Genetic Variance Components Research Articles

Combining ability estimates and gene action studies from full diallel mating design in maize (Zea mays L.)

A study was under taken during kharif season of 2016 at College of Agriculture, Bheemarayanagudi and UAS, GKVK, Bengaluru to estimate the combining ability and investigate gene action involved in inheritance of yield and its components traits of maize inbreds through 20×20 full diallel cross analysis. 380 SCHs synthesized through full diallel mating design were evaluated in simple lattice square lattice design at two locations. Analysis of variance revealed significant differences among the hybrids, parents vs. hybrids and straight crosses for all the characters and among the parents for all the characters except ASI, ear circumference and shelling %. Significant differences were also recorded in reciprocal crosses for all the characters except ear circumference and shelling %. Significant GCA variance for grain yield revealed the role of additive components of genetic variance. SCA variance was also highly significant for all characters except ear circumference and test weight indicating the importance of both additive and non additive components of genetic variance. However, there was predominance of additive gene action recorded for all the characters. GCA: SCA variance ratio was less than unity for all the traits, suggesting the predominance of non-additive gene action. Inbreds MAI 283 and VL 109252 were identified as good general combiners as they registered significant gca effects in positive direction for grain yield and its component traits. Straight cross MAI-283×KDMI-16 and reciprocal cross M 04×KDMI 16 registered highest significant sca effects in positive direction for grain yield along with high and significant sca effects in negative direction for ASI.

Combining ability estimates and gene action studies from full diallel mating design in maize (Zea mays L.)

A study was under taken during kharif season of 2016 at College of Agriculture, Bheemarayanagudi and UAS, GKVK, Bengaluru to estimate the combining ability and investigate gene action involved in inheritance of yield and its components traits of maize inbreds through 20×20 full diallel cross analysis. 380 SCHs synthesized through full diallel mating design were evaluated in simple lattice square lattice design at two locations. Analysis of variance revealed significant differences among the hybrids, parents vs. hybrids and straight crosses for all the characters and among the parents for all the characters except ASI, ear circumference and shelling %. Significant differences were also recorded in reciprocal crosses for all the characters except ear circumference and shelling %. Significant GCA variance for grain yield revealed the role of additive components of genetic variance. SCA variance was also highly significant for all characters except ear circumference and test weight indicating the importance of both additive and non additive components of genetic variance. However, there was predominance of additive gene action recorded for all the characters. GCA: SCA variance ratio was less than unity for all the traits, suggesting the predominance of non-additive gene action. Inbreds MAI 283 and VL 109252 were identified as good general combiners as they registered significant gca effects in positive direction for grain yield and its component traits. Straight cross MAI-283×KDMI-16 and reciprocal cross M 04×KDMI 16 registered highest significant sca effects in positive direction for grain yield along with high and significant sca effects in negative direction for ASI.

Heritability of facial soft tissue growth in mono- and dizygotic twins at 12 and 17 years of age: A retrospective cohort study.

The purpose of this investigation of untreated monozygotic and dizygotic twins was to identify the genetic and environmental components to the facial soft tissue growth. The sample consisted of 52 untreated monozygotic twins (36 male and 16 female) and 46 untreated dizygotic twins (23 male and 23 female) from the Forsyth Moorrees Twin Study (1959-1975). Lateral cephalograms were taken at 12 and 17years of age and traced to analyse facial convexity, nasolabial angle, upper and lower lip thickness, upper and lower lip profile and nose prominence. The genetic and environmental components of variance were analysed with structural equation modelling for multilevel mixed-effects model. At 12years of age, strong additive genetic influence was seen for facial convexity (70%), upper lip profile (66%) and nose prominence (65%), whereas strong dominant genetic components were found for upper lip thickness (56%). Nevertheless, under unique environment influence were nasolabial angle (58%), lower lip profile (51%) and lower lip thickness (64%). At 17years of age, only upper lip thickness (55%) and nose prominence (84%) were under strong additive genetic control, while the rest of the variables were under strong dominant genetic control. The only exception was lower lip thickness (61%), which is still influenced by the unique environment. Although monozygotic/dizygotic twins share at least part of their genome, at both times either additive, dominant or environmental components were found. Nevertheless, at 17years of age most of the variables are either under additive or dominant genetic influence.

Estimation of genetic parameters and resistance to Meloidogyne spp. in melon genotypes

Root-knot nematodes (Meloidogyne spp.) are one of the major pests of agricultural crops worldwide. In Brazil, these nematodes are widely distributed in melon fields, and there are no reports of resistant melon cultivars. This study aimed to estimate genetic variance components for the selection of melon genotypes resistant to Meloidogyne incognita, M. javanica, and M. enterolobii. Two experiments were carried out in a completely randomized design, the first with 14 replications and the second with 10 replications, in a factorial design. Thirteen melon genotypes were tested. In both experiments, the total number of eggs and juveniles (TNEJ) was estimated and used to determine the reproduction factor (RF) and reproduction index (RI) of nematodes. Melon genotypes showed wide genetic variability in resistance to the three nematode species, resulting in high estimates of heritability (92%) and accuracy (96%). Such findings indicate the possibility of genetic gains with selection. Melon AC-09, PI157082, and ‘Ouro’ were found to be sources of resistance to M. incognita, M. javanica, and M. enterolobii, respectively.

Evaluation of yield and agronomic components by triallel cross and selection of high essential oil yielding hybrids in Basil

The basil (genus Ocimum) is a medicinal and fragrant herb or shrub with a wide range of applications as an ornamental plant, culinary ingredient, flavoring agent, and bioactive fragrance ingredient in foods cosmetics, and household items. Basil essential oil is in high demand, especially for novel high-quality oils with distinct aromas and chemical properties. The objectives of this study were, i) to increase the essential oil yield of better quality by gathering different genes responsible for the above economic characters scattered among different genotypes belonging to the same species or in other species of basil, and ii) the estimation of nature and amount of different genetic parameters. In the Ocimum, the single crosses and their corresponding three-way crosses/hybrids developed during the cropping season 2017–18 (single crosses) and 2018–2019 (three-way crosses). The three-way crosses/hybrids were evaluated in the field experimental trials during the 2019–20 at the CSIR-CIMAP, Lucknow (India) research farm. The analysis of variance (ANOVA) worked out for general and specific line effects for the eleven traits, and they were found highly significant for all the eleven traits. All the three-way crosses exhibited high variations for oil yield and yield contributing characters. For all eleven attributes, the additive genetic components of variance (σ2A) were higher than the dominant genetic components of variance (σ2 D), indicating that selection is simple for these attributes. For all the traits in the study, additive × dominance (σ2AD) gene action was higher than additive × additive (σ2AA), and dominance × dominance (σ2 DD), indicating that epistasis component of variance was present. Based on the genetic components of variance and mean performance of oil yield, only two tri-hybrids, C46.1 and C35.1, for the high oil yield and linalool (%), tri-hybrids C14.5 and C24.3 (47.13%), were found better. One tri-hybrid rich in Chavibetol, C26.1 (14.58%), is also selected for the extensive area cultivation in the North Indian plain. In addition, the three-way cross can combine desirable features from three genotypes into a single genotype. In conventional plant breeding, by a three-way cross design, the hybrids can be improved by crossing between an F1 (single cross) (A×B) as a female parent and a genotype (C) as the male parent. The essential oil of promising Ocimum tri-hybrids indicates aromatic compounds, such as methyl chavicol, linalool, β-ocimene, Chavibetol, and camphor content are present in adequate amounts. It is the first report using a triallel mating design in the basil. These tri-hybrids can be recommended for cultivation on a large scale.

COMBINING ABILITY ANALYSIS IN F1 AND F2 POPULATION FOR COTTON LEAF CURL VIRUS DISEASE AT MULTIPLE LOCATIONS

Genetic studies were conducted to examine the heritage of resistant to cotton leaf curl virus. Genetic components of variance revealed higher σ2GCA and Additive (σ2A) than σ2SCA and Dominance (σ2D), which indicated additive genes were more reliable for inheritance of resistance to CLCV. The ratio of variances σ2gca/σ2sca was higher than unity (one) and further proved from degree of dominance [σ2A/σ2D]0.5 which was greater than one and confirmed supremacy of additive genes at both locations and generations. The heritability narrow sense (h2) and broad sense (H2) was found higher which suggested role of additive genes, which are fixable. Therefore selection would be effective in early segregating generation according to the symptoms of cotton leaf curl virus. The GCA effects for CLCV showed that among the parents, Mac-7 found as good general combiner with highest significant negative GCA effects at both locations in F1 and F2 which considered as CLCV resistant parent. The SCA effects exhibited that hybrid, Mac-7 x USD16-3058, CIM-602 x Mac-7 and NIA-Noori x Mac-7 showed significant negative SCA effect in both generations and locations. It was noted that cross combinations involved good x poor and poor x good general combiner with significant SCA effect was due to complementary gene action which produce desirable transgressive segregants, these can be further studies through bi-parental mating of diallel selective mating or any other form of recurrent selection in early generation with single plant selection to exploited both additive an non-additive gene action.

Delovanje gena za prinos zrna i njegova povezanost sa komponentama prinosa u dijalelnom ukrštanju ozime pšenice

Magnitude and type of gene actions in a specific population are the main criteria for the parents' selection that will develop the best recombinants after hybridization. Information about the genetic control of complex traits is useful for the further development of efficient breeding programs. In order to identify action of genes for grain yield plant-1 and its correlation with main yield components, incomplete diallel crossing was applied. The field trial was conducted at the experimental field of the Agricultural Advisory Service in southeastern Europe, during season 2012-2013. Mean values of F1 generation showed that crosses Apache × Prima had the highest value of grain yield plant-1 and Jackson × Balkan had the lowest. Common type of inheritance for grain yield plant-1 was over dominance. The ANOVA revealed that this trait was controlled by additive and non-additive effects. The best general combiner for grain yield plant-1 was Apache, and two crosses (Dragana × Jackson; Balaton × Nevesinjka) showed significant SCA effects. Components of genetic variance showed that dominant was more important than additive component, and the total number of dominant genes were in excess over the number of recessive genes in all parents. Furthermore, moderately low value of narrow sense heritability (h2=31.96%) was observed for grain yield plant-1 . Parent Sana contained maximum dominant genes, whereas parent Jackson had maximum recessive genes. Grain yield plant-1 was significantly correlated with tillers numbers plant-1 at genotypic level (rg=0.494). The results from this study might be helpful for creating new wheat cultivars with highyielding potential.

The farming and husbandry ofColossoma macropomum: From Amazonian waters to sustainable production

AbstractWithin the rich diversity of South American freshwater fish,Colossoma macropomum(Characiformes: Serrasalmidae), known as tambaqui, cachama or blackfin pacu, can reach 30 kg, is a traditional product in regional fish markets and has drawn the attention of fish farmers since the 1930s. Considerable progress achieved in different fields of aquaculture science has contributed to the growth of tambaqui production. Tambaqui has proven suitable for both monoculture and polyculture systems, and for both extensive and intensive production systems aimed at achieving sustainable, higher productivity with minimal environmental impact. Studies of the reproductive anatomy and physiology of the species proved fundamental to development of techniques to boost commercial production, contributing to development of protocols for hormonally induced spawning and artificial propagation in the 1970s. Newly hatched larvae must be fed with live foods until they can be weaned to artificial feeds at about 100 mg weight. Despite its importance for aquaculture, only a few studies have reported components of quantitative genetic variance and parameters for weight at age, morphometric traits and disease resistance. Genomic tools currently available can be applied to detect variation relevant to performance and to accelerate the process of genetic improvement. While the species’ feeding habit allows the use of diets containing 75%–85% plant protein, much more work needs to be done to optimize aquafeeds. Refinement of tambaqui production methods has the potential to significantly boost South American aquaculture. We recommend research on diets, genetic improvement and system optimization to spur further productivity and achieve sustainable tambaqui culture.

How genetic and environmental variance in personality traits shift across the life span: Evidence from a cross-national twin study.

Decades of research have shown that about half of individual differences in personality traits is heritable. Recent studies have reported that heritability is not fixed, but instead decreases across the life span. However, findings are inconsistent and it is yet unclear whether these trends are because of a waning importance of heritable tendencies, attributable to cumulative experiential influences with age, or because of nonlinear patterns suggesting Gene × Environment interplay. We combined four twin samples (N = 7,026) from Croatia, Finland, Germany, and the United Kingdom, and we examined age trends in genetic and environmental variance in the six HEXACO personality traits: Honesty-Humility, Emotionality, Extraversion, Agreeableness, Conscientiousness, and Openness. The cross-national sample ranges in age from 14 to 90 years, allowing analyses of linear and nonlinear age differences in genetic and environmental components of trait variance, after controlling for gender and national differences. The amount of genetic variance in Extraversion, Agreeableness, and Openness followed a reversed U-shaped pattern across age, showed a declining trend for Honesty-Humility and Conscientiousness, and was stable for Emotionality. For most traits, findings provided evidence for an increasing relative importance of life experiences contributing to personality differences across the life span. The findings are discussed against the background of Gene × Environment transactions and interactions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Optimum breeding strategies using genomic and phenotypic selection for the simultaneous improvement of two traits

Key message A breeding strategy combining genomic with one-stage phenotypic selection maximizes annual selection gain for net merit. Choice of the selection index strongly affects the selection gain expected in individual traits.Selection indices using genomic information have been proposed in crop-specific scenarios. Routine use of genomic selection (GS) for simultaneous improvement of multiple traits requires information about the impact of the available economic and logistic resources and genetic properties (variances, trait correlations, and prediction accuracies) of the breeding population on the expected selection gain. We extended the R package “selectiongain” from single trait to index selection to optimize and compare breeding strategies for simultaneous improvement of two traits. We focused on the expected annual selection gain (ΔGa) for traits differing in their genetic correlation, economic weights, variance components, and prediction accuracies of GS. For all scenarios considered, breeding strategy GSrapid (one-stage GS followed by one-stage phenotypic selection) achieved higher ΔGa than classical two-stage phenotypic selection, regardless of the index chosen to combine the two traits and the prediction accuracy of GS. The Smith–Hazel or base index delivered higher ΔGa for net merit and individual traits compared to selection by independent culling levels, whereas the restricted index led to lower ΔGa in net merit and divergent results for selection gain of individual traits. The differences among the indices depended strongly on the correlation of traits, their variance components, and economic weights, underpinning the importance of choosing the selection indices according to the goal of the breeding program. We demonstrate our theoretical derivations and extensions of the R package “selectiongain” with an example from hybrid wheat by designing indices to simultaneously improve grain yield and grain protein content or sedimentation volume.

Estimation of epistasis and genetic components of variance for different traits in cucumber (Cucumis sativus)

To estimate epistasis and components of genetic variance a study was carried out during 2016 and 2017 at Experimental Research Farm of Department of Vegetable Science, Dr YSP UH & F Nauni, Solan, (HP) and data were recorded for different qualitative and quantitative traits using triple test cross (TTC) analysis of an inter-varietal cross LC-1-1 × K-75 of cucumber (Cucumis sativus L.). Three testers of cucumber named LC-1-1, K-75 and their F1 (LC-1-1 × K-75) were crossed to 15 inbred lines for detecting the additive, dominance and epistatic components of genetic variance. Good quantum of genetic variability has been generated through triple test cross progenies with respect to different traits studied as revealed by the significant analysis of variance. TTC analysis revealed that overall epistasis and j+l type component were found to be significant for majority of the traits except fruit breadth and total soluble solids. Further, experimental results showed that (i) type of epistasis were also significant for majority of the traits under study. The components of genetic variance were estimated using analysis of variance for sums and differences revealed the importance of both additive (D) as well as dominance (H) components of genetic variance in controlling various traits and showed partial dominance except over dominance for fruit breadth and severity of downy mildew. Therefore, kind of genetic variance revealed from triple test cross can be exploited by intermating selected individuals in early segregating generations with delayed selection in later generations, or recurrent selection followed by pedigree method to exploit both additive and non-additive components along with epistasis in cucumber.

Estimation of additive and non-additive genetic variances of average daily gain traits in Adani goats

• Dominance and epistasis effects are important for the average daily gain traits and could be added to evaluation models. • Adding the non-additive genetic effects to models led to increase the accuracy of estimated breeding values. • The adgbww3 and adgbww6 traits can be the basis of selection for the next generation. Considering the dominance and epistasis effects in the analysis can increase the accuracy of estimating breeding values. The objective of this study was to fit the best model for each average daily gain trait (average daily gain from birth to weaning (adgbwww), from birth to 3 months (adgbww3), from birth to 6 months (adgbww6), from weaning to 3 months (adgwww3), from 3 to 6 months (adgw3w6), from 6 to 9 months (adgw6w9), and from 9 to 12 months (adgw9w12)) and the estimation of the genetic parameters and variance components, especially non-additive genetic effects, in Adani goats. Analyses were carried out using the Bayesian method via the Gibbs sampler animal model by fitting 18 different models. With the best model, direct heritability estimates were 0.093, 0.250, 0.256, 0.084, 0.036, 0.048, and 0.151 for adgbwww, adgbww3, adgbww6, adgwww3, adgw3w6, adgw6w9 and adgw9w12 traits, respectively. Maternal genetic and maternal permanent environmental effects were significant only for adgbwww trait. Dominance and epistasis effects were significant almost for all traits and as a proportion of phenotypic variance was the range from 0.068 to 0.221 and 0.106 to 0.237, respectively. Adding dominance and epistasis effects to models reduced the error variance and the accuracy of estimating breeding values was increased. The accuracy of breeding values of these traits with the best models ranged from 0.456 to 0.674, 0.493 to 0.656, and 0.424 to 0.674 for all animals, 10 % of best males and 50 % of the best females, respectively. The result of the present study suggests that dominance and epistasis effect was important for average daily gain traits of Adani goats and should be included in evaluation models.

Genomic Prediction and the Practical Breeding of 12 Quantitative-Inherited Traits in Cucumber (Cucumis sativus L.).

Genomic prediction is an effective way for predicting complex traits, and it is becoming more essential in horticultural crop breeding. In this study, we applied genomic prediction in the breeding of cucumber plants. Eighty-one cucumber inbred lines were genotyped and 16,662 markers were identified to represent the genetic background of cucumber. Two populations, namely, diallel cross population and North Carolina II population, having 268 combinations in total were constructed from 81 inbred lines. Twelve cucumber commercial traits of these two populations in autumn 2018, spring 2019, and spring 2020 were collected for model training. General combining ability (GCA) models under five-fold cross-validation and cross-population validation were applied to model validation. Finally, the GCA performance of 81 inbred lines was estimated. Our results showed that the predictive ability for 12 traits ranged from 0.38 to 0.95 under the cross-validation strategy and ranged from −0.38 to 0.88 under the cross-population strategy. Besides, GCA models containing non-additive effects had significantly better performance than the pure additive GCA model for most of the investigated traits. Furthermore, there were a relatively higher proportion of additive-by-additive genetic variance components estimated by the full GCA model, especially for lower heritability traits, but the proportion of dominant genetic variance components was relatively small and stable. Our findings concluded that a genomic prediction protocol based on the GCA model theoretical framework can be applied to cucumber breeding, and it can also provide a reference for the single-cross breeding system of other crops.

A multivariate heterogeneous variance components model for multi-environment studies with locational genetic effects

In this paper, a multivariate heterogeneous variance components model was developed which allows for determination of location specific variance components in the analysis of multiple related traits. In addition to spatial heterogeneity, genetic similarities are also considered by assigning genetic variance components. The performance of the developed model was evaluated through an extensive simulation study and comparison of models was conducted by heritability estimations. The simulation study reveals that the developed method can control the locational heterogeneity well and the heritability estimations are close to desired proportions for the developed model. A real plant breeding data set was used for illustration.

Body-shape trajectories and their genetic variance component in Gilthead seabream (Sparus aurata L.)

The phenotype of juvenile fish is closely associated with the adult phenotype, thus consisting an important quality trait for reared fish stocks. In this study, we estimated the correlation between the juvenile and adult body-shape in Gilthead seabream, and examined the genetic basis of the ontogenetic trajectories. The body shape of 959 pit-tagged fish was periodically examined during the juvenile-to-adult period. Individual shape ontogenetic trajectories were studied in respect to the initial (juvenile) and final (adult) phenotypes, as well as to the rate that adult phenotype is attained (phenotypic integration rate). We found that the juvenile body-shape presented a rapid change up to 192.7 ± 1.9 mm standard length, followed by a phenotypically stable period (plateau). Depending on the shape component considered, body-shape correlations between juvenile and adult stages ranged from 0.22 to 0.76. Heritability estimates (h2) of the final phenotype ranged from 0.370 ± 0.077 to 0.511 ± 0.089, whereas h2 for the phenotypic integration rate was 0.173 ± 0.062. To our knowledge, this is the first study demonstrating that the variance of the ontogenetic trajectories has a substantial additive genetic component. Results are discussed in respect to their potential use in selective breeding programs of Gilthead seabream.

Triple full‐sibs: A method for estimating components of genetic variance and progeny selection in plants

AbstractQuantifying the genetic variability present in plant populations is crucial for the success of selection plans. The partitioning of genetic variance into its components allows inferences about the inheritance of quantitative traits and prediction of the gain from selection. The present study aimed to present an alternative method to estimate components of genetic variance with applications in recurrent selection. The mating scheme is based on biparental cyclic crossing involving three parents in each chain, here called the triple full‐sibs (TFS) family, each of which is composed of three biparental progenies in which individuals are full‐sibs within each progeny and half‐sibs among progenies. The progenies are evaluated in experimental trials, and the total effect of progenies is hierarchically partitioned into the effects of TFS families and progenies within families. From the components of variance, additive and dominance variance, as well as the associated errors, can be estimated. Simulated data are used to illustrate the method of analysis and parameter estimation. The method combines the advantages of North Carolina Design I regarding estimation of variance components with the practicality of conventional full‐sib selection. The TFS method allows different selection strategies according to the selection unit and provides expected genetic gain equal to or greater than unrelated full‐sib selection. There is no further advantage to using more than three parents in each chain‐cross.

On the Genetic and Environmental Relationship Between Suicide Attempt and Death by Suicide.

The authors examined the extent to which the genetic and environmental etiology of suicide attempt and suicide death is shared or unique. The authors used Swedish national registry data for a large cohort of twins, full siblings, and half siblings (N=1,314,990) born between 1960 and 1990 and followed through 2015. They conducted twin-family modeling of suicide attempt and suicide death to estimate heritability for each outcome, along with genetic and environmental correlations between them. They further assessed the relationship between suicide attempt by young people compared with adults. In bivariate models, suicide attempt and death were moderately heritable among both women (attempt: additive genetic variance component [A]=0.52, 95% CI=0.44, 0.56; death: A=0.45, 95% CI=0.39, 0.59) and men (attempt: A=0.41, 95% CI=0.38, 0.49; death: A=0.44, 95% CI=0.43, 0.44). The outcomes were substantially, but incompletely, genetically correlated (women: rA=0.67, 95% CI=0.55, 0.67; men: rA=0.74, 95% CI=0.63, 0.87). Environmental correlations were weaker (women: rE=0.36, 95% CI=0.29, 0.45; men: rE=0.21, 95% CI=0.19, 0.27). Heritability of suicide attempt was stronger among people ages 10-24 (A=0.55-0.62) than among those age 25 and older (A=0.36-0.38), and the genetic correlation between attempt during youth and during adulthood was stronger for women (rA=0.79, 95% CI=0.72, 0.79) than for men (rA=0.39, 95% CI=0.26, 0.47). The genetic and environmental etiologies of suicide attempt and death are partially overlapping, exhibit modest sex differences, and shift across the life course. These differences must be considered when developing prevention efforts and risk prediction algorithms. Where feasible, suicide attempt and death should be considered separately rather than collapsed, including in the context of gene identification efforts.

A triple test cross analysis to detect epistatic gene effects in cabbage (Brassica oleracea var. capitata L.): An updated methodology.

The cross-pollinated crop Brassica oleracea var. capitata L. shows good heterotic heterosis at high output; better standing of the plants; early maturity; larger and more homogeneous heads; consistency of head compactness; and disease-tolerance in F1 hybrids. There is very limited information documented on the epistasis of essential cabbage characters. We expand the research in this study to include an upgraded test to cross-design for enrolling and estimating epistasis and other genetic variance components controlling head yield and component traits in cabbage. The data was obtained from 45 families produced by crossing 15 lines with three testers; SC 2008–09, E-1-3-1&2, and their single cross F1, was subjected to triple test cross analysis. The current study results confirmed “j + 1” form of epistasis which is a major component for all traits. The plant spread, non-wrapper leaves, nethead/grossweight, polar/equatorial diameter, marketable head yield per plot, iron content and dry matter lugged both “j + 1” and 'i' type with the predominance of the 'i' type of interaction. Except for head shape index, equatorial diameter, head compactness was more noticeable when observed in dominance component. The degree of dominance is in the partial range, but both the head shape index/compactness and equatorial diameter showed over dominance. For maximum part, superiority was shown in both the directions. Appropriate breeding procedures are proposed to exploit the different forms of gene effects discovered for genetic improvement of head yield and quality traits.

Genetic estimation of grain yield and its attributes in three wheat (Triticum aestivum L.) crosses using six parameter model

Grain yield is a complex polygenic trait representing a multiplicative end product of contributing yield attributes governed by simple to complex gene interactions. Deciphering the genetics and inheritance of traits/genes influencing yield is a prerequisite to harness the yield potential in any crop species. The objective of the present investigation was to estimate genetic variance components and type of gene action controlling yield and its component traits using six populations (P1, P2, F1, F2, BC1 and BC2) of the three bread wheat crosses. Cross I (25th HRWSN 2105 × WH 1080), cross II (22ndSAWYT323 × RSP 561) and cross III (22ndSAWYT333 × WH 1080) involving elite stripe rust resistant wheat genetic stocks in combination with commercial check varieties were used for analysis. A combination of morpho-physiological, biochemical and disease influencing traits were evaluated, thus exploring the possibility of multi-trait integration in future. Results revealed that the estimated mean effects (m) were highly significant for all the traits in all crosses, indicating that selected traits were quantitatively inherited. The estimate of dominant gene effect was highly significant for plant height, number of tillers per plant in all the three crosses. Grain yield per plant was highly significant in the cross II while total protein content was highly significant in both crosses II and III. Glycine betaine content showed significant additive genes effect. Duplicate epistasis was the most significant for traits like plant height, total protein content and grain yield per plant. Dominance gene effect was more important than additive gene effects in the inheritance of grain yield and most other traits studied. The magnitude of additive X additive gene effects was high and positively significant whereas dominance × dominance was negatively significant for most of the traits studied in the three crosses. Additive × dominance gene effects was of minor significance, thus indicating that selection for grain yield and its components should be delayed to later generations of breeding.

Familial Risk and Heritability of Hematologic Malignancies in the Nordic Twin Study of Cancer.

Simple SummaryHematologic malignancies account for 8–9% of all incident cancers. Both genetic and environmental risk factors contribute to cancer development, but it is unclear if there is shared heritability between hematologic malignancies. This study aimed to investigate familial predisposition to hematologic malignancies using the largest twin study of cancer in the world. We compared individual risk in the general population and the risk of cancer in one twin before some age given that the other twin had (another) cancer before that age. Furthermore, by analyzing information about whether the twins were identical or fraternal, we could estimate the relative importance of genetic and environmental influences on the risk for developing hematologic cancers. This study confirmed previous findings of familial predisposition to hematologic malignancies and provides novel evidence that familial predisposition decreases with increasing age. The latter points to the importance of taking age into account in the surveillance of hematological cancers.We aimed to explore the genetic and environmental contributions to variation in the risk of hematologic malignancies and characterize familial dependence within and across hematologic malignancies. The study base included 316,397 individual twins from the Nordic Twin Study of Cancer with a median of 41 years of follow-up: 88,618 (28%) of the twins were monozygotic, and 3459 hematologic malignancies were reported. We estimated the cumulative incidence by age, familial risk, and genetic and environmental variance components of hematologic malignancies accounting for competing risk of death. The lifetime risk of any hematologic malignancy was 2.5% (95% CI 2.4–2.6%), as in the background population. This risk was elevated to 4.5% (95% CI 3.1–6.5%) conditional on hematologic malignancy in a dizygotic co-twin and was even greater at 7.6% (95% CI 4.8–11.8%) if a monozygotic co-twin had a hematologic malignancy. Heritability of the liability to develop any hematologic malignancy was 24% (95% CI 14–33%). This estimate decreased across age, from approximately 55% at age 40 to about 20–25% after age 55, when it seems to stabilize. In this largest ever studied twin cohort with the longest follow-up, we found evidence for familial risk of hematologic malignancies. The discovery of decreasing familial predisposition with increasing age underscores the importance of cancer surveillance in families with hematological malignancies.