GENETIC VARIABILITY AND SELECTION CRITERIA OF SOME SESAME GENOTYPES FOR THEIR AGRONOMIC TRAITS AND SEED QUALITY

: The identification of genetic variation, mean performance, and selection criteria for twelve sesame genotypes is required for the genetic enhancement of agronomic traits and seed quality. Thus, using a randomized complete block design with three replications, these genotypes were evaluated in a field trial at the Kafr-El-Hamam Agricultural Research Station, Agricultural Research Center, Sharkia Governorate, Egypt, and laboratory experiments at the Seed Technology Research Department, ARC, Giza, Egypt, during the two consecutive seasons of 2018 and 2019. For earliness in flowering, N.A. 130 and Shandweel 3 were the most promising sesame genotypes, while N.A. 114 and RH 1 F 3 had the heaviest weight of seed plant -1 and one or more yield-related traits, and NA 114 , Shandweel 3 , and Zahar 12 had the best seed quality traits. Furthermore, Shandweel 3 and M 1 A 12 had the highest proportion of seed oil, Shandweel 3 and Zahar 12 had the largest amount of oleic acid, N.A. 114 and RH 1 F 3 had the highest content of linoleic acid, and Zahar 12 and N.A. 114 had the highest proportion of linolenic acid. Seed weight plant -1 can be improved through selecting genotypes having the lengthiest fruiting zone, more branches and capsules, and the high electrical values of seed conductivity, accelerated aging germination as demonstrated by selection criteria. Moreover, the oleic acid proportion had the greatest direct and indirect effect on seed oil content, demonstrating its relevance as sesame oil quality selection criteria. and joint effects, fatty acid compositions, phenotypic and genotypic correlation, Sesamum indicum L. height of the 1 st capsule, number of productive capsules per plant, number of seeds per capsule, biological yield per plant, harvest index, 1000-seed weight, stearic acid, linolenic acid, linoleic acid, oleic acid, palmitic acid, oil content, oil yield per plant and seed weight plant -1 (g). This study indicates the preponderance of an additive gene effect, which will help to make the selection in an early segregating generation. However, high heritabilities coupled with low (less than 10%) expected genetic advance as percent of the mean were recorded for standard germination, root length, shoot length, seedling length, seed vigor index, seedling vigor index, oleic acid, linoleic, total saturated and total unsaturated fatty acids. This indicated that an increased influence of environment on these traits and thus the selection procedures involving progeny testing are recommended for these traits. Similar results were found by Mourad et al. (2019), who recorded that the expected genetic advance ranged from 2.28% for standard germination to 22.31% for seedling dry weight.


Introduction
Sesame (Sesamum indicum L.) is one of the oldest and most significant oilseed crops worldwide, not only in Egypt (Bhattachary et al., 2014). It is a major industrial crop as well as a nutritious food source. There is a significant disparity between oil output and consumption in Egypt. The development of genotypes with high seed and oil yield potential is deemed required to close this significant gap. As a result, much emphasis must be placed on improving the genetic yield of sesame genotypes, which may be achieved by determining the degree of genetic diversity in breeding materials. This information will assist sesame breeders in selecting the best breeding approach for their sesame crop development program. In this regard, Fahmy et al. (2015), Abd EL-Satar et al. (2016), Teilep et al. (2018), Anbanandan (2018), Bhuiyan et al. (2019), Sultana et al. (2019), Pavani et al. (2020), and Abdelsatar et al. (2020) found that significant genetic variability had the greatest effect on improving yield and its components. Furthermore, yield components have a positive impact on seed yield. As a result, investigating the relationship between seed yield and its components, as well as identifying the direct and indirect effects of yield components on seed yield will help in improving it directly. Moreover, Sultana et al. (2019) and Abdelsatar et al. (2020) reported that yield components had a positive effect on seed yield.
Seed germination and seedling vigor are two factors that determine a seed's ability to germinate rapidly and uniformly and develop into healthy seedlings under a wide range of conditions. Farmers' most common difficulties are a low sesame germination rate and poor seedling establishment (Khare and Bhale, 2016). Poor seedling vigor is one of the primary causes of poor germination and irregular seedling establishment (Khan et al., 2017). As a result, seed quality parameters such as germination % and vigor index affect yield by influencing plant population density, which includes field emergence, spatial arrangements, and crop duration (Khare and Bhale, 2016). Therefore, the current investigation was designed to study mean performance, genetic parameters and selection criteria represented in correlation and path analyses at both phenotypic and genotypic levels of some sesame genotypes for agronomic traits and seed quality.

Site description
During the two consecutive summer seasons of 2018 and 2019, a field experiment was conducted at the Experiment Farm of the Kafr-El-Hamam Research Station, Zagazig, Sharkia Governorate, Agricultural Research Center, Egypt (30 o 58 ' N, 31 o 50'E).

Experimental design
The experiment was laid out in a randomized complete block design with three replications. After harvesting wheat in both seasons, each genotype was sown in five ridges with a ridge length of 4 m spaced at 60 cm between ridges and 20 cm from hill to hill. Tested sesame genotypes, i.e. N.A 52 , M 2 A 5 , Shandweel 3 , M 1 A 12 , NA 32 , RH 1 F 3 , NA 114 , RH 6 F 6 , NA 130 , Zahar 12 , H 88 A 2 and M 2 A 24 , were received from the Department of Oil Crops Research, Field Crop Research Institute, Agricultural Research Center, Egypt.

Agricultural practices
Sesame genotype seeds were hand-planted in 60-centimeter-wide ridges at the 20-centimeter spacing between hills. In both seasons, this was done during the first week of June. At 15 days following planting, plants of the sesame genotypes under investigation were thinned to maintain two plants hill -1 . Other cultural practices were used in accordance with the recommendations.

Data collected
Agronomic traits: Days to 50% flowering (days) were recorded on the basis of the number of plants in the plot. Plant height (cm), length of fruiting zone (cm), number of branches plant -1 , number of capsules plant -1 , weight of 1000-seed (g), and seed weight plant -1 (g) were all measured on ten competitive plants randomly selected from the 2 nd and the 4 th ridges. Seed yield per m 2 was determined from plants in each plot's central ridge and converted to seed yield in kg per hectare.
Seed quality: During the 2018 and 2019 seasons, seed quality testing for several seed quality parameters was done at the Seed Technology Research Department, ARC, Giza, Egypt.
Germination test: Seedlings were counted according to ISTA (1993) international criteria based on normal seedlings. The percentage of germination was determined using the Krishnasamy and Seshu's methodology (1990). The seed vigor index (S.V.I.) was computed using Copeland's (1976) formula: S.V.I. = (Number of germinated seeds (first count) / Days to the first count) + (Number of germinated seeds (final count) / Days to final count), with the first count made after 3 days of germination.
Seedling evaluation: According to the rules of the Association of Official Seed Analysis, normal seedlings were used for seedling evaluation (AOSA, 1983). After a six-day germination test, the seedling shoot and root lengths were measured. The shoots and roots were also dried for 72 hours at 70 degrees Celsius. Seedling vigor index was computed using ISTA's (1985) formula: Seedling vigor index = seedling length (cm) × germination percentage.
Accelerated aging: The seeds were maintained in an aging chamber for three days at 45°C and 100% relative humidity. The seeds were dried in the sun after aging, and the percentage survival of the seeds was measured using a standard germination test at 25 degrees Celsius, and the mean normal seedling percentage was computed using AOSA guidelines (1983).
Electrical conductivity test: The electrical conductivity of the leachate was determined using the techniques outlined by ISTA (1999). Fifty seeds of each cultivar were weighed to 0.001g, put in plastic cups with 250 ml of distilled water, and kept at 25 o C for four sub-samples. The electrical conductivity of the leachates was measured using an EC metre after 24 hours. The average values were given in Scm -1 g -1 .
Seed oil content and its quality Crude oil percentage: According to AOSA (2000), crude oil percentage was measured using the Soxhlet apparatus with hexane as the solvent. A Hewlett Packard gas chromatograph model 5890 with a cabowa × Hp 20 M column was used to examine the methyl esters of fatty acids.
Fatty acid compositions: Fatty acid compositions were determined in samples of roughly 50 g of air-dried seeds of each genotype that were picked at random from two replications and finely ground for chemical composition estimation.

Statistical analysis
For all examined traits in field and laboratory trials, an analysis of variance was performed using a randomized complete block design with three replications according to Gomez and Gomez (1984). After confirming that the error variance for the studied traits was homogeneous using the Hartley's (1950) F-max test technique, a combined analysis of variance was conducted over two seasons. Genotypic and phenotypic coefficients of variation were estimated as described by Burton and DeVane (1953). The estimate of broad-sense heritability (h 2 b ) was done by the formula suggested by Hansen et al. (1956). Moreover, the genetic advance as percent of the mean was performed according to Johnson et al. (1955). For the identification of selection criteria, the phenotypic and genotypic correlation coefficient was computed according to Weber and Moorthy (1952). Moreover, phenotypic and genotypic path analysis was computed as described by Dewey and Lu (1959).
Seed quality: Germination traits: The results revealed highly significant differences between sesame genotypes with regard to all studied traits (Table 2). Meanwhile, N.A. 114 (96.67) achieved higher standard germination %, followed by M 2 A 5 (96.17), Shandweel 3 (96.00) and Zahar 12 (95.33) genotypes, respectively. RH 6 F 6 (91.17) and N.A. 32 (92.67), on the other hand, had lower standard germination percentages. These variations in sesame genotypes might be ascribed to genetic impacts on sesame seed germination ability. The seed vigor index findings in Table 2 showed the same normal germination percent patterns, with N.A. 114 (48.33), M 2 A 5 (48.03), Shandweel 3 (48.00), and Zahar 12 (47.89) having the highest seed vigor index. On the other hand, N.A. 32 (44.50) and RH 6 F 6 (44.75) gave the lower value of this trait. These results mostly took the same trend of seed weight plant -1 and its attributes and seed oil content traits. Zahar 12 (80.50) had the greatest value of accelerated aging germination % in Table 2, followed by M 2 A 5 (78.50) and H 88 A 2 (78.00), without any significant differences between them. These results indicated that these genotypes could be tolerant to bad storage or environment conditions. Meanwhile, RH 6 F 6 (62.33) and M 1 A 12 (62.33) had a lower proportion of accelerated aging germination. The electrical conductivity (EC) is more often employed to determine seed vigor of crops because, as seed degradation advances, cell walls become less stiff and more water-permeable, enabling cell contents to escape into solution with the water and increasing electrical conductivity. Shandweel 3 (100.18), Zahar 12 (102.75) and N.A. 114 (103.47) recorded the lower EC values, respectively, without any differences between them (Table 2). However, the high EC values were recorded in H 88 A 2 (134.60), followed by N.A. 32 (124.730). Standard germination percent, seed vigor index, and accelerated aging germination % were among the seed viability and vigor outcomes that were usually in the opposite direction of the forms provided. The results are in agreement with those reported by El Shakhess, Samar et al. (2008), Eraky, Hania et al. (2010) and Ahmed, Fadia et al. (2013).
Seedling traits: On the one hand, the data in Table 2 revealed no significant variations between genotypes in both radical and seedling length traits. Shoot length, seedling dry weight, and seedling vigor index traits, however, showed highly significant variations among genotypes. The longest shoot length was found in Zahar 12 (2.89 cm), followed by N.A. 114 (2.73 cm), N.A. 130 (2.71 cm), Shandweel 3 (2.63 cm), and M 2 A 5 (2.57 cm). Meanwhile, the short root length was given by N.A. 32 (2.41 cm.) and H 88 A 2 (2.42 cm.). The higher seedling dry weight came from M 1 A 12 (8.46 mg), while the lower seedling dry weight came from N.A. 52 (4.86 mg). M 1 A 12 (888.42), N.A. 114 (883.96), Shandweel 3 (872.82), and Zahar 12 (869.14) had the highest seedling vigor index values, whilst H 88 A 2 (784.66) had the lowest. Other traits such as seed weight plant -1 and its attributes, germination, and seedling traits followed a similar trend as these results.
Seed oil content and its quality Again, highly significant differences in seed oil contents and fatty acid compositions were found among examined sesame genotypes (Table 3), suggesting that sesame genotypes have large genetic variability that allows for the successful selection of favorable genotypes. Mohanty et al. (2020) observed similar findings.
According to the sesame breeder, the best genotypes have low total saturated fatty acid compositions along with high total unsaturated fatty acid compositions. Shandweel 3 (7.53 %), followed by M 1 A 12 (7.54 %), had a low percentage of palmitic acids (C16:0), and N.A. 114 (4.22%), followed by N.A. 130 (4.23%), had a low proportion of stearic acids (C18:0). On the other hand, a high proportion of seed oil was detected in Shandweel 3 (60.08%), followed by M 1 A 12 (56.27%). Shandweel 3 (45.90%), followed by Zahar 12 (45.67%), was found to have the highest content of oleic acids (C18:1). The highest proportion of linoleic acids (C18:2) came from N.A. 114 (43.79 %), followed by RH 1 F 3 (43.45%). The highest content of linolenic acids (C18:3) was achieved by Zahar 12 (0.74 %), followed by N.A. 114 (0.72 %). Genetic parameters for agronomic traits and seed quality The phenotypic (PCV) and genotypic (GCV) coefficients of variation, heritability in the broad sense (h 2 b ), and expected genetic advance as percent mean for seed weight plant -1 and its related traits were computed to gain a better understanding of the extent of genetic variability for twelve sesame genotypes, as shown in Table 4. For all traits studied, PCV was slightly greater than GCV, indicating that the environment had a little effect on their expression. In the same line, Bhuiyan et al. (2019) and Abdelsatar et al. (2020) found that the differences between genotypic and phenotypic components of variance were narrow for investigated traits, indicating that phenotypic variation had a large genetic component in nature. Saravanan et al. (2020) also found that seed weight plant -1 , the number of branches per plant, and the number of capsules per plant had higher PCV and GCV values.
Consequently, selection for these traits would be successful in improving these breeding materials. Fruiting zone length, capsule number plant -1 , seedling vigor index and seed oil content had high PCV and GCV, while electrical conductivity, accelerated aging germination, plant height, branch number plant -1 , and seed weight plant -1 had moderate PCV and GCV, while the remaining traits had drastically reduced PCV and GCV.
Most studied traits have high heritability in the broad sense, indicating that a genotype can be recognized by its phenotypic performance, allowing for more effective selection to improve these traits.
As demonstrated in Table 4, heritability estimates combined with expected genetic advance as percent of the mean are usually more effective in predicting genetic gain under selection than heritability estimates alone, as validated by Johnson et al. (1955). High values of heritability coupled with high (more than 20%) values of genetic advance (as % of mean) were detected for fruiting zone length, branch number, capsule number, 1000-seed weight, seed weight plant -1 , palmitic, stearic and linolenic acid contents. As a result of the significance of additive gene effects in the inheritance of these traits, selection for these traits would be successful. In the same sense, Umamaheswari et al. (2019) and Abdelsatar et al. (2020) found that plant height at maturity, number of branches per plant, number of capsules per plant, length of the capsule, number of seeds per capsule, 1000-seed weight, and seed weight plant -1 had high heritability and high genetic advance as percent of the mean. This might be due to additive gene action influencing the expression of these traits; as a result, simple selection would likely be efficient in improving these traits. Moreover, Saravanan et al. (2020) found that the number of branches per plant and 1000-seed weight had a high heritability as well as a high genetic advance as percent of the mean. For days to 50% flowering, plant height, seedling dry weight, electrical conductivity, accelerated aging germination, seed oil content, and total saturated/total unsaturated ratio, high heritability combined with moderate (10-20%) expected genetic advance as percent of the mean were recorded, indicating that these traits appear to be controlled by both additive and non-additive gene actions. The variability study of Mohanty et al. (2020) indicated high to moderate genetic advance as percent of the mean for traits like plant height, days to first flowering, days to 50% flowering, days to maturity, number of productive branches plant -1 , height of the 1 st capsule, number of productive capsules per plant, number of seeds per capsule, biological yield per plant, harvest index, 1000-seed weight, stearic acid, linolenic acid, linoleic acid, oleic acid, palmitic acid, oil content, oil yield per plant and seed weight plant -1 (g). This study indicates the preponderance of an additive gene effect, which will help to make the selection in an early segregating generation. However, high heritabilities coupled with low (less than 10%) expected genetic advance as percent of the mean were recorded for standard germination, root length, shoot length, seedling length, seed vigor index, seedling vigor index, oleic acid, linoleic, total saturated and total unsaturated fatty acids. This indicated that an increased influence of environment on these traits and thus the selection procedures involving progeny testing are recommended for these traits. Similar results were found by Mourad et al. (2019), who recorded that the expected genetic advance ranged from 2.28% for standard germination to 22.31% for seedling dry weight. Genetic variability and selection criteria of sesame for agronomic traits and seed quality 257 Selection criteria Phenotypic and genotypic correlations Seed weight plant -1 and its related traits Phenotypic and genotypic correlations were estimated between seed weight plant -1 and its related traits for 12 sesame genotypes based on the average of 2018 and 2019, as presented in Table 5. Seed weight plant -1 was positively and significantly or highly significantly correlated with its related traits, i.e. days to 50% flowering, plant height, fruiting zone length, branch number, capsule number and 1000-seed weight at phenotypic and genotypic levels. This indicates that selection will be more successful for a long period to 50% flowering, tall height, long fruiting zone length, more branches, more capsules, and the heaviest weight of 1000 seeds.
These findings were confirmed by Roy and Pal (2019), Umamaheswari et al. (2019), and Abdelsatar et al. (2020), who found that the number of branches per plant, number of capsules per plant, number of seeds per capsule, and weight of 1000-seeds per capsule were strongly related to sesame yield.
As a result, these traits may be used to select advanced sesame lines with higher seed yields. Furthermore, these traits might be used as selection criteria for improving sesame seed yield in the future agricultural system. Similarly, Saravanan et al. (2020) indicated that yield per plant had a significant positive correlation with the number of capsules per plant followed by 1000-seed weight, plant height and the number of branches per plant. Furthermore, the positive and significant or highly significant phenotypic and genotypic correlation was detected among the studied traits, i.e. days to 50% flowering, plant height, fruiting zone length, branch number, capsule number and 1000-seed weight at phenotypic and genotypic levels. This demonstrated that selecting for any of the previous traits would immediately enhance the others, particularly seed weight plant -1 . As a result, these traits might be used as indications for achieving desired genetic improvements in sesame seed weight plant -1 .

Seed oil content and its quality
Phenotypic and genotypic correlations were estimated between seed oil content and its contents of fatty acid composition for 12 sesame genotypes based on the average of 2018 and 2019 summer seasons as presented in Table 6. Seed oil content was positively and significantly or highly significantly correlated at both levels with the proportion of stearic and oleic acids on the one hand. On the other hand, a negative and valuable correlation at both levels was observed between seed oil content and the proportion of palmitic acid and linoleic acid. Moreover, fatty acid composition exhibited various trends of association among them. However, a highly significant negative phenotypic and genotypic correlation of the proportion of palmitic acid was detected with stearic acid along with oleic with linoleic and linolenic acids.
While significant positive associations of the proportion of stearic acid with oleic acid content along with the proportion of linoleic acid were noticed, an unsaturated fatty acid with the proportion of linolenic acid at both phenotypic and genotypic levels was observed. In the same sense, Khayambashi and Asadi-Gharneh (2020) showed a negative correlation between saturated and unsaturated fatty acid contents. Moreover, they showed that arachidic acid was positively correlated with stearic acid (r=0.8; p<0.05). In addition, palmitic acid was negatively correlated with oleic acid (r=-0.78; p<0.05). Table 6. Phenotypic (above diagonal) and genotypic (below diagonal) correlations of 12 sesame genotypes for seed oil content and its contents of fatty acid composition across 2018 and 2019. Phenotypic and genotypic path analyses Seed weight plant -1 and its related traits The phenotypic and genotypic path analyses were used to separate phenotypic and genotypic correlations into direct and joint effects, with seed weight plant -1 as a dependent variable and yield-related traits as independent variables, as shown in Table 7  The high positive direct effects of the previously mentioned traits, in addition to their highly significant correlation coefficient with seed weight plant -1 , indicated that the direct selection through these traits would be effective for sesame improvement. Moreover, the direct impacts of fruiting zone length on seed weight plant -1 were negative and insignificant, despite a positive and significant phenotypic and genotypic correlation with seed weight plant -1 . Consequently, the indirect effect of fruiting zone length through plant height (P=0.931, G=1.460) had a positive effect on improving seed weight plant -1 of these materials than direct effect of fruiting zone length.
The high positive phenotypic and genotypic indirect effects on seed weight plant -1 were detected for days to 50% flowering through plant height (P= 0.844, G=1.354 .306) and seedling vigor index (P=0.348, G=1.115) through fruiting zone length, and seedling vigor index via seedling length (P=0.516, G=3.531). It is apparent from the above-mentioned results that the preferred improvement of seed weight plant -1 can be achieved through selecting genotypes having the long fruiting zone length, more branches plant -1 , more capsules plant -1 , the heaviest weight of 1000 seeds, the longest root length, shoot length and seedling length, the heaviest dry weight of seedling and the highest index of seedling vigor. These results agreed with those of Umamaheswari et al. (2019), who reported that the traits of plant height at maturity, number of capsules per plant and number of seeds per capsule directly influenced the seed weight per plant.  Moreover, Saravanan et al. (2020) revealed that the number of capsules per plant had a highly positive direct effect on yield per plant. So, the selection based on these traits such as the number of capsules per plant, plant height, 1000-seed weight and the number of branches per plant would be a benefit for crop improvement. The residual effect at the phenotypic and genotypic levels was 0.268 and 0.170, indicating that independent traits included in the phenotypic and genotypic path analyses explained 73.23% and 82.98% of the total variance in seed weight plant -1 , respectively. The largest residual effects of phenotypic and genotypic path analyses revealed that the existence of other traits not included in the current study was linked with the greatest influence on seed weight plant -1 .

Seed oil content and its quality
The phenotypic and genotypic path analyses were used to split phenotypic and genotypic correlations into direct and joint effects to identify interrelationships between seed oil content and its contents of the fatty acid composition. As indicated in Table 8 and Figure 2, the seed oil content was regarded as a dependent variable, whereas oil proportions of fatty acid composition were considered independent variables.
Oleic acid content had a positive direct impact (P=0.1081, G=2.0683), and there was a correlation at both levels (P=0.615*, G=0.791**). This demonstrates that seed oil content is influenced by oleic acid. Furthermore, oleic acid content has a significantly positive indirect impact via its association with linolenic acid content (P=0.0998, G=0.0649) and stearic acid content (P=0.0779, G=1.9637). These findings suggest that increasing the oleic fatty acid component of these materials effectively increases oil content. The residual effect was 0.378 and 0.426 at phenotypic and genotypic levels, respectively. This indicated that independent variables included in the phenotypic and genotypic path analyses explained 62.17 and 57.43 percent of the overall variance in seed oil content, respectively. The largest residual effects of phenotypic and genotypic path analyses revealed that the existence of other traits not included in the current study was linked with the greatest influence on seed oil content.

Conclusion
In conclusion, all studied traits showed a significant genetic diversity among genotypes, indicating the possibility of improving sesame yield and oil quality. As a result, selection within this population or hybridization among members of this population can result in genetic improvement in seed weight plant -1 and oil quality for assessed genotypes.