Mitigating NaCl stress in Vigna radiata L. cultivars using Bacillus pseudomycoides

Abstract

Salt stress is one of the significant abiotic stress factors that exert harmful effects on plant growth and yield. In this study, five cultivars of mung bean (Vigna radiata L.) were treated with different concentrations of NaCl and also inoculated with a salt-tolerant bacterial strain to assess their growth and yield. The bacterial strain was isolated from the saline soil of Sahiwal District, Punjab, Pakistan and identified as Bacillus pseudomycoides. Plant growth was monitored at 15-days interval and finally harvested after 120 days at seed set. Both sodium and potassium uptake in above and below-ground parts were assessed using a flame photometer. Fresh and dry mass, number of pods, seeds per plant, weight of seeds per plant and weight of 100 seeds reduced significantly as the concentration of NaCl increased from 3 to 15 dSm^-1. There was a significant reduction in the growth and yield of plants exposed to NaCl stress without bacterial inoculum compared to the plants with bacterial inoculum. The latter plants showed a significant increase in the studied parameters. It was found that the cultivar Inqelab mung showed the least reduction in growth and yield traits among the studied cultivars, while Ramzan mung showed the maximum reduction. Among all the cultivars, maximum Na⁺ uptake occurred in roots, while the least uptake was observed in seeds. The study concludes that NaCl stress significantly reduces the growth and yield of mung bean cultivars, but Bacillus pseudomycoides inoculum alleviates salt stress. These findings will be helpful to cultivate the selected cultivars in soils with varying concentrations of NaCl.

Keywords: Biomass; Cultivars; Growth; Mung bean; Salt-tolerant bacteria; Stress; Yield.

Figure 1. Dendrogram showing the homology of Bacillus pseudomycoides bacterium (16S rRNA report).

SDSC101_contig_1 showing the present study bacterial sample.

Figure 2. The mean dry weight of the studied plants-Inqelab mung (A), NIFA-19 (B), NIFA-17 (C), Sona mung (D) and Ramzan mung (E).

Bars indicate mean (±) standard error and different letters represent significant differences. Grey bars indicate soil with NaCl treatment, while black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 3. Mean root nodules number plant⁻¹ (A–E), pods number plant⁻¹(F–J), seeds pod⁻¹plant⁻¹ (K–O), seeds weight pod⁻¹plant⁻¹ (P–T) and 100 seeds weight (U–Y) across five mung bean cultivars.

Bars indicate mean (±) standard error and different letters represent significant differences. Grey bars indicate soil with NaCl treatment, while black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 4. The mean photosynthetic rate (A–E), transpiration rate (F–J), stomatal conductance (K–O) and water use efficiency (P–T) across the studied five mung bean cultivars.

Bars indicate mean (±) standard error and different letters mean significant differences. Grey bars indicate soil with NaCl treatment while black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 5. Sodium ion uptake in root (A–E), stem (F–J), leaves (K–O) and seeds (P–T) across the five mung bean cultivars.

Bars indicate mean (±) standard error and different letters represent significant differences. Grey bars indicate soil with NaCl treatment and black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 6. Potassium ion uptake in root (A–E), stem (F–J), leaves (K–O) and seeds (P–T), across the five mung bean cultivars.

Bars indicate mean (±) standard error and different letters mean significant differences. Grey bars indicate soil with NaCl treatment while black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 7. Chlorophyll a (A–E), chlorophyll b (F–J) and total chlorophyll contents (K–O), across the five mung bean cultivars.

Bars indicate mean (±) standard error and different letter (s) represent significant differences. Grey bars indicate soil with NaCl treatment while black bars indicate NaCl treatment combined with B. pseudomycoides inoculum.

Figure 8. Relationship of NaCl concentrations with plant fresh weight, dry weight, plant length (A–C), pods number plant⁻¹, seeds number plant⁻¹, and seeds weight (D–F) in mung bean cultivars.

Dotted lines indicate plant without bacteria inoculum, while solid lines represent plants with bacteria inoculum. Grey dots = V1, Dark blue dots = V2, Yellow dots = V3, Blue dots = V4, Purple dots = V5.