Inferring the genetic basis of inbreeding depression in plants

Genome ◽  
1996 ◽  
Vol 39 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Kermit Ritland
Keyword(s):  
Life Cycle ◽  
Inbreeding Depression ◽  
Statistical Models ◽  
Recent Progress ◽  
Genetic Basis ◽  
Genetic Load ◽  
Life Cycle Stage ◽  
Mutation Rates ◽  
Single Cross ◽  
Self Fertilization

Recent progress in the genetic analysis of inbreeding depression in plants is reviewed. While the debate over the importance of genes of dominance versus overdominance effect continues, the scope of inferences has widened and now includes such facets as the interactions between genes, the relative abundance of major versus minor genes, life cycle stage expression, and mutation rates. The types of inferences are classified into the genomic, where many genes are characterized as an average, and the genic, where individual genes are characterized. Genomic inferences can be based upon natural levels of inbreeding depression, purging experiments, the comparison of individuals of differing F (e.g., prior inbreeding), and various crossing designs. Genic inferences mainly involve mapping and characterizing loci with genetic markers, involving either a single cross or, ideally, several crosses. Alternative statistical models for analyzing polymorphic loci causing inbreeding depression should be a fruitful problem for geneticists to pursue. Key words : inbreeding depression, genetic load, self-fertilization, QTL mapping.

scholarly journals Recent approaches into the genetic basis of inbreeding depression in plants

2003 ◽  
Vol 358 (1434) ◽  
pp. 1071-1084 ◽  
Author(s):  
David E. Carr ◽  
Michele R. Dudash
Keyword(s):  
Inbreeding Depression ◽  
Genetic Basis ◽  
Genetic Load ◽  
Strong Support ◽  
Major Effect ◽  
Inbred Lines ◽  
Recessive Mutations ◽  
Deleterious Alleles ◽  
Experimental Approaches ◽  
Marker Segregation Distortion

Predictions for the evolution of mating systems and genetic load vary, depending on the genetic basis of inbreeding depression (dominance versus overdominance, epistasis and the relative frequencies of genes of large and small effect). A distinction between the dominance and overdominance hypotheses is that deleterious recessive mutations should be purged in inbreeding populations. Comparative studies of populations differing in their level of inbreeding and experimental approaches that allow selection among inbred lines support this prediction. More direct biometric approaches provide strong support for the importance of partly recessive deleterious alleles. Investigators using molecular markers to study quantitative trait loci (QTL) often find support for overdominance, though pseudo–overdominance (deleterious alleles linked in repulsion) may bias this perception. QTL and biometric studies of inbred lines often find evidence for epistasis, which may also contribute to the perception of overdominance, though this may be because of the divergent lines initially crossed in QTL studies. Studies of marker segregation distortion commonly uncover genes of major effect on viability, but these have only minor contributions to inbreeding depression. Although considerable progress has been made in understanding the genetic basis of inbreeding depression, we feel that all three aspects merit more study in natural plant populations.

scholarly journals Mutational load, inbreeding depression and heterosis in subdivided populations

2018 ◽  
Author(s):  
Brian Charlesworth
Keyword(s):  
Population Size ◽  
Inbreeding Depression ◽  
Population Genomics ◽  
Local Population ◽  
Genetic Load ◽  
Mutation Rates ◽  
Weak Selection ◽  
Empirical Estimates ◽  
Numerical Predictions ◽  
Subdivided Populations

AbstractThis paper examines the extent to which empirical estimates of inbreeding depression and inter-population heterosis in subdivided populations, as well as the effects of local population size on mean fitness, can be explained in terms of estimates of mutation rates, and the distribution of selection coefficients against deleterious mutations provided by population genomics data. Using results from population genetics models, numerical predictions of the genetic load, inbreeding depression and heterosis were obtained for a broad range of selection coefficients and mutation rates. The models allowed for the possibility of very high mutation rates per nucleotide site, as is sometimes observed for epiallelic mutations. There was fairly good quantitative agreement between the theoretical predictions and empirical estimates of heterosis and the effects of population size on genetic load, on the assumption that the deleterious mutation rate per individual per generation is approximately one, but there was less good agreement for inbreeding depression. Weak selection, of the order of magnitude suggested by population genomic analyses, is required to explain the observed patterns. Possible caveats concerning the applicability of the models are discussed.

Identification of asset life cycle stage: case study in heavy-duty truck fleet

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Oscar Daniel Rivera Baena ◽  
Maria Valentina Clavijo Mesa ◽  
Carmen Elena Patino Rodriguez ◽  
Fernando Jesus Guevara Carazas
Keyword(s):  
Life Cycle ◽  
Design Methodology ◽  
Life Cycle Stage ◽  
Waste Collection ◽  
Content Type ◽  
Heavy Duty Truck ◽  
Maintenance Work ◽  
Operational Decision Making ◽  
The Moment

PurposeThis paper aims to determine the stage of the life cycle where the trucks of a waste collection fleet from a Colombian city are located through a reliability approach. The reliability analysis and the evaluation of curve of operational costs allow to know the moment in which it is necessary to make decisions regarding an asset, its maintenance or possible replacement.Design/methodology/approachFor a dataset presented as maintenance work orders, the time to failures (TTFs) for each vehicle in the fleet were calculated. Then, a probability density function for those TTFs was fitted to locate each vehicle in a region of the bathtub curve and to calculate the reliability of the whole fleet. A general functional analysis was also developed to understand the function of the vehicles.FindingsIt was possible to determine that the largest proportion of the fleet was in the final stage of the life cycle, in this sense, the entire fleet represent critical assets which in most of cases could be worth replacement or overhaul.Originality/valueIn this study, an address is exposed for the identification of critical equipment by reliability and statistical analysis. This analysis is also integrated with the maintenance management process. This is a broadly interested topic since it allows to support the maintenance and operational decision-making process, indicating the focus of resource allocation all over the entire asset life cycle.

Developmental gene expression in Leishmania donovani: differential cloning and analysis of an amastigote-stage-specific gene

1994 ◽  
Vol 14 (5) ◽  
pp. 2975-2984
Author(s):  
H Charest ◽  
G Matlashewski
Keyword(s):  
Life Cycle ◽  
Leishmania Donovani ◽  
Repetitive Sequences ◽  
Protozoan Parasite ◽  
Life Cycle Stage ◽  
Immune Serum ◽  
Sand Fly ◽  
Specific Gene ◽  
Reading Frame ◽  
Developmental Gene Expression

Leishmania protozoans are the causative agents of leishmaniasis, a major parasitic disease in humans. During their life cycle, Leishmania protozoans exist as flagellated promastigotes in the sand fly vector and as nonmotile amastigotes in the mammalian hosts. The promastigote-to-amastigote transformation occurs in the phagolysosomal compartment of the macrophage cell and is a critical step for the establishment of the infection. To study this cytodifferentiation process, we differentially screened an amastigote cDNA library with life cycle stage-specific cDNA probes and isolated seven cDNAs representing amastigote-specific transcripts. Five of these were closely related (A2 series) and recognized, by Northern (RNA) blot analyses, a 3.5-kb transcript in amastigotes and in amastigote-infected macrophages. Expression of the amastigote-specific A2 gene was induced in promastigotes when they were transferred from culture medium at 26 degrees C and pH 7.4 to medium at 37 degrees C and pH 4.5, conditions which mimic the macrophage phagolysosomal environment. A2 genes are clustered in tandem arrays, and a 6-kb fragment corresponding to a unit of the cluster was cloned and partially sequenced. An open reading frame found within the A2-transcribed region potentially encoded a 22-kDa protein containing repetitive sequences. The recombinant A2 protein produced in Escherichia coli cells was specifically recognized by immune serum from a patient with visceral leishmaniasis. The A2 protein repetitive element has strong homology with an S antigen of Plasmodium falciparum, the protozoan parasite responsible for malaria. Both the A2 protein of Leishmania donovani and the S antigen of P. falciparum are stage specific and developmentally expressed in mammalian hosts.

Sign in / Sign up

Export Citation Format

Share Document