Introduction: Cumin (Cuminum cyminum L.), belonging to the family Apiaceae, is one of the most well-known aromatic spices in the world. Iran is also one of the leading producers of cumin globally, but no improved cultivar has yet been introduced to farmers in the country. To introduce new cumin cultivars, it is essential to understand genetic diversity, desirable traits, genotype-environment interactions, and production stability, given the varied climatic conditions across regions. When genotypes are evaluated in different environments, their performance compared to each other varies across environments. A genotype may exhibit the highest yield in some environments, while other genotypes may outperform it in other environments. This variation in the relative performance of genotypes across different environments is referred to as genotype-by-environment interaction (G×E). G×E interaction is a critical issue in plant breeding and plays a significant role in the release and introduction of improved genotypes. The objective of this study was to analyze G×E interactions using AMMI (Additive Main Effects and Multiplicative Interaction) and GGE (Genotype + Genotype-by-Environment) biplot methods to evaluate genotypes, environments, and their relationships, ultimately identifying ideal cumin genotypes with high essential oil percentage and essential oil yield.
Materials and Methods: To assess the stability of essential oil percentage and essential oil yield in 36 cumin genotypes, an experiment was conducted in a randomized complete block design (RCBD) with three replications at four agricultural research stations (Jiroft, Mashhad, Birjand, and Karaj) during the 2022-2023 growing season. Seeds of each genotype were sown on two ridges, with two rows per ridge (each 3 meters long, totaling 4 rows), and a row spacing of 20 cm. At the end of the growing season, plants were harvested at maturity, dried, threshed, and the seeds were separated from the straw. The essential oil percentage was measured using a Clevenger apparatus, and the essential oil yield was calculated by multiplying the seed yield per unit area by the essential oil percentage.
After verifying the assumptions of ANOVA, AMMI, and GGE biplot analyses were performed for essential oil percentage and essential oil yield using GenStat software (Version 12).
Results and Discussion: The results of the combined analysis of variance for the four locations indicated that the effects of environment, genotype, and genotype × environment interaction were highly significant (at the 1% probability level) for both essential oil percentage and essential oil yield traits. Due to the significance of the genotype × environment interaction, the interaction effect was analyzed using AMMI and GGE biplot methods. The genotype × environment interaction analysis revealed that, regarding essential oil percentage, genotype No. 17 exhibited high specific adaptability to Birjand and Jiroft environments. Additionally, genotypes No. 27 and 11 showed high specific adaptability to Karaj and Mashhad regions, respectively. For essential oil yield, genotype No. 27 demonstrated high specific adaptability to the Karaj region, while genotypes No. 3 and 4 were most suitable for the Jiroft region, and genotype No. 30 performed optimally in the Mashhad and Birjand regions. Based on the GGE biplot analysis, genotypes No. 22, 25, 31, and 10 were identified as ideal genotypes for essential oil percentage. For essential oil yield, genotypes No. 30 and 25 were the closest to the ideal genotype. These genotypes can be recommended as parental lines in breeding programs or as superior cultivars for farmers. Given the importance of cumin in medicinal and spice applications, it is essential to have both high yield and high essential oil percentage. The genotypes with the highest essential oil yield possessed both characteristics. Therefore, genotypes No. 30 and 25 were identified as the most ideal genotypes and can be utilized as parents in breeding programs or introduced as new cultivars.
Conclusion: The results of this study demonstrated that genotypes No. 22, 25, 31, and 10 were the most ideal for essential oil percentage. For essential oil yield, genotypes No. 30 and 25 were the closest to the ideal genotype. Considering the significance of cumin in medicinal and spice uses, which requires high yield and high essential oil content, the genotypes with the highest essential oil yield that exhibited both traits were recognized as the most suitable. Thus, genotypes No. 30 and 25 are considered the most ideal genotypes and can be introduced to farmers as stable genotypes with high essential oil percentage and yield. Furthermore, their potential can be effectively exploited as parental lines in breeding programs.