Document Type : Research Paper

Authors

• Najmeh Hadi ¹
• Faezeh Daryaei ²
• Mahdi Yahyazadeh ²
• Samaneh Asadi Sanam ²

¹ Medicinal plants and by-products devision- Research Institute of Forests and Rangelands- Agricultural Research, Education and Extension

² Medicinal Plants and By-products Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO)

Abstract

     Background and Objectives: Phenological studies are essential for developing agronomic management practices, production strategies, and plant breeding programs. Nepeta L. is one of the largest genera in the family Lamiaceae, and Iran is one of its major centers of origin and diversity. Given the importance of this genus and the reported biological activities of its specialized metabolites, investigating national germplasm collections is important for their future use in breeding and crop management programs. The present study investigates phenological diversity and the timing and rate of reproductive structure formation under ex situ conditions in 21 populations of N. kotschyi Boiss. This species was selected for potential breeding and cultivation based on previous research by the first author, which evaluated flowering shoot production in terms of rate and frequency, as well as the quantity and quality of its phytochemical compounds, including essential oil and phenolic compounds. The present study contributes to the broader research needed to support the future breeding and cultivation of this species.
Methodology: Twenty-one populations of Nepeta kotschyi, representing two varieties, var. kotschyi and var. persica, were cultivated in a field in western Tehran to minimize environmental effects on the evaluations. Phenological observations were conducted during the second year of cultivation, following the onset of growth in early March. The phenological stages assessed included vegetative growth, budding, three successive stages of bud development, and flowering.
To quantify the rate of formation and development of reproductive structures, measurements were taken at two time points: Phase 1, 40 days after the onset of growth, and Phase 2, at the stage when more than 75% of the plants were flowering. The timing of Phase 2 was determined by recording the number of days elapsed since the onset of growth. At both phases, the average plant area and height were measured, and plant volume was estimated by multiplying these two measurements. The proportions of total plant volume occupied by vegetative and reproductive structures were then calculated for each phase. The rate of reproductive structure formation and development was calculated as the change in the proportion of reproductive structures between Phase 1 and Phase 2, divided by the number of days elapsed between the two phases. The resulting rate was expressed as a percentage per day (% day⁻¹). Cluster analysis was performed to identify the contributions of individual phenological traits to variation among populations, while principal component analysis (PCA) was used to characterize and group the populations based on their phenological traits.
Results: The results revealed significant differences among populations in the timing of growth and developmental stages, allowing them to be classified into three flowering groups: early-, intermediate-, and late-flowering populations. Although all populations were cultivated under the same environmental conditions, their distinct growth patterns suggest a substantial genetic contribution to the regulation of phenological development. The Kohgiluyeh and Boyer-Ahmad (Kb and K), Ardakan 2, and Ardakan 3 populations were identified as the most promising populations in terms of reproductive development, exhibiting the highest flowering percentages within the shortest periods. The occurrence of plants with markedly different flower colors and developmental stages within the same population, as observed in the Bafgh and Ardakan 3 populations, suggests the presence of considerable within-population diversity that could provide valuable genetic resources for future breeding programs. Cluster analysis classified the populations into four groups based on their phenotypic and phenological characteristics. Bootstrap analysis (100 replicates) supported the separation of the Isfahan and Kohgiluyeh and Boyer-Ahmad populations from those originating from Yazd, Khorasan, and Chaharmahal and Bakhtiari. Populations in Groups 1 and 2 were characterized by early flowering, whereas Group 3 consisted of late-flowering populations. Group 4, which contained the largest number of populations, encompassed all three flowering patterns, with intermediate-flowering populations being the most prevalent. The results of principal component analysis (PCA) were consistent with those of cluster analysis. The first two principal components explained 82.49% of the total variation among the studied populations.
Conclusion: This study revealed structured variation in the growth patterns of N. kotschyi populations and provided a valuable basis for the systematic use of this diversity in agricultural, medicinal, and conservation programs. These findings can support the selection of superior genotypes for developing improved cultivars, the sustainable management and conservation of genetic resources, and the enhancement of cultivation productivity for this valuable medicinal plant.

Keywords

• Nepeta kotschyi
• cultivation
• diversity
• phenology
• ex situ

Main Subjects

• Improvement and breeding