scholarly journals Quantitative and molecular genetic variation in sympatric populations of Medicago laciniata and M. truncatula (Fabaceae): relationships with eco-geographical factors

2007 ◽  
Vol 89 (2) ◽  
pp. 107-122 ◽  
Author(s):  
MOUNAWER BADRI ◽  
HOUCINE ILAHI ◽  
THIERRY HUGUET ◽  
MOHAMED ELARBI AOUANI
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Local Adaptation ◽  
Quantitative Traits ◽  
Gene Diversity ◽  
Sympatric Populations ◽  
Widespread Species ◽  
Geographical Factors ◽  
Significant Difference ◽  
Selection For

SummaryMedicago laciniata is restricted to south of the Mediterranean basin and it extends in Tunisia from the inferior semi-arid to Saharan stages, whereas M. truncatula is a widespread species in such areas. The genetic variability in four Tunisian sympatric populations of M. laciniata and M. truncatula was analysed using 19 quantitative traits and 20 microsatellites. We investigated the amplification transferability of 52 microsatellites developed in M. truncatula to M. laciniata. Results indicate that about 78·85% of used markers are valuable genetic markers for M. laciniata. M. laciniata displayed significantly lower quantitative differentiation among populations (QST=0·12) than did M. truncatula (QST=0·45). However, high molecular differentiations, with no significant difference, were observed in M. laciniata (FST=0·48) and M. truncatula (FST=0·47). Several quantitative traits exhibited significantly smaller QST than FST for M. laciniata, consistent with constraining selection. For M. truncatula, the majority of traits displayed no statistical difference in the level of QST and FST. Furthermore, these traits are significantly associated with eco-geographical factors, consistent with selection for local adaptation rather than genetic drift. In both species, there was no significant correlation between genetic variation at quantitative traits and molecular markers. The site-of-origin explains about 5·85% and 11·27% of total quantitative genetic variability among populations of M. laciniata and M. truncatula, respectively. Established correlations between quantitative traits and eco-geographical factors were generally more moderate for M. laciniata than for M. truncatula, suggesting that the two species exhibit different genetic bases of local adaptation to varying environmental conditions. Nevertheless, no consistent patterns of associations were found between gene diversity (He) and environmental factors in either species.

scholarly journals EFFECT OF SELECTION ON HERITABILITY AND GENETIC CORRELATION OF TWO QUANTITATIVE TRAITS IN MICE

1974 ◽  
Vol 16 (3) ◽  
pp. 599-609 ◽  
Author(s):  
T. K. Cheung ◽  
R. J. Parker
Keyword(s):  
Body Weight ◽  
Genetic Correlation ◽  
Quantitative Traits ◽  
Random Mating ◽  
Tail Length ◽  
Control Group ◽  
Mass Selection ◽  
Initial Population ◽  
Significant Difference ◽  
Selection For

The effects of different intensities of single trait directional selection on the heritability and genetic correlation of two quantitative traits in random mating populations of mice were observed during 14 generations. The initial population was divided at random into five groups (A, B, C, D and E). Group A and Group B were under 30% and 60% mass selection for large 6-week body weight, respectively. Group C and Group D were under 30% and 60% mass selection for long 6-week tail length, respectively. Group E acted as control group with no selection applied. In all groups, the parent population consisted of 15 males and 30 females each generation, mated at random.Direct selection had no apparent effect on the heritability of either the trait under selection or the correlated trait over the 14 generations. Heritability of 6-wk tail length was higher than the heritability of 6-wk body weight. Estimates of heritability of 6-wk tail length ranged from 0.15 ± 0.22 to 0.68 ± 0.24, while estimates of heritability of 6-wk body weight ranged from 0.05 ± 0.17 to 0.33 ± 0.09. There was no significant difference among the estimates of genetic correlation between the two traits in the five selection groups. Estimates of realized genetic correlation between 6-wk body weight and 6-wk tail length seemed to indicate that more intense selection led to some decrease in genetic correlation between the two traits.

Genetic variation in populations of the endemic Achillea millefolium ssp. megacephala from the Athabasca sand dunes and the widespread ssp. lanulosa in western North America

1996 ◽  
Vol 74 (7) ◽  
pp. 1138-1146 ◽  
Author(s):  
Brett G. Purdy ◽  
Randall J. Bayer
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Gene Diversity ◽  
Sand Dunes ◽  
Achillea Millefolium ◽  
Starch Gel Electrophoresis ◽  
Widespread Species ◽  
Polymorphic Loci ◽  
Endemic Taxon ◽  
Starch Gel

As part of an analysis of genetic diversity in endemic taxa of the Athabasca sand dunes in northern Saskatchewan, Canada, genetic variation was examined by starch gel electrophoresis in six populations of the endemic Achillea millefolium ssp. megacephala, and 13 populations of the closely related widespread taxon, A. millefolium ssp. lanulosa. Endemic populations had more alleles per locus, a higher percentage of polymorphic loci, and greater genetic diversity than did populations of the widespread taxon. At polymorphic loci, total gene diversity was comparable in both taxa, although within-population gene diversity was higher in the endemic taxon. Population differentiation (GST) was considerably lower in ssp. megacephala than in ssp. lanulosa, although GST values were reduced when the parameter was calculated separately for geographic subdivisions of the widespread taxon. Our results differ from previous studies in which the endemic is typically depauperate of genetic variation relative to related widespread species. We suggest that obligate sexual reproduction and the absence of long-term asexual reproduction may be one of a number of factors that help populations of ssp. megacephala maintain higher levels of genetic variation on the Athabasca sand dunes. Keywords: genetic variation, endemic, rare species, Athabasca sand dunes, Achillea millefolium.

scholarly journals Genetic Variation, Heritability and Genetic Advance in Some Promising Rice Hybrids

2021 ◽  
Vol 18 (2) ◽  
pp. 39-49
Author(s):  
LF Lipi ◽  
MJ Hasan ◽  
A Akter ◽  
MR Quddus ◽  
PL Biswas ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Plant Height ◽  
Quantitative Traits ◽  
Genetic Advance ◽  
Reliable Index ◽  
Genotypic Variance ◽  
Additive Gene ◽  
High Heritability ◽  
Almost All

Eleven rice hybrids including two check varieties were evaluated to approximate their genetic variability, heritability and genetic advance for ten quantitative traits. The analysis of variance illustrated that all the quantitative traits differed significantly indicating that enough variation is presenting the studied materials. Among the desirable quantitative traits number of filled spikelet’s per panicle was found to have highest both phenotypic and genotypic variance followed by total number of spikelet’s per panicle. Almost all the characters showed a little variation between PCV and GCV revealing little influence of the environment on the expression of traits. High phenotypic and genotypic variance coupled with high heritability and high genetic advance was observed for number of filled spikelet’s per panicle, total number of spikelet’s per panicle, plant height and number of unfilled spikelet’s per panicle. Such findings stipulated that these traits were governed by additive gene actions which are fixable and these traits may be accounted for reliable index of selection. The genotypes G3 (IR79156A × EL108R) and G6 (IR79156A × EL253R) were selected as high response superior promising rice hybrids for achievable yield advantage 49% and 23%, respectively over best check varieties. Therefore, the G3 and G6 are proposed to be extensively evaluated for further trial of variety release. SAARC J. Agri., 18(2): 39-49 (2020)

scholarly journals The reasons for low intrapopulation genetic variation in Lamium incisum Willd

2011 ◽  
Vol 60 (1) ◽  
pp. 79-84
Author(s):  
Katarzyna Wąsowicz ◽  
Monika Szczecińska ◽  
Jakub Sawicki
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Diversity Index ◽  
Gene Diversity ◽  
Weed Species ◽  
Preliminary Screening ◽  
Low Genetic Diversity ◽  
The Mean ◽  
Intrapopulation Genetic Variation ◽  
Issr Primers

The reasons for low intrapopulation genetic variation in Lamium incisum Willd The paper presents results of a study which aim was preliminary screening of intrapopulation genetic variability in Lamium incisum Willd. This weed species is rarely distributed in Poland and lessening its count during the last years. As a plant inhabiting anthropogenic sites it is exposed to extreme conditions and disturbances caused mostly by the progressive intensification of agriculture. In order to investigate the genetic variability of the selected population markers of ISSR category were used. The analysis of chosen individuals with use of three ISSR primers revealed total of 49 loci, of which only 15 were polymorphic. Nei's gene diversity index (HE=0.099) and the mean number of alleles per locus (AE=1.160) indicated low genetic diversity within the examined population. The research presented in this paper allows for a better learning of the genetic variability of the investigated species and considers probable factors influencing its level.

scholarly journals Genetic variability of three natural populations of Maytenus aquifolium (Celesteraceae) from Telêmaco Borba, Paraná, Brazil

2010 ◽  
Vol 53 (5) ◽  
pp. 1037-1042 ◽  
Author(s):  
Sandra Aparecida Sahyun ◽  
Eduardo Augusto Ruas ◽  
Claudete de Fátima Ruas ◽  
Cristiano Medri ◽  
José Roberto Pinto de Souza ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Variability ◽  
Bayesian Analysis ◽  
Rapd Markers ◽  
Gene Diversity ◽  
Natural Populations ◽  
Soil Types ◽  
Number Of Clusters ◽  
Analysis Of Molecular Variance ◽  
Molecular Variance

Three populations of Maytenus aquifolium from Monte Alegre farm, Telemaco Borba county, Paraná, Brazil were analyzed by RAPD markers. A total of 13 primers were applied wich yielded 283 well amplified markers in all the studied populations (Mortandade, Vila Preta and Trinita), producing different values of gene diversity and polymorphic loci. The analysis of molecular variance (AMOVA) indicated that 21.77% of the genetic variation was among the population. Pairwise F ST analysis showed that the most divergent populations were closer geographically, demonstrating that other factors such as different soil types could explain this variation. Bayesian analysis for K number of clusters and the Principal Coordinate indicated that these three populations were highly structured, corroborating the high values found for the F ST and indicating that for conservation purposes all populations should be maintained.

scholarly journals Molecular Genetic Variability of Spigelia marilandica and S. gentianoides

2015 ◽  
Vol 140 (2) ◽  
pp. 120-128
Author(s):  
Amanda J. Hershberger ◽  
Tracie M. Jenkins ◽  
Carol Robacker
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Variability ◽  
Gene Diversity ◽  
Molecular Genetic ◽  
Genetic Distances ◽  
Population Variation ◽  
Group Method ◽  
Polymorphism Analysis ◽  
Two Samples

Despite the ecologic and ornamental potential of southeastern U.S. native Spigelia, little is known about the intraspecific or the interpopulation genetic variation. The southeastern U.S. native Spigelia habitat is becoming more and more fragmented as a result of human activity, making it imperative to gain an understanding of natural genetic variation among and within species and populations for the purpose of obtaining variability for plant breeding and preserve the genetic variability in Spigelia. Therefore, the objective of this study was to use amplified fragment length polymorphism analysis to determine interspecific and intraspecific genetic variation and to evaluate gene flow. Thirteen populations of two species of native Spigelia, S. marilandica (SM), S. gentianoides var. gentianoides (SGG), and S. gentianoides var. alabamensis (SGA), were analyzed using four primer pairs that amplified a total of 269 bands. Based on analysis of molecular variance and estimates of Nei’s coefficients of gene diversity (percentage of polymorphic loci, average genetic diversity within populations, average genetic diversity within species, and proportion of species genetic diversity attributed to among population variation), the majority of variation found in Spigelia occurs within populations. Both among-species and among-population variation was low, likely the effect of common ancestry as well as relatively frequent introgression among individuals (and populations) of Spigelia. When all individuals were evaluated using Nei’s unbiased genetic distances and viewed as a unweighted pair group method with arithmetic mean phenogram, three main groups were shown, one with two samples of SGG from one population, one with 13 individuals from both SGG populations used in this study, and one with all of the SM, SGA, and remaining SGG individuals. Further evaluation using STRUCTURE software showed introgression between populations and species, although all allele clusters have not entirely introgressed into all populations. The significance of these results is discussed in relation to breeding in Spigelia.

scholarly journals Genetic Variability and Inter-relationship between Yield and Yield Components in Jhum Rice (Oryza sativa L.) Genotypes of Khagrachhari District in Bangladesh

2020 ◽  
Vol 18 (1) ◽  
pp. 1-9
Author(s):  
Mohammad Zahidul Islam ◽  
Nadia Akter ◽  
Md Ferdous Rezwan Khan Prince ◽  
Nashirum Monir ◽  
Mohammad Khalequzzaman
Keyword(s):  
Genetic Variability ◽  
Grain Yield ◽  
Plant Height ◽  
Coefficient Of Variation ◽  
Grain Weight ◽  
Genetic Advance ◽  
Significant Difference ◽  
Selection For ◽  
Positive Direct ◽  
1000 Grain Weight

The present investigation consists of 47 rice genotypes and the experiment was conducted during Aus season, 2016 in Randomized Block Design with three replications. The data were recorded for 13 quantitative characters to study genetic variability, heritability, genetic advance, correlation coefficient analysis and path analysis. Analysis of variance among 47 genotypes showed a significant difference for all characters studied. The highest genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were observed for grain yield followed by the number of effective tillers, the number of filled grains per panicle and 1000 grain weight indicating that these characters could be used in selection for the crop improvement program. High estimates of heritability was observed for grain yield, grain length, plant height, number of filled grain per panicle, 1000 grain weight and days to 50% flowering. High genetic advance was observed for the number of filled grains per panicle and plant height, indicating predominance of additive gene effects and possibilities of effective selection for the improvement of these traits. Grain yield showed positive association with number of effective tiller and number of filled grain per panicle at genotypic in conjunction with phenotypic level. Days to maturity possessed the highest positive direct effect and significant indirect correlation with yield. The Agriculturists 2020; 18(1) 01-09

scholarly journals Genetic Variation Maintained in Multilocus Models of Additive Quantitative Traits Under Stabilizing Selection

Genetics ◽  
1999 ◽  
Vol 152 (2) ◽  
pp. 807-820 ◽  
Author(s):  
Reinhard Bürger ◽  
Alexander Gimelfarb
Keyword(s):  
Genetic Variation ◽  
Quantitative Traits ◽  
Genetic Variance ◽  
Initial Conditions ◽  
Complete Analysis ◽  
Stabilizing Selection ◽  
Recombination Rates ◽  
Mean Values ◽  
Selection For ◽  
Quantities Of Interest

Abstract Stabilizing selection for an intermediate optimum is generally considered to deplete genetic variation in quantitative traits. However, conflicting results from various types of models have been obtained. While classical analyses assuming a large number of independent additive loci with individually small effects indicated that no genetic variation is preserved under stabilizing selection, several analyses of two-locus models showed the contrary. We perform a complete analysis of a generalization of Wright’s two-locus quadratic-optimum model and investigate numerically the ability of quadratic stabilizing selection to maintain genetic variation in additive quantitative traits controlled by up to five loci. A statistical approach is employed by choosing randomly 4000 parameter sets (allelic effects, recombination rates, and strength of selection) for a given number of loci. For each parameter set we iterate the recursion equations that describe the dynamics of gamete frequencies starting from 20 randomly chosen initial conditions until an equilibrium is reached, record the quantities of interest, and calculate their corresponding mean values. As the number of loci increases from two to five, the fraction of the genome expected to be polymorphic declines surprisingly rapidly, and the loci that are polymorphic increasingly are those with small effects on the trait. As a result, the genetic variance expected to be maintained under stabilizing selection decreases very rapidly with increased number of loci. The equilibrium structure expected under stabilizing selection on an additive trait differs markedly from that expected under selection with no constraints on genotypic fitness values. The expected genetic variance, the expected polymorphic fraction of the genome, as well as other quantities of interest, are only weakly dependent on the selection intensity and the level of recombination.

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