Assessment of genetic diversity for qualitative and quantitative traits in pumpkin (Cucurbita moschata)

Introduction

Pumpkin (Cucurbita moschata Duch. ex Poir.) is one of the important vegetable crops belongs to the family Cucurbitaceae with chromosome number 2n=40. It is an annual, monoecious, climbing vine which is natural amphidiploid and cross-pollinated species which is grown all over the world for nutrition and higher return to the farmers. It is believed that pumpkin have been originated in Central America (Stuart 2004) [11] . Among the five cultivated species, pumpkin (Cucurbita moschata Duch. ex Poir.), summer squash (Cucurbita pepo L.), winter squash (Cucurbita maxima) are of great economic importance (Rana, 2014) [8] . Pumpkin is a nutritious, adaptable food that contains fiber, vitamins, minerals, and antioxidants. Pumpkin's health advantages are primarily related to its fiber content and micronutrients, such as beta carotene and vitamin A (Anonymous 2023) [1] . India occupies a unique position as the second-largest producer of veggies globally, following China. A total of 12.1 lakh hectares of pumpkin were grown, yielding 26.59 metric tons of product. Orissa, Uttar Pradesh, Karnataka, Chhattisgarh, Punjab, Madhya Pradesh, and Andhra Pradesh are among the Indian states with successful cultivation. The nutrient content of 100 g edible pieces of fruit is 90 ml water, 8 g carbohydrate, 1 g protein, 0.5 g fiber, 20 mg calcium, 0.8 mg iron, 210 mg beta-carotene, 0.05 mg thiamine, 0.05 mg riboflavin, 0.5 mg niacin, and 15 mg ascorbic acid (28).

diversity is one of the important pre-requisites for obtaining higher yield through hybridization programme. Morphological diversity testing is the most efficient method for identifying variability across genotypes and forming a heterotic pool. Increased diversity increases the likelihood of enhancing economic characteristics in the program.

Materials and Methods

The experiment material consists of 25 genotypes, including one check variety, Narendra Agrim. The experiment was carried out in a randomized block design with three replications during Zaid 2023 at Main Experimental Station (MES) of Department of Vegetable Science Farm of Acharya Narendra Deva University of Agriculture and Technology, Narendra Nagar (Kumarganj), Ayodhya, which is geographically situated at 25.56° N latitude, 82.12° E longitude and at an elevation of 112m above the mean sea level. This area falls in sub-tropical area of Eastern India. The row to row spacing was 3.0 m apart with a plant to plant spacing of 0.60 m. The duration of experiment was from March to June, 2023 and recommended plant practices were followed to raise the healthy crops. Five guarded plants were selected at random from every genotype from each plot for the assessment of diversity. The observation was recorded on thirteen quantitative and seven qualitative traits. The data were subjected to Mahalanobis D2 statistics as per the Mahalanobis (1936) [3] method, and genotypes were grouped into different clusters following Toucher's method as suggested by Rao (1952) [9] .

Results and Discussion

The statistical analysis of divergence shows significant variation within pumpkin genotypes for all the characters under study. All the 25 genotypes were grouped into five clusters (table 1). The maximum number of genotypes was found in cluster I (9 genotypes), followed by cluster III (8 genotypes) and cluster IV (6 genotypes). The remaining two clusters are monogenotypic. Monogenotypic clustering demonstrates that such genotypes may have a completely different genetic makeup from the other genotypes, resulting in the creation of a unique cluster, whereas genotypes belonging to the same cluster exhibit a close link between them. The intra-cluster distance between 25 genotypes ranged from 0.00 to 122.82 (Table 2). Intra-cluster distance values indicate the closeness of genotypes inside the same cluster. High intra-cluster D2 values indicate greater genetic divergence and variability across genotypes within the same cluster compared to genotypes with an intra-cluster distance of 0.00, indicating monogenotypic and less diverse. Cluster I have the highest intra-cluster distance (122.82), followed by clusters IV (99.05) and III (82.07). Murty and Arunachalam discovered that choosing parents with high genetic diversity for desirable traits significantly impacts hybridization and selection success. This investigation discovered intra-cluster variance in constituent genotypes, which can be used to select parents for recombination breeding.

The average inter-cluster distance between genotypes ranged from 124.18 to 1283.61. Clusters II and V had the maximum inter-cluster distance, followed by clusters I and V, IV and V, III and V. The genotypic composition of cluster pairings in this study consisted of genes from the most distantly related parents, indicating the features under examination. Using genotypes from clusters separated by a high statistical distance can reveal inheritance patterns for pumpkin traits and boost crop production through hybridization. Gongopadhyay et al. (2008) [2] , Nagar et al.

(2017) [5] , Rajput et al. (2021) [7] have all reported similar results. To improve yield and related characteristics in breeding programs, consider cluster means (Table 3) for seed yield per plant and key components when selecting genotypes.

The result revealed that days to 50% flowering were recorded highest mean value for cluster III (61.59) followed by cluster I (60.12), cluster IV (59.58) and lowest in cluster V (51.33). The result revealed that days to node at first male flower appearance were recorded highest mean value for cluster II (6.20), cluster IV ( [6] and Ribeiro et al. (2022) [10] . Table 4 shows the percentage of contribution of 13 characters to the expression of genetic divergence. Fruit yield per hectare had the highest contribution (30.00),

followed by node at first male flower appearance (17.33), fruit length (15.67), flesh thickness (7.67) and lowest for number of fruits per plant (0.33). Node at first male flower appearance 17.33% 3.

Node at first female flower appearance 1% 4.

Inter nodal length (cm) 5.67% 6.

No. of fruits per plant .33% 8.

Average fruit wt. (kg) 6.33% 9.

Fruit length (cm) 15.67% 10.

Fruit diameter (cm) 5.33% 11.

Flesh thickness (cm) 7.67% 12.

Fruit yield per plant (kg) 2.33% 13.

Fruit yield per hectare (q/hec) 30%

Conclusion

This study suggests that selecting parental lines from clusters III (VRPK-2309) for number of fruits per plant, fruit yield per plant, days to 50% flowering, fruit yield per hectare, flesh thickness, fruit diameter and average fruit weight per plant could aid in future breeding programs for desired segregants.

References

1. Anonymous. Pumpkin nutrition review [Internet]. Healthline; c2023 [cited 2024 Aug 2]. Available from: https://www.healthline.com/nutrition/pumpkinnutrition-review
2. Gangopadhyay KK, Gunjeet K, Meena BL. Genetic diversity studies in ash gourd [Benincasa hispida (Thunb.) Cogn.] from Northern India. J Plant Genet Resour. 2008;21(3):206-212.
3. Mahalanobis PC. On the generalized distance in statistics. Proc Natl Acad Sci India. 1936;2:49-55.
4. Murty BR, Arunachalam V. The nature and divergence in relation to breeding system in some crop plants. Indian J Genet. 1966;26:188-198.
5. Nagar A, Sureja AK, Munshi AD, Bhardwaj R, Kumar S, Tomar BS. Heritability, correlation and genetic divergence for different seed traits in pumpkin (Cucurbita moschata). Indian J Agric Sci. 2017;87(11):1519-1523. Available from: https://doi.org/10.56093/ijas.v87i11.75740
6. Narayan K, Verma LS, Agrawal S, Paikra MS, Kar S. Evaluation of ash gourd genotypes grown as an intercrop in coconut garden under Bastar (Chhattisgarh) condition. Asian J Hort. 2011;6(2):439-441.
7. Rajput R, Prakash S, Alam K, Ahmad M, Pandey V, Sonkar S, et al. To assess the genetic divergence among the genotypes in pumpkin (Cucurbita Mochata L.). Ann Hortic. 2021;14(2):133-137.
8. Ribeiro RMP, Pereira CCA, Lins HA, Barboza M, de Carvalho IDE, de Sousa Nunes GHA, Júnior APB. Genetic divergence between pumpkin accessions for morpho agronomic characters. Biosci J. 2022;38(e38002):1981-3163.
9. Stuart ME. All about pumpkins [Internet]. The University of Arizona Cooperative Extension in Yavapai County; 2004 [cited 2024 Aug 2]. Available from: [URL needed]