scholarly journals Multilocus Diversity in an Outbreeding Weed, Echium piantagineum L.

1983 ◽  
Vol 36 (6) ◽  
pp. 503 ◽  
Author(s):  
AHD Brown ◽  
JJ Burdon
Keyword(s):  
Biological Control ◽  
Linkage Disequilibrium ◽  
Genetic Structure ◽  
Population Size ◽  
Gene Diversity ◽  
Genotypic Variation ◽  
Vast Array ◽  
Multilocus Genotypes ◽  
Isozyme Loci

A population of E. plantagineum was surveyed for its genetic structure at 23 isozyme loci. More than half (13) of these loci were polymorphic, with an average number of three alleles per locus, a gene diversity of 38% and heterozygosity of 35%. More importantly, the distribution of multilocus heterozygosity over individuals was found to approximate that assuming independence among loci or no linkage disequilibrium. The population consisted of a vast array of multilocus genotypes. This pattern indicates that the outbreeding system encourages recombination sufficient to outweigh the effects on multilocus structure of bottlenecks in population size. Genic and genotypic variation presumably allows high levels of biochemical flexibility in populations of E. plantagineum. Such flexibility could hamper attempts at biological control.

scholarly journals Population Genetics of Echium plantagineum L.Target Weed for Biological Control

1986 ◽  
Vol 39 (4) ◽  
pp. 369 ◽  
Author(s):  
JJ Burdon ◽  
AHD Brown
Keyword(s):  
Genetic Diversity ◽  
Biological Control ◽  
Gene Diversity ◽  
Breeding Systems ◽  
Isozyme Loci ◽  
Source Populations ◽  
High Level ◽  
Similar Stage ◽  
Isozyme Diversity ◽  
European Populations

Eight Australian and two European populations of E. plantagineum were surveyed for their genetic structure at 16 variable isozyme loci. On average, the Australian and European populations possessed 2�7 and 2�6 alleles per locus, a gene diversity of 34 and 35% and heterozygosity of 32 and 29% respectively. Estimates of the outcrossing rate in one Australian population were 61 and 73% for mean single-locus and multi-locus methods respectively. The levels of genetic diversity detected in this species consistently exceed those detected in a range of other species that occupy a similar stage in succession or that have similar breeding systems. Moreover, contrary to expectation, genetic diversity was equally great in the colonial populations in Australia as in European-source populations. If this high level of isozyme diversity reflects the diversity likely to be found in other parts of the genome, attempts to achieve substantial biological control may require the use of many different control agents.

scholarly journals Low effective population size and high spatial genetic structure of black poplar populations from the Oder valley in Poland

2021 ◽  
Vol 78 (2) ◽  
Author(s):  
Błażej Wójkiewicz ◽  
Andrzewj Lewandowski ◽  
Weronika B. Żukowska ◽  
Monika Litkowiec ◽  
Witold Wachowiak
Keyword(s):  
Genetic Structure ◽  
Genetic Resources ◽  
Population Size ◽  
Effective Population Size ◽  
Spatial Genetic Structure ◽  
Demographic History ◽  
River Valley ◽  
Ex Situ ◽  
Effective Population ◽  
Black Poplar

Abstract Context Black poplar (Populus nigra L.) is a keystone species of European riparian ecosystems that has been negatively impacted by riverside urbanization for centuries. Consequently, it has become an endangered tree species in many European countries. The establishment of a suitable rescue plan of the remaining black poplar forest stands requires a preliminary knowledge about the distribution of genetic variation among species populations. However, for some parts of the P. nigra distribution in Europe, the genetic resources and demographic history remain poorly recognized. Aims Here, we present the first study on identifying and characterizing the genetic resources of black poplar from the Oder valley in Poland. This study (1) assessed the genetic variability and effective population size of populations and (2) examined whether gene flow is limited by distance or there is a single migrant pool along the studied river system. Methods A total of 582 poplar trees derived from nine black poplar populations were investigated with nuclear microsatellite markers. Results (1) The allelic richness and heterozygosity level were high and comparable between populations. (2) The genetic structure of the studied poplar stands was not homogenous. (3) The signatures of past bottlenecks were detected. Conclusion Our study (1) provides evidence for genetic substructuring of natural black poplar populations from the studied river catchment, which is not a frequent phenomenon reported for this species in Europe, and (2) indicates which poplar stands may serve as new genetic conservation units (GCUs) of this species in Europe. Key message The genetic resources of black poplar in the Oder River valley are still substantial compared to those reported for rivers in Western Europe. On the other hand, clear signals of isolation by distance and genetic erosion reflected in small effective population sizes and high spatial genetic structure of the analyzed populations were detected. Based on these findings, we recommend the in situ and ex situ conservation strategies for conserving and restoring the genetic resources of black poplar populations in this strongly transformed by human river valley ecosystem.

Genetic and Nongenetic Bases for the L-Shaped Distribution of Quantitative Trait Loci Effects

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1773-1787 ◽  
Author(s):  
Bruno Bost ◽  
Dominique de Vienne ◽  
Frédéric Hospital ◽  
Laurence Moreau ◽  
Christine Dillmann
Keyword(s):  
Linkage Disequilibrium ◽  
Quantitative Trait Loci ◽  
Population Size ◽  
Quantitative Trait ◽  
Metabolic Flux ◽  
Genetic Model ◽  
Small Population ◽  
Additive Genetic Model ◽  
Metabolic Mechanism ◽  
Qtl Effects

Abstract The L-Shaped distribution of estimated QTL effects (R2) has long been reported. We recently showed that a metabolic mechanism could account for this phenomenon. But other nonexclusive genetic or nongenetic causes may contribute to generate such a distribution. Using analysis and simulations of an additive genetic model, we show that linkage disequilibrium between QTL, low heritability, and small population size may also be involved, regardless of the gene effect distribution. In addition, a comparison of the additive and metabolic genetic models revealed that estimates of the QTL effects for traits proportional to metabolic flux are far less robust than for additive traits. However, in both models the highest R2's repeatedly correspond to the same set of QTL.

scholarly journals Genetic Structure of Rhynchosporium secalis in Australia

1999 ◽  
Vol 89 (8) ◽  
pp. 639-645 ◽  
Author(s):  
B. A. McDonald ◽  
J. Zhan ◽  
J. J. Burdon
Keyword(s):  
Genetic Structure ◽  
Gene Diversity ◽  
Sampling Site ◽  
Geographic Distance ◽  
South Australia ◽  
Rflp Markers ◽  
Rhynchosporium Secalis ◽  
Fungal Isolates ◽  
Fungal Populations ◽  
Average Gene

Restriction fragment length polymorphism (RFLP) markers were used to determine the genetic structure of Australian field populations of the barley scald pathogen Rhynchosporium secalis. Fungal isolates were collected by hierarchical sampling from five naturally infected barley fields in different geographic locations during a single growing season. Genetic variation was high in Australian R. secalis populations. Among the 265 fungal isolates analyzed, 214 distinct genotypes were identified. Average genotype diversity within a field population was 65% of its theoretical maximum. Nei's average gene diversity across seven RFLP loci was 0.54. The majority (76%) of gene diversity was distributed within sampling site areas measuring ≈1 m2; 19% of gene diversity was distributed among sampling sites within fields; and 5% of gene diversity was distributed among fields. Fungal populations from different locations differed significantly both in allele frequencies and genotype diversities. The degree of genetic differentiation was significantly correlated with geographic distance between populations. Our results suggest that the R. secalis population in Western Australia has a different genetic structure than populations in Victoria and South Australia.

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