Evaluation and Selection of superior cumin ecotypes through quantitative and qualitative traits via multivariate methods under Jiroft climatic conditions

Due to the decrease in rainfall and the need for low-water plants in cultivation patterns, cumin is considered a potential candidate for this purpose. Cumin (Cuminum cyminum L.) is one of the oldest and most economical plants, are cultivated due to its high tolerance to drought in Mediterranean climates. It is currently the second most commonly used spice in the world, after pepper (Pepper nigrum), making its cultivation important. This research was conducted to determine the superior ecotypes of cumin in terms of earliness, quality traits, and yield in southern Kerman.

To evaluate cumin ecotypes in the collection of the National Plant Gene Bank of Iran, 64 ecotypes were selected and planted. These ecotypes were evaluated during the 2021-2022 season based on a statistical design of a simple lattice (8x8) with two replications at the Southern Kerman Agricultural and Natural Resources Research and Education Center. The study recorded traits such as date of umbel appearance, date of flowering, date of end of flowering, date of physiological maturity, number of umbels per plant, number of umbellets per umbel, number of grains per umbellets, number of grains per umbel, number of grains per plant, thousand-grain weight, biomass, grain yield, essential oil percentage, and essential oil yield.

Descriptive statistics showed that the traits with the highest coefficient of variation were grain yield, biomass, essential oil yield, and number of grains per plant, with values of 43.01, 40.32, 39.22, and 31.31, respectively. These traits have a high potential for use in cumin selection programs. The ANOVA results indicated that the effect of cumin ecotypes was significant in all studied traits, indicating a high diversity among the ecotypes. The study of the days to maturity trait showed that the earliest ecotypes, with an average of 123, 124, and 125 days, were TN 135, TN143, TN150, TN131, TN136, TN132, TN148, and TN53. These ecotypes have a shorter growth period and can avoid stress at the end of the growing season. TN178, TN141, TN180, TN150, TN16, TN15, TN17, TN81, TN113, and TN124 were found to have the highest grain yield per square meter, with an average of 178, 165, 165, 145, 139, 137, 135, 127, 125, and 120 g/m2, respectively, exceeding the control treatments. These ecotypes have a high potential for use in breeding programs. There was a positive and significant correlation between grain yield and all components of grain yield, indicating that improving each yield component results in an increase in grain yield. A negative and significant relationship was found between essential oil percentage and grain yield and biomass. This suggests that ecotypes with high grain yield have a lower essential oil percentage. However, because there was a positive and significant correlation between essential oil yield and grain yield, ecotypes with high grain yield also had a higher essential oil yield. To group and select the superior ecotypes, it is necessary to use multivariate methods, such as factor analysis and SIIG method, which were used in this research. In the factor analysis method, the top group consists of five ecotypes (TN141, TN15, TN16, TN17, and TN51). Based on the SIIG index, six cumin ecotypes (TN-178, TN-180, TN-16, TN-150, TN-15, and TN-141) were placed in the top group. A comparison of the two methods revealed that three cumin ecotypes were common, indicating their high efficiency in selecting the best ones. However, the SIIG method was found to be superior as it groups the genotypes according to desirable traits (such as low values for day to umbel appearance and days to maturity), whereas these traits are not considered in multivariate analysis methods like factor analysis.

Based on the results and the observed diversity of traits, it is recommended to introduce grain yield, biomass, grains number per plant, and essential oil yield as suitable traits for selecting superior cumin ecotypes. It can be concluded that TN-178, TN-180, TN-16, TN-150, TN-15, and TN-141 ecotypes are superior and have potential for breeding programs, considering both desirable and undesirable traits.