Marker-based inferences about fecundity genes contributing to inbreeding depression in Mimulus guttatus

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1005-1010 ◽  
Author(s):  
Yong-Bi Fu ◽  
Kermit Ritland
Keyword(s):  
Genetic Markers ◽  
Inbreeding Depression ◽  
Phenotypic Variation ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Number Of Genes ◽  
Isozyme Loci ◽  
Deleterious Genes

Eight unlinked isozyme loci were used as genetic markers to characterize fecundity genes contributing to inbreeding depression in two selfed progeny arrays of Mimulus guttatus. Five fecundity traits were measured. Six of eight marked chromosomal segments were significantly associated with the expression of these traits. The number of genes detected for five traits in two progeny arrays varied, with an average of 2.8 genes per trait. Individual segments explained 1.44–9.29%, and together accounted for 3.85–11.32%, of phenotypic variation. Of 20 significant associations, 10 could be interpreted as exhibiting partial dominance, 7 overdominance, 3 partial recessivity, and 0 underdominance. Significant pairwise epistasis was rare. The results of this study suggest that inbreeding depression is caused by many deleterious genes of relatively small, partially dominant effects.Key words: linkage, isozymes, QTLs, inbreeding depression, Mimulus guttatus.

scholarly journals Evidence for the partial dominance of viability genes contributing to inbreeding depression in Mimulus guttatus.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 323-331
Author(s):  
Y B Fu ◽  
K Ritland
Keyword(s):  
Inbreeding Depression ◽  
Wild Plant ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Complete Dominance ◽  
Model Free ◽  
Segregation Ratios ◽  
Marker Loci ◽  
In The Wild

Abstract The relative importance of different modes of gene expression of viability genes contributing to inbreeding depression was investigated in the wild plant, Mimulus guttatus. Viability genes were identified by self-fertilizing 31 outbred plants, each heterozygous for three to nine unlinked allozyme markers, and analyzing segregation ratios of selfed progeny at maturity for deviations from 1:2:1 ratios. In this study, 24 linkages of viability genes to marker loci were detected. To infer the nature of gene action for these viability genes, a "model-free" graphical method was developed that examines the "space" of segregation ratios allowed by each of seven selection models (i.e., overdominance, complete recessivity, partial recessivity, additivity, partial dominance, complete dominance and underdominance). Using this method, we found that, of 24 linkages detected, 18 were consistent with either partial dominance, complete dominance or underdominance. Six were consistent with either partial recessivity, complete recessivity or overdominance. This finding indicates that, in these chromosomal segments identified by allozyme markers, partial dominance plays the predominant role in inbreeding depression. This is inconsistent with either the dominance or overdominance hypotheses proposed to account for inbreeding depression.

scholarly journals Point estimation and graphical inference of marginal dominance for two viability loci controlling inbreeding depression

1997 ◽  
Vol 70 (2) ◽  
pp. 143-153 ◽  
Author(s):  
YONG-BI FU ◽  
DEBORAH CHARLESWORTH ◽  
GENE NAMKOONG
Keyword(s):  
Inbreeding Depression ◽  
Gene Action ◽  
Marker Locus ◽  
Point Estimation ◽  
Relative Role ◽  
Selfed Progeny ◽  
Deterministic Analysis ◽  
Partial Dominance ◽  
Segregation Ratios

A deterministic analysis is conducted to examine marginal dominance for two linked viability loci influencing inbreeding depression and its graphical inferences. Four estimators of marginal dominance are derived, assuming a biallelic marker locus completely linked to one of the viability loci, and the biases in expected estimates due to the other deleterious locus are discussed. Three conditions under which apparent partial dominance or underdominance could occur are found, i.e. when two multiplicative, partially recessive loci are linked in coupling phase and when two synergistic, highly overdominant loci are linked in coupling or repulsion phases. Expected frequencies of the three marker genotypes in selfed progeny are derived, considering two linkage phases, two types of marker locus position with respect to the viability loci, and the multiplicative and synergistic fitness models. Segregation ratios are generated for the marker locus linked to either two overdominant or partially recessive loci and plotted in gene action graphs to examine the robustness of the graphical inferences of gene action due to the presence of an additional linked viability locus. Under a multiplicative fitness model, the presence of an additional partially recessive or overdominant locus in the vicinity of the marker locus does not greatly affect the graphical inferences of the relative role of partially recessive or overdominant genes in expression of inbreeding depression. A marker linked to two synergistic, highly overdominant loci can behave as though linked to a partially recessive, partially dominant or underdominant locus, even with relatively weak synergism.

scholarly journals Inbreeding depression and the maintenance of deleterious genes by mutation: model of a Drosophila chromosome

1989 ◽  
Vol 53 (2) ◽  
pp. 119-128 ◽  
Author(s):  
John A. Sved ◽  
Alan N. Wilton
Keyword(s):  
Inbreeding Depression ◽  
Gene Interaction ◽  
Mutation Rates ◽  
Deleterious Mutations ◽  
Partial Dominance ◽  
Mutation Model ◽  
Recessive Genes ◽  
Deleterious Genes ◽  
Selective Interactions ◽  
Lethal Genes

SummaryInbreeding experiments in Drosophila, particularly those carried out using the ‘balancer equilibration’ technique, have revealed high levels of inbreeding depression. It has been estimated that non-lethal chromosomes have a fitness of 20% or less in homozygous condition compared to chromosome heterozygotes. Deleterious recessive genes are, in principle, capable of explaining such inbreeding depression. In this paper we have asked quantitatively whether the observed high levels are consistent with what is known about numbers of loci and mutation rates. We find that accepted mutation rates are easily high enough, provided that the deleterious genes are fully recessive. Partial dominance, even to the extent of 10% or less, reverses this conclusion. These calculations have been made assuming the multiplicative model. However the arguments are potentially sensitive to certain types of selective interactions, and a model which proposes quadratic gene interaction allows for higher levels of partial dominance. We also test the effect of taking into account a further constraint. Crow and Mukai have argued from estimates of the persistence of new deleterious mutations affecting viability that heterozygotes have a reduction in fitness of around 1–2% per locus, similar to the estimate for lethal genes. Application of this additional constraint would markedly reduce the range of permissible selection coefficients. However we argue that the selective disadvantages in heterozygotes of most mutations affecting fitness are unlikely to be as high as estimated for mutations affecting viability.

scholarly journals DYNAMICS OF HERITABILITY IN DIFFERENT CHARACTERS OF LETTUCE

2021 ◽  
Vol 34 (3) ◽  
pp. 514-526
Author(s):  
ALISSON HENRIQUE GAMA DE OLIVEIRA ◽  
GABRIEL MASCARENHAS MACIEL ◽  
ANA CAROLINA SILVA SIQUIEROLI ◽  
JOSÉ MAGNO QUEIROZ LUZ ◽  
ERNANI CLARETE DA SILVA
Keyword(s):  
Chlorophyll Content ◽  
Gene Action ◽  
Gene Interactions ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Additive Variance ◽  
Dominant Type ◽  
Partial Dominance ◽  
Number Of Genes ◽  
Number Of Leaves

ABSTRACT The lack of knowledge of the genetic parameters and the type of gene action results in difficulties to obtain varieties that combine agronomic and functional characteristics. The objective of this study was to determine the type of gene action associated with the contents of chlorophyll and agronomic characteristics in lettuce populations. The research was conducted at the Experimental Station of Vegetables, Monte Carmelo, Brazil. To perform the crosses and obtain the generations P1, P2, F1, F2, Bc1 and Bc2 the genotypes UFU-Albina#2, UFU-Albina#3, UFU-Lisa124#2#1, UFU-Crespa199#1#1 and UFU-Lisa217#5#2 were used as parents. The generations were evaluated for three characteristics: number of leaves, plant diameter and chlorophyll content. The parameters: genetic, phenotypic, environmental and additive variance, the dominance in F2, heritability in the broad and narrow-sense, the average degree of dominance based on averages, number of genes, the measure of the dominance deviations, additive effects and all interactions of ‘additive x additive’, ‘additive x dominant’ and ‘dominant x dominant’ type, were evaluated. Chlorophyll content was the most influenced by the environment. Plant diameter had the highest narrow-sense heritability for the cross UFU-Lisa-124#2#1 x UFU-Albina#3 (82.1%). The number of genes for the number of leaves varied from inconclusive to a minimum of 9 genes. The gene interactions for number of leaves were of overdominance type, while for plant diameter and for chlorophyll content the gene interactions were of partial dominance. The characteristics are suggested as being of polygenic or oligogenic nature.

scholarly journals Reproductive Assurance Maintains Red-Flowered Plants of Lysimachia arvensis in Mediterranean Populations Despite Inbreeding Depression

2020 ◽  
Vol 11 ◽  
Author(s):  
Francisco J. Jiménez-López ◽  
Pedro L. Ortiz ◽  
María Talavera ◽  
Montserrat Arista
Keyword(s):  
Genetic Diversity ◽  
Genetic Differentiation ◽  
Inbreeding Depression ◽  
Abiotic Factors ◽  
Natural Populations ◽  
Flower Color ◽  
Selfed Progeny ◽  
Mediterranean Populations ◽  
Mediterranean Areas ◽  
Flower Color Polymorphism

Flower color polymorphism, an infrequent but phylogenetically widespread condition in plants, is captivating because it can only be maintained under a few selective regimes but also because it can drive intra-morph assortative mating and promote speciation. Lysimachia arvensis is a polymorphic species with red or blue flowered morphs. In polymorphic populations, which are mostly Mediterranean, pollinators prefer blue-flowered plants to the red ones, and abiotic factors also favors blue-flowered plants. We hypothesize that the red morph is maintained in Mediterranean areas due to its selfing capacity. We assessed inbreeding depression in both color morphs in two Mediterranean populations and genetic diversity was studied via SSR microsatellites in 20 natural populations. Results showed that only 44–47% of selfed progeny of the red plants reached reproduction while about 72–91% of blue morph progeny did it. Between-morph genetic differentiation was high and the red morph had a lower genetic diversity and a higher inbreeding coefficient, mainly in the Mediterranean. Results suggest that selfing maintaining the red morph in Mediterranean areas despite its inbreeding depression. In addition, genetic differentiation between morphs suggests a low gene flow between them, suggesting reproductive isolation.

Environmental pressure rather than ongoing hybridization is responsible for an altitudinal cline in the morphologies of two oaks

2020 ◽  
Vol 13 (4) ◽  
pp. 413-422
Author(s):  
Ichiro Tamaki ◽  
Yae Yamada
Keyword(s):  
Contact Zone ◽  
Genetic Markers ◽  
Phenotypic Variation ◽  
Altitudinal Gradient ◽  
Morphological Traits ◽  
Leaf Morphology ◽  
Environmental Gradients ◽  
Reference Population ◽  
Environmental Pressure ◽  
Nuclear Microsatellite

Abstract Aims In a contact zone between related taxa, phenotypic variation can result from genetic and/or environmental gradients. This study aimed to clarify the cause of phenotypic variation in leaf morphology of two Quercus crispula varieties—crispula (QCC) and mongolicoides (QCM)—in their contact zone along an altitudinal gradient. Methods We measured 6 morphological traits of leaves and recorded genotypes of 13 nuclear microsatellite loci for 48 individuals in the contact zone and 24 individuals in each of the reference populations of QCC and QCM. We constructed a model explaining the phenotypic variation (leaf morphology) in relation to environmental (altitude) and genetic (ancestry from the reference population) gradients. Important Findings Both morphological and genetic markers distinguished the two varieties in the reference populations well. We were able to confirm the power of both morphological and genetic markers. Individuals within the contact zone population had intermediate ancestry that was slightly biased to QCM ancestry, and the distribution of their morphologies overlapped with those of the two varieties in the reference populations. The effect of altitude on leaf morphological traits was significant, while that of ancestry was not. Distributions of ancestry and interclass heterozygosity in the contact zone population resembled those in F2 or later generation hybrids. These results indicate that in the contact zone between QCC and QCM, there is no ongoing hybridization, but environmental pressure has created an altitudinal gradient in morphological traits through phenotypic plasticity and/or variation in functional genes.

EFFECTS OF STRESS AND PHENOTYPIC VARIATION ON INBREEDING DEPRESSION INBRASSICA RAPA

Evolution ◽  
2008 ◽  
Vol 62 (4) ◽  
pp. 917-931 ◽  
Author(s):  
Donald M. Waller ◽  
Jefferey Dole ◽  
Andrew J. Bersch
Keyword(s):  
Inbreeding Depression ◽  
Phenotypic Variation ◽  
Effects Of Stress
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