Performance assessment of onion (Allium cepa L.) genotypes based on growth, yield attributes and bulb quality

Introduction

Onion (Allium cepa L.), a bulbous crop belonging to the family Alliaceae, is one of the most extensively cultivated vegetable-cum-spice crops worldwide and constitutes an indispensable component of human diets owing to its distinctive flavour, aroma, storability and wide culinary applications. It is consumed in fresh, cooked and processed forms and plays a vital role in daily food preparation across cultures. In addition to its culinary importance, onion possesses considerable nutritional and medicinal value, as the bulbs are rich in carbohydrates, vitamins, minerals and sulphur-containing compounds that exhibit antioxidant and health-enhancing properties (Griffiths et al., 2002; Patil et al., 2016) [10,16] . Owing to its wide adaptability, onion is cultivated across diverse agro-climatic regions ranging from temperate to tropical zones. India is the second largest producer of onion, cultivating the crop over 16-19 lakh hectares with a production ranging from 242.44 to 289 lakh tonnes [Department of Agriculture and Farmers' Welfare (2024)]. The national average productivity ranges between 15 and 20 t ha⁻¹ (NHB, 2023), which remains lower than that of countries such as the Netherlands and the United States, where yields often exceed 40-50 t ha⁻¹ due to the adoption of hybrid cultivars and advanced production technologies (Brewster, 2008; Havey, 2013) [12] . Globally, onion is cultivated on about 5.2 million hectares with an annual production exceeding 100 million tonnes, highlighting its importance as a major vegetable crop (FAO, 2023). Despite its significance, onion productivity and quality exhibit wide variation due to genetic diversity and environmental influences. Growth traits such as number of leaves and plant height affect photosynthetic efficiency and biomass accumulation, while yield attributes including bulb size, bulb weight and harvest index largely determine economic yield (Havey, 1999; Falconer and Mackay, 1996) [11,7] .

In recent years, quality characteristics such as total soluble solids, sugars, pungency and antioxidant compounds have gained importance owing to changing consumer preferences and increased nutritional awareness (Goldman et al., 1996; Slimestad et al., 2007) [9,25] . Since these traits are quantitatively inherited and influenced by genotype × environment interactions, systematic evaluation of onion genotypes is essential. Therefore, the present study was undertaken to assess thirty onion genotypes for growth, bulb yield and quality traits with the objective of identifying superior genotypes suitable for cultivation and future improvement programmes.

Materials and Methods

The experiment was conducted during the Rabi season of 2022-23 at the Vegetable Block, College of Horticulture, Anantharajupeta, situated in the Southern Agro-climatic Zone of Andhra Pradesh, India (13°09′ N latitude, 79°32′ E longitude) at an elevation of 162 m above mean sea level. The soil of the experimental field was sandy loam, well drained and neutral in reaction (pH 7.2). Thirty onion (Allium cepa L.) genotypes comprising white and red bulb types were used in the present study. The genotypes were procured from ICAR-Directorate of Onion and Garlic Research (DOGR), Pune and ICAR-Indian Institute of Horticultural Research (IIHR), Bengaluru. The list of genotypes along with their sources is presented in Table 1. The experiment was laid out in a Randomized Block Design (RBD) with 30 genotypes as treatments and two replications. Each plot measured 1.5 m × 1.0 m and seedlings were transplanted at a spacing of 30 cm × 15 cm. Seeds of all genotypes were raised in pro-trays under greenhouse conditions during the third week of November 2022. The seedlings germinated within 10-14 days and were transplanted into the main field during the second week of January 2023. Healthy and uniform seedlings were selected for transplanting. Light irrigation was applied immediately after transplanting to ensure proper establishment. The field was prepared to fine tilth by ploughing and harrowing. Well-decomposed farmyard manure @ 20 t ha⁻¹ was incorporated during final land preparation. A recommended fertilizer dose of 100:50:50 kg N:P₂O₅:K₂O ha⁻¹ was applied, with the full dose of phosphorus and potassium and half of nitrogen as basal and the remaining nitrogen in two equal splits at 30 and 45 days after transplanting. Irrigation was provided at 7-10-day intervals during early growth and 5-6-day intervals during bulb development. Irrigation was stopped 10-12 days before harvest. All intercultural and plant protection practices were followed as per the recommendations. Harvesting was done manually when plants showed yellowing and bending of tops. Bulbs were harvested genotype-wise and replication-wise and cured in the field for 3-4 days. Observations on the growth traits i.e., plant height and the number of leaves were recorded from five randomly selected plants in each replication 60 DAT and at the time of harvest. Yield attributing traits viz., bulb weight (g), equatorial bulb diameter (mm), polar bulb diameter (mm), per cent double/splits, neck thickness (mm), average weight of 10 bulbs (kg), bulb yield per plot (Kg) and harvest index (%) were recorded from five randomly selected bulbs after harvest. Whereas, Quality traits viz., TSS ( O Brix), Total sugars (%) using Anthrone method suggested by Ranganna (1986) [20] , Ascorbic acid content in bulb (mg 100g -1 ) using titrimetric method by Srivastava and Kumar, (2005), Total phenols in bulb (mg 100g 1 ) by Singleton et al. (1999), Anthocyanin content (mg 100g -1 ) by spectrophotometric method given by Ranganna (1986) [20] , Pyruvic acid content (µ moles/gram fresh weight) (Anthon and Barrett (2003) [1] . The data recorded for growth, yield and quality traits were subjected to statistical analysis following the procedures appropriate for a Randomized Block Design (RBD). Analysis of variance (ANOVA) was carried out to test the significance of differences among the onion genotypes. The significance of treatment effects was evaluated at the 5% level of probability. Standard error of mean (SEm) and critical difference (CD) values were computed to compare treatment means wherever the F-test was found significant. All statistical analyses were performed using standard statistical methods.

Results and Discussion

The mean performance of genotypes in onion is the average expression of important traits and mean performance of genotypes is a key criterion for selecting high-yielding, good quality and widely adapted varieties, forming the foundation for genetic improvement and variety development. The mean performance of 30 genotypes of onion for various vegetative, yield and quality traits are described under below.

Plant growth traits

The growth parameters, namely number of leaves and plant height at 60 days after transplanting (DAT) and at harvest, exhibited significant variation among the thirty onion genotypes, indicating the presence of considerable genetic variability. The number of leaves at 60 DAT ranged from 4.69 to 7.00, with a general mean of 6.17 leaves per plant. [3] ; Dangi et al. (2018) [5] and Prakash et al. (2022) [17] noticed the similar results. [19] ; Behera et al. (2017) [3] ; Dangi et al.

(2018) [5] ; Bal et al. (2019) [2] ; Rahaman et al. (2021) [18] ; Rashid et al. (2021) [21] and Prakash et al. (2022) [17] , respectively. [5] ; Bal, et al. (2019) [2] and Islam et al. (2019) [22] .

Conclusion

The present study revealed substantial variability among onion genotypes for growth, bulb yield and quality traits. Bhima Shakti and Bhima Dark Red emerged as superior genotypes for yield and quality attributes, respectively. These genotypes may be recommended for cultivation and can serve as valuable genetic resources for onion improvement programmes.

References

1. Anthon GE, Barrett DM. Modified method for the determination of pyruvic acid with dinitrophenylhydrazine in the assessment of onion pungency. J Sci Food Agric. 2003;83(12):1210-3.
2. Bal S, Singh SR, Kumhar SR. Genetic variability in onion genotypes for growth and yield traits. Indian J Hortic. 2019;76:123-9.
3. Behera TK, Mandal J, Mohanta S, Padhiary AK, Behera S, Behera D, et al. Assessment of growth, yield and quality of onion genotypes under red and laterite zone of West Bengal. J Pharmacogn Phytochem. 2017;6(6):493-7.
4. Brewster JL. Onions and other vegetable alliums. 2nd ed. Abingdon: CABI; 2008.
5. Dangi R, Kumar A, Khar A. Genetic variability, heritability and diversity analysis studies in short day tropical onion (Allium cepa L.). Indian J Agric Sci. 2018;88(6):140-9.
6. Department of Agriculture and Farmers' Welfare. Horticultural statistics. Ministry of Agriculture and Farmers' Welfare, Government of India; 2024.
7. Falconer DS, Mackay TFC. Introduction to quantitative genetics. 4th ed. London: Longman Group Ltd; 1996.
8. Food and Agriculture Organization of the United Nations. FAOSTAT statistical database. Rome: FAO; 2022.
9. Goldman IL, Havey MJ, Schauer D. Genetic control of pungency in onion (Allium cepa L.). J Am Soc Hortic Sci. 1996;121(5):815-8.
10. Griffiths G, Trueman L, Crowther T, Thomas B, Smith B. Onions-A global benefit to health. Phytother Res. 2002;16:603-15.
11. Havey MJ. Onion breeding. In: Kalloo MJ, Bergh BO, editors. Breeding vegetable crops. Wallingford: CAB International; 1999, p. 35-50.
12. Havey MJ. Onion breeding. In: Janick J, Editor. Plant breeding reviews. Hoboken: Wiley-Blackwell; 2013, p. 39-85.
13. Lakshmi RR. Studies on genetic variability, correlation and path analysis of yield and yield components in onion. J Hortic Sci. 2015;10(2):237-241.
14. Lu X, Wang J, Al-Qadiri HM, Ross CF, Powers JR, Tang J, et al. Determination of total phenolic content and antioxidant capacity of onion (Allium cepa L.) and shallot (Allium cepa var. aggregatum). J Food Compos Anal. 2011;24(8):1059-65.
15. National Horticulture Board. Indian horticulture database. Ministry of Agriculture & Farmers Welfare, Government of India; 2023.
16. Patil BT, Kale PB, Suryawanshi YB. Nutritional and medicinal importance of onion (Allium cepa L.). Int J Agric Sci. 2016;8(58):3167-3170.
17. Prakash S, Singh B, Kumar V, Kumar A, Kumar M, Singh J, et al. Correlation and Path Coefficient analysis in Onion (Allium cepa L.) Germplasm under Western Uttar Pradesh Conditions. J Theor Biol Forum. 2022:21-6.
18. Rahaman S, Mandal J, Saha D, Mohanta S. Varietal screening of short day onions (Allium cepa L.) under Coastal Saline Area. Agric Sci Dig. 2021;41:181-5.
19. Rajya Lakshmi R. Genetic variability and character association studies in onion. Indian J Agric Res. 2015;49:234-239.
20. Ranganna S. Handbook of Analysis and Quality Control for Fruit and Vegetable Products. New Delhi: Tata McGraw Hill; 1986, p. 190-210.
21. Rashid MH, Islam AKMA, Mian MAK, Hossain T, Kabir ME. Multivariate analysis in onion (Allium cepa L.). Bangladesh J Agric Res. 2012;37(4):573-582.
22. Islam SI, Khar A, Singh S, Tomar BS. Variability, heritability and trait association studies for bulb and antioxidant traits in onion (Allium cepa) varieties. Indian J Agric Sci. 2019;89(3):450-457.
23. Singh SR, Ahamed N, Srivastava KK, Kumar D, Yousuf S. Assessment of genetic divergence in long day onion (Allium cepa L.) through principal component and single linkage cluster analysis. J Hortic 2020;15(1):17-26.
24. Singleton VL, Orthofer R, Lamuela-Raventos RM. Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Methods Enzymol. 1999;299:152-178.
25. Slimestad R, Fossen T, Vagen IM. Onions: A source of unique dietary flavonoids. J Agric Food Chem. 2007;55:10067-80.
26. Srivastava RP, Kumar S. Fruit and Vegetable Preservation: Principles and Practices. Lucknow: International Book Distributing Co.; 2007, p. 217-21.