scholarly journals Strong genetic influence on hypocone expression of permanent maxillary molars in South Australian twins

2018 ◽  
Vol 22 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Denice Higgins ◽  
Toby E. Hughes ◽  
Helen James ◽  
Grant C. Townsend
Keyword(s):  
Phenotypic Expression ◽  
Forensic Odontology ◽  
Genetic Influence ◽  
Population Variation ◽  
Narrow Sense Heritability ◽  
Maxillary Molars ◽  
Heritability Estimates ◽  
Parsimonious Model ◽  
Dental Traits ◽  
Additive Genetic Effects

An understanding of the role of genetic influences on dental traits is important in the areas of forensic odontology, human evolution and population variation. The aims of this study were: to calculate the frequency of occurrence and degree of expression of hypocones on permanent maxillary first and second molars in a sample of South Australian twins; to compare trait expression between males and females; to compare concordance rates for trait expression between monozygotic (MZ) and dizygotic (DZ) twins; and to fit genetic models to the data derived from twins and determine heritability estimates. Using stone dental casts, hypocone expression was scored on maxillary permanent first and second molars of 45 MZ twin pairs and 43 DZ pairs. Degrees of expression were scored from absence, through minor wrinkles or ridges, to very large cusps (score 0 – 5) using the standardized method of Turner et al. (1991). Hypocones were found to be more common and larger on first molars than second molars and there was a tendency for them to be larger in males although this was not statistically significant. No significant differences in occurrence or expression were noted between antimeres, with fewer differences observed between first than second molars. The percentage concordance for expression in MZ twin pairs was higher than in DZ twin pairs indicating a genetic influence determining the variation observed in hypocone expression. The most parsimonious model to explain observed variation was an AE model, incorporating additive genetic and unique environmental effects. Narrow-sense heritability estimates for both the first and second molars were high indicating that a large portion of the phenotypic variation could be explained by additive genetic effects. The greater range of phenotypic expression shown by the second molars compared with the first molars may reflect a common genetic liability that is modulated by differences in tooth size, location and/or developmental timing between these teeth.

scholarly journals Combining ability and heritability estimates of main agronomic characters in rapeseed breeding lines using line × tester analysis

2012 ◽  
Vol 57 (3) ◽  
pp. 111-120 ◽  
Author(s):  
Valiollah Rameeh
Keyword(s):  
Seed Yield ◽  
Combining Ability ◽  
Yield Components ◽  
Seed Weight ◽  
Oil Content ◽  
Genetic Effects ◽  
Narrow Sense Heritability ◽  
Breeding Lines ◽  
Heritability Estimates ◽  
Additive Genetic Effects

To estimate the general and specific combining ability (GCA and SCA) effects of plant height, yield components, seed yield and oil content, three testers and six lines of spring type of rapeseed varieties were crossed using line ? tester fashion. Significant mean squares of parents and crosses for all the traits indicated significant genetic variation among the parents and their F1 crosses. Significant mean squares of parents vs crosses revealed significant average heterosis for all the traits except seeds per pod, 1000-seed weight and oil content. High narrow-sense heritability estimates for all the traits except seeds per pod, indicating the importance of additive genetic effects for these traits. Due to more importance of additive genetic effects for most of the traits, only a few of the crosses exhibited significant SCA effects. A significant positive correlation between seed yield and some of yield components including pods on main axis, pods per plant and 1000-seed weight indicates that these traits can be used as suitable selection criteria for improving of seed yield. The crosses including Opt ? R01, RG06 ? R01, RG06 ? R08 and RGS3 ? R08 with 3241.91, 3213.68, 3334.28 and 3237.45 kg ha-1 of seed yield detected as prior combinations for improving of this trait and all of these combinations had also positive SCA effect for this trait.

Combining Ability of Plant Height and Yield components in Indian Mustard (Brassica junceaL.Czern & Coss.) under Salt affected Soil using Line×Tester Analysis

2016 ◽  
Vol 3 (2) ◽  
Author(s):  
SHAILESH CHAND GAUTAM ◽  
MP Chauhan
Keyword(s):  
Plant Height ◽  
Seed Yield ◽  
Combining Ability ◽  
Yield Components ◽  
Indian Mustard ◽  
Heritability Estimate ◽  
Genetic Effects ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Additive Genetic Effects

Line × tester analysis of twenty lines and three testers of Indian mustard (Brassica juncea L. Czern & Coss.) cultivars were used to estimate general combining ability (GCA), specific combining ability (SCA) effects, high parent heterosis and narrow-sense heritability estimate for plant height, yield components and seed yield. Significant variance of line x tester for the traits like pods per plant and seed yield indicating non additive genetic effects have important role for controlling these traits. Significant mean squares of parents v/s crosses which are indicating significant average heterosis were also significant for all the traits except seeds per pod. High narrow-sense heritability estimates for all the traits except seeds per pod exhibited the prime importance of additive genetic effects for these traits except seeds per pod. Most of the crosses with negative SCA effect for plant height had at least one parent with significant negative or negative GCA effect for this trait. For most of the traits except pods per plant, the efficiency of high parent heterosis effect was more than SCA effect for determining superior cross combinations.

Heritability of Metribuzin Tolerance in Sweet Potatoes (Ipomoea batatas)

Weed Science ◽  
1987 ◽  
Vol 35 (5) ◽  
pp. 715-719 ◽  
Author(s):  
Howard F. Harrison ◽  
Alfred Jones ◽  
Philip D. Dukes
Keyword(s):  
Ipomoea Batatas ◽  
Selection Process ◽  
Mass Selection ◽  
Fresh Weight ◽  
Sweet Potatoes ◽  
Narrow Sense Heritability ◽  
Shoot Fresh Weight ◽  
Potting Medium ◽  
Wide Range ◽  
Heritability Estimates

Twenty-two sweet potato [Ipomoea batatas(L.) Lam.] clones with a wide range in metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] tolerance were used to establish narrow sense heritability estimates (h2) using a greenhouse procedure. The heritability estimates were obtained from simple linear regressions (h2= 2b) of injury rating, shoot fresh weight, and change in shoot fresh weight of offspring against the same responses of parents at metribuzin concentrations of 0, 0.3, and 0.6 ppm in the potting medium and averaged data for the two concentrations. These values ranged from 0.85 to 1.0, indicating that a recurrent mass selection process should be an appropriate approach to developing metribuzin-tolerant cultivars. Several highly tolerant clones were identified.

scholarly journals Accelerating Genetic Gain in Sugarcane Breeding Using Genomic Selection

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 585 ◽  
Author(s):  
Seema Yadav ◽  
Phillip Jackson ◽  
Xianming Wei ◽  
Elizabeth M. Ross ◽  
Karen Aitken ◽  
...  
Keyword(s):  
Genomic Selection ◽  
Genetic Gain ◽  
Cycle Length ◽  
Primary Source ◽  
Genetic Effects ◽  
Breeding Cycle ◽  
Narrow Sense Heritability ◽  
Breeding Values ◽  
Sugarcane Breeding ◽  
Additive Genetic Effects

Sugarcane is a major industrial crop cultivated in tropical and subtropical regions of the world. It is the primary source of sugar worldwide, accounting for more than 70% of world sugar consumption. Additionally, sugarcane is emerging as a source of sustainable bioenergy. However, the increase in productivity from sugarcane has been small compared to other major crops, and the rate of genetic gains from current breeding programs tends to be plateauing. In this review, some of the main contributors for the relatively slow rates of genetic gain are discussed, including (i) breeding cycle length and (ii) low narrow-sense heritability for major commercial traits, possibly reflecting strong non-additive genetic effects involved in quantitative trait expression. A general overview of genomic selection (GS), a modern breeding tool that has been very successfully applied in animal and plant breeding, is given. This review discusses key elements of GS and its potential to significantly increase the rate of genetic gain in sugarcane, mainly by (i) reducing the breeding cycle length, (ii) increasing the prediction accuracy for clonal performance, and (iii) increasing the accuracy of breeding values for parent selection. GS approaches that can accurately capture non-additive genetic effects and potentially improve the accuracy of genomic estimated breeding values are particularly promising for the adoption of GS in sugarcane breeding. Finally, different strategies for the efficient incorporation of GS in a practical sugarcane breeding context are presented. These proposed strategies hold the potential to substantially increase the rate of genetic gain in future sugarcane breeding.

scholarly journals Genetic influence on electrocardiogram time intervals and heart rate in aging mice

2009 ◽  
Vol 296 (6) ◽  
pp. H1907-H1913 ◽  
Author(s):  
Shuqin Xing ◽  
Shirng-Wreng Tsaih ◽  
Rong Yuan ◽  
Karen L. Svenson ◽  
Linda M. Jorgenson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Inbred Strains ◽  
Genetic Influence ◽  
Cardiac Conduction ◽  
Qrs Complex ◽  
Time Intervals ◽  
Age Related ◽  
Males And Females ◽  
Heritability Estimates ◽  
Age Related Changes

Understanding the genetic influence on ECG time intervals and heart rate (HR) is important for identifying the genes underlying susceptibility to cardiac arrhythmias. The objective of this study was to determine the genetic influence on ECG parameters and their age-related changes in mice. ECGs were recorded in lead I on 8 males and 8 females from each of 28 inbred strains at the ages of 6, 12, and 18 mo. Significant interstrain differences in the P-R interval, QRS complex duration, and HR were found. Age-related changes in the P-R interval, QRS complex duration, and HR differed among strains. The P-R interval increased with age in 129S1/SvlmJ females. The QRS complex duration decreased with age in C57BR/J males and DBA2/J females but increased in NON/ShiLtJ females. HR decreased in C57L/J females and SM/J and P/J males but increased in BALB/cByJ males. Differences between males and females were found for HR in SJL/J mice and in the P-R interval in 129S1/SvlmJ mice. Broad-sense heritability estimates of ECG time intervals and HR ranged from 0.31 for the QRS complex duration to 0.52 for the P-R interval. Heritability estimates decreased with age for the P-R interval. Our study revealed that genetic factors play a significant role on cardiac conduction activity and age-related changes in ECG time intervals and HR.

Estimates of genetic parameters for growth and skeletal measurements in Thai swamp buffalo

2000 ◽  
Vol 70 (3) ◽  
pp. 399-406
Author(s):  
K. Meyer ◽  
H. -U. Graser ◽  
A. Na-Chiangmai
Keyword(s):  
Total Variation ◽  
Genetic Association ◽  
Maternal Effects ◽  
Genetic Parameters ◽  
Genetic Effects ◽  
Environmental Correlations ◽  
Length Measurements ◽  
Swamp Buffalo ◽  
Heritability Estimates ◽  
Additive Genetic Effects

AbstractEstimates of genetic parameters were obtained for weight, hip height, heart girth and shoulder to pin length measurements on Thai swamp buffalo, recorded at birth and weaning. Direct heritability estimates were 0·26 for weights at both ages and were low for skeletal measurements, ranging from 0·11 to 0·19. Low values could, in part at least, be caused by inaccuracies in recording. All traits were subject to maternal effects, permanent environmental maternal effects on traits recorded at weaning explaining proportionately up to 0·14 of the total variation. Estimates of genetic (direct and maternal) and permanent environmental correlations between traits recorded at the same time were high throughout, ranging from 0·83 to 0·97 for additive genetic effects and being close to unity otherwise. Except for heart girth measured at weaning, there appeared to be comparatively little genetic association between traits recorded at different times, direct additive correlation estimates ranging from 0·18 to 0·55 in contrast to estimates of 0·38 to 0·65 for correlations with heart girth at weaning.

scholarly journals Statistical properties of simple random-effects models for genetic heritability

2016 ◽  
Author(s):  
David Steinsaltz ◽  
Andrew Dahl ◽  
Kenneth W. Wachter
Keyword(s):  
Random Effects ◽  
Large Scale ◽  
Score Function ◽  
Singular Values ◽  
Statistical Properties ◽  
Shared Environment ◽  
Small Subset ◽  
Narrow Sense Heritability ◽  
Random Effects Models ◽  
Heritability Estimates

AbstractRandom-effects models are a popular tool for analysing total narrow-sense heritability for simple quantitative phenotypes on the basis of large-scale SNP data. Recently, there have been disputes over the validity of conclusions that may be drawn from such analysis. We derive some of the fundamental statistical properties of heritability estimates arising from these models, showing that the bias will generally be small. We show that that the score function may be manipulated into a form that facilitates intelligible interpretations of the results. We use this score function to explore the behavior of the model when certain key assumptions of the model are not satisfied — shared environment, measurement error, and genetic effects that are confined to a small subset of sites — as well as to elucidate the meaning of negative heritability estimates that may arise.The variance and bias depend crucially on the variance of certain functionals of the singular values of the genotype matrix. A useful baseline is the singular value distribution associated with genotypes that are completely independent — that is, with no linkage and no relatedness — for a given number of individuals and sites. We calculate the corresponding variance and bias for this setting.MSC 2010 subject classifications: Primary 92D10; secondary 62P10; 62F10; 60B20.

scholarly journals Trait Heritability Estimates of an Open-pollinated Onion Population

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 812A-812
Author(s):  
Christopher S. Cramer*
Keyword(s):  
Selection Response ◽  
Planting Date ◽  
Realized Heritability ◽  
Outer Scale ◽  
Narrow Sense Heritability ◽  
Scale Thickness ◽  
Basal Rot ◽  
Family Analysis ◽  
Fusarium Basal Rot ◽  
Heritability Estimates

Heritability estimates of bolting percentage (BP), pink root (PR) and Fusarium basal rot (FBR) incidences, and percentage of single centered (PSC) bulbs were calculated for an intermediate-day, open-pollinated onion population using selection response and half-sib (HS) family analyses. BP was determined by counting the number of seedstalks per plot when the population was seeded at an earlier planting date to induce bolting. PR and FBR incidences were determined by rating 30 bulbs/plot for the severity of PR and FBR, and calculated an incidence rate from the number of infected bulbs out of 30 rated. The PSC bulbs was determined by cutting transversely 30 bulbs at the vertical center of the bulb and looking for the presence of a single growing point or multiple growing points within 1.3 cm from the center of the bulb. Families were also evaluated for bulb quality that consisted of shape, size, maturity, firmness, number of scale layers, and dry outer scale thickness, adherence, retention, and color. Families were selected based upon an index that equally weighted BP, PR and FBR incidences, PSC bulbs, and bulb quality. No progress was made for BP even though the narrow sense heritability (h2) estimate was 0.51. PR and FBR incidence was reduced by 18% and 12%, respectively, and realized heritability (RH) estimates of 0.65 and 0.60, respectively, were calculated. h2 estimates calculated through HS family analysis was 0.46 and 0.37, respectively, for these two traits. Very little progress was made for the PSC bulbs and this was reflected in a RH estimate of 0.17. However, the h2 estimate was 0.71, suggesting that progress should be possible.

scholarly journals Genetic Variance Component and Heritability Estimates of Freedom from Weevil Injury to Sweetpotato

1994 ◽  
Vol 119 (3) ◽  
pp. 620-623 ◽  
Author(s):  
P.G. Thompson ◽  
John C. Schneider ◽  
Boyett Graves
Keyword(s):  
Variance Component ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Component Analysis ◽  
Variance Component Analysis ◽  
Breeding Cycle ◽  
Individual Plant ◽  
Root Number ◽  
Narrow Sense Heritability ◽  
Heritability Estimates

Narrow-sense heritability for component traits of freedom from weevil injury and yield of sweetpotato were estimated by parent-offspring regression and variance component analysis. Heritability estimates by variance component analysis based on half-sib families for percent and number of uninjured roots were 0.25 and 0.83, respectively. Individual plant heritability estimates for uninjured root percent and number were 0.03 and 0.13, respectively. Heritability estimates by parent-offspring regression for uninjured root percent and number were 0.35 and 0.52, respectively. Genetic variance was mostly additive for all traits except stem diameter. Genetic correlations between total root number, uninjured root number, and percent uninjured roots ranged from 0.66 to 0.87, indicating that selection for uninjured root number should most effectively increase uninjured root number and percent, as well as total root numbers. Predicted gains in uninjured root percent and number were 8.8% and 0.87 in the progeny derived from intermating the highest four out of 19 families for uninjured root number. The 0.87 gain in uninjured root number equals a 24% increase in one breeding cycle.

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