An Evaluation of the Relationship between Seed Yield and Oil Percentage with Some Important Agronomic Traits in Sesame by Using Path Analysis and Principal Component Analysis

Sesame (Sesamum indicum L.) is considered as the queen of oilseeds for its high oil quality. Sesame oil is rich in micronutrients, antioxidants and essential amino acids as well as polyunsaturated fatty acids. Proper understanding of the relationship between grain yield and its components can significantly improve the performance of the breeding program through the proper use of selection indicators. In order to determine the relationship between the seed yield and oil percentage with some important agronomic traits, and to find the direct and indirect effects of important agronomic traits on both seed yield and oil percentage and also select best genotypes in terms of different traits, 91 sesame genotypes (received from botanical gene banks of Germany, Canada and Australia) were studied based on an augmented design with 3 checks (Oltan, Yellow white, Naz tak shakheh) at seed and plant improvement institute, Karaj, Iran in 2016. 17 agronomic traits including flowering date, maturity date, first capsule height from surface of earth, height of plant, number of branches, number of capsule per branches, number of capsule per main stem, number of total capsule per plant, seed number per capsule, seed weight per capsule, 100-seed weight, capsule weight, capsule diameter, capsule length, oil percentage, biological yield and seed yield were studied. The results of simple correlation indicated that seed yield per plant had a high correlation with total number of capsules per plant, number of capsules in branches, biological yield, number of capsules per main stem and plant height. Also 100 seed weight, seed yield per plant, number of capsules per main stem, number of capsules per plant and seeds weight per capsules were in a high correlation with oil percentage. The result of path analysis showed that the number of capsules per plant, number of capsules per branch, biological yield and capsule length exerted the greatest positive effects on seed yield and therefore suggest that they can used as selection criteria in seed yield improvement. Also seeds weight per capsule, capsule length, seed yield and number of capsules per main stem exerted the greatest positive effects on oil percentage. The results of principal component analysis showed that 6 components comprised 82.77 % of the total variations in genotypes. In the first components of this study biological yield, seed yield, capsule weight, number of capsules in the branches and number of capsules per plant had high positive coefficients. The number of seeds per capsule, the seed weight of a capsule and the weight of a capsule had the highest coefficients in the second component. In the third component, the traits of the day to the beginning of flowering and the day to the beginning of the maturity had the highest positive coefficients and the height of the plant had a high negative coefficient. In the fourth component, the weight of 100 seeds, oil percent and seed weight per capsule had the highest positive coefficients and the height of the first capsule from the ground surface had the highest negative coefficient. The fifth component, including oil percent, capsule length and height of the first capsule from the ground had positive coefficients and the numbers of capsules in the main branch were negative. Finally, the sixth component included the number of seeds per capsule and the number of capsules in the main branch with positive and 100-seed weight and the height of the first capsule from the surface with negative coefficients. Lao hong zhi ma and Black c-2-c, Dulce 101/87 and Bukbak had the highest yield in component 1 and 2 biplot. The genotype number 79, with the name of White c323-2, had a good relative yield and also a good relative seed oil content. In addition, genotypes number 79 and 51, with the names of White c323-2 and Local 123, have a good relative yield and also relatively early. Finally, genotype number 49, with the name of Lao hong zhi ma, had the highest relative yield and seed number per capsule. For improvement of each component, we must pay attention to the related traits because gene or genes which control number of capsules per plant, probability control biological yield, capsule weight and other significant traits in this component too, and the component or gene which control this traits is similar gene or factor. By identifying these phenological and morphological patterns that effective in the structure of sesame and determining the relationships between them, breeders can use them in future programs.