Genetic Analysis of Yield and its Components in Wheat (Triticum aestivum L.) using Generation Mean Analysis

In this study, the six generational clans (P1, P2, F1, F2, B1, and B2) were used for two crosses of bread wheat. (Triticum aestivum. L), (the first cross was between the two cultivars (Milan * Abu Ghraib 3) and the second cross between (Milan * Sham 6). The six generations of the two crosses were cultivated according to the randomized complete block design in three replications for each of them. The averages of the generations were analyzed for the studied quantitative traits. For the six generations in the two crosses, the arithmetic averages and their standard errors showed that the values of the generations differed significantly from zero and in both crosses. F2 clans outperformed P1 in their performance and for some traits, and this indicates more frequency of the alleles responsible for this trait in the second generation clan and thus the expression of this trait. Through superior dominance as well as ultra-border genetic isolations, as well as the superiority of BC2 over F2 clans, which indicates more frequency of the alleles responsible for this trait in the second generation clan and for some traits. This means the dominance of the dominant variance that controls the inheritance of traits, and heritability in the narrow sense was low due to the low additional genetic variance.was significant in all traits except for the number of grains per spike and yield efficiency in the first cross, while the values of [d] were significant and positive for leaf area and protein content, which makes early selection beneficial for these traits, and were significant and negative for the traits of number of grains per spike and grain yield, and the dominance effects were [h] Positive and significant values for the characteristics of plant height, total number of tillers, number of spikes per plant, number of grains per spike, biological yield, grain yield, weight of 1000 grains, protein content and gluten content, while significant did not appear in the rest of the studied traits, in the first cross, and in the characteristics of plant height and total number of tillers The number of grains per spike, grain yield, harvest index, weight of 1000 grains, yield efficiency, protein content and gluten content, the second cross, and the superior effects (i) were the first contributors to the inheritance of these traits, followed by the part of the superior genetic action dominant x dominant (l) and then the superior genetic action additional × dominant (j) followed by the dominant genetic act and then the additive genetic action were significant in most of the traits studied in both crosses.


Introduction
Wheat is one of the most important crops compared to other grain crops in Iraq in terms of area and production.The total production of wheat in Iraq reached (2.5) million tons, with an area of (6.33 ) million dunums, according to the latest statistics [1].The wheat crop is the main food for the world's population, being a source of food equivalent to 52 % of it, and studies in recent years have shown that in 5252 the world's population needs To one billion tons, by 5 % , due to an increase in the population of wheat if compared to the current production of 747 million tons, and the constant increase in the population's annual need [2].The best methods for improving quantitative traits, to estimate the average degree of dominance of multiple genes by alleles for one gene, assuming that there is no superiority between these genes, and that knowledge of heritability has an important role in predicting the results of selection.A number of geneticists have developed several methods for estimating heritability in both the broad and narrow senses, and there are several genetic models for estimating genetic parameters from the arithmetic averages of generations.[3][4][5][6], which were able to identify the genetic structure of plants of the six generations.It relied on estimates of the three or six genetic features, environmental factors present during the growing season, and the method of estimating them.Therefore, this speed of obtaining complete information about the various analyzes is very important for genetic systems that provide information on tracking isolated generations, which leads to the possibility of reaching the goals of the breeding program with a quick result [7].The analysis of generational averages contributes to estimating the superior effect, which was also shown by [8], which can identify the genetic structure of plants of the six generations, relied on the estimates of the three or six genetic parameters and the environmental factors during the growing season and the method of their estimation.These results in almost most of the traits [9], as they are consistent with the findings of [10,11], found a superiority of the average of the first generation clans in these traits compared to the two clans of the second generation and the two retrograde generations.And the superior effects of the type (dominance*dominance) (I) occupied the greatest importance in the inheritance of most of the studied quantitative traits and the presence of the diploid pattern, which is an undesirable inheritance pattern, and therefore selection is made in the later generations.Knowledge of the components of genetic variation and the environment can be used to determine the best methods for improving quantitative traits to estimate the average degree of dominance of multiple genes by two alleles for one gene, assuming that there is no superiority among those genes.

Materials and Methods
The six generation populations (P1, P2, F1, F2, B1, and B2) were used in this study, and interbreeding took place between them to produce the two retrograde generations B1 and B2, and self-pollination of the first generation populations to produce the second generation populations.Between (Milan * Abu Ghraib 3).The field located in Kirkuk Governorate (Hawija district) was prepared based on sprinkler irrigation.Dab fertilizer was added at a rate of (320) kg / ha -1 (48% P2O5 and 18% N) and urea fertilizer was added at a rate of ( 200 (kg / ha) 1-Half of it was added at the beginning of the branching and the other half at the beginning of the lining stage.Planting took place in the last week of November 2018 using the design block complete randomized (with three replicates for both crosses separately: each replicate contained).One replicate included 16 experimental units in which the six populations were randomly planted, as P1, P2, and F1 included two experimental units, F2 included four experimental units, and BC1 and BC2 included three experimental units each.Clan Each experimental unit included a line of 1.2 m length containing 12 plants, the distance between one plant and another was 10 cm, and between one line and another was 30 cm.For all the populations of the six crosses used, the distance between one repeater and the last was 1 m.Genetic generations lines were planted randomly, and guard lines from other varieties were planted at the beginning, end and sides of the experiment.Other field operations were carried out according to the recommendations [1], the plants according to the recommendations, then after maturity, measurements were made on The studied traits were estimated on the basis of the individual plant and the number of plants varies according to each of these generations and as follows : P1 and P2 twenty plants each (two lines) ,F1 twenty plants (two lines in each repeat),F2 Forty plants (four lines in each repeat) ,BC1 and BC2 1259 (2023) 012120 IOP Publishing doi:10.1088/1755-1315/1259/1/0121203 Thirty plants planted on three lines each, and the quantitative characteristics were studied: the number of days for heading at 50%, plant height (cm), number of spikelets, leaf area (m 2 ), number of total tillering, number of spikes (plant), number of grains per spike, and biological yield g. Plant -1 ), cereal yield (gm-plant -1 ), yield index, weight of 1000 grains (gm), yield efficiency of gm -2 , protein content (%), and the gluten content (%) All six population averages were applied for statistical analysis by generational analysis method from [5], using both models with three genetic parameters model Parameter -Three and Six models parameter, to study the third and six genetic parameters and segment the apparent variation into its genetic and environmental components and calculate the additional variation, dominance, superiority, the average degree of dominance and heritability in the broad and narrow senses, the expected genetic improvement from selection in the second generation, the strength of the hybrid and inbreeding, The six genetic parameters [j] and [l] are estimated when the equations are derived from the components of the generational averages between Mather and [4], and the test The common measure presented by [7] Calculation equations values and variance which he detailed in (Al-Zubaidi and [12].The standard deviation of these six genetic parameters from zero was tested by relying on the standard deviation of these parameters.The phenotypic variance was estimated for the studied traits, which were divided into environmental variance (VE) and genetic variance (VG) and divided into additive genetic variance (VD) and dominance genetic variance (VH) on the assumption that there was no environmental overlap, as well as the value of the additional combined dominance variance (VE) and average degree Dominance (ā) which is between [5] and heritability in the broad sense is denoted by (h² s.b) and narrow denoted by (h² s.n) and the expected genetic improvement as a percentage of [13] and the vigor of the hybrid and inbreeding) [12].

Results and Discussion
It is noted from Table (1) that there is a difference in the values of the arithmetic mean for the six generations for each cross and for all the studied qualities As the values of the generations differed significantly from zero and for all crosses.It is noted in the cross (Milan × Abu Ghraib 3) that the averages of the second generation F2 gave the highest value for the characteristic of the number of days until flowering 50% and the lowest value for the first father P1, and this indicates more frequency of the alleles responsible for this trait in the second generation population and thus the expression of this trait Through super-dominance as well as ultra-limited genetic isolation, the plant height trait gave the highest average value for the second retrograde generation BC2 and the lowest value for the second generation F2.F1 and the lowest value for the second father is P2.While the leaf area gave the highest value for the second generation, F2, and the lowest value for the second father, P2.In the characteristic of the number of prunings, the average value was highest for the first father, P1, and the lowest value for the second generation, F2, and the number of spikes per plant was the highest value for the first generation, F1, and the lowest value for the first father, P1.The value of the average of the first generation is F1 and the lowest value of the average of the first father is P1 and for the biological yield trait the highest value was for F1 and the lowest value for P1, and in the grain yield trait the highest value was for F1 and the lowest value for P2 and in the trait for harvest index the highest value was for P1 and the lowest value for F1, and for the trait The weight of 1000 grains gave the highest value for F1 and the lowest value for P2, and for yield efficiency the highest value was for P1 and the lowest value for BC2.In the protein content characteristic, the highest value was for F1 and the lowest value for F2, and for the gluten content characteristic, the highest value was for F1 and the lowest value for P1.While in the cross (Milan x Sham 6) the highest values of F2 and the lowest values of P2 were for the characteristic of the number of days until the flowering of 50% of the plants, and this is evidence of more frequency of the alleles responsible for this trait in the second generation population and thus the expression of this trait through superdominance As well as the genetic isolates that are hyperbolic, and for the plant height trait, the highest value was for P1 and the lowest value for F2, which indicates the importance of this strain in the formation of the hybrid, as this trait is subject to the breeder's desire and need for tall or relatively short varieties.The number of spikelets was the highest for F2 and the lowest for P2.As for the characteristic of leaf area, the highest values were for F1 and the lowest values for P2, and this reflects the phenomenon of the strength of the hybrid enjoyed by the hybrid compared to its parents and the isolated generations of this trait.As for the number of erasures, the highest values were for P1 and the lowest for F2, while the highest values were for P1 and the lowest for BC2.For both the number of spikes and the number of grains per spike, the highest values were for F1 and the lowest values for P1.For the characteristic of biological yield, the highest values were for F1 and the lowest for P2.As for the grain yield, the highest values were for F1 and the lowest for P2.In the trait of harvest index, the highest value was for P1 and the lowest value for F2, and for the weight of 1000 grains, the highest value was for F1 and the lowest value for P2.While the highest value of the yield efficiency trait was for P1 and the lowest value for F1, and in the protein content trait the highest values were for F1 and the lowest value for F2, and for the gluten content trait the highest value for the trait was for F1 and the lowest value for P1.  2) shows these two tests for the inheritance of the studied traits, and it is noted in the cross (Milan × Abu Ghraib 3) to a significant chi-square value for all studied traits at the level of probability (1%) except for the characteristic of the number of days until flowering 50%, which was significant at the level of probability (5%) The chi-square value did not reach the significant limits in the characteristic of the number of spikelets in the spike, which indicates the inappropriateness of the three genetic parameters model in the inheritance of these traits.This means that the multiple genes that control these traits were not independent in their effects, and Digenetic epistasis is likely to be involved in their inheritance, assuming the absence of other genetic phenomena.This is because it is not significant from zero, as the standard deviation of it is smaller than its values.Therefore, it passes zero for each of the three relationship values for the single scale test and the chi-square value at three degrees of freedom for the combined scale test, which is more efficient and accurate because it includes all tests in the single scale with an integrated test.Common, and the use of weights works to homogenize the variations of generational averages, so selection is ineffective in the early isolated generations in improving these characteristics, due to the lack of significant additional effects and the significant dominance effects.Since the significance of one or more of the values of the scale and corelationships means that the model of the three genetic parameters is not appropriate.
In the cross (Milan × Abu Ghraib 3), the values of the single and combined scale were significant for the characteristics of the number of days until flowering 50%, plant height, number of spikelets per spike, leaf area, total tillering number, number of spikes per plant, number of grains per spike, biological yield, grain yield and Harvest index, weight of 1000 grains, yield efficiency, protein content, and gluten content.In the cross (Milan × Sham 6), the values of the single and combined measure were significant for the number of days until flowering 50%, plant height, number of spikes per spike, leaf area, total tillering number, number of spikes per plant, number of grains per spike, biological yield, grain yield, and index Harvest, weight of 1000 grains, yield efficiency, protein content and gluten content.Table (3) shows the values of the six genetic parameters.In the cross (Milan × Abu Ghraib 3) the values of m were significant for all studied traits, which indicates the contribution of the environment in addition to the influence of genetic sites, as well as the interaction between these sites, which indicates that these traits have quantitative inheritance.The values of [d] were significant and positive for leaf area traits.Grain yield, harvest index, and gluten content were significant and negative for the two characteristics, number of grains per spike, and yield efficiency, while the rest of the traits did not reach significant limits.The dominant effects [h] showed positive and significant values for the characteristics of plant height, number of total shoots, number of spikes per plant, number of grains per spike, biological yield, grain yield, weight of 1000 grains, protein content, and gluten content, while significant effects did not appear in the rest of the studied traits, and the superior effects showed (extra x extra) [i] Significant and positive values for the characteristics of plant height, total number of tillers, number of grains per spike, harvest index, protein content and gluten content, and significant and negative values for the characteristics of number of days until flowering 50%, number of spikelets per spike, leaf area, biological yield, and weight of 1000 grains .The (additive × dominance) [j] effects were positive and significant in the characteristics of the number of grains per spike, significant and negative in the characteristics of the total number of tillers, the number of spikes per plant, grain yield, harvest index, weight of 1000 grains, negative for gluten content, and negative for leaf area.The effects (dominion × dominance) [14], were significant and positive for the characteristics of the number of spikelets per spike, leaf area, number of spikes per plant, biological yield, grain yield, weight of 1000 grains, yield efficiency, protein content and gluten content, and significant and negative for the two characteristics of plant height and number of The results of the analysis of the components of the genetic act for these traits showed that the superior genetic act of the type additive × additive (i) is the first contributor to the inheritance of these traits followed by the part of the genetic act of the superior dominant × dominant (l) and then the superior genetic act additional × dominant (j) followed by the dominant hereditary act and then the additive hereditary act.The results showed that the components of the superior genetic act contributed significantly and mainly, along with the additional and dominant genetic agents, in the inheritance of these traits, where the contrast between the two signs of the dominant and dominant x dominant genetic factors for some traits indicated the duplicate pattern of the superior genetic action in this hybrid, and this indicates The selection is effective in the late solitary generations, which indicates that the selection of the lineage method can be useful in the breeding programs for this hybrid.However, the negative values of the additive and dominance genetics indicate that the clues responsible for the decrease in the values of the traits are dominant over the clues that control the increase in the values of these traits.
In the cross (Milan × Sham 6), the mean values of m were significant and positive in all traits, which indicates the contribution of the environment in addition to the genetic interaction in the inheritance of these traits, as this indicates that these traits are of quantitative inheritance.The values of [d] were significant and positive for the two characteristics of leaf area and protein content, which makes early selection beneficial for these characteristics, and were significant and negative for the characteristics of number of grains per spike and grain yield.The effects of [h] were significant and positive For the characteristics of plant height, total number of tillers, number of grains per spike, grain yield, harvest index, weight of 1000 grains, yield efficiency, protein content and gluten content.Significant and negative for the characteristics of the number of days until flowering 50%, the number of spikelets in the spike, the leaf area, and the biological yield, as these characteristics can be improved through a number of polling cycles, as selection in late generations is effective.As for the superior effects (additional x additive) [i], positive and significant for the characteristics of plant height, total number of tillers, grain yield, harvest index, yield efficiency, and gluten content, significant and negative for the characteristics of number of days until flowering 50%, number of spikelets per spike, leaf area and biological yield, while The rest of the attributes did not reach the moral limits.While the superior effects (additive × dominance) [j] were significant and positive for the number of grains per spike, and significant and negative for the characteristics of leaf area, number of spikes per plant, weight of 1000 grains, and protein content, where the significance of these effects indicates that these characteristics can be improved by selection in the middle generations.The effects (dominion × dominion) [14], were significant and positive for the characteristics of number of days until flowering 50%, number of spikelets per spike, leaf area, number of spikes per plant, number of grains per spike, biological yield, grain yield, weight of 1000 grains, protein content and gluten content. .While it was significant and negative for the characteristics of plant height, harvest index and yield efficiency.As the selection is useful in the late solitary generations to increase the frequency of good genes for these traits, which are controlled by the dominance x dominance genetic action.
Table 3. Estimation of the six genetic parameters for the studied traits that were not suitable for the model of the three genetic parameters and for all crosses.We conclude from the foregoing that the dominant effects (h) were greater than the additional effects (d) in most traits, which indicates the dominance of the dominant genetic action on the inheritance of these traits, and that the positive genetic action values indicate the possibility of exploiting this type of genetic action through the phenomenon of hybrid strength.to improve this feature.The results also showed that the components of the superior genetic action contributed along with the two dominant and additional genetic actions, and the contrast between the signs of the two dominant and dominant genetic actions indicated the duplicate type of the superior genetic action, and this type of action hinders the development of traits through the selection process, as it cannot Predicting the amount of both dominant and dominant x dominant genetic factors, and that selection should take place in the later generations in order to obtain high levels of stable genes.The values of the additional, dominant and environmental variation components were given for the studied traits in the six generations and for all the crosses in Table (4), where it is noted that the values of the additional variations (d) were non-significant for all the studied traits and for all the crosses as a result of the decrease in the additional variation, which means the dominance of the dominant variation that controls the inheritance of traits.Except for the characteristic of the biological yield, which was significant in the crosses, with the exception of the cross (Milan × Abu Ghraib 3), which did not reach the limits of significance.The values of dominance genetic variance were highly significant for all studied crosses, and for all traits except for leaf area, they were not significant in all crosses.Therefore, it is suggested to use the crossbreeding program to improve these traits and then select in the late solitary generations.As for the values of the additional co-dominant variance (F), were significant and positive in the hybridization (Milan × Abu Ghraib 3) for the characteristics of the number of spikelets per spike, the number of total tillers, the number of grains per spike, the biological yield, the grain yield, the harvest index, the weight of 1000 grains, the protein content, and the content of gluten.It was not significant for the number of days until flowering 50%, plant height, leaf area, number of spikes per plant, and yield efficiency.In the (Milan × Sham 6) multiplication, the (F) values were significant and positive for all the studied traits except for the leaf area and the number of spikes per plant.The values of environmental variance were significant in all studied traits and for all crosses.This indicates that there are environmental influences on the studied traits.These results agreed with what was obtained [15,16].Table (5) shows that the average degree of dominance was greater than one correct for all the studied traits, which means a high dominance variance in the inheritance of the studied traits, which was calculated based on the values of D and H, and this indicates the presence of the superior dominance of these traits towards the higher father.In a cross (Milan × Abu Ghraib 3), breeding for the strength of the hybrid can be used to improve these traits.The results show that the values of the dominance difference in different sites were different, as they were positive and ranged from (0.3549) for the number of days until flowering 50% to (3.7808) for the grain yield characteristic, and were negative for the two characteristics of plant height and reached (-0.2217) and (-0.0248) for the crop efficiency characteristic.While the number of genes controlling the trait.It ranges from (0.0001) for plant height to (0.2468) for weight of 1000 grains.As for the amount of decrease as a result of indoor breeding (ID%), it was positive and not significant for the characteristics of plant height, number of spikes per spike, leaf area, total tillering number, number of spikes per plant, number of grains per spike, biological yield, grain yield, weight of 1000 grains, yield efficiency, protein content, and gluten content.And negative for my adjective, the number of days until 50% flowering and the evidence of harvest.The values of the strength of the hybrid were positive and highly significant in relation to the average of the parents for the traits of the number of spikes.Plant-1, number of grains per spike, biological yield, grain yield, and gluten content at a probability level (1%) and significant at a probability level (5%) for the two traits: leaf area and weight of 1000 grains, while the rest of the traits did not reach the limits of significance.From the data of Table (5), the values of heritability in the narrow sense were low in all studied traits.These differences are due to low additive genetic action compared to the high dominance variance in these traits, and the reason is due to the low value of additive genetic variance compared to the high dominance variance.As for the values of heritability in the broad sense, they were medium to high in all traits and ranged between (54.9982-99.685).The expected genetic improvement was as a percentage of the average, which is the difference between the average offspring resulting from the elected parents and the average of the first generation before selection.

1981). High values of genetic improvement indicate high values of additive genetic variance, while low values indicate high values of non-additive variance.
Table 5. Estimation of genetic constants (degree of dominance, difference of dominance in different sites, number of genes controlling the trait, deterioration by inbreeding, strength of the hybrid, inheritance in the broad and narrow sense, genetic improvement as a percentage, coefficient of genetic variation %).We note that the value of the expected genetic improvement as a percentage was low in all studied traits and the value ranged between (0.0001-0.0052%) and the values of genetic improvement were low in all studied traits.As for the coefficient of genetic variation, it was a value and ranged from (2.8564) for the number of days until flowering 50% to (39.7396) for the characteristic of harvest index.
As for the cross (Milan × Sham 6), we note that the degree of dominance and towards the supreme father was superior for all studied traits, which indicates that these traits can be improved through cross-breeding and late selection programs.As for the values of the dominance difference in the different sites, they were low and ranged from (0.29576-2.5838),and the values of the rest of the traits varied between these two values.In the number of genes controlling the trait, the values were low and less than one for all traits, and ranged between (0.0001) for the plant height trait and (0.2075) for the 1000 grain weight trait, and the values of the rest of the traits ranged between these two values.The amount of deterioration as a result of indoor breeding (ID%) was positive and not significant for plant height, leaf area, total number of tillers, number of spikes per plant, number of grains per spike, biological yield, grain yield, harvest index, weight of 1000 grains, protein content and gluten content.Negative and insignificant in the characteristics of the number of days until flowering 50%, the number of spikelets in the spike, and the efficiency of the crop, as their values were (-1.45), (-0.39), and (-2.0423), respectively.The vigor of the cross with respect to the average parents showed high significant at the level of probability 1% for the characteristics of the number of grains per spike, biological yield, grain yield and gluten content, and significant at the level of probability 5% in the characteristic of leaf area only, while the rest of the traits did not reach the limits of significance.As for the values of heritability in the narrow sense, they were low for all the studied traits, which indicates a high effect of the dominant gene action compared to the additional genetic action.The contribution of the additive cumulative genetic action was small, and the largest percentage of the noncumulative genetic action in the inheritance of these traits.Likewise, the values of genetic improvement were low and ranged from (0.0002 -1.2213).Evaluating the heritability ratio with the expected genetic improvement is useful if accompanied by calculating the heritability ratio in the narrow sense, as this allows the breeder to determine the date and intensity of selection and in which

Table 1 .
The arithmetic averages of the studied traits in the six generations and for all crosses.

Table 2 .
The single and combined scale tests of the three genetic parameters model for the inheritance of the studied traits for all crosses.

Table 4 .
Estimates of additive variance D and dominance H for the studied traits and for all crosses.