Additive-dominance Model Research Articles

Nature of gene action for yield and its components in mungbean (Vigna radiata)

The assessment of gene effect for some yield characters and detection of epistasis in mungbean [Vigna radiata (L.) Wilczek] was studied in four crosses involving five parents through generation mean analysis during kharif 2012 at Banaras Hindu University (BHU), Varanasi, UP. Six populations, viz. P1, P2, F1, F2, B1 and B2 of four crosses involving five parents were evaluated. The nature and magnitude of gene effects for yield and its components in mungbean was studied using six parameter model of generation mean analysis. The presence of epistasis was detected by joint scaling test and inadequacy of additive-dominance model was established except seeds/pod. Additive (d), dominance (h) gene effects along with one or more type of non-allelic interactions (i, j, l) contributed significantlytowards the inheritance of all the quantitative characters in majority of the crosses. Duplicate type of epistasis andpredominant dominance effects was also prevalent in most of the cases except in days to maturity in HUM 8 x ML 713 cross. Thus, postponement of selection in later generations may be suggested to obtain transgressive segregants for improvement of mungbean populations.

Why SR52 is such a great maize hybrid? I. Heterosis and generation mean analysis

SR52 is the first single cross maize hybrid to be commercialised in the world and forms the basis of maize breeding in Zimbabwe and Eastern and Southern Africa region. Although SR52 is such an exceptional hybrid, the genetic basis of its outstanding yield and heterosis has never been explained. Therefore genetic components of yield and associated traits in SR52 were studied using a generation mean analysis. Parents (P1 and P2), F1 and segregating F2 and backcross generations (BCP1 and BCP2) were evaluated. The experiment was laid out as a randomised complete block design with two replications across two sites in South Africa, during the 2012/2013 season. The study confirms high levels of heterosis exceeding 300 % for grain yield potential and revealed a significant lack of fit of the additive–dominance model for yield and most secondary traits. Consequently, the role of epistasis was investigated by partitioning it into additive × additive , additive × dominance and dominance × dominance gene effects. The full model confirmed presence of epistasis of highly significant (P ≤ 0.01) additive × additive nature for grain yield though negligible in magnitude (<10 %). Both dominance and additive gene effects were highly significant for yield and associated traits. However, dominance gene action contributed over 80 % to grain yield potential. Additive and additive × additive gene effects played a significant but minor role for grain yield potential (less than 20 %). We therefore concluded that dominance gene action is the basis for exceptional heterosis displayed by SR52.

Gene action of elite rice lines for yield and lodging resistance related traits

Knowledge of gene action on yield and lodging related traits would help in framing suitable breeding strategy for the development of lodging resistance genotypes with high yield. Present investigation aimed at studying gene action among the eight yield and six lodging resistance related traits in two crosses MTU 7029/II 110-9-1-1-1-1 and MTU 7029/MTU 1121 using six-parameter model of generation mean analysis. The results revealed significance of scaling test for all the traits indicating inadequacy of additive dominance model for explanation of inheritance of 14 traits in both the crosses except for number of ear bearing tillers/plant, test weight and grain yield/plant in case of MTU 7029/MTU 1121. In both the crosses, characters number of filled grains/panicle, spikelet fertility, test weight, culm diameter and panicle length expressed complementary epistasis besides dominance x dominance interaction. Hence, biparental mating followed in early generations and selection could be practised in advanced generations to fix favourable alleles. Rest of the traits such as number of ear bearing tillers/plant, grain yield/plant, culm thickness, culm strength, basal internodal length and per cent of lodging exhibited duplicate type of epistasis. Characters with non-additive gene action coupled with duplicate type of gene interaction can be improved by recurrent selection or diallel selective mating.

Diallel cross analysis of plesiomorphic traits in Triticum aestivum L. genotypes

We conducted a 5 x 5 complete diallel cross experiment in bread wheat (Triticum aestivum) with the genotypes 6309, Chkwal-50, Dhrabi, Bhkhar-02, and FS-08. Our objective was to evaluate the type of gene action and the general and specific combining abilities required for various morphological traits in wheat. The results of analysis of variance revealed highly significant differences among genotypes for all the investigated traits. The results of joint regression analysis showed that the data for all the investigated traits fitted a simple additive dominance model. Graphical representation of variance and covariance suggested that most of the investigated traits were controlled by overdominance gene action. However, the peduncle length and plant height were controlled by additive gene action. Variety 6309 carried the highest number of dominant genes for the number of spikelets per spike, number of tillers per plant, plant height, number of fertile tillers per plant, and grain yield per plant. Chakwal-50 carried the highest number of recessive genes for grain yield per plant, number of tillers per plant, number of grains per spike, number of fertile tillers per plant, and plant height. Chakwal-50 and 6309 were the best general combiners for number of spikelets per spike, number of grains per spike, grain yield per plant, 1000-grain weight, number of fertile tillers per plant, and number of tillers per plant. On other hand, 6309 performed well in specific crosses with Chakwal-50, FS-08, and Bhakhar-02 for spike length and number of tillers per plant.

Generation Mean Analysis of Fibre Quality Characters in Upland Cotton (Gossypium hirsutum L.)

Generation mean analysis was carried out to estimate the nature and magnitude of gene effects for fibre quality traits in three crosses of upland cotton (Gossypium hirsutum L). The presence of epistasis was reflected by scaling tests and inadequacy of simple additive-dominance model for most of the characters studied. The results obtained revealed that the nature and magnitude of gene effects differed in different crosses and showed importance of additive as well as non-additive gene effects in the inheritance of different characters. In view of the parallel role of additive and non-additive gene effects in the inheritance of different characters, selection in the segregating generations should be delayed when dominance gene effects would have diminished or sophisticated selection procedures as recurrent selection and population improvement programmes may be followed. However, additive gene effects may be fixed with respect to some specific traits such as micronair value and fibre strength.

Genetic analysis of yield and yield related attributes in Brassica napus

Diallel analysis in Rapeseed (Brassica napus L.) was carried out during 2011-2012 at The University of Agriculture, Peshawar to estimate the pattern of inheritance and heritability for important traits. During 2010-2011 four contrasting genotypes of Brassica napus. viz. G2, G4, G6 and G9 were crossed in a diallel manner and in the following season (2011-2012) all the F1 hybrids along with parents were evaluated under field condition in a randomized complete block design. Highly significant (P ≤ 0.01) differences were observed for plant height, primary branches plant -1 , seeds pod -1 , pods plant -1 , weight of 1000 seed, seed weight plant -1 . Additive-dominance model was fully adequate for plant height, primary branches plant -1 , pods plant -1 , seeds pod -1 , whereas for the rest of the traits it was partially adequate. Diallel analysis showed significant additive (a) and dominance (b) variances for all parameters. Genetic parameters estimation showed significant and higher magnitude of dominance component for all the studied traits. Graphical analysis showed overdominance for all of the parameters. The value of average degree of dominance for plant height (1.858), primary branches plant -1 (4.355), pods plant -1 (3.704), seeds pod -1 (2.417), 1000 seed weight (3.995) and seed weight plant -1 (1.852) also indicated the presence of overdominance gene action controlling these yield attributes, as it was greater than one. Low narrow (0.16-0.31) and broad (0.81-0.96) sense heritabilities were estimated for all the studied parameters, suggesting the low value of additive gene action and genetic potential for the improvement of such traits through selection in later generations.

Gene action for quantitative traits through Generation means analysis in sesame (Sesamum indicum)

Understanding the nature of gene action in the breeding material is helpful for breeders in formulating breeder strategy. In order to understand the type of gene action operating in the breeding materials six generation means (P1, P2, F1, F2, BC1 and BC2) from five crosses were used to estimate the genetic effects of yield and some quantitative traits in sesame (Sesamum indicum L.) The analysis showed the presence of additive, dominance and epistatic gene interactions. The additive dominance model was adequate for capsule length in the KMR 108 × JCS 507 and KKS 98049 × IS 562 B crosses. An epistatic digenic model was assumed for the remaining crosses. Duplicate- type epistasis played a greater role than complementary epistasis. The study deciphered that simple additive dominance model exhibited lack of good fit for all the traits in five crosses studied, indicating the role of non-allelic interactions. Dominance and epistatic interactions played a major role in the inheritance of yield and yield contributing characters in sesame. It can be categorically stated that reciprocal recurrent selection or diallel selective mating system are the need of the hour to modify the genetic architecture of sesame for attaining higher yields with desirable oil content.

Differential inheritance of pepper (Capsicum annuum) fruit pigments results in black to violet fruit colour

AbstractColour is a critical determinant of fruit and vegetable quality. We characterized the inheritance of black and violet immature pepper fruit colour and chlorophyll, carotenoid and anthocyanin pigments responsible for fruit colour. Segregation for black vs. violet fruit colour deviated from expectations for simple inheritance. The primary determinant of fruit colour was the concentration of chlorophyll and carotenoid pigments relative to anthocyanin concentration. Whereas anthocyanin concentration was 34% greater in violet fruit, chlorophyll and carotenoid concentrations were 20‐fold and fourfold greater, respectively, in black fruit relative to concentrations found in violet fruit. Measurement of Commission Internationale d'Eclairage (CIE) colour space scores revealed larger a* values and smaller b* values for violet fruit relative to corresponding parameters for black fruit. An additive–dominance model was sufficient to explain the variation in individual fruit pigments as well as the CIE parameter a*. Addition of additive × additive effects to the additive–dominance model resulted in the best‐fit model m[d][h][i] for L* and b* colour space parameters. For all pigment classes, significant additive effects contributed to the genetic variance for fruit colour.

English

Inheritance, general combining ability and specific combining ability were studied using four parents: FH-901, NIAB-Karishma, CIM-496 and MS-84 for different plant traits in Upland cotton (Gossypium hirsutum L.). Mean values of all genotypes were significantly different from each other for all the traits studied. Epistasis was not found to be involved in any of the traits. The inheritance of all the traits was controlled by additive type of gene action with partial dominance except seed cotton yield that was controlled by over-dominance type of gene action. It was further noticed that the parent MS-84 was best general combiner for the traits like plant height, number of monopodial branches and number of bolls. The cross MS-84 &times; NIAB-Karishma showed greater specific combining ability for plant height, number of monopodial branches and number of sympodial branches. Key words: Inheritance, additive-dominance model, over-dominance, combining ability.

English

The genetic effect of grain yield plant-1 and its correlation with yield components were investigated in a 7 &times; 7 incomplete diallel cross of seven wheat parents during the crop season of 2009 to 2010. Mean square of general combining ability (GCA) effect was 2.90 for grain yield plant-1, which was highly significant (P&lt;0.01), indicating that additive effect played important role in the inheritance of the trait. Specific combining ability (SCA) effect was highly significant (P&lt;0.01) for grain yield plant-1 (0.68), suggesting that the trait was also controlled by non-additive effect. The estimates of GCA showed that the best combiner for grain yield plant-1 was Ningmai 9. The additive-dominance model was partially adequate for grain yield plant-1 and it was controlled by the over dominance type of gene action. Ningmai 8 possessed maximum dominant genes, whereas Yangmai 9 had maximum recessive genes. Grain yield plant-1 might be controlled by two groups of genes and exhibited moderately high value of narrow sense heritability (h2N=69.51%). The statistical analysis revealed that grain yield plant-1 was positively and significantly correlated with tillers plant-1 (rp=0.584, rg=0.595) and number of grains spike-1 (rp=0.528, rg=0.507) at phenotypic and genotypic levels. The information obtained from the study might be helpful for wheat breeders trying to develop new varieties with high-yielding potential. &nbsp; Key words: Combining ability, diallel cross, grain yield, inheritance, Triticum aestivum L.

Generation mean analysis of gluten strength in bread wheat (Triticum aestivum): An effective utilization of micro-sedimentation test in early generation progenies

Better bread-making quality is one of the most important targets in the quality improvement programmes of wheat (Triticum aestivum L.). Gluten strength is a major indicator of bread making quality and is measured by various methods such as the SDS-sedimentation test. However, the nature of gene action for gluten strength has not been studied so far. In the present study, generation mean analysis was undertaken to estimate the nature and magnitude of gene effects for gluten strength in two sets of crosses involving contrasting parents using a less known microsedimentation test. Scaling test indicated the involvement of epistasis on the expression of the trait and inadequacy of additive-dominance model. Therefore, both six and five parameter models were used to understand the nature and direction of gene action further. Similar types of gene-action for gluten strength were recorded, albeit with some differences in the direction and magnitude of the effects, in the two sets of crosses. Among the different epistatic components, dominance × dominance effect had the maximum contribution and was acting in the negative direction in both the crosses. Analysis of both the cross combinations using Castle-Wright' equation for 'number of effective genes/blocks' revealed that at least one major gene block besides several minor genes could be involved for the micro-sedimentation volume.

Inheritance of Graın Yield and Its Correlation with Yield Components In Bread Wheat (Triticum aestivum L.)

The inheritance of grain yield plant-1 and its correlation with other yield components were investigated in a diallel cross of seven wheat parents during the crop season of 2011-2012. Mean square of GCA effect was 2.90 for grain yield plant-1, which was highly significant (P<0.01), indicating that additive effect played important role in the inheritance of the trait. SCA effect was also highly significant (P<0.01) for grain yield plant-1 (0.68), suggesting that the trait was also controlled by non-additive effect. The estimates of GCA showed that the best combiner for grain yield plant-1 was Ningmai 9. The additive-dominance model was partially adequate for grain yield plant-1 and it was controlled by the over dominance type of gene action. Ningmai 8 possessed maximum dominant genes, whereas Yangmai 9 had maximum recessive genes. Grain yield plant-1 might be controlled by two groups of genes and exhibited moderately high value of narrow sense heritability (h2N=69.51%). The statistical analysis revealed that grain yield plant-1 was positively and significantly correlated with tillers plant-1 (rp=0.584, rg=0.595) and number of grains spike-1 (rp=0.528, rg=0.507) at phenotypic and genotypic levels

Genetic Analysis of Salt Tolerance in Safflower (Carthamus tinctorius L.)

Aim: The mode of agronomic traits inheritance was investigated in safflower (Carthamus tinctorius L.) in salt stress as a new report in this study. Place and Duration of Study: This experiment was carried out in Agricultural Research Farm of Shahid Bahonar University at Ekhtiarabad, Kerman, Iran, in 2011 -2012. Methodology: Five generation including P1, P2, F1, F2 and F3 that derived from the cross of IL.111 (salt sensitive) × Mex.22-191 (salt tolerance) were used in a randomized complete block design with two replications. Results: According to generation mean analysis, different types of gene action was obtained for studied traits. The additive model [d] was fitted for branches/plant, seeds/capsule and seed yield/plant. The simple additive dominance model [d, h] was fitted for number of seeds/plant. Also, dominance× dominance epistasis [l] was added to fit the model as [d, h, l] for capsule/plant and dry weight/plant. The genetic model of [d,h,i] and [d, i] was fitted for genetic control of plant height and seed weight, respectively. Conclusion: Obtained results could be suitable for designing of breeding strategies to Research Article Annual Research & Review in Biology, 4(1): 337-346, 2014 338 improve seed yield of safflower in salt stress.

The mode of inheritance and gene effects for spike length in different wheat genotypes

In this work were selected five wheat varieties (Pobeda, Renesansa, Sara, Partizanka and Pesma) in order to analyze the gene effects and the mode of inheritance of spike length. The above mentioned varieties were diallel crossed and F1, F2, and Fbc1 was produced. The gene effects were estimated using additive-dominance model which was adequate for two crossing combination Pobeda/Renesansa and Renesansa/Sara. In most crosses the value of dominant gene effect was more significant than additive. The inheritance of the spike length was influenced by additive x additive and dominance x dominance type of non-allelic interactions. In the most number of cases, inheritance of spike length was expressed domination.

Identification of Transgressive Segregants for Yield and Its Components in Basil (Ocimum basilicumL.)

The objective of this study was to estimate gene effects and identification of transgressive segregants for five quantitative traits of seven crosses of Ocimum basilicum L. viz. EC388788 × IC333322, EC387893 × IC326711, EC388896 × IC369247, EC388887 × IC386833, EC387837 × EC338785, IC369247 × IC370846 and IC344681 × IC326735 by generation mean analysis. In cases both type of epistasis (complementary and duplicate) model was sufficient to explain variation in generation means. Generation mean analysis with three parameter model with χ2 test indicated that additive-dominance model was inadequate for all the traits like number of inflorescence, length of inflorescence, fresh herb yield, dry herb yield and oil content in all the crosses used of six parameter models to estimate the gene effects. The observed frequencies of transgressive segregants for trait oil content (4.942), fresh herb yield (11.824), dry herb yield (13.97) and length of inflorescence (5.820). A comparison of generation mean analysis for observed and predicted frequencies of transgressive segregants indicated that the potential crosses for transgressive segregants were those that had additive and dominance gene effects. The adequacies of certain models of inheritance as well as the importance and significance of gene effects and identifications of transgressive segregants for analyzed traits were dependent upon the particular crossing combination and experimental site. The present study indicated that early generation selection is effective and should be practiced for future breeding programme.

Mode of gene action, heterosis and inbreeding depression for yield and its components in tomato (Solanum lycopersicum L.)

The objectives of this study were to determine heterosis and the type of gene action controlling some economical traits of tomato. Six populations of the cross CastleRock×CLN 2498E (P1, P2, F1, F2, BC1 and BC2) were used to study the genetic parameters of tomato traits. Means of the six populations were widely differed for most of the studied traits. One or more of the three scaling tests (A, B and C) were significant for some studied traits indicating that additive dominance model was inadequate to know the role of the type of gene action in the inheritance of these traits. Additive gene effects were found to be important in the inheritance of average fruit weight. Dominance and dominance×dominance gene effects were important in the inheritance of plant height, number of branches per plant fruit firmness and early yield. Heterosis relative to better parent was present for number of branches per plant, early yield, total yield and fruit firmness. The heritability estimates in broad sense were high for early yield, total yield, average fruit weight, fruit firmness and TSS content. However, heritability estimates in narrow sense were high for early yield and average fruit weight and moderate for TSS content. The estimated potence ratio (P) was larger than one for all studied traits except for average fruit weight and TSS content.

Influence of knee alignment on gait in patients with knee osteoarthitis

The objectives of this study were to determine heterosis and the type of gene action controlling some economical traits of tomato. Six populations of the cross CastleRock × CLN 2498E (P1, P2, F1, F2, BC1 and BC2) were used to study the genetic parameters of tomato traits. Means of the six populations were widely differed for most of the studied traits. One or more of the three scaling tests (A, B and C) were significant for some studied traits indicating that additive dominance model was inadequate to know the role of the type of gene action in the inheritance of these traits. Additive gene effects were found to be important in the inheritance of average fruit weight. Dominance and dominance × dominance gene effects were important in the inheritance of plant height, number of branches per plant fruit firmness and early yield. Heterosis relative to better parent was present for number of branches per plant, early yield, total yield and fruit firmness. The heritability estimates in broad sense were high for early yield, total yield, average fruit weight, fruit firmness and TSS content. However, heritability estimates in narrow sense were high for early yield and average fruit weight and moderate for TSS content. The estimated potence ratio (P) was larger than one for all studied traits except for average fruit weight and TSS content.

Inheritance of Resistance to Powdery Mildew Race 2 in Citrullus lanatus var. lanatus

Information on the mode of inheritance of powdery mildew resistance in watermelon is important for designing a breeding strategy for the development of new cultivars. Resistance in the watermelon accession PI 270545 was investigated by generation means analysis by crossing it with susceptible PI 267677. The analyses showed involvement of two genes, a recessive resistance gene, pmr-1, and a dominant gene for moderate resistance, Pmr-2. Resistance to powdery mildew in the leaf had a large dominance effect and a heritability of 71%. The additive-dominance model was inadequate in explaining variation in leaf resistance as revealed by the joint scaling test. However, nonallelic interactions could not be detected by the nonweighted six-parameter scaling test. For stem resistance, the additive-dominance model was adequate, and inheritance was controlled mainly by additive effects. A high narrow-sense heritability of 79% suggested that selection for stem resistance in early generations would be effective.

TES HETEROSIS AND GENETIC PARAMETERS AFFECTING INHERITANCE in IMPORTANT TRAITS OF TOMATOES (Lycopersicon esculentum, Mill)

Tomatoes is one of the most important vegetable crop not only in Egypt, but also all over the world. Therefore, there are many different continues effort to produce superior hybrids and varieties. In this respect, the present investigation was directed to exploit the amounts of heterosis that could be obtained from the hybrids and determine the nature of gene action associated with it using Mather and Jinks (1982) scaling test. For this purpose, four varieties were used. These varieties were: Edkawy (P1), Super streen B (P2), Peto 86 (P3) and Flourdade (P4). Three hybrids were obtain during 2009 growing season by crossing Edkawy with each of the other three varieties to produce three different hybrids. In the growing season of 2010, each hybrid was used to generate six populations which included(P1, P2,F1,F2, BC1 and BC2). Amounts of heterosis from mid – parent were 100.3 and 62.3% for the hybrid (P1 X P2) indicating that it had the heaviest fruit weight per plant and No. of fruits/plant. The hybrid (P1 X P4) gave (16%), for shape index. The hybrid (P1 X P3)gave (43.2%), for hardness in kg. For chemical traits, the hybrid (P1 X P4) gave 17.09 for total soluble soileds .The best hybrid for lycopene and ascorbic acid were the hybrid (P1 X P2) which gave 129.2 and 15.7% , respectively. Proportion amounts of heterosis from better -parent were 64.4 and 38.4 for the hybrid (P1 X P2) indicating that it had the heaviest fruit weight per plant and No. of fruits/plant.The hybrid (P1 X P4)gave 25%, for hardness in kg. For chemical traits, the hybrid (P1 X P4) gave 14.0 %for total soluble soiled .The best hybrid for lycopene and ascorbic acid was the hybrid (P1 X P2) which gave 75.6 and -19.0% , respectively. In the same time , all the F2 generations showed inbreeding depression. The six population were setup in scaling test analyses to determine the nature of gene action and to test the adequacy of additive dominance model.

THE NATURE OF GENE ACTION AND THE PERFORMANCES OF HYBRIDS WITH RESPECT TO EARLINESS AND YIELD TRAITS UNDER NORMAL AND LATE SOWING DATES IN WHEAT (Triticum aestivum , L.).

This investigation was made to evaluate three bread wheat hybrids and their six populations generated from each of them under normal and late sowing dates. The three hybrids were obtained where hybrid 1 was a result of crossing (Late × Late) cultivars; hybrid 2 was a result of crossing (Early × Early) cultivars and hybrid 3 was a result of crossing (Late × Early) ones. The early parental in breed lines included: Line1, Line2 and Line3 while, thelate parental onesincluded: Misr2 and Gemmeiza9. The two sowing dates were: normal sowing on 29 November 2011 and the late sowing on 29 December 2011. Therefore, the total genetic materials were obtained from the three hybrids included 18 genotypes which were evaluated at Sakha Agricultural Research Station Farm, Wheat Section, Egypt. Earliness traits showed that late sowing date required fewer days than normal sowing date for days to heading; days to maturity and grain filling period. This trend was present for all populations of the three hybrids. It appeared that late sowing shorten the life span of plants. Yield component characters which included: plant height; 100- kernel weight and grain yield/ plant showed the advantage of hybrid 1 for plant height and grain yield/plant than the other two hybrids. These two characters showed a modest amounts of heterosis for the three hybrids. Nature of gene action which estimated from the six populations and evaluated using the scaling test analysis proposed by Mather and Jinks (1971). The results indicated the importance of additive genetic variance than dominance genetic variance one for most studied traits. These results were also supported by the results obtained from the scaling test analysis as the quantities A,B and C indicated the adequacy of the additive dominance model.