Heritability and genetic variability estimates in F3 populations of bread wheat (Triticum aestivum L.)

The wheat breeders are concentrating to improve the yield potential of bread wheat by developing new varieties with desirable genetic makeup in order to overcome the consumption pressure of the everincreasing human population. For resolving this situation, research was carried out on eight F3 populations along with their six parents grown in the Experimental Field. The experiment was carried out in a Randomized Complete Block Design with four replications. The characters studied were; plant height (cm), peduncle length (cm), tiller plant, spike length (cm), spikelets spike, grains spike, seed index (g), grain yield plant (g), biological yield plant (g) and harvest index (%). The analysis of variance revealed significant differences among genotypes, hybrids and parents vs. hybrids for all the traits studied. Such results signified the worth of breeding material for further exploitation. The present research indicated that based on average performance, F3 populations performed better than their parents for most of the traits studied. It means transgressive segregants were present in F3 populations. If the selection of such potential plants is successful, then they may be utilized for further improvement of bread wheat. The genetic parameters of F3 progenies indicated that cross TJ-83 x TD-1 displayed higher heritability estimates coupled with more genetic gains for plant height, spike length, spikelets per spike and grains per spike; TJ-83 x Sarsabz for tillers per plant and biological yield plant; TJ-83 x Moomal for peduncle length, grain yield per plant and harvest index and Moomal x TD-1 for seed index. These F3 populations may be kept on priority for selection from subsequent filial generations to improve the studied traits in bread wheat.


Introduction
Wheat breeders are emphasizing the potential to increase the yield of bread wheat by developing new varieties with the desired genetic makeup to overcome the increasing consumption pressure of the population [1]. Therefore, the increase in production and output is still the main goal of the prehistoric period and current breeding programs. Genetic manipulation of plant traits is the best way to increase wheat yield [2,3]. Grain yield is a product of many yield components, including most economic characteristics. Yield components and their inherent physiological mechanisms interact with crop growth environments and management practices to increase grain yield ha -1 . The researchers found significant differences in the bread wheat genotypes of the yield components [4,5]. This variation in yield between varieties indicates that there is a genetic variation between wheat varieties, which is responsible for the success of the breeding program [6]. Among other reasons, food production is strongly influenced by many genetic factors and environmental fluctuations [7]. The heritability estimate determines the extent to which a character is passed from one generation to the next and is a more valuable genetic attribute used with other parameters to predict genetic gain after a particular feature selection [8]. It is speculated that the higher the estimate of heritability, the simpler the selection procedure [9]. It has been emphasized that hereditary power alone is not sufficient to substantially improve the overall selection of late generations unless accompanied by substantial genetic advancement [10]. Estimates of heritability and genetic progression provide parents with knowledge of the inheritance of their offspring and their response to selection. Heritability and genetic progression values help breeders make choices more effective and predict choice responses [11]. For this purpose, genetic information about yield and its components is important for breeders to select and develop new and high yield cultivars. This is why selective genetic manipulation becomes extremely important [12]. In order to select the desired genotype, knowledge of the extent of gene action and variation in the breeding material is important for successful breeding programs [13,14]. In the wheat yield improvement program, the selection based on phenotypic variation is not efficient unless the genetic variation of the breeding material is fully evaluated and utilized. Therefore, it is necessary to obtain information on phenotypic and genotypic differences, hereditary and genetic progression. Several studies conducted at different locations in Ethiopia assessed genetic variability between tested bread wheat genotypes [1,4]. Therefore, this study aimed to study the heritability of F3 progeny yield and its components and to understand how many phenotypic differences have been passed on to future generations. Therefore, the purpose of this study was to estimate the heritability in the broad sense and the genetic progress of the bread wheat F3 population to obtain yield and yield-related traits.

Materials and methods
Eight F3 populations along with their six parents viz. Sunhri, PBGST-1, Sarsabz, TD-1, TJ-83, and Moomal were grown in the growing season. The experiment was carried out in Randomized Complete Block Design with four replications. At maturity, fifteen plants per genotype from each replication were randomly tagged as treated index plants for recording the data on plant height (cm), peduncle length (cm), Tillers per plant, spike length (cm), Spikelets per pike, Grains per spike, seed index (1000 grain wt, g), Grain yield per plant (g), biological yield (g) and harvest index (%). The data were analyzed according to the statistical technique outlined by Gomez and Gomez [15] through Statistix 8.1 computer software so as to work-out the differences among the genotypes for various traits. The Phenotypic variance usually combines the genotype variance with the environmental variance. Genetic variance has three major components: the additive genetic variance, dominance variance, and epistatic variance. The portion of phenotypic variance that is due to differences in the environments to which the individuals in a population have been exposed is called environmental variance.
The genetic, phenotypic, environmental variances, broad-sense heritability (h 2 ) and expected response to selection were estimated according to the procedure adopted by Baloch et al. [16]. All the inputs are given, and cultural practices were done according to the recommendations of the wheat crop. L.S.D at P≤ 0.05 for pairwise comparisons was used to determine the critical differences between the mean of genotypes consisted of seven parents and their eight F3 progenies by using the following formula: L.S.D (5%) = S.E xt value by using error degrees of freedom Where S.E = Results Analysis of variance The genetic improvement of any crop species depends on the size of the genetic variation and the heritability of the yield and its contribution characteristics. The purpose of this study was to assess the genetic variance, generalized heritability, and genetic progression under the 20% selection pressure of the wheat F3 population, for 10 important traits. The results regarding the genetic parameters are listed in graphs 1 to 10. The analysis of variance in table 1 reveals significant differences between the parents of all traits studied and the F3 population, indicating the presence of genetic variability between the parent and its F3 progeny. The characteristics of the study were: plant height, spike length, tillers per plant, ear length, spikelet per spike, Grains per spike, seed index (1000-grain weight), grain yield per plant, biomass yield per plant and harvest index. After finding that the mean square differences are significantly different, the data is further processed to determine genetic parameters. Researchers also found significant differences in various polygenic traits of the bread wheat genotype (Triticum aestivum L.) [17]. The average performance of the parent and F3 hybrids shown in table 2. In graphs 1 to 10 their genetic parameters are presented.

Mean performance of parents and their F3 progenies
The average performance of the different traits of the 6 parents and their 8 F3 populations is shown in table 2. The results indicate that for most of the studied traits, the F3 progeny gave an average higher than their parental mean. The parental line TD-1 showed the smallest plants (58.1 cm), while Sarsabz produced the tallest plants (102.9 cm) compared to the other parents. In the F3 progeny, the shortest plant (75.4 cm) was observed in the cross TD-1 x Sarsabz, while the TJ-83 x Sarsabz produced the highest plant (91.5 cm), followed by Moomal x TD-1 (90.1 cm). In the parental line, the lower peduncle length was measured in TD-1 (25.9), followed by TJ-83 (26.0 cm), and the highest value was given by Sarsabz (39.5 cm). The offspring TD-1×Sarsabz showed the lowest value (33.8). The highest value was shown by TJ-83 x Sarsabz (40.0 cm), followed by Sarsabz x Moomal (38.3). The maximum is the tiller produced by the parent TD-1 (5.6), followed by PGBST-01 (5.2), and the minimum tiller is observed in Moomal (4.4). From the offspring, Sunhari x TD-1 (5.9) produced the most bifurcation, followed by TJ-83 x Sarsabz (5.7), while the minimum bifurcation was generated by TJ-83×Moomal and TJ-83 x TD-1 (4.8). In the parent, the maximum ear length (12.9 cm) recorded in PBGST-1 was obtained from Sarsabz (12.4 cm), and the smallest spike was measured by TD-1 (10.2). In hybridization, the highest value of ear length was recorded by TJ-83×Moomal (13.9 cm), and the second-highest value was recorded in PGBST-01×TD-1 (13.2 cm). The lowest value was crossed by Sunhari x TD-1. The parental line PBGST-1 weighted highest seed index (37.0g), then TD-1 (31.1 g), the lowest is given by Sarsabz (26.6 g). The maximum seed index in the isolated population was weighted by PBGST-1×TD-1 (37.5 g), weighted by Moomal x TD-1 (35.8 g), and recorded by Sunhari x TD-1 (30.4 g). value. For the trait yield per plant, the maximum kernel weight was observed in the parental PBGST-1 (7.7 g), followed by Sarsabz (7.5 g), and the minimum kernel weight was recorded in Moomal (4.7 g). The progeny from Moomal x TD-1 (9.52 g) showed the maximum grain yield per plant, followed by TJ-83×Moomal (8.8 g), and TJ-83×TD-1 and TD-1×Sarsabz produced the smallest but similar yield (7.3, 7.3g). Regarding the biomass yield per plant, Sarsabz produced a maximum (21.3 g), followed by PBGST-1 (18.0 g), while Moomal produced 13.7 g. The offspring Moomal x TD-1 produced the maximum harvest index (22.0%), followed by two F3 hybrids, such as Sunhari x TD-1, TJ-83 x Sarsabz (21.5, 21.4%), and the minimum value was expressed in TD-1×Sarsabz. In the parental line, PBGST-1 had the highest (43.1%) harvest index, Sunhari (40.5%) ranked second, and TJ-83 (33.9%) had the lowest. The highest percentage of the harvest index came from the cross TJ-83×Moomal (46.9%), then the cross TD-1×Sarsabz (45.2%), and the lowest from TJ-83×Sarsabz (38.1%). The highest heritability with maximum genetic advances were observed in progenies TJ-83 x TD-1 (98.8%, 24.5) closely followed by Sunhri x TD-1 (98.7%, 23.8), yet lowest heritability was observed in cross Moomal x TD-1 (57.5%, 6.3). On individual population basis, their phenotypic variances were very closer to their respective genotypic variances, consequently higher heritability estimates were recorded ranging from 57.5 to 98.8%.

Graph 1. Heritability estimates and genetic advance of eight F3 populations of bread wheat for Plant height
Peduncle length Graph 2 describes the genetic variance (σ2g), phenotypic variance (σ2p), environmental variance (σ2e), heritability estimates (b.s.), and genetic progression of peduncle length. The results showed that the F3 population expressed a broader genotype variance (σ2g = 8.5 to 55.6). The F3 population also expressed a moderate to high heritability estimate for this feature. The maximum heritability and the highest hereditary progression were estimated from the cross TJ-83×Sarsabz (89.5%, 9.8), while the minimal heritability was observed in the cross Sarsabz x Moomal (47.4%). However, the lowest genetic progression was calculated from the progeny Moomal x TD-1 (2.8).

Graph 2. Heritability estimates and genetic advance of eight F populations for of bread wheat for Peduncle length
Tillers per plant Genetic parameters such as phenotype (σ2p), genotype (σ2g) and environmental (σ2e) variance, heritability estimates (bs) and genetic progression of each plant tiller are shown in graph 3. The results showed that F3 hybrids exhibited different phenotypic variation ranges (σ2p = 17.3 to 62.1). Low to moderate heritability was observed for the tillering of each plant. The highest heritability with the greatest genetic progression was measured in F3 progeny like TJ-83 x Sarsabz (55.6%, 1.94). However, minimal heritability with low genetic progression was observed in the cross Sarsabz x Moomal (22.3%, 0.6). Phenotypic variation in the F3 population is usually twice as high as its corresponding genetic variation, so almost all populations have lower heritabilities.

Spikelets per pike
High and moderate heritability of spikelets per ear was observed. The genotypes (σ2g = 1.7 to 10.6), the phenotype (σ2p = 3.3 to 13.0) and the environmental variance (σ2e = 1.64 to 3.9) were recorded and listed in graph 5. High heritability (81.6%) plus high showed genetic progression by crossover TJ-83 x TD-1 (4.1). However, the lowest heritability is estimated by the offspring Sunhari x TD-1 (40.3). The minimum genetic progression is estimated to be cross TD-1 x Sarsabz (1.2). Two populations, TJ-83×TD-1 and TJ-83×Moomal, which express very close genetic and phenotypic variations, provide higher estimates of heredity (above 80%). A population with a low heritability variance for its phenotypic variation recorded a low heritability estimate for spikelet spike -1 .

Grains per spike
The low to moderate heritability of the number of grains per panicle in the F3 population was estimated. The variance of genotype ranged from σ2g=30.7~96.8, the variance of phenotype was σ2p=121.2~204.9, and the environmental variance was σ2e= 71.3~164.7. The F3 from the cross TJ-83×TD-1 represents the largest but moderate heritability (57.6%), with the highest genetic progress (10.4), followed by TD-1×Sarsabz, the heritability rate is 47.4%, and the genetic progression is 9.31. However, TJ-83×Moomal (19.6%) recorded minimal heritability, but the lowest genetic progression was observed in cross-PBGST-1×TD-1 (3.6). Almost all F3 populations provide low heritability estimates because environmental differences are greater than their genotypic differences and the boundaries of genetic differences ultimately lead to a reduction in heritability estimates (Graph 6).

Seed index
The characteristic seed index represents a high to medium heritability estimate. The genetic variance ranged from σ2g = 11.4 to 29.9; the phenotypic variance was σ2p = 17.6 to 32.4, and the environmental variance was σ2e = 2.1 to 12.5. The highest heritability was tested in crossover Moomal x TD-1 (92.4%) and maximum genetic progression (7.3) and crossover Sunhari x TD-1 (90.4%). However, the minimal heritability comes from the offspring of the cross TJ-83×Sarsabz (45.4%) and the lowest genetic progression (3.0). Populations with large genetic differences provide relatively more genetic progression, indicating that the added genes control the seed index in these offspring (Graph 7).

Graph 7. Heritability estimates and genetic advance of eight F3 populations of bread wheat for Seed index (1000-grain wt.)
Grain yield per plant A low to high heritability estimate was observed for each plant's grain yield (Graph 8). Genotype differences ranged from 2.1 to 13.4, phenotypic differences ranged from 9.86 to 18.1, and environmental differences ranged from 4.7 to 10.9. Low heritability estimates were recorded because the genotype differences in the F3 population were much lower than their respective phenotypic variations. However, the highest heritability (4.40) was observed in the progeny TJ-83 x Moomal (73.6%) associated with the greatest genetic progression. The minimum heritability was estimated in the offspring TJ-83 x TD-1 (21.5%) and minimal genetic progression (0.9). In general, almost all F3 populations exhibit low heritability, thus indicating that environmental differences are not effectively controlled.

Biological yield per plant
The F3 progeny of the biological yield of each plant was estimated to have a moderate to low heritability (Graph 9). The genetic variance ranged from 8.3 to 67.1; the phenotypic differences ranged from 68.0 to 118.4, and the environmental differences ranged from 33.2 to 65.2. The highest heritability (56.6%) and the highest genetic progression (8.6) were observed after TJ-83×Sarsabz crosses, followed by TJ-83×Moomal (51.1%). However, the minimum heritability was estimated to be cross Sarsabz x TD-1 (11.3%) and the lowest genetic progression (1.3). Except for a small number of people, most of them estimate that the genetic yield of per plant is low. These results indicate that selection can be postponed increasing the biomass production of per plant until later segregation.

Harvest index
Observe the moderate heritability estimates for the harvest index as shown in (Graph 10). The variance range is recorded in the following manner. Genotypes ranged from 8.0 to 85.4; phenotypes ranged from 74.9 to 151.3, and the environment ranged from 60.2 to 75.4. The highest heritability (57.0%) was shown by crossover TJ-83 x Moomal and maximum genetic progression (11.0), while the minimum heritability (10.0%) was represented by cross Sarsabz x TD-1 with the lowest genetic progression (1.3).

Plant height
Most researchers believe that plant height is a polygenic trait due to the genetic pattern in the isolated population. Among wheat, semidwarf plants with high productivity are more desirable. The results in table 2 indicate that pro-Sarsabz produced the tallest plant (102.9 cm) compared to the other parental lines and F3 progeny, while TD-1 produced the shortest plant (58.1 cm). In the cross, the offspring TJ-83 x Sarsabz produces the tallest plant, 91.5 cm long, while the shortest plant is recorded by TD-1 x Sarsabz (75.4 cm). The results shown in (Graph 1) indicate that the maximum (98.8%) of the heritability associated with high plant height (24.5) of plant height is represented by the offspring TJ-83 x TD-1. However, other F3 progeny showed moderate to high heritability estimates and considerable genetic gain. Our results are consistent with the other's findings [3, 17-19] they also studied genetic parameters and recorded higher genotypic variability; medium to high heritability values and plant height greater inheritance the combination of progress. They also observed highly significant differences between parents and hybrids. Existing results with higher heritability estimates and significant genetic progression indicate that plant height is primarily controlled by additive genes, so direct selection may be effective in isolated generations. Furthermore, the results indicate that offspring with ideal genetic parameters TJ-83 x TD-1, Sunhari x TD-1, TJ-83 x Sarsabz, PBGST-1 x TD-1, Sarsabz x Moomal and TD-1 x Sarsabz may be Breeding materials are selected for selection to increase the plant height of subsequent generations.

Peduncle length
Peduncle length is a portion of wheat plant which is measured from top node to the base of spike. The mean performance shown in

Tillers per plant
Tiller is the main yield component and has a direct impact on food production, so this improvement in characteristics will ultimately increase food production. Regarding the average performance, the parental line TD-1 produced maximum tillers per plant (5.6) closely followed by PBGST-1 (5.2), while parent Moomal produced minimum tillers plant -1 (4.4). Among the F3 progenies, cross Sunhari x TD-1 recorded maximum tillers per plant (5.2), while minimum tillers plant -1 (4.8) were produced by TJ-83 x Moomal and TJ-83 x TD-1. The results presented in graph 3 regarding genetic parameters revealed that most of the F3 progenies displayed appreciable amount of genetic variability and low to moderate values of heritability, however progenies from cross TJ-83 x Sarsabz expressed highest heritability percentage (h²=55.6%) with greater genetic advance (GA=1.94), while minimum (h²=22.3) was shown by progenies Sarsabz x Moomal coupled with generic advance of 0.62. Results generally suggested that the F3 progenies from the crosses like TJ-83 x Sarsabz and Sunhari x TD-1 may be the choice segregating material for selection to improve the tillers per plant. Similar to our results, significant genetic variation and low to moderate heritability estimates for tillering of each plant were also observed [3, 18, 23]. Spike length On average, among the parents, PBGST-1 exhibited maximum spike length (12.97cm), while minimum spike length was measured by parent TD-1 (10.2cm). Among the F3 populations TJ-83 x Moomal produced longer spikes (13.8cm) closely followed by Sarsabz x Moomal (13.6cm). The results regarding phenotypic variance (σ²p), genetic variance (σ²g), environmental variance (σ²e), heritability percentage in broad sense (h 2 b.s) and genetic advance (GA) summarized in graph 4 revealed that F3 populations showed considerable amount of genetic variability. However progenies from cross TJ-83 x TD-1 displayed highest heritability (h 2 =80.9%) coupled with maximum genetic advance (GA=2.9).The other F3 progenies like TJ-83 x Moomal (h 2 =68.9%), PBGST-1 x TD-1 (h 2 =68.7%) and Sarsabz x Moomal (h 2 =68.3%) also exhibited higher heritability estimates. Present results are in conformity with those who also observed higher heritability percentage for spike length and controlled by additive genetic factors [3, 20, 24, 25].

Spikelets per spike
The spikelets of each ear steadily promote the grain yield of wheat. Therefore, plant breeders and researchers suggest that spikelets per ear are indeed a good standard for selecting high-yielding wheat varieties. The mean performance of genotypes, shown in table 2 indicated that, among the parents, maximum spikelets per spike (21.7) were produced by Sarsabz. Whilst among the F3 progenies, Sarsabz x Moomal (20.82) closely followed by Moomal x TD-1 (20.8) and TJ-83 x TD-1(20.70) recorded a higher number of spikelets per spike. Results regarding genetic parameters presented in graph 5 demonstrated that the several F3 progenies exhibited moderate to high heritability and genetic advances. The highest heritability percentage (h2=81.7%) associated with greater genetic advance (GA=4.1) were expressed by the progenies from cross TJ-83 x TD-1. These results suggested that the progenies TJ-83 x TD-1 and TJ-83 x Moomal with desirable genetic parameters may be considered valuable breeding material for selection of desirable plants in further filial generations to improve this trait. Our findings are consistent with the findings of who observed a moderate to high heritability of spikelets per ear [3, 20, 11, 17]. Grains spike - 1 The number of grains per spike -1 is the main yield component, so an increase in the number of grains per panicle will eventually increase the yield of wheat. Based on mean performance, parent Moomal counted maximum grains per spike (63.04), closely followed by Sarsabz (63.0). The genetic parameters presented in graph 6 demonstrated that most of the progenies expressed moderate to low heritability percentages in broad sense indicating the presence of substantial genetic variability. The progenies from crosses TJ-83 x TD-1 displayed the highest percentage of heritably in broad sense (57.6%) coupled with higher genetic advance (10.7). Further, these results suggested that the progenies TJ-83 x TD-1 and TD-1 x Sarsabz may be the choice segregating populations to improve grains per spike. Others also noted the low-medium heritability of the number of grains per panicle [20, 26-28]. Seed index (thousand-grain weight) Seed index is also a polygenic trait that imposes great impact on grain yield in wheat. The parental mean value for seed index ranged from 24.2 to 37.1g, while the mean value in F3 progenies ranged from 30.4 to 37.5g. Results in graph 7 representing the genetic parameters for seed index revealed that almost all the F3 progenies displayed moderate to high heritability estimates, however maximum heritability percentage in broad sense (h 2 =92.4%) and maximum genetic advance (GA=7.4) were manifested by progenies Moomal x TD-1 followed by Sunhari

Biological yield per plant
Based on mean performance, parent Sarsabz gave maximum biological yield plant -1 (21.3g), whereas, among the F3 progenies, the top ranker was Moomal x TD-1 (22.05g). The genetic parameters presented in graph 9 established that most of the progenies expressed low heritability percentages in the broad sense therefore selection for biological yield plant -1 may carry out in later segregating generations. The progenies from the crosses TJ-83 x Sarsabz displayed highest heritability percentage in broad sense (56.6%) coupled with maximum genetic advance (8.6). The other F3 progenies such as TJ-83 x Moomal (h 2 =51.5%) and Sunhari x TD-1 (h 2 =47.6%) also exhibited higher but moderate heritability estimate. The current results are consistent with the results of other researchers they also observed a moderate heritability of individual plant biomass [3, 19, 20].

Harvest index
Harvest index is also a polygenic trait that has direct impact on grain yield of wheat. The parental mean value for harvest index ranged from 33.9% to 43.1%, while the mean value in F3 progenies varied from 38.1% to 46.9%. Results shown in graph 10 representing the genetic parameters for harvest index revealed that almost all the F3 progenies displayed low to moderate heritability estimates, however highest heritability percentage in broad sense (h 2 =57.0%) and maximum genetic advance (GA=11.0) were manifested by progenies from cross TJ-83 x Moomal, while Sarsabz x TD-1 expressed lowest heritability percentage in broad sense (h 2 =10.0%) which was also associated with the lowest genetic advance (1.3). Our findings are consistent with the findings of another researcher they also observed a low to moderate heritability of the seed index in a broad sense [3, 19, 20].

Conclusion
Result as a whole indicated that most of the F3 progenies displayed considerable hereditary variation which resulted into high amount heritability observes, and a considerable amount of foretelling genetic gains, suggested that lines under present work trustworthy subjected to phenotypic isolating for desirable segregants from subsequent filial generations so as to improve studied traits in bread wheat. The study generally indicates the genetic variation between the genotypes studied. Most of them have high heritability and genetic, so direct selection has good results for these populations.