Snake Bean and Cucumber Show Strong Salinity Tolerance at Germination in Coastal Bangladesh Study

A screening study conducted at Patuakhali Science and Technology University in Bangladesh has identified snake bean, cucumber, and gima kalmi as promising salt-tolerant crops at the germination stage, while classifying mung bean, jute, and kenaf as moderately tolerant. The research, published in Discover Plants, evaluated 14 locally relevant crop species and varieties under both laboratory petri dish conditions and saline pot culture, providing preliminary evidence for prioritizing candidate crops for saline coastal farmland where dry-season cultivation is currently limited by high soil salinity.

The stakes for coastal agriculture are substantial. Bangladesh’s coastal region spans 19 districts, covers 32 percent of the country’s total area, and is home to more than 35 million people. Salinity-affected land was recorded at 0.833 million hectares in 1973, rising to 1.020 million hectares in 2000 and 1.056 million hectares by 2009, and researchers have observed that soil salinity rose by more than 60 percent during dry seasons in the south-central coastal region between 1973 and 2021. Between 1970 and 2017, approximately 10 percent of total crop yield losses in these areas were attributed to salinity. As a result, much of the cultivable coastal land remains fallow during the dry season from November to May, when freshwater scarcity and high soil salinity restrict cropping, leaving many farms with only one wet-season rice crop per year.

The research team designed the work as a comparative and applied crop-screening investigation rather than a mechanistic study of salinity tolerance. They selected 14 economically important crops from vegetable, pulse, food and fodder, and fibrous groups: three vegetables, three pulses, one kenaf variety and five jute cultivars, and two food and fodder crops. Selection prioritized non-rice crops with potential for dry-season diversification of salinity-affected coastal land, based on their contribution to household food supply, nutrition, livestock feeding, fiber production, and livelihood diversification. Seeds were sourced from the Bangladesh Jute Research Institute, the Bangladesh Institute of Nuclear Agriculture, the Bangladesh Agricultural Research Institute, and local sources near the university. The authors noted that the selection was not statistically representative of all species or cropping systems in coastal Bangladesh, but was intended to compare early-stage salinity responses among contrasting and locally relevant crop-use categories.

The first phase of the experiment took place in petri dishes in the university’s central laboratory. Twenty seeds of each crop were placed on sterile cotton beds in 90-millimeter dishes and exposed to four salinity levels of 0, 4.50, 8.65, and 13.07 dS m⁻¹, delivered as NaCl solutions. For context, most vegetable crops have salinity thresholds ranging from 1 to 2.5 dS m⁻¹, so the highest treatment represented a severe challenge. The team measured germination percentage, shoot and root length, fresh and dry weight, the salinity tolerance index, the sensitivity index, and the Na⁺:K⁺ ratio in seedlings. A completely randomized design with three replications per treatment was used, and factorial analysis of variance with Tukey’s honestly significant difference test at p < 0.05 separated treatment effects. The authors noted that no independent seed viability or vigor test was conducted before the experiment, so the control treatment served as the experimental baseline.

Germination generally decreased with increasing salinity, but five species—kenaf, mung bean, snake bean, triticale, and cucumber—maintained average germination rates exceeding 80 percent across the salinity gradient. Snake bean posted the highest average germination percentage at 92.92 percent, while lentil recorded the lowest at 36.67 percent. Among the jute cultivars, germination declined progressively with increasing salinity, with Deshi Shak Pat-1 and BJRI Deshi-8 showing the lowest germination percentages, while Corchorus olitorius cv. O-9897 maintained 80 percent germination at salinity levels up to 8.65 dS m⁻¹. The researchers attributed reduced germination under salt stress to increased seed dormancy, low external osmotic potential, and the toxic effects of sodium and chloride ions, which restrict water uptake and may interfere with the activation of hydrolytic enzymes. Notably, lentil and millet showed low germination even under control conditions, at 40.0 and 48.3 percent respectively, suggesting lower initial seed viability or vigor in those seed lots.

The five best-performing species from the petri dish phase—mung bean, kenaf cv. HC-3, snake bean, triticale, and cucumber—were then advanced to pot culture using saline clay loam soil sourced from the Patabunia riverbank in Dumki, Patuakhali. The soil had a pH of 7.71 and a baseline electrical conductivity of 0.73 dS m⁻¹, and was mixed with NaCl to achieve treatment levels of 0.73, 4.26, 8.21, 11.44, and 15.42 dS m⁻¹. Seventy-five pots were arranged in a net house, each containing 10 kilograms of processed soil and ten seeds per pot, with three replications. Germination in pot culture exceeded 87 percent, higher than the petri dish results across the tested salinity gradients.

The contrast between the two screening systems proved informative. In petri dishes, seeds are directly exposed to NaCl solutions, resulting in immediate contact with dissolved salts and potentially higher ionic stress around the germinating seed surface. Soil, by contrast, acts as a heterogeneous buffering medium that regulates salt availability through adsorption, ion exchange processes, and uneven salt distribution within the soil matrix, reducing the immediate exposure of germinating seeds to soluble Na⁺ and Cl⁻ ions. Soil also provides a larger rooting environment in which water movement and salt diffusion create spatial variability in salinity exposure, potentially allowing developing roots to explore microsites with comparatively lower salt concentrations. Despite these differences, the ranking of crop performance remained generally consistent between the two approaches, suggesting that in vitro screening can serve as an efficient preliminary method for identifying salt-tolerant crops, although pot and field evaluations remain essential for confirming tolerance under realistic growing environments.

Based on salinity tolerance index values, cucumber and snake bean were classified as salt-tolerant at all salinity levels, with tolerance index values greater than 1.0, while gima kalmi received the same designation at 4.50 and 8.65 dS m⁻¹. Mung bean, grass pea, BJRI Deshi-8, BJRI Tosha-8, kenaf, and lentil were classified as moderately salt-tolerant, with tolerance index values from 0.5 to less than 1.0. Cucumber showed strong tolerance following seedling establishment, with positive sensitivity index values for dry weight of at least 66 percent recorded up to 13.07 dS m⁻¹. The fresh and dry weights of snake bean and cucumber increased with increasing salinity in the petri dish experiment, reaching maximum values at 8.65 dS m⁻¹, while other crops showed declining trends. However, the researchers issued an important caveat regarding millet: although it maintained or apparently increased germination under some salinity treatments compared with control, its low control germination of approximately 48 percent means the response may reflect seed viability or vigor, so millet was not considered a reliable indicator of salinity tolerance in this study and requires further evaluation with seed lots of confirmed viability.

Ionic analysis provided an associated pattern worth noting. Sodium accumulation in seedlings increased with increasing salinity, and the Na⁺/K⁺ ratio of cucumber, snake bean, triticale, kenaf, and mung bean remained within 4.0 under saline conditions. These same species exhibited relatively higher germination performance in both petri dish and pot culture experiments, indicating an association between maintaining a lower Na⁺/K⁺ ratio and improved salinity tolerance during early seedling establishment, while other species showed Na⁺/K⁺ ratios ranging from 4 to 16, likely contributing to low germination through electrolyte imbalance. Pearson correlation analysis, conducted on species-level means with n = 14, reinforced this descriptive pattern: at 13.07 dS m⁻¹, germination percentage was strongly and positively correlated with the tolerance index (r = 0.774, p = 0.001), while the Na⁺/K⁺ ratio showed significant negative correlations with both germination percentage (r = −0.668, p = 0.009) and the tolerance index (r = −0.821, p < 0.001). The authors emphasized that these correlations describe associations among species responses and should not be interpreted as evidence of causal relationships or independent physiological mechanisms, since whole-seedling Na⁺ and K⁺ measurements cannot determine the specific processes responsible.

The researchers framed their findings as preliminary evidence of early-stage salinity responses rather than confirmation of complete crop-cycle tolerance. The study did not assess flowering, reproductive development, final yield, product quality, or economic performance under salinity stress, and environmental factors such as irrigation-water quality, rainfall, soil-water interactions, and nutrient availability may influence crop responses under field conditions. Electrical conductivity was not monitored continuously during the experiments, limiting assessment of actual salt exposure, and independent seed viability and vigor tests were not conducted. Recognized tolerance mechanisms, including selective K⁺ retention, reduced Na entry into metabolically active tissues, and vacuolar Na⁺ sequestration, were not directly evaluated, and explanations involving osmotic adjustment through compatible solutes or enhanced antioxidant defense remain hypothetical because the relevant measurements were not taken. Nevertheless, the study delivers a locally relevant dataset for prioritizing candidate crops for more comprehensive agronomic and field-level evaluation, and the authors call for multi-location and multi-season field trials with periodic electrical conductivity monitoring to validate crop performance in saline coastal conditions.

Subject of Research: Salinity tolerance screening of 14 crop species at the germination stage under laboratory and pot conditions in coastal Bangladesh

Article Title: Salinity tolerance dynamics in selected crop species at germination stage under in vitro and in situ conditions in Patuakhali, Bangladesh

Article References: Islam, M. S., Roy, A., Mondal, S., Uddin, M. N., Bhuyan, M. I., Al Zabir, A., Kabir, M. A., Uddin, M. E., Kumar, G. M., Bruning, B., & de Vos, A. (2026). Salinity tolerance dynamics in selected crop species at germination stage under in vitro and in situ conditions in Patuakhali, Bangladesh. Discover Plants, 3(1), Article 478. https://doi.org/10.1007/s44372-026-00952-y

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00952-y

Keywords: salinity tolerance, germination, coastal Bangladesh, snake bean, cucumber, gima kalmi, Na+/K+ ratio, soil salinity, crop screening, Patuakhali, dry-season cropping, salinity tolerance index