Morphological evaluation of long-day onion (Allium cepa L.) cultivars for identification and commercialization

Document Type : Original Article

Authors

Seed and Plant Certification and Registration Institute (SPCRI), Agricultural Research, Education and Extension Organization (AREEO), karaj, Iran

10.22034/plant.2026.145369.1193

Abstract

Introduction: Onion (Allium cepa L.) with chromosome number (2n=2x=16) is a bulbous crop, belongs to Alliaceae family and order Asparagales. It is the second most lucrative vegetable crop globally, after tomato. A detailed understanding of phenotypic variation is required to improve breeding efficiency and trait selection. Testing for distinctivness, uniformity, and stability (DUS) is required prior to the release for protection of novel cultivars' intellectual property rights. Furthermore, detailed morphological assessment is required to discover the distinguishing characteristics of each cultivar.
Materials and Methods: Experiment was conducted in the spring and summer (2023/2024) at the Seed and Plant Certification and Registration Institute (SPCRI), Agricultural Research Education and Extension Organization (AREEO) in Karaj, Iran, using a complete randomized block design with two replications. This study conducts a detailed examination of the DUS morphological features of twelve onion hybrid cultivars, using quantitative and visual characteristics to identify and commercialization/registeration biological differences. A modified UPOV (The International Union for the Protection of New Varieties of Plants) descriptive term list was used to explore thirty-twoss features of diverse organs such as plant, foliage, leaf, pseudostem, and bulb qualities. The DUS test was developed to identify, organize, and protect commercial cultivars having specific superior traits. The Spearman rank correlation analysis was performed to determine the correlations between various DUS traits. Principal component analysis (PCA) was applied on 26 polymorphic test traits to determine their primary traits. The phenotypic data were further used for calculating standardized Euclidean distance matrix and constructing dendrogram using SR Plot website.
Results: PCA and clustering revealed considerable genetic difference among long-day onion cultivars. The eigenvalues associated with the main components reflect their relevance to specific traits. The PCA results showed that the first seven main components, which had eigenvalues greater than one, collectively accounted more than 90.64% of the overall variability observed in 12 cultivars for DUS characteristics. The first two components accounted for 51.30% variability. PC1 accounted for 30.96% variability, and PC2 for 20.40%. Correlation analysis revealed the highest positive correlation between color of the bulb base dry skin and hue of color of dry skin on the bulb (r=0.97), and the highest negative correlation between bulb diameter and height/diameter of the bulb (r=-0.76).
Ward clustering based on usual Euclidean distances for the polymorphic morphological markers grouped the cultivars into four major clusters, indicating the high diversity level present among the cultivars. This analysis revealed three multi- and one mono-genotypic clusters of the cultivars. Cluster I had two cultivars (Hitit and Kilgarsalan). Cluster II had one cultivar (White Valencia) and cluster III had four cultivars (Belmar, Calista, Tucanon and PX07713119). Cultivars like Red Amposta, MT120, Dolaney, Redmoon and Surin were grouped in cluster IV
Conclusion: The study identified genetically diverse cultivars, establishing a solid foundation for targeted selection and breeding. The findings offer critical insights for selecting high-performing genotypes appropriate for cultivation and emphasizes the significance of thorough phenotyping in revealing the genetic capabilities of long-day onions and designing crop improvement programs for sustainable agriculture and food security.

Keywords

References

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