Estimation of Genetic Parameters and Path Analysis of Sesame Genotypes under Three Plant Distributions

A field experiment was carried out at research station of Department of Field Crops at the College of Agriculture at the University of Tikrit under gypsum soil conditions during the summer agricultural season (2022 AD). plants, which are (60 x 10, 40 x 15, and 30 x 20) cm2. genetic parameters were estimated in the three environments for studied traits under study. path was analyzed to determine most traits in single plant yield. The most important results were as follows: genetic variation was higher than the environmental in the three studied environments and for all traits, and values of the coefficient of genetic and phenotypic variation were average for most of the traits studied in the three environments and broad sense heritability was high in most of the studied traits and in three environments, and expected genetic advance was high as mean for traits of single plant yield in (the second and third environment) and it is possible to adopt the two traits of number of capsules per plant and seeds 1000weight with direct selective evidence to improve single plant yield because the direct effect of these two inpath analysis was positive and high.


Introduction
Sesame crop, whose scientific name is( Sesamum indicum L.), is one of crops of sesame family (Pedaliaceae) and one of main oil crops cultivated in country.cultivated area in Iraq for the year (2021) was estimated to be about (7736) thousand hectares and production amounted to (2134) tons.hectares and productivity per hectare amounted to (1103.412),kg.ha, and cultivated area of it in world for the year 2020 AD was about (13965.84)thousand hectares and production amounted to (6803.82)thousand tons and productivity per hectare amounted to (1948.72)kg.ha [1] and this difference shows large gap production between Iraq and world and it is imperative for plant breeders to benefit from vertical expansion in developing and increasing the productivity of genotypes through use of plant breeding and improvement methods.genotypes vary in phenotypic traits resulting from the interaction between genetic and environmental variation and for quantitative traits.Each genotype is characterized by certain traits that differ from other.Cultivating new high-yielding accessions and comparing their production with local variety is one of most important goals of breeders of this crop, as well as the suitability of these inputs for the prevailing environmental conditions in region, which is one of main factors that contribute to increasing the cultivation and spread of the crop.estimating genetic parameters is one of priorities of the program.appropriate breeding to obtain genetic progress, as well as establishes an appropriate breeding method for each trait, an amount of vinegar to use of statistical analysis, which is one of important measures for selection of superior genotypes by 1259 (2023) 012090 IOP Publishing doi:10.1088/1755-1315/1259/1/012090 2 identifying main yield components, which gives a more effective indicator of selection for the yield trait because this trait is a complex trait and is controlled by many genes that cannot be improved without relying on its basic components that depend mainly on direct effects.Indirect and indirect, and the total effect of a non-independent trait on those independent traits [2], in an experiment applied to six genotypes of sesame, the environmental variance was higher than genetic for the two traits of number of capsules per plant seeds 1000 weight, while genetic variance was greater than environmental for trait of plant height [3]in their study of eleven sesame genotypes, concluded that genetic variation was more important than environmental variation for traits of plant height, number of capsules per plant, number of seeds per capsule, seeds 1000 weight and yield of single plant yueld [4] explained in a field experiment in which 33 were used.genotype of sesame showed that the coefficient of genetic and phenotypic variation was average for traits of plant height, number of capsules per plant, number of seeds per capsule, and seeds thousand weight and high for the single plant yield trait, [5] noted in a study that included several sesame genotypes that coefficient of genetic and phenotypic variation was low for plant heigh ttrait, [6] confirmed that the plant height trait and number of seeds per capsule were low in which degree of briad sense heritability in and high for trait of number of capsules per plant, [7] when they estimated the degree of broad sense heritability in that it was low for trait of number of seeds per capsule and high for trait of number of capsules per plant, it was found [8] that values of expected genetic advance as mean were low for two trait of plant height and single plant yield [9] the trait of number of capsules per plant, number of seeds per capsule, and seeds1000 weight of had a direct positive effect on single plant yield.This study aims at estimating the genetic parameters of traits under study, as well as analyzing the pathway by identifying most important traits in their direct impact on single plant yield and adopting them as electoral guides for distinct genotypes.

Materials and Methods
A factorial experiment was arried out during the summer agricultural season of year (2022) in research station of field crops department of faculty of Agriculture at Tikrit University, which is located on a longitude (43.679) east and latitude (34.616) north with the aim of evaluating performance of six phenotypes of sesame, which are (local, wadea،, had, Sumer, Rafidain and Paytm) and three plant distributions (60 × 10), (15 x 40) and (30 x 20) cm2, and genotypes came from the Center for Desert Studies at Anbar University and resulted from mutations breeding for local variety and the cultivation land was plowed with plow of disc plow and smoothed with smoothing machines and added nitrogen fertilizer in the form of urea as a source of nitrogen and in two batches the first half the quantity with agriculture and the other half in the stage of vegetative growth by (120) kg.Potassium and phosphorus is one batch of agriculture [10], and area of the experimental unit reached (2 x 3) m 2 and the genetic compositions were cultivated in 15-5-2022 m according to the plant distributions which are (10 x 60) cm2 and five lines and second plant distribution (15 x 40) cm2 with nine lines and 13 plants, while third plant distribution (20 x 30) cm 2 cm 2wiith ten lines and in each line ten plants, as plant density reached (66,666) thousand plants per hectare for all distributions, and plants were watered whenever the need arises.results of the statistical analysis of the traits under study showed that interaction between two study factors was highly significant, and this means that genotypes took a different behavior from one environment to another and this is governed by their genetically analysis on the basis of the independent environments (three plant distributions).data was analyzed statistically according to the SAS program and the genetic analysis according to the (OPSTAT) program.Genetic parameters and path analysis are as follows -Genetic, environmental and variations of studied traits.Genetic, environmental and variations were estimated in three environments and for qualities studied according to method he explained [11], and according to following laws: Standard error (S.E) was calculated for both genetic, environmental and variations in manner mentioned [12] according to the following equations.

S . E =√
As for calculating standard error of phenotypic variance, it was calculated according to the two equations presented by [13].
S .E =√ Genetic, environmental, and phenotypic variance and studied traits .thetransactions of genetic, environmental, and phenotypic differences and qualities studied and in three environments were estimated according to the following equations.
. √ √ √ Degree of broad sense heritability and for studied traits.Degree of heritability was estimated in broad sense hertiability and for three environments and for traits studied and in the manner explained by [14] according to the following equation.h2b.s: degree of broad sense heritability , σ2G: genetic variance for the trait, and σ2P: phenotypic variance for the trait.expected genetic advance as mean of for trait and for studied traits.

E.G.A(%) = ×100
Less than (10) low and between (10-30) medium and more than (30) high.As: E.G.A = expected genetic advance = h2b.sdegree of broad sense heritability M.EG A = expected genetic advance as mean E.G.A = advance expected , general mean of trait the overall ean of the trait .Path analysis and studied traits.explained [16] that correlation between two variables measures the degree of relationship between the influencing and affected variables, and that the value of (r) ranges between (-1 and +1), but it does not give us a clear picture of the full truth of the relationship between the influencing and affected variables.

Results and Discussion
Variance components and some genetic parameters in the primary environment and for all the studied traits.We note from Table (1) that genetic, environmental, phenotypic variances and studied traits differed from zero for the studied traits, and this means importance of estimating these variations on one correct and on other , genetic variation values were higher than environmental and studied traits, and this is evidence of greater role in inheritance of these traits It is due to the genetic variation in comparison with environmental variation and thus represented the largest value of phenotypic variation for these traits, and these results were consistent with [3].Coefficient of genetic variation was mean for traits of seeds1000 weight and single plant yield and low for traits and plant height , leaf area per plant, number of capsules per plant and the number of its seeds coefficients of genetic and phenotypic variation give evidence of high heritability, and their height indicates the largest variances among plant populations [5].The results of the same table show that the values of degree of heritability in broad sense were high in first environment and for traits studied, and this indicates a greater participation of genetic variation compared to environmental variation In inheritance of these traits and can be improved genetically (management of genetic variation) and obtained similar results [6] and that the values of genetic advance as mean were average for traits of plant height, the number of capsules per plant, seeds wei 1000 seeds, and single plant and the high values of expected genetic advance give an indication of possibility exercise of direct election and these results are consistent with [8].

Components of Variances and Genetic Parameters in t(Second Environment) and for the Studied Traits
We note from Table (3) that the genetic, environmental, and phenotypic variations of the studied traits differed from zero.The significance of these variations indicates the importance of their assessment and their role in the inheritance of these traits and that values of coefficients of genetic and phenotypic variation were average for trait of single plant yield and low for rest of the traits.The result agreed with [4] and that values of the degree of broad sense heritability in were high and for studied traits, except for number of days from planting until emergence of the first flower, it was medium, and the high values of genetic variation for these traits were attributed to the comparison of environmental variation, and degree of heritability ranged between low and high [7] and that The values of the expected genetic advance as mean of were high for trait of single plant yield and average for traits, leaf area per plant, number of seeds per capsule and seeds 1000 weight, reason is attributed to the high degree of broad sense heritability of these traits and obtained consistent results [8].

Components of Variance and Genetic Parameters in t (Third Environment) of Studied Traits
Genetic, environmental and phenotypic variances of the studied traits differed from zero, and significance of these variances illustrates importance of estimating these variances in inheritance of these traits on one direct , and on other direct , values of genetic variance were greater than environmental variance in phenotypic variance and for studied traits, and this confirms importance of genetic variance for these traits and can be improved genetically and obtained consistent values [3].
Values of the coefficient of genetic and phenotypic variation were average for characteristics of leaf area, weight of a thousand seeds, and single plant yield of while values of environmental coefficient of variation were low for studied traits, while values of coefficient of phenotypic variation were average for trait, leaf area, weight of a thousand seeds, and yield of an single plant High and high values indicate existence of heterogeneity between these genotypes, as well as the average values of the coefficients of genetic and phenotypic variation for these traits give an indication of high heritability.
Values of the coefficients of genetic, environmental and phenotypic variation ranged between low and high were obtained from [5] and that values of the degree of heritability are in the broad sense It was high and for studied traits it was medium, which is evidence of the contribution of genetic and epidemiological variation E in apparent variance and gives evidence of possibility of improvement by managing genetic and environmental variance, and this result agreed with [6] and that the expected genetic advance values as a mean were high for two traits of weight of a thousand seeds and single plant yield and reason is due to the high values of heritability in broad sense of these traits and high values for improvement, it gives an indication of the exercise of direct selection and obtained values that ranged between low and high for the expected genetic advance as mean [8].

Path Analysis
Traitc of plant height (X1) had a negative direct effect (-0.388) on the single plant yield, while indirect effects were negative through trait leaf area (-0.254), number of capsules per plant (-0.139), and number seeds per capsule (-0.139).-0.518) and weight of one thousand seeds (-0.833), while the total effects had a negative value (-0.426).for leaf area (X2), the direct effect was positive (0.764) with single plant yield, and indirect effects were positive for traits of plant height (0.129), number of capsules per plant (0.521), and weight of 1000 seeds (0.180), while indirect effects were negative for number of seeds per capsule.(-0.462), while total effect had a positive value (0.840) and for number of capsules per plant (X3).weight of 1000 seeds was (0.266) and negatively indirectly number of seeds per capsule (-0.344), while total effects had a positive value (0.973) and for traits of number of seeds in per capsule (X4) direct effect was negative (-0.617) with single plant yield and effect was indirect.Direct was positive for trait of number of seeds per capsule with trait trait of plant height (0.325), leaf area (0.573), number of seeds per capsules (0.355), and weight of 1000 seeds (0.137), while the total effects were of a positive value (0.711), and for weight of 1000 seeds (5X) ,Effects were Direct is positive (0.246) with a quotient single plant, while indirect effects were positive with the characteristics of plant height (0.131), leaf area (0.559), and the number of capsules per plant (0.584), and indirect effects were negative for characteristic of the number of seeds per capsule (0.342), while the total effects had a positive value (0.940).And the yield of the individual plant (X6), the direct effects were positive for characteristics of leaf area (0.840), the number of capsules per plant (0.973), the number of seeds per capsule (0.711) and weight of one thousand seeds (0.940), while the indirect effects were negative for characteristic of plant height (0.426).And the total effects have a positive value (1.000), and the results obtained [9].

Conclusion
We conclude through this study that the genetic variation was higher than environmental for studied traits, while coefficient of environmental variation was low fortraits studied in three environments, and degree of heritability in broad sense was high for all traits, and expected genetic advance as mean was high for trait of single plant yield in second environment, weight of 1000 seeds and single plant yield in the third environment, and results of two-track analysis showed that direct effect was positive and high for number of capsules, number of seeds per capsule, and weight of 1000 seeds in the single plant yield, and they can be adopted as electoral evidence for superior genotypes.

Figure 1 .
Figure 1.Path analysis for the studied traits.Xi :causative factors ( six traits studied).Y : Responding factor (characteristic of single plant yield).R : remaining factors.Pxiy: A vector representing a path parameter from the causer to the effector.rxixi: a vector representing the correlation coefficient between the two traits.From the above diagram, single plant yield is Y, which is the result of the causative agents (X1, x2, x3, x4, x5, and x6).

Table 1 .
Analysis of variance for studied traits according to the use of Randomized complete blocks design and split plot arrangement.

Table 2 .
Components of variance genetic parameters and all studied traits in one environment.

Table 3 .
Components of Variance and genetic parameters in (Second environment) and for studied traits.

Table 4 .
Components of variance and genetic parameters in (third environment) and for studied traits.