Analysis of pest resistance in alfalfa with a new autotetraploid genetic model

1985 ◽  
Vol 27 (1) ◽  
pp. 39-46 ◽  
Author(s):  
R. R. Hill Jr. ◽  
J. H. Elgin Jr.
Keyword(s):  
Population Genetics ◽  
Gene Action ◽  
Genetic Model ◽  
Pest Resistance ◽  
Additive Effects ◽  
Approach To Equilibrium ◽  
Parent Population ◽  
Medicago Sativa L ◽  
The Mean ◽  
Resistance Data

A genetic model for the analysis of crosses and advanced generations between autotetraploid populations had been developed and applied to an analysis of pest resistance data in an experiment on alfalfa (Medicago sativa L.). The model had the form [Formula: see text] where [Formula: see text] is the observed mean of combination ij in generation n, C is a constant, u, is a parameter for the mean of parent population i, kn and mn are constants computed from the theoretical approach to equilibrium in the population, Gij is the digenic parameter in the equilibrium population that would arise from the population cross, and Qij is the quadrigenic parameter for that population. Nonadditive genetic effects were observed for most of the traits subjected to analysis under the model. The mode of gene action varied from one population to another in many cases. Variances of estimates of Gij were small, but those of Qij were very large. The large covariance between estimates of Gij and Qij was caused by a correlation between coefficients of these parameters.Key words: pest resistance, Medicago, autotetraploid, additive effects, population genetics.

Multiplicative vs. arbitrary gene action in heterosis.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 461-469 ◽  
Author(s):  
F W Schnell ◽  
C C Cockerham
Keyword(s):  
Gene Action ◽  
Extensive Literature ◽  
Additive Effects ◽  
Nonlinear Functions ◽  
Epistatic Effects ◽  
Genetic Significance ◽  
The Mean ◽  
The Difference ◽  
Multiplicative Models ◽  
Multiplicative Effects

Abstract In this article we investigate multiplicative effects between genes in relation to heterosis. The extensive literature on heterosis due to multiplicative effects between characters is reviewed, as is earlier work on the genetic description of heterosis. A two-locus diallelic model of arbitrary gene action is used to derive linear parameters for two multiplicative models. With multiplicative action between loci, epistatic effects are nonlinear functions of one-locus effects and the mean. With completely multiplicative action, the mean and additive effects form similar restrictions for all the rest of the effects. Extensions to more than two loci are indicated. The linear parameters of various models are then used to describe heterosis, which is taken as the difference between respective averages of a cross (F1) and its two parent populations (P). The difference (F2 - P) is also discussed. Two parts of heterosis are distinguished: part I arising from dominance, and part II due to additive x additive (a x a)-epistasis. Heterosis with multiplicative action between loci implies multiplicative accumulation of heterosis present at individual loci in part I, in addition to multiplicative (a x a)-interaction in part II. Heterosis with completely multiplicative action can only be negative (i.e., the F1 values must be less than the midparent), but the difference (F2 - P) can be positive under certain conditions. Heterosis without dominance can arise from multiplicative as well as any other nonadditive action between loci, as is exemplified by diminishing return interaction. The discussion enlarges the scope in various directions: the genetic significance of multiplicative models is considered.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Why most Principal Component Analyses (PCA) in population genetic studies are wrong

2021 ◽  
Author(s):  
Eran Elhaik
Keyword(s):  
Population Genetics ◽  
Population Genetic ◽  
Genetic Model ◽  
Principal Component ◽  
Population Data ◽  
Test Cases ◽  
Validity Of Results ◽  
Genetic Studies ◽  
Minimal Loss ◽  
Admixture Population

Principal Component Analysis (PCA) is a multivariate analysis that allows reduction of the complexity of datasets while preserving data's covariance and visualizing the information on colorful scatterplots, ideally with only a minimal loss of information. PCA applications are extensively used as the foremost analyses in population genetics and related fields (e.g., animal and plant or medical genetics), implemented in well-cited packages like EIGENSOFT and PLINK. PCA outcomes are used to shape study design, identify and characterize individuals and populations, and draw historical and ethnobiological conclusions on origins, evolution, whereabouts, and relatedness. The replicability crisis in science has prompted us to evaluate whether PCA results are reliable, robust, and replicable. We employed an intuitive color-based model alongside human population data for eleven common test cases. We demonstrate that PCA results are artifacts of the data and that they can be easily manipulated to generate desired outcomes. PCA results may not be reliable, robust, or replicable as the field assumes. Our findings raise concerns on the validity of results reported in the literature of population genetics and related fields that place a disproportionate reliance upon PCA outcomes and the insights derived from them. We conclude that PCA may have a biasing role in genetic investigations. An alternative mixed-admixture population genetic model is discussed.

scholarly journals Analysis of population and heterosis effects in crossbred cattle of Czech Fleckvieh and Beef Simmental parentage for growth traits

2008 ◽  
Vol 51 (3) ◽  
pp. 207-215
Author(s):  
L. Vostrý ◽  
V. Jakubec ◽  
W. Schlote ◽  
M. Bjelka ◽  
J. Bezdíček ◽  
...  
Keyword(s):  
Fixed Effects ◽  
Genetic Model ◽  
Growth Traits ◽  
Crossbred Cattle ◽  
Method Of Least Squares ◽  
Beef Cow ◽  
Heterosis Effect ◽  
Sex Type ◽  
The Mean ◽  
Population Effects

Abstract. Genetic effects, e.f. population and heterosis effects have been estimated for: Czech Fleckvieh, Beef Simmental and various types of their crosses produced in beef cow-calf operations. The best genetic-statistical model was chosen for the analyze of these effects. The fallowing traits were analyzed: birth weight, weights at 210 and at 365 days of age as well as average daily gains between birth and 210 days, between 210 and 365 days and between birth and 365 days of age. Parameters for all the traits were estimated by the method of least squares means with fixed effects year of birth, herd, sex, type of birth (single or multiple), age of dam and genotype. Genetic models involved the means and two to four crossbreeding effects: i.e. direct and maternal population effect and direct and maternal heterosis effect. The results showed that the genetic model including the mean and all four crossbreeding effects was more accurate and advantageous that the others. For all growth traits crossbreds exceeded both purebred populations. Positive values were estimated for most direct and maternal population effects. Direct and maternal heterosis effects in global showed negative values.

scholarly journals Interplay of population genetics and dynamics in the genetic control of mosquitoes

2014 ◽  
Vol 11 (93) ◽  
pp. 20131071 ◽  
Author(s):  
Nina Alphey ◽  
Michael B. Bonsall
Keyword(s):  
Population Genetics ◽  
Overlapping Generations ◽  
Large Scale ◽  
Genetic Model ◽  
Homing Endonuclease ◽  
Wild Type ◽  
Larval Competition ◽  
Selfish Genetic Elements ◽  
Fitness Effects ◽  
Ecological Aspects

Some proposed genetics-based vector control methods aim to suppress or eliminate a mosquito population in a similar manner to the sterile insect technique. One approach under development in Anopheles mosquitoes uses homing endonuclease genes (HEGs)—selfish genetic elements (inherited at greater than Mendelian rate) that can spread rapidly through a population even if they reduce fitness. HEGs have potential to drive introduced traits through a population without large-scale sustained releases. The population genetics of HEG-based systems has been established using discrete-time mathematical models. However, several ecologically important aspects remain unexplored. We formulate a new continuous-time (overlapping generations) combined population dynamic and genetic model and apply it to a HEG that targets and knocks out a gene that is important for survival. We explore the effects of density dependence ranging from undercompensating to overcompensating larval competition, occurring before or after HEG fitness effects, and consider differences in competitive effect between genotypes (wild-type, heterozygotes and HEG homozygotes). We show that population outcomes—elimination, suppression or loss of the HEG—depend crucially on the interaction between these ecological aspects and genetics, and explain how the HEG fitness properties, the homing rate (drive) and the insect's life-history parameters influence those outcomes.

MULTILOCUS POPULATION GENETICS WITH WEAK EPISTASIS. I. EQUILIBRIUM PROPERTIES OF TWO-LOCUS TWO-ALLELE MODELS

Genetics ◽  
1985 ◽  
Vol 109 (4) ◽  
pp. 799-812
Author(s):  
Alan Hastings
Keyword(s):  
Population Genetics ◽  
Experimental Design ◽  
Recombination Rate ◽  
Allele Frequencies ◽  
Perturbation Techniques ◽  
Biological Importance ◽  
Mean Fitness ◽  
The Mean ◽  
Neutral Models

ABSTRACT Using perturbation techniques, I determine the equilibrium of two-locus two-allele models with overdominance and weak epistasis. To lowest order, the allele frequencies, the mean fitness and the covariance between heterokaryotic and homokaryotic flies arising in the Sturtevant experimental design are independent of the recombination rate, r. The disequilibrium varies as one divided by the recombination rate, in contrast to neutral models. Although the disequilibrium generated by weak epistasis is small, too small to be experimentally detected, it can be large enough to have biological importance.

scholarly journals Correlations and selection of parents to technological traits of upland cotton

2019 ◽  
Vol 49 (6) ◽  
Author(s):  
Luiz Paulo de Carvalho ◽  
Francisco José Correia Farias ◽  
Josiane Isabela Silva Rodrigues ◽  
Katiane Secco Castro ◽  
Alan Mario Zuffo ◽  
...  
Keyword(s):  
Textile Industry ◽  
Upland Cotton ◽  
Fiber Strength ◽  
Diallel Analysis ◽  
Additive Effects ◽  
Lint Percentage ◽  
Medium Length ◽  
The Mean ◽  
Selection Of ◽  
Partial Diallel

ABSTRACT: Technological traits improvement of cotton fiber is a constant demand by textile industry. This research aimed to identify the potential of improved materials with high lint percentage to contribute with alleles that increase the lint percentage in Extra long staple fiber (ELS) upland cotton. Two contrasting materials for lint percentage (LP) and fiber length (FL) were used, one with long fiber and a low lint percentage (parent A) and another with high lint percentage and medium length (parent B). The following variables were evaluated: lint percentage (LP), upper half mean length (UHML), fiber uniformity (FU), fiber strength (FS), and elongation (EL). Diallel analysis was performed using the Griffing’s Method 4 adapted to partial diallel. Additive effects were predominant over non-additive effects. The mean LP was higher when using parent B. The opposite occurred for UHML. A negative correlation was detected between LP and UHML, showing the difficulty of obtaining genetic gain for both traits at the same time.

scholarly journals Distribution of Anacardic Acids Associated with Small Pest Resistance among Cultivars of Pelargonium ×hortorum

1995 ◽  
Vol 120 (2) ◽  
pp. 343-346 ◽  
Author(s):  
Richard Grazzini ◽  
David Hesk ◽  
Ellen Yerger ◽  
Diana Cox-Foster ◽  
June Medford ◽  
...  
Keyword(s):  
Acid Composition ◽  
Pest Resistance ◽  
Glandular Trichome ◽  
Sticky Trap ◽  
Anacardic Acid ◽  
Anacardic Acids ◽  
Commercial Cultivars ◽  
Diploid Cultivar ◽  
The Mean ◽  
Trichome Exudate

Composition of anacardic acids (phenolic acids known to be associated with small pest resistance in Pelargonium ×hortorum) was examined in 13 diploid and 25 tetraploid cultivars by high-performance liquid chromatography (HPLC). The presence of an unusual desaturation (omega (ω)-5) in the alkyl tail of anacardic acids present only in glandular trichome exudate of pest-resistant diploid inbred lines had previously been associated with a sticky-trap pest-resistance phenomenon. In this study, we examine Pelargonium cultivars for variability in anacardic acid composition to assess the distribution of ω5 desaturation among commercial cultivars, to determine possible interactions between ω5 desaturation and other plant desaturation mechanisms, and to examine the possible impact of ploidy on ω5 desaturation. An unsaturation index (UI) is derived to compare exudates differing widely in composition yet which may provide a similarly effective sticky-trap pest-resistance mechanism based on exudate viscosity. ω-5 Anacardic acids were observed in the glandular trichome exudate of all 38 commercial cultivars examined. No diploid cultivar produced ω5- and ω9- anacardic acids, although the simultaneous production of ω5 and ω9- anacardic acids was observed in three tetraploid cultivars. Total ω5- anacardic acids comprised from 42.4% (tetraploid cultivar Perlenkette-syn. Snowhite, Weiss) to 86.8% (tetraploid cultivar Amanda). Commercial P. ×domesticum cultivars had no ω5 anacardic acids. UIs ranged from 60.9 (tetraploid cultivar Dixieland) to 103.4 (diploid cultivar Pinto White). In contrast, anacardic acids collected from a pest-susceptible inbred line contained no ω5- anacardic acids and had a UI of 38.7. No significant differences among ploidy levels were observed for UIs or for most specific anacardic acid components, with the exception of 24:1 ω5- anacardic acid, in which the mean diploid value (32.1%) was significantly higher than that of the mean tetraploid value (27.6%). We conclude that ω5- anacardic acid production occurs in all Pelargonium cultivars observed and that these cultivars are predicted to exhibit resistance to small arthropod pests. Significant genetic variability in specific anacardic acid composition appears to exist among Pelargonium cultivars, suggesting that breeding for pest resistance can be readily monitored by HPLC of anacardic acids.

scholarly journals Study of Combining Ability and Nature of Gene Action for Yield and Yield Related Traits in Maize (Zea mays L.)

2019 ◽  
pp. 1-8
Author(s):  
Birender Singh ◽  
Abhinav Abhishek ◽  
R. B. P. Nirala ◽  
S. S. Mandal ◽  
Tushar Ranjan
Keyword(s):  
Grain Yield ◽  
Zea Mays L ◽  
Gene Action ◽  
Block Design ◽  
Diallel Mating Design ◽  
Randomized Complete Block Design ◽  
Additive Gene ◽  
Ear Height ◽  
The Mean ◽  
Half Diallel

The present investigation was carried out using thirty eight genotypes (eight parents, twenty eight F1's and two checks) using Griffing's half diallel mating design. The experiment was laid out in a randomized complete block design with three replications during kharif 2017 at the research farm of Bihar Agriculture College, Sabour. Observations were recorded for six pre-harvest characters viz days to 50% anthesis, days to 50% silking, anthesis silking interval, days to 75% brown husk, plant height, ear height and seven post-harvest characters viz cob length, cob diameter, number of kernel rows per cob, number of kernels per row, 1000 seed weight, shelling percentage and grain yield at 15% moisture. The mean sum of square of treatments was found to be significant for days to 75% brown husk and shelling per cent and highly significant for all other characters. The mean sum of square for GCA was found to be significant for cob length, no. of kernel row per cob, no. of kernels per row and highly significant for remaining all the characters except days to 75% brown husk and shelling%. The mean sum of square for SCA was significant for days to 75% brown husk and highly significant for all the remaining characters. On the basis of GCA effect for grain yield at 15% moisture, the parents BML-7, VQL-1 and SML-1 were found to be good general combiners. The ratio of GCA variance to SCA variance was found to be less than 1 for all the traits which indicated the preponderance of non-additive gene action. On the basis of SCA effects better performing crosses for grain yield at 15% moisture were DTPYC-9 × LM-13, CLQRCY-44 × VQL-1, CML-161 × SML-1 and CML-161× BML-7.

scholarly journals Analysis of conditional genetic effects and variance components in developmental genetics.

Genetics ◽  
1995 ◽  
Vol 141 (4) ◽  
pp. 1633-1639 ◽  
Author(s):  
J Zhu
Keyword(s):  
Variance Components ◽  
Quantitative Traits ◽  
Genetic Variance ◽  
Genetic Model ◽  
Genetic Effects ◽  
Unbiased Estimation ◽  
Developmental Genetics ◽  
Additive Effects ◽  
Genotype X Environment ◽  
Worked Example

Abstract A genetic model with additive-dominance effects and genotype x environment interactions is presented for quantitative traits with time-dependent measures. The genetic model for phenotypic means at time t conditional on phenotypic means measured at previous time (t-1) is defined. Statistical methods are proposed for analyzing conditional genetic effects and conditional genetic variance components. Conditional variances can be estimated by minimum norm quadratic unbiased estimation (MINQUE) method. An adjusted unbiased prediction (AUP) procedure is suggested for predicting conditional genetic effects. A worked example from cotton fruiting data is given for comparison of unconditional and conditional genetic variances and additive effects.

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