Effect of Hydropriming on Seedling Growth of Different Bambara Groundnut (Vigna subterranea (L.) Verdc.) Landraces

Abstract

Bambara groundnut (Vigna subterranea (L.) Verdc.) is a drought-tolerant, underutilised legume with the potential to improve food security, but its slow, uneven germination due to hard seed coats constrains cultivation. This study investigated the effects of hydropriming (0, 12, 24, and 36 h) on the seed imbibition, emergence, and early seedling growth in four landraces (NW, Nov4, ARC, and 519) under greenhouse conditions. The results showed genotype-specific variation in the water uptake, with Genotype 519 exhibiting the highest water imbibition (17.31%) at 36 h, while NW displayed slower but steadier hydration (13.51%). These differences reflect contrasting seed coat permeability and hydration strategies, which influenced the subsequent emergence patterns. Hydropriming significantly reduced the time to emergence (50% emergence by Day 5 in NW) and increased the seedling vigour. After 9 days of growth, the shoot length increased from 7.8 cm to 12.7 cm, the root length from 11.6 cm to 18.1 cm, and the dry mass from 0.38 g to 0.67 g. Analysis of variance (ANOVA) revealed significant effects (p < 0.01) of the genotype, the priming duration, and their interaction on traits such as the root length, dry mass, and root-to-shoot ratio. PCA identified the whole-plant dry mass, root dry mass, and root-to-shoot ratio as key contributors to performance. Pearson correlation showed a strong positive association (r = 1.0, p < 0.001) between the priming duration and seedling biomass, although the extended imbibition time may partially explain this trend. Hydropriming, particularly for 36 h, showed promise in promoting early growth, indicating that it is a favourable low-cost intervention. Field-level validation is recommended to assess the practical scalability under diverse environmental conditions.

1. Introduction

Bambara groundnut (Vigna subterranea (L.) Verdc.) is a hardy, drought-tolerant legume indigenous to sub-Saharan Africa, where it is cultivated primarily by smallholder farmers [1]. It is rich in carbohydrates (63–69%) and protein (18–24%), and it contains essential amino acids such as lysine and methionine, making it a valuable contributor to food and nutritional security in resource-poor environments [2,3]. According to FAO estimates, the global annual production of Bambara groundnut is estimated to be 0.2 million tonnes from an area of 0.25 million hectares worldwide [4]. West Africa is the main Bambara groundnut production region in SSA, where Burkina Faso, Niger, and Cameroon are the leading producers, contributing to 74% of the global production [5,6]. Despite its agronomic potential and resilience to marginal growing conditions, Bambara groundnut (BGN) remains underutilised in formal agricultural systems due to low yields (~0.8 t/ha), poor market integration, and inconsistent germination [7,8].

As efforts to mainstream climate-resilient agriculture intensify, BGN has received renewed attention for its adaptability to low-input farming systems and its potential to diversify cropping portfolios in drought-prone regions [9,10]. However, one of the key physiological constraints limiting its wider adoption is the hard seed coat [11,12], which impedes water uptake, delays germination (up to 21 days), and leads to variable seedling establishment [13]. These delays are particularly detrimental in environments with short rainfall windows, where rapid and uniform emergence is critical for crop success and yield stability.

Seed priming, a pre-sowing treatment involving controlled hydration followed by re-drying, has emerged as a practical technique to overcome dormancy and enhance seed performance [14,15]. It initiates key metabolic processes that improve water uptake, enzymatic activity, and protein synthesis, resulting in faster and more uniform seedling emergence [16,17]. Among the various priming methods, hydropriming, a method that involves soaking seeds in water for a defined period, is the most accessible and environmentally sustainable [13]. It requires no specialised inputs, making it especially suitable for smallholder farmers who often face economic and infrastructural constraints [18].

Previous research has demonstrated the effectiveness of hydropriming in improving seedling vigour and early growth across major crops such as rice, wheat, sunflower, pigeon pea, and chickpea [19,20,21,22]. However, its efficacy is highly genotype-dependent, with the optimal soaking durations varying widely across species and cultivars. Excessive priming can also lead to reduced viability due to over-imbibition or premature radicle protrusion [22]. In the case of BGN, although there is growing interest in seed enhancement technologies such as biopriming, nutri-priming, and treatments using compost tea or livestock urine [22], many of these methods are either resource-intensive or lack scalability in smallholder contexts.

Furthermore, while some studies on BGN priming exist [12,23,24], few have examined genotype-specific responses to hydropriming under controlled conditions. This is a critical knowledge gap given that BGN is predominantly cultivated as landraces, with no commercially standardised varieties currently available. Applying a one-size-fits-all priming protocol may therefore overlook important variations in the seed coat permeability, metabolic activation, and emergence rates among landraces.

This study investigates the effects of hydropriming on the germination, emergence, and early seedling growth across four BGN landraces by evaluating key physiological and morphological parameters, including the days to emergence, shoot and root length, leaf development, biomass accumulation, and root-to-shoot ratio. This research aims to identify the optimal priming durations for enhancing early vigour. The findings will contribute to developing cost-effective and scalable seed enhancement practices that support the broader adoption of Bambara groundnut in climate-smart agricultural systems, particularly in drought-prone and resource-constrained environments.

2. Materials and Methods

2.1. Plant Material

Four BGN landraces (Nov4, NW, ARC, and 519) were selected for this study. All seeds were obtained from the University of KwaZulu-Natal’s Bambara groundnut germplasm collection. To ensure uniform germination and minimise variation due to environmental history, seeds were harvested during the same growing season and stored under controlled ambient conditions until use.

2.2. Seed Priming and Sowing

Hydropriming was conducted by soaking seeds in distilled water at room temperature for 0 (unprimed control), 12, 24, or 36 h. After soaking, seeds were blotted with paper towels and air-dried for two hours at room temperature to remove surface moisture. Primed seeds were sown directly into 8-litre (L) thermoform pots filled with Gromor Potting Mix (30 dm³ per pot), a commercially available sterile medium. This substrate was selected to ensure consistency in the texture, drainage, and nutrient baseline across all experimental units. All pots were watered with 250 mL of water before sowing to establish a uniform starting condition.

2.3. Experimental Design and Greenhouse Conditions

The experiment was conducted under greenhouse conditions at the Controlled Research Facility (CERU), University of KwaZulu-Natal, Pietermaritzburg, South Africa (29°37′37.5″ S; 30°24′10.4″ E). The greenhouse maintained a mean air temperature of 25 ± 2 °C and a relative humidity of 60 ± 3%.

The experimental design was a 4 × 4 factorial completely randomised design (CRD), consisting of four landraces and four priming durations. Each treatment combination was replicated three times, with five seeds per pot, resulting in a total of 48 experimental units. Pots were arranged randomly on raised benches and irrigated with 250 mL of tap water every two days. Watering frequency was adjusted based on visual inspection of moisture levels to prevent both drought stress and over-saturation.

2.4. Emergence Assessment

Emergence was monitored daily and defined as the visible appearance of the hypocotyl above the soil surface. Days to 50% emergence were calculated per pot to evaluate uniformity across treatments.

2.5. Water Imbibition

The water uptake capacity during priming was assessed using a digital precision balance (±0.01 g). For each priming interval (0, 12, 24, 36 h), five seeds per landrace were weighed before and after priming. Seeds were gently blotted before final weighing to remove excess surface water. The imbibition percentage was calculated using Equation (1):

$$\text{Water} \text{imbibition}\left(\text{WI}\right)={\displaystyle \frac{\text{WSAP}-\text{WSBP}}{\text{WSBP}}}\times 100\%$$

(1)

where WSAP is the weight of the seed after priming; WSBP is the weight of the seed before priming.

2.6. Seedling Growth and Morphological Measurements

The seedling height was measured every four days from the soil surface to the apical meristem using a ruler. At 30 days after sowing (DAS), three seedlings per pot were randomly selected and sampled for morphological analysis. The shoot length was measured from the base of the stem to the tip of the longest leaf; the root length was measured from the stem base to the tip of the longest root after gentle washing. Leaf number and length (longest leaf per seedling) were also recorded.

Preliminary observations were made at 28 DAS to assess developmental uniformity, but all final measurements and data reported were standardised to 30 DAS.

2.7. Root and Shoot Biomass Allocation

Shoots were separated from roots by cutting at 5 cm above soil level. Roots were washed with distilled water to remove soil residue. Shoot and root components were oven-dried at 60 °C for 48 h. Dry weights were recorded using an analytical balance (±0.001 g).

The root mass ratio (RMR), shoot mass ratio (SMR), and root-to-shoot ratio (RSR) were calculated using Equations (2)–(4):

$$\text{Root} \text{mass} \text{ratio}={\displaystyle \frac{\text{Dry} \text{mass} \text{of} \text{root}}{\text{Total} \text{dry} \text{mass} \text{of} \text{plant}}}$$

(2)

$$\text{Shoot} \text{mass} \text{ratio}={\displaystyle \frac{\text{Dry} \text{mass} \text{of} \text{shoot}}{\text{Total} \text{dry} \text{mass} \text{of} \text{plant}}}$$

(3)

$$\text{Root} \text{shoot} \text{ratio}={\displaystyle \frac{\text{Root} \text{dry} \text{mass}}{\text{Shoot} \text{dry} \text{mass}}}$$

(4)

2.8. Statistical Analysis

All statistical analyses were performed using Genstat 23rd Edition (VSN International, Hemel Hempstead, UK). Two-way ANOVA was applied to evaluate the effects of the genotype, the priming duration, and their interaction. Treatment means were separated using Fisher’s protected least significant difference (LSD) test at the 5% significance level.

Multivariate analysis was conducted using OriginPro 2025 (OriginLab Corp., Northampton, MA, USA). Principal component analysis (PCA) and Pearson correlation analysis were performed on standardised, averaged trait values for each genotype × priming duration combination (n = 16) in order to explore trait co-variation patterns and genotype-specific responses to priming. Results were visualised using biplots and correlation heatmaps.

3. Results

3.1. Imbibition Responses of BGN Genotypes

The genotypes displayed distinct water uptake patterns in response to the increasing priming durations (Figure 1;

Table 1. Water imbibition (%) of BGN genotypes at different priming durations (0–36 h).

Genotype	0	12	24	36
ARC	10.5	10.7	11.5	13.5
B	8.7	11.6	14.5	17.3
NW	10.1	11.2	11.8	13.5
Nov4	4.9	5.9	6.6	11.1

Water imbibition (%) was calculated from Equation (1), where WSBP is the initial seed weight before priming and WSAP is the seed weight after the respective priming duration. Values represent the means of replicates. For duplicate time points, average values were used.

). Genotype 519 exhibited the fastest and most pronounced hydration rate, with the seed weight increasing from 0.6884 g (unprimed) to 1.366 g after 36 h of hydropriming. Correspondingly, the water imbibition for 519 rose from 8.72% to 17.31%, the highest among all the genotypes evaluated. This rapid and sustained uptake suggests superior seed coat permeability or internal mechanisms facilitating water absorption, making 519 a highly responsive candidate for priming interventions. Genotype NW, in contrast, showed the slowest water uptake, with the seed weight rising from 0.794 g to 1.0608 g over 36 h, and a corresponding water imbibition increase from 10.11% to 13.51%. ARC and Nov4 demonstrated moderate water absorption capacities. ARC recorded a final weight of 1.0734 g and an imbibition of 12.5% at 24 h, while Nov4 increased from 4.93% to 11.10% over the priming period, despite starting with the lowest initial water uptake. The delayed but sharp increase in Nov4 suggests that extended priming durations may be essential to overcome the physiological dormancy or hard seed characteristics in certain genotypes. Overall, these results reveal genotype-specific differences in the hydration capacity and responsiveness to hydropriming. Such variation has practical implications for seed management strategies, as selecting genotypes like 519 could enhance uniform emergence, particularly under water-limited conditions. Meanwhile, slower-imbibing types such as Nov4 may benefit from extended priming durations to optimise field establishment.

3.2. Effects of Priming Duration on Seedling Growth of BGN Genotypes

The seedling growth improved progressively with the increasing priming duration (Figure 2, Figure 3 and Figure 4). The unprimed controls showed poor development, while 12 h priming induced moderate improvement. By 24 h, the root and shoot elongation had increased substantially. At 36 h, all genotypes exhibited enhanced shoot heights, leaf expansion, and root biomasses. Genotype 519 showed the most robust response to the longer priming durations, while ARC and Nov4, although improved, remained less responsive compared to NW and 519.

Quantitative data confirmed these visual trends. The analysis of variance (

Table 2. Analysis of variance showing mean squares and significant tests of key plant traits when primed at different time intervals.

Source of Variation	df	DE	SL	RL	LL	RFM	SFM	WPFM	RDM	SDM	WPDM	RSR	SMR	RMR
Genotype (G)	3	98.139 **	19.833 *	315.50 **	3.951 **	1.970 **	15.419 **	18.072 **	0.957 **	0.195 **	1.728 **	1.108 **	0.086 **	0.086 **
Time (T)	3	831.694 **	141.722 **	807.93 **	13.076 **	8.802 **	18.757 **	52.598 **	1.523 **	2.739 **	8.322 **	0.035 *	0.003 NS	0.003 NS
G × T	9	11.083 *	16.037 *	221.37 **	1.001 *	0.679 **	1.394 **	1.593 **	0.463 **	0.039 *	0.408 **	0.518 **	0.044 **	0.044 **
Residual	32	2.750 NS	6.963 NS	18.77 NS	0.322 NS	0.012 NS	0.062 NS	0.067 NS	0.009 NS	0.013 NS	0.021 NS	0.035 NS	0.003 NS	0.003 NS

df: degrees of freedom; NS: not significant. * p < 0.05; ** p < 0.01. Emergence (DE), shoot length (SL), root length (RL), leaf length (LL), root fresh mass (RFM), shoot fresh mass (SFM), whole-plant fresh mass (WPFM), root dry mass (RDM), shoot dry mass (SDM), whole-plant dry mass (WPDM), root shoot ratio (RSR), shoot mass ratio (SMR), and root mass ratio (RMR).

; Figure 4) showed that the genotype (G) significantly affected the days to 50% emergence (DE) (p < 0.01), root length (RL) (p < 0.01), and whole-plant dry mass (WPDM) (p < 0.01). The priming time (T) significantly influenced the DE, shoot length (SL), root length (RL), and shoot dry mass (SDM), all with p < 0.01. The G × T interaction also significantly influenced the root dry mass (RDM), shoot mass ratio (SMR), and root mass ratio (RMR). The bars in Figure 4 are labelled with letters indicating statistically grouped means; identical letters represent no statistically significant difference. The sample size for each treatment was n = three pots, with three seedlings sampled per pot.

3.3. Principal Component Analysis (PCA)

Table 3. Summary of factor loadings, eigenvalue measures of sampling adequacy, and percent and cumulative variation for plant traits.

	0 h			12 h			24 h			36 h
Variables	PC1	PC2	PC3	PC1	PC2	PC3	PC1	PC2	PC3	PC1	PC2	PC3
WPDM	0.328	−0.170	−0.035	0.318	−0.193	0.107	0.372	0.073	0.118	0.372	0.073	0.118
RSR	0.285	−0.269	−0.167	0.300	−0.032	−0.313	0.324	−0.244	0.023	0.324	−0.244	0.023
RDM	0.310	−0.219	−0.110	0.331	−0.098	−0.134	0.369	−0.101	0.091	0.369	−0.101	0.091
SL	0.286	0.131	0.370	0.035	−0.550	0.134	0.204	0.381	0.181	0.204	0.381	0.181
RL	−0.306	−0.150	0.274	−0.269	0.022	−0.399	0.263	0.311	0.232	0.263	0.311	0.232
WPFM	0.308	0.236	−0.001	0.332	0.120	0.099	0.265	0.221	−0.438	0.265	0.221	−0.438
LL	0.293	0.227	0.219	0.193	0.437	−0.189	0.005	0.436	−0.294	0.005	0.436	−0.294
RFM	0.283	−0.251	0.222	0.308	−0.253	−0.001	−0.274	0.229	0.398	−0.274	0.229	0.398
SFM	0.191	0.414	−0.128	0.297	0.262	0.128	0.271	0.204	−0.445	0.271	0.204	−0.445
DE	0.026	0.247	−0.633	0.042	0.385	0.463	0.265	0.174	0.497	0.265	0.174	0.497
SMR	−0.254	0.322	0.186	−0.312	0.099	0.247	−0.331	0.229	−0.054	−0.331	0.229	−0.054
RMR	0.254	−0.322	−0.186	0.312	−0.099	−0.247	0.331	−0.229	0.054	0.331	−0.229	0.054
SDM	0.272	0.172	0.383	0.102	−0.272	0.530	−0.039	0.464	0.059	−0.039	0.464	0.059
Eigenvalue	8.216	3.894	1.891	8.447	3.129	2.425	6.911	4.571	1.518	6.911	4.571	1.518
Variability (%)	58.685	27.811	13.504	60.332	22.350	17.318	53.163	35.162	11.675	53.163	35.162	11.675
Cumulative (%)	58.685	86.496	100	60.332	82.682	100	53.163	88.325	100	53.163	88.325	100

DE: days to emergence; SL: shoot length; RL: root length; LL: leaf length; RFM: root fresh mass; SFM: shoot fresh mass; WPFM: whole-plant fresh mass; RDM: root dry mass; SDM: shoot dry mass; WPDM: whole-plant dry mass; RSR: root shoot ratio; SMR: shoot mass ratio; RMR: root mass ratio.

and Figure 5 present the results of the principal component analysis (PCA), which was used to examine the trait co-variation in response to the hydropriming durations. At all the time points, PC1 explained the largest proportion of the total variation, ranging from 50% to 58.69%, and was strongly influenced by traits related to biomass accumulation and partitioning—namely, the whole-plant dry mass (WPDM), root-to-shoot ratio (RSR), root dry mass (RDM), and shoot length (SL). This indicates that these traits are the most responsive to priming and are key indicators of the early seedling growth performance across genotypes. The PCA biplots revealed distinct clustering patterns, highlighting genotype-specific trait associations. Genotype 519 consistently aligned with the WPDM, shoot dry mass (SDM), and leaf length (LL), especially under 36 h of priming, suggesting that this genotype may exhibit greater biomass allocation and canopy development under extended priming conditions. NW grouped closely with the root fresh mass (RFM) and shoot mass ratio (SMR), indicating a stronger allocation to shoot structures relative to the total mass. ARC was more closely associated with the RSR and root mass ratio (RMR), pointing to a tendency for root-biased biomass distribution. In contrast, Nov4 showed limited associations with the key growth traits across the priming durations, suggesting a relatively weaker or less distinct response to priming. These genotype-specific associations provide insights into how each landrace responds physiologically to hydropriming, reinforcing the value of tailoring priming protocols to specific genetic backgrounds. Overall, the PCA highlights the WPDM, RDM, and SL as consistent indicators of the seedling performance and responsiveness to priming.

3.4. Pearson Correlation Analysis

The Pearson correlation analysis (Figure 6) revealed strong and consistent relationships among the traits related to biomass partitioning and overall plant development across all the priming durations. The whole-plant dry mass (WPDM) was positively and significantly correlated with the root dry mass (RDM) and root-to-shoot ratio (RSR) (r = 1.0, p < 0.001), indicating that the plants with higher total biomasses also tended to invest proportionally more in root structures. This suggests that hydropriming, particularly at longer durations, may support balanced growth and improved root development, which are important for early establishment and resilience under water-limited conditions.

In contrast, the shoot mass ratio (SMR) showed a strong negative correlation with both the RDM and RSR, reflecting the trade-off between shoot dominance and root development. This inverse relationship suggests that genotypes or treatments promoting greater root allocation may do so at the expense of the shoot mass proportion, highlighting distinct biomass partitioning strategies among landraces. While some correlations—such as those between the derived ratios and their component traits—were expected due to mathematical relationships, their consistent direction and strength across the priming durations underscore the stability of these patterns. These findings contribute to identifying reliable physiological indicators of the seedling performance under hydropriming and offer a basis for the future trait-based screening of responsive genotypes.

4. Discussion

Seed imbibition is the initial and critical phase of germination [25], triggering metabolic reactivation and influencing the subsequent seedling performance [26]. In this study, the BGN genotypes exhibited distinct and statistically significant variations in their water uptake across the priming durations, reaffirming the importance of genotype-specific physiological traits in early-stage seed responses.

Genotype 519 demonstrated the highest water imbibition, increasing from 8.72% at 0 h to 17.31% at 36 h, alongside a final seed weight of 1.366 g. This steep hydration gradient likely reflects a superior seed coat permeability or heightened metabolic predisposition to absorb water [27]. Conversely, NW, despite having the highest initial seed weight (0.794 g), showed the slowest imbibition trajectory, culminating in 13.51% at 36 h. This more controlled water uptake pattern suggests a less permeable seed coat, which may serve as a buffering mechanism to mitigate imbibitional injury, especially under fluctuating moisture conditions [28]. ARC and Nov4 exhibited moderate hydration responses, with Nov4 showing the lowest initial uptake but a marked increase by 36 h. These observations align with earlier reports linking seed coat composition, porosity, and dormancy traits to differential water uptake in legumes [20,21,29]. It is important to note, however, that the initial seed weights used for hydration varied among the genotypes, while the same volume of water was applied across the treatments. This could introduce unequal seed-to-water ratios, which may have influenced the imbibition rates and hydration efficiency. Although consistent volumes were maintained, future studies should standardise the substrate-to-solvent ratio either by weight or volume to ensure fairer comparisons and a more robust interpretation of the water uptake dynamics.

Interestingly, rapid hydration in genotype 519 did not translate to the fastest emergence. Despite its high water uptake, 519 exhibited delayed emergence, potentially due to imbibitional stress or asphyxiation from rapid water entry limiting the oxygen availability to the embryo [30,31,32]. This paradox highlights that faster water uptake does not always equate to an improved early performance. In contrast, NW’s slower but steady imbibition may have allowed for a more regulated activation of enzymatic and metabolic pathways, resulting in earlier and more uniform emergence [33]. These genotype-specific dynamics underscore the importance of balancing the hydration rate with metabolic coordination to optimise germination outcomes.

The priming duration emerged as a critical determinant of seedling development across all the genotypes. While unprimed seeds consistently showed poor shoot and root development, notable improvements were observed at 24 and 36 h. These durations appeared to facilitate the uniform hydration and physiological activation necessary for robust seedling establishment. These findings align with previous studies showing that hydropriming initiates enzymatic activity, repairs oxidative damage, and promotes embryo elongation [10,18].

Visual and quantitative assessments revealed genotype-specific responses to priming. At 36 h, genotypes 519 and NW exhibited the strongest seedling performances, characterised by greater shoot heights, root biomasses, and whole-plant dry masses. ARC and Nov4 responded positively, though to a lesser degree. These differences may reflect intrinsic genetic variation in the seed vigour, metabolic capacity, or responsiveness to hydration stimuli, as similarly observed in chickpea, soybean, and other legume crops [19,34,35].

The ANOVA results confirmed that the genotype (G), the priming time (T), and their interaction (G × T) significantly influenced key seedling traits. The genotype had a strong effect on the root length, whole-plant dry mass (WPDM), and root-to-shoot ratio (RSR) (p < 0.01), while the priming time significantly influenced the days to 50% emergence (DE), shoot length (SL), and shoot dry mass (SDM) (p < 0.01). The significant G × T interaction effects observed for the root dry mass (RDM), shoot mass ratio (SMR), and root mass ratio (RMR) suggest that priming outcomes are not only time-dependent but also genotype-specific. This supports the need for customised priming protocols to enhance early seedling vigour under diverse environmental conditions, especially in water-limited settings [36].

Principal component analysis (PCA) provided further insight into the trait coordination and genotype performance under different priming durations. PC1 consistently accounted for the majority of the variance (>50%) and was primarily influenced by traits linked to biomass accumulation (e.g., WPDM, RDM, SL, RSR). Genotype 519 clustered closely with the WPDM and SDM at 36 h, indicating high biomass investment under prolonged priming. NW associated more with the SMR and RFM, while ARC aligned with the RSR and RMR, revealing differing allocation strategies among the genotypes. These patterns support findings that suggest that seed priming can influence biomass partitioning and shape early developmental trajectories [37,38,39].

The correlation analysis reinforced these relationships. The WPDM was positively correlated with the RDM and RSR, suggesting that the coordinated allocation of resources toward root development enhances overall vigour [40,41]. The expected negative correlations between the SMR and both the RDM and RSR reflect trade-offs in the allocation between the shoot and root compartments and further highlight the strategic adjustments induced by priming.

Taken together, the findings of this study demonstrate that BGN genotypes vary in their physiological responses to hydropriming. Longer priming durations, particularly 36 h, generally showed potential in promoting seedling vigour. However, the extent of the benefit was genotype-dependent. Optimising priming for each genotype based on their imbibition behaviour, emergence timing, and trait performance can inform scalable seed enhancement strategies. These findings offer a starting point for practical implications to improving BGN establishment in semi-arid and climate-vulnerable regions, where early crop establishment is critical for yield resilience and food security.

5. Conclusions

This study demonstrates the effectiveness of hydropriming as a low-cost, pre-sowing intervention to enhance the early seedling performance in Bambara groundnut (BGN). Significant improvements in the shoot elongation, root development, and whole-plant biomass were observed across the genotypes, particularly at a priming duration of 36 h. Genotypes 519 and NW exhibited the most pronounced responses to extended priming, underscoring their suitability for seed enhancement strategies aimed at improving early vigour in water-limited environments.

The water imbibition patterns varied significantly among the genotypes, with 519 showing the fastest hydration rate but delayed emergence, while NW demonstrated slower yet more regulated water uptake and earlier emergence. These differences highlight the importance of aligning the priming duration with genotype-specific physiological traits to avoid imbibitional injury and maximise seedling establishment.

Multivariate analyses further revealed that traits such as the root-to-shoot ratio (RSR), root dry mass (RDM), and whole-plant dry mass (WPDM) were key contributors to early vigour under priming conditions. The strong associations between these traits and the seedling performance support the utility of trait-based approaches in selecting genotypes for priming optimisation.

Hydropriming for 36 h appears to be a promising and scalable approach for smallholder farmers, particularly in semi-arid and resource-constrained regions where rapid and uniform crop establishment is essential. However, the findings are based on controlled greenhouse experiments, and broader applicability requires validation under field conditions.

Future research should prioritise multi-location field trials, integration with diverse agroecological zones, and in-depth physiological and biochemical profiling to better understand the mechanisms underlying genotype-specific priming responses. Such work will contribute to developing climate-resilient seed systems and support the broader adoption of underutilised legumes like Bambara groundnut for improved food and nutritional security in sub-Saharan Africa.