repeat, microsatellite) markers in soybean germplasm analysis was determined by evaluating information content (expected heterozygosity), number of loci simultaneously analyzed per experiment (multiplex ratio) and effectiveness in assessing relationships between accessions. SSR markers have the highest expected heterozygosity (0.60), while AFLP markers have the highest effective multiplex ratio (19). A single parameter, defined as the marker index, which is the product of expected heterozygosity and multiplex ratio, may be used to evaluate overall utility of a marker system. A comparison of genetic similarity matrices revealed that, if the comparison involved both cultivated (Glycine max) and wild soybean (Glycine soja) accessions, estimates based on RFLPs, AFLPs and SSRs are highly correlated, indicating congruence between these assays. However, correlations of RAPD marker data with those obtained using other marker systems were lower. This is because RAPDs produce higher estimates of interspecific similarities. If the comparisons involvedG. max only, then overall correlations between marker systems are significantly lower. WithinG. max, RAPD and AFLP similarity estimates are more closely correlated than those involving other marker systems.
2,521 citations
TL;DR: Analysis of allozymic variation in natural populations of plants, animals, and humans based on studies published prior to early 1976 and involving 243 species, suggests that the amounts of genetic polymorphism and heterozygosity vary nonrandomly between loci, populations, species, habitats, and life zones, and are correlated with ecological heterogeneity.
964 citations
01 Jan 1984
TL;DR: The evolutionary significance of genetic diversity of proteins in nature remains controversial despite the numerous protein studies conducted electrophoretically during the last two decades.
Abstract: The evolutionary significance of genetic diversity of proteins in nature remains controversial despite the numerous protein studies conducted electrophoretically during the last two decades. Ironically, the discovery of extensive protein polymorphisms in nature (reviewed by Lewontin, 1974; Powell, 1975; Selander, 1976; Nevo 1978, 1983b; Hamrick et al., 1979; Nelson and Hedgecock, 1980), did not resolve the disagreement between the die ho torn ou s explanatory models of selection (e.g., Ayala, 1977; Milkman, 1978; Clarke, 1979; Wills, 1981) versus neutrality (Kimura, 1968; Kimura and Chta, 1971; Nei, 1975; and modifications in Kimura, 1979atb). The more general problem of the relative importance of the evolutionary forces interacting in genetic population differentiation at the molecular levels of proteins and DNA, i.e., mutation, migration, natural selection and genetic drift, remains now as enigmatic as ever.
735 citations
TL;DR: Evidence indicates that inbreeding plant species show more intense geographic and microgeographic differentiation, and more intense multilocus associations than outbreeders, and a closer integration of the joint microevolution of mating systems, and of genetic variation is required.
606 citations
TL;DR: Results show that each of the four techniques can on their own, individually identify each cultivar, but that techniques differ in the mean number of profiles generated per primer (or primer pair) per cultivar.
Abstract: Several DNA marker systems and associated techniques are available today for fingerprinting plant germplasm but information on their relative usefulness in particular crops is limited. The study investigated PCR based DNA fingerprinting in a set of 39 potato cultivars using RAPDs (20 primers), ISSRs (6 primers), AFLPs (2 primers) and SSRs (5 primer pairs). Results show that each of the four techniques can on their own, individually identify each cultivar, but that techniques differ in the mean number of profiles generated per primer (or primer pair) per cultivar, referred to as Genotype Index (GI). The order of merit based on this criterium and in this material was AFLPs (GI = 1.0), a multi-locus SSR (GI = 0.77),RAPDs (GI = 0.53), ISSRs (GI = 0.47) and single locus SSRs (GI = 0.36). Problems in relating banding patterns to individual loci and alleles for polyploid genomes, using these techniques as they are currently employed, are also discussed.
341 citations
Cites methods from "Isozyme polymorphisms in natural po..."
...Estimates of allele frequencies can then be computed from the band data (Liu & Furnier, 1993; Powell et al., 1996; Russell et al., 1997), and the polymorphism expressed in terms of expected mean heterozygosity averaged over all loci, the standard measure of genetic diversity in population genetics ( Marshal & Allard, 1970; Nei, 1973)....
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References
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TL;DR: This study shows that there is a considerable amount of genic variation segregating in all of the populations studied and that the real variation in these populations must be greater than the authors are able to demonstrate.
Abstract: S pointed out in the first paper of this series (HUBBY and LEWONTIN 1966), A no one knows at the present time the kinds and frequencies of variant alleles present in natural populations of any organism, with the exception of certain special classes of genes. For human populations we know a good deal about certain polymorphisms for blood cell antigens, serum proteins, and metabolic disorders of various kinds but we can hardly regard these, a priori, as typical of the genome as a whole. Clearly we need a method that will randomly sample the genome and detect a major proportion of the individual allelic substitutions that are segregating in a population. In our previous paper, we discussed a method for accomplishing this end by means of a study of electrophoretic variants at a large number of loci and we showed that the variation picked up by this method behaves in a simple Mendelian fashion so that phenotypes can be equated to homozygous and heterozygous genotypes at single loci. It is the purpose of this second paper to show the results of an application of the method to a series of samples chosen from natural populations of Drosophila pseudoobscura. In particular, we will show that there is a considerable amount of genic variation segregating in all of the populations studied and that the real variation in these populations must be greater than we are able to demonstrate. This study does not make clear what balance of forces is responsible for the genetic variation observed, but it does make clear the kind and amount of variation at the genic level that we need to explain. An exactly similar method has recently been applied by HARRIS (1966) for the enzymes of human blood. In a preliminary report on ten randomly chosen enzymes, HARRIS describes two as definitely polymorphic genetically and a third as phenotypically polymorphic but with insufficient genetic data so far. Clearly these methods are applicable to any organism of macroscopic dimensions.
1,169 citations
TL;DR: A starch gel electrophoresis procedure which yields discrete separation of pre-albumins, transferrins and haptoglobins in pig serum is described, and evidence concerning the genetic mechanism underlying the prealbumin polymorphism which has been observed is presented.
Abstract: HREE loci controlling the synthesis of serum proteins in the pig have been Tidentified to date. KRISTJANSSON ( 1960a, b) has identified two alleles controlling the synthesis of transferrins in the pig and has demonstrated (1961) three alleles involved in the synthesis of pig haptoglobins. ASHTON (1960) has described three Yhread protein” phenotypes and on the basis of preliminary mating data has suggested that two alleles are involved in determining these phenotypes. In the same paper, ASHTON reports three P-globulin phenotypes which appear to be the same as the transferrin types described by KRISTJANSSON. KING (1961, personal communication) has identified a third transferrin allele and a fourth haptoglobin allele. Serum protein polymorphisms in several species have been reviewed by OGDEN (1961). Plasma protein polymorphisms in man have been reviewed by HARRIS ( 1961 ) , In the course of starch gel electrophoresis technique experiments, we have observed differences between individuals with respect to protein fractions (prealbumins) which migrate in advance of the serum albumin fraction. This report describes a starch gel electrophoresis procedure which yields discrete separation of pre-albumins, transferrins and haptoglobins in pig serum, and presents evidence concerning the genetic mechanism underlying the prealbumin polymorphism which has been observed.
202 citations
TL;DR: This paper describes a breeding System in which there is selection of a genecomplex which affects that system and which at the same time reduces species fitness, and evidence is presented which shows that such a system probably exists in two recently discovered groups of populations of Prinula vulgaris.
Abstract: It has been the general basis of the theory of natural selection that genes or gene-combinations improving the "fitness" of a species will tend to increase in frequency within the species, while those which are harmful will tend to decrease, as a result of selection. But Fisher (1941) has shown theoretically that a gene affecting the breeding system but not species fitness can be strongly selected; that is, intense selective activity need not be accompanied by an increase in the survival value of the species. This paper describes a breeding System in which there is selection of a genecomplex which affects that system and which at the same time reduces species fitness, and evidence is presented which shows that such a system probably exists in two recently discovered groups of populations of Prinula vulgaris. Selection of unfavourable genes must be clearly distinguished from the purely fortuitous increase in frequency of such genes which Wright (1940) has shown to be possible in small populations.
144 citations
TL;DR: The present paper reports an investigation of genetic variability in another predominantly self-pollinated species, wild oats (Auena fatua L.) and provides information of a quantitative nature concerning the mating system of this species.
Abstract: M U C H recent work points to the conclusion that remarkable stores of genetic variability exist in natural and in domestic species of plants and animals. Among the requirements for understanding the nature of this variability, and the forces by which it is maintained, are adequate data concerning the magnitude of genetic variability within populations. However, the evidence on variability in naturally occurring species of plants is largely observational and subjective and only a few studies have provided quantitative estimates of the genetic variability respecting measurement characters which exists within populations (e.g. BAKER 1957; BRADSHAW 1959; WEIL and ALLARD, in press). Precise quantitative estimates of genetic variability within naturally occurring populations of predominantly self-pollinating species is even more limited, apparently being restricted to that provided by KNOWLES' (1947) study of Bromus mollis. The present paper reports an investigation of genetic variability in another predominantly self-pollinated species, wild oats (Auena fatua L.) . The experiment was designed to permit quantification of three aspects of genetic variability within this species: that occurring between three geographically distinct regions, that due to spatial differentiation between sites within these regions, and that due to variability within individual sites. The experiment also provided information of a quantitative nature concerning the mating system of this species.
141 citations