Morphological characterization of long melon genotypes

Introduction

Melon (Cucumis melo L.), a member of the family Cucurbitaceae, is a highly diverse species exhibiting extensive morphological variation, particularly in fruit characteristics. The species encompasses numerous botanical varieties that differ widely in size, shape, flavour, texture and biochemical composition, making it one of the most polymorphic cultivated cucurbits (Fanourakis et al., 2000; Forouzandeh et al., 2010) [5,6] . Within this complex species, long melon (Cucumis melo var. utilissimus) represents a distinct horticultural type, cytogenetically a diploid with chromosome number, 2n = 2x = 24. It is widely known by several vernacular names, such as tar, kakri, serpent melon, snake melon, oriental cucumber, snake cucumber and Armenian cucumber reflecting its elongated fruit form and diverse regional uses. Long melon is considered as the second most important salad cucurbit after cucumber, valued for its tender texture, refreshing taste and culinary versatility. The genus Cucumis includes more than 50 species (Poonia et al., 2025) [11] underscoring its taxonomic richness. However, classification within C. melo remains complex and sometimes ambiguous (Pitrat et al., 2000); therefore, varieties such as C. melo var. utilissimus require precise morphological and taxonomic characterization to support accurate identification, breeding programmes and germplasm conservation (Poonia et al., 2025) [11] . The phenotypic diversity of long melon was documented through several morphological descriptors, including fruit length, diameter, shape index, rind colour, surface texture, taste, and internal characteristics by Stepansky et al., (1999) [13] . Despite this variability, reliance solely on external morphological traits is often insufficient for distinguishing closely related genotypes. The widespread adoption of high yielding commercial cultivars has accelerated the displacement of indigenous varieties, leading to the loss of valuable local diversity. In this context, the characterization and conservation of long melon genotypes are essential for sustainable utilization, varietal improvement and long term genetic resource management (Ali Shtayeh et al., 2015) [2] . Long melon differs markedly from most cultivated melon types, which typically bear fruits with varied fruit length to width ratios. In many genotypes, fruits grow beyond 50 cm in length and around 5 cm in diameter and immature fruits may appear light green, dark green, or variegated (Merheb et al., 2020) [9] with different depths of ribbing. This pronounced morphological diversity further highlights the genetic complexity and adaptive potential of the variety. Systematic research on the phenotypic characterization of long melon is limited and remains relatively scarce. A comprehensive evaluation of the morphological variability among long melon genotypes is essential to enhance their utility in breeding and conservation. The present study aimed to assess morphological diversity among fifteen long melon genotypes and to analyse the diversity of the key morphological traits.

Materials and Methods

The study comprised evaluation of fifteen long melon genotypes collected from various sources during 2024-2025. A comprehensive set of morphological data was recorded, including traits of flowers, stems, fruits, and seeds. The descriptor list used for this study was based on the predefined morphological characters for melons outlined by Stepansky et al. (1999) [13] , the International Plant Genetic Resources Institute (IPGRI, 2003) [8] and Soltani (2010) [6] .

These descriptors were refined and applied to characterise long melon genotypes, assessing seventeen morphological traits (Table 1). Observations of the characters were recorded from ten plants in the field evaluation study. The immature fruits were harvested from each genotype and the following traits were scored which included fruit shape, fruit length from stem end to blossom end, width at the broadest point, predominant skin colour (covering the largest surface area of the fruit), skin texture, fruit flesh colour, taste, fruit weight and the presence or absence of fruit hair. For the floral data, five plants from each genotype were evaluated for sex type and ovary shape. For stem characterization, hair density was recorded. The genotypes were also harvested upon maturity at which seeds were extracted from the mature fruits and recorded hundred seed weight and number of seeds per fruit. Blackish-green IPGRI (2003) [8] 2 FC Flesh colour 1. White 2.

Pale green Stepansky et al., (1999) [13] 3 T Taste 1. Non sweet 2.

Sweet

Stepansky et al., (1999) [13] 4 FS Fruit size 1. <100 g 2.

150-200 g IPGRI ( 2003) [8] 5 FLWR Fruit length and width ratio

>20 cm IPGRI (2003) [8] 6 FSH Fruit shape 1. Oblate 2.

Elongate IPGRI (2003) [8] 7 ST Skin texture 1. Wrinkled 2.

Ribbed

Stepansky et al., (1999) [13] 8 FH Fruit hairs 1. Presence 2.

Absence Soltani (2010) [6] 9 STY Sex type 1. Monoecious 2.

Andromonoecious

Stepansky et al., (1999) [13] 10 OS Ovary shape

Very long IPGRI (2003) [8] 11 HD Hair density 1. Sparse 2.

Medium 3. Dense

Stepansky et al., (1999) [13] 12 SW Seed weight 1.

3.1-4.0 g IPGRI ( 2003) [8] 13 FR Fruit ribbing 1.

7-Deep IPGRI (2003) [8] 14 BES Blossom end shape 1. Depressed 2. Flattened 3. Rounded 4.

Pointed IPGRI (2003) [8] 15 FB Flesh bitterness 1.

Low bitterness 2. Intermediate 3.

7-High bitterness IPGRI (2003) [8] 16 PC Placenta colour 1. White 2. Green 3. Yellow 4.

99-Other IPGRI (2003) [8] 17 NSPF Number of seeds per fruit 1.

High (> 100) IPGRI (2003) [8]

Results and Discussion

The assessment of the data revealed that out of the seventeen traits studied, five were monomorphic and twelve were polymorphic (Table 2). Five traits such as fruit shape, sex type, flesh bitterness, number of seeds per fruit and stem hair density were monomorphic, showing uniform expression across all accessions. Fruit shape was consistently elongate across all the genotypes and sex type was uniformly monoecious with sparse stem hair density. The characters like flesh bitterness and seed number per fruit were also largely uniform, with all genotypes exhibiting low bitterness and high seed count. These consistent patterns highlight strong monomorphism for the morphological traits within the collected materials. These stable traits are commonly reported in Cucumis melo subsp. flexuosus, where elongated fruit shape, ribbed skin, monoecious sex type, and pubescent ovaries represent stable diagnostic features of the group (Stepansky et al., 1999; IPGRI, 2003) [13,8] . Similarly, the uniform expression of low flesh bitterness and high seed number per fruit aligns with earlier observations in snake melon landraces, which tend to maintain stable qualitative traits under farmer selection (Soltani et al., 2010) [6] . The polymorphic qualitative traits including predominant fruit skin colour, flesh colour, taste, fruit size, skin texture, ovary shape, seed weight, fruit ribbing, blossom end shape, placenta colour, fruit length: width ratio, and fruit hairiness were exhibited measurable diversity, with overall phenotypic variation being substantial, reflecting broad variability among the studied genotypes. Within these traits, the white and pale green skin colour with predominantly ribbed and non sweet pale green fleshed fruits appeared most frequently. Similarly, the ovary shape remained long or very long in most of the genotypes.

The study recorded that the predominant fruit skin colour showed greater variability. Three distinct classes such as white, pale green and green were reported for this trait. Among these, the pale green colour was the most common across the genotypes (86.67%), while green colour fruit with intermediate ribbing was observed only in LM 3 among the genotypes (6.67%). Comparable diversity in fruit skin pigmentation has been reported in Middle Eastern snake melon collections, where white and pale green colours dominate regional landraces (Stepansky et al., 1999) [13] .

The pale green colour flesh non sweet fruits was dominant among the genotypes.

Fruit length to width ratio (FLWR) showed substantial variation, with three distinct classes. This degree of size and proportion variability aligns with the results of Staub et al.

(2004) [12] , who reported wide variation in fruit dimensions among Greek snake melon accessions. The shortest fruits belonging to Class 0 were the least frequent. Class 1 was predominant, representing nearly half of the accessions, while Class 2 accounted for a moderate proportion of genotypes. Most of the genotypes had fruit weight ranging from 150 g to 250 g with rounded blossom end shape. Among the 15 genotypes, placenta colour ranged from white to yellow, and white placenta colour was observed more frequently. Similar patterns of morphological variation in snake melon accessions have been documented in Greece (Staub et al., 2004) [12] and Jordan (Abdel-Ghani and Mahadeen, 2014) [1] , where traditional landraces exhibit broad phenotypic ranges due to natural cross-pollination and limited breeding for uniformity.

Fruit weight (150 g-250 g range) and blossom end shape also exhibited moderate diversity, mirroring patterns documented in Palestinian and Middle Eastern collections (Stepansky et al., 1999; Soltani et al., 2010) [13,6] . Placenta colour ranged from white to yellow, with white being more common; variation in internal fruit colour traits has likewise been reported as moderately polymorphic in multiple studies on C. melo landraces.

Conclusion

The study revealed a combination of highly uniform and markedly variable traits among the long melon genotypes. The traits such as fruit shape, sex type, flesh bitterness, seed number per fruit and stem hair density were predominantly monomorphic, indicating a high degree of genetic uniformity. In contrast, traits including predominant skin colour, flesh colour, taste, fruit size, seed weight, ribbing, skin texture, placenta colour, ovary shape, and the fruit length: width ratio exhibited substantial polymorphism. Overall, the long melon genotypes demonstrated considerable phenotypic diversity, providing meaningful variability for selection, facilitating the identification of promising parental lines, and guiding future breeding strategies for crop improvement.

Acknowledgement

AcknowledgmentWe gratefully acknowledge the College of Agriculture, Vellayani, Kerala Agricultural University, for the support and facilities provided, which made this research possible. We also declare that there are no conflicts of interest associated with this study or its publication.

References

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