Morpho-agronomic characterization of hybrid melon (Cucumis melo L.) cultivars based on qualitative and quantitative traits in open field

Extended Abstract
Background & Introduction
Melon (Cucumis melo L.) with chromosome number (2n=24) is a globally popular horticultural crop known for its remarkable morphological and agronomic diversity. A detailed understanding of phenotypic variation is required to improve breeding efficiency and trait selection. Testing for distinctness, uniformity, and stability (DUS) is required prior to the release for protection of plant breeders' 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. However, commercial varieties in Iran remain poorly characterized. This study conducts a detailed examination of the modified DUS morphological features of fifty melon hybrid cultivars, using quantitative and qualitative characteristics to identify and commercialization biological differences. A modified UPOV (The International Union for the Protection of New Varieties of Plants) descriptive term list was used to explore thirty features (18 quantitative and pseudo- quantitative and 12 qualitative) of diverse organs such as plant, leaf, fruit, and seed qualities. The DUS test was developed to identify, organize, and protect commercial cultivars having specific superior traits. The Pearson correlation analysis was performed to determine the correlations between various DUS traits. A TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) algorithm was designed to establish a comprehensive multi-criteria decision-making model. Using this model, the breeding potential of fifty hybrid melon cultivars was assessed and ranked.
Results
The pooled Variance Analysis (ANOVA) over the two years revealed significant differences among cultivars (p>0.05). According upon the modified DUS features of the investigated melon cultivars, the fruit warts was detected with no variance across all melon commercial cultivars. A pair-wise examination of the Pearson correlation coefficients of the 12 quantitative DUS testing traits revealed certain quantities were rather independent, whereas others grouped due to a considerably tight positive or negative significant correlation. Correlation analysis revealed the highest positive correlation between time of male flowering with time of female flowering (r= 0.80) and seed width with time of fruit ripening (r= 0.65) and time of male flowering with time of fruit ripening (r= 0.64), and the highest negative correlation between petiole length with fruit flesh thickness (r= -0.54). Based on the TOPSIS multidimensional evaluation model, for 12 DUS testing traits and economic DUS traits (fruit trats) five germplasm resources with excellent comprehensive performance, including Bahram, Ashoor, Iran, Dargazi93, Barang and Bahram, Ashoor, Iran, Selena, Barang, were screened, respectively. It is worth noting that these superior plants generally showed synergistic advantages of key traits rather than extreme performance of a single trait, which provided core materials and multi-trait synergistic optimization for the collaborative breeding of evaluated traits in C. melo. Cluster analysis categorized melon cultivars into three and four major groups based on quantitative and also qualitative and pseudo- qualitative traits, respectively.
Conclusion
These findings suggested that these methods could benefit future investigations, particularly for large-scale analyses of cultivars plenty. These findings highlight key morphological features for varietal classification and breeding, and provide a phenotypic framework for future genetic studies of melon in Iran.