Evaluation of seed priming treatments for improving germination and seedling vigour in onion (Allium cepa L.)

Introduction

Onion (Allium cepa L.; 2n = 16) is one of the most important bulb vegetable crops belonging to the family Amaryllidaceae. It is cultivated extensively throughout temperate, subtropical, and tropical regions and is valued for its culinary, nutritional, medicinal, and economic importance. Onion bulbs are rich sources of carbohydrates, dietary fibre, vitamins, minerals, flavonoids, phenolic compounds, and sulphur-containing metabolites that impart their characteristic flavour, pungency, antioxidant activity, and health-promoting properties. Successful onion production largely depends on rapid and uniform seed germination and vigorous seedling establishment, both of which can be enhanced through appropriate seed enhancement techniques (Yanchenko et al., 2024) [11] . Improved seed quality and early seedling vigour have also been reported to contribute to better crop establishment and productivity under field conditions (Afifa et al., 2024) [2] . India is the second-largest producer of onion globally and occupies a prominent position in its cultivation and export. Despite the large cultivation area, onion productivity is often limited by poor crop establishment resulting from low seed vigour, uneven germination, and rapid deterioration of seed quality during storage. Onion seeds are naturally short-lived because of their high oil content, delicate seed coat, and susceptibility to oxidative damage, membrane deterioration, and lipid peroxidation. Consequently, seed viability and vigour decline rapidly under conventional storage conditions, leading to poor field emergence, non-uniform crop establishment, and ultimately reduced bulb yield and quality (Singh et al., 2018) [9] . Several investigators have reported positive effects of seed priming on onion and other vegetable crops. Pagano et al., (2023) [7] reviewed recent advances in seed priming for onion and related Allium species and highlighted its role in improving germination, seedling establishment, and stress resilience. Naveenkumar et al., (2023) [6] observed significant improvements in germination and seed vigour following different priming treatments in onion. Das and Prabha (2025) [3] reported that appropriate priming treatments effectively mitigated seed ageing effects and enhanced germination and vigour. Likewise, Vij et al., (2025) [10] demonstrated that GA₃-mediated priming improved physiological processes associated with germination, resulting in superior seedling growth and vigour. Collectively, these studies confirm that seed priming enhances metabolic efficiency, antioxidant defence, and reserve mobilization, thereby improving seed quality and early crop establishment. Therefore, the present investigation was undertaken to comparatively evaluate different hormonal, nutrient, organic, and biological seed priming treatments for their effects on germination, seedling growth, and vigour of onion under laboratory conditions. It was hypothesized that appropriate seed priming would enhance pre-germinative metabolic processes, leading to improved germination, vigorous seedling growth, and superior seed physiological quality compared with untreated seeds. The findings of the present study are expected to provide a scientific basis for recommending an effective and economically feasible seed priming technique for improving onion seed quality and ensuring rapid, uniform crop establishment.

Materials and Methods

Experimental site

The laboratory experiment was conducted during 2025-26 at Department of Horticulture, S.K.N. College of Agriculture, Sri Karan Narendra Agriculture University (SKNAU), Jobner, Jaipur, Rajasthan, India. The experiment was performed under controlled laboratory conditions to ensure uniformity during seed germination and seedling growth evaluation. The experiment was laid out in a Completely Randomized Design (CRD) comprising 13 treatments with 3 replications. Each replication consisted of 100 seeds.

Table 1: Treatment details with their symbols

Treatment Description T₀ Unprimed control T₁ GA₃ @ 100 ppm for 6 h T₂ GA₃ @ 100 ppm for 12 h T₃ KNO₃ @ 1% for 6 h T₄ KNO₃ @ 1% for 12 h T₅ Humic acid @ 0.05% for 6 h T₆ Humic acid @ 0.05% for 12 h T₇ Biochar extract @ 3% for 6 h T₈ Biochar extract @ 3% for 12 h T₉ Trichoderma viride @ 10 g kg⁻¹ seed for 6 h T₁₀ Trichoderma viride @ 10 g kg⁻¹ seed for 12 h T₁₁ Pseudomonas fluorescens @ 10 g kg⁻¹ seed for 6 h T₁₂ Pseudomonas fluorescens @ 10 g kg⁻¹ seed for 12 h

The concentrations and soaking durations were selected based on previous studies on onion seed priming and seed enhancement (Paparella et [8,4,7] .

Germination test

The germination test was conducted using the Between Paper (BP) method following the International Rules for Seed Testing (ISTA, 1993) [5] . One hundred seeds from each replication were placed uniformly between moistened germination papers, rolled carefully, and incubated in a seed germinator maintained at 25±1 °C under optimum moisture conditions. Normal seedlings were counted on the 15 day of the germination test, and germination percentage was calculated as:

Number of normal seedlings Germination (%) =

x 100 Total number of seeds placed

Seedling growth measurements

Ten normal seedlings were selected randomly from each replication for recording seedling growth parameters. Seedling length was calculated by summing root length and shoot length.

Seedling length (cm) = shoot length (cm) + root length (cm) Dry weight (g) Tan normal seedlings were dried in a hot-air oven at 80±2 °C for 24 h until constant weight and weighed again to determine seedling dry weight.

Seed vigour indices

Seed vigour indices were calculated according to the method of Abdul-Baki and Anderson (1973) [1] .

Seed vigour index-II = Germination (%) × dry weight of seedling (g)

Results and Discussion

Effect of seed priming treatments on germination, seedling growth and vigour of onion. The present investigation revealed that seed priming significantly improved germination, seedling growth, biomass accumulation, and seed vigour of onion under laboratory conditions (Table 2). Significant differences among priming treatments indicated that both the priming agent and soaking duration played a decisive role in enhancing seed physiological quality. Among the treatments, GA₃ @ 100 ppm for 12 h (T₂) recorded the highest germination (90.07%), root length (2.51 cm), shoot length (3.63 cm), seedling length (6.14 cm), fresh weight (0.417 g), dry weight (0.0262 g), vigour index-I (553.01) and vigour index-II (2.357). These values were significantly superior to the unprimed control and most other treatments, while GA₃ @ 100 ppm for 6 h (T₁) and KNO₃ @ 1% for 12 h (T₄) also produced statistically comparable improvements for several traits. Among the seed priming treatments, GA₃ @ 100 ppm for 12 h (T₂) proved to be the most effective in improving germination, seedling growth and seed vigour of onion. The superior performance of GA₃ may be attributed to its role in stimulating α-amylase activity, promoting reserve mobilization, enhancing water uptake, and accelerating cell division and elongation, which collectively improved seedling establishment and biomass accumulation. Similar findings were reported by Vij et al., (2025) [10] , who observed significant improvements in germination and seedling vigour following GA₃ priming in onion. Likewise, Das and Prabha (2025) [3] reported that GA₃ priming enhanced seed physiological quality by improving metabolic activity and antioxidant defence. Likewise, Pagano et al., (2023) [7] and Yanchenko et al., (2024) [11] highlighted that seed priming enhances metabolic activity, antioxidant defence and early seedling growth in onion and related Allium crops. The statistically comparable performance of GA₃ @ 100 ppm for 6 h (T₁) and KNO₃ @ 1% for 12 h (T₄) further suggests that both hormonal and nutrient priming effectively improve seed physiological quality by enhancing reserve mobilization and germination processes. These findings are also consistent with the observations of Naveenkumar et al., (2023) [6] , who reported significant improvements in onion seed germination and vigour through seed priming.

Conclusion

Overall, the findings indicate that GA₃ priming at 100 ppm for 12 h is the most effective treatment for enhancing germination, seedling growth and seed vigour in onion under laboratory conditions. Although GA₃ @ 100 ppm for 6 h and KNO₃ @ 1% for 12 h exhibited statistically comparable performance for several parameters, GA₃ priming for 12 h consistently produced the highest overall response. These results suggest that hormonal priming with GA₃ provides a simple, economical and efficient strategy for improving seed physiological quality and ensuring rapid, uniform seedling establishment, thereby offering a practical seed enhancement technique for onion cultivation.

Acknowledgement

AcknowledgementThe author is thankful to management and the Dean S.K.N. Collage of Agriculture Jobner, Jaipur for providing laboratory facilities to carry out this study. This research would not have been possible without the inspiration and support of several wonderful individuals.

References

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