# Evaluation of Salinity Tolerance Potentials of Two Contrasting Soybean Genotypes Based on Physiological and Biochemical Responses

## TL;DR

This study compares two soybean varieties to identify physiological and biochemical traits that help them tolerate salty soil conditions.

## Contribution

The study identifies specific physiological and biochemical markers linked to salinity tolerance in soybean genotypes.

## Key findings

- YAKARTA showed higher relative water content, stomatal conductance, and K+/Na+ ratio compared to POCA under salinity stress.
- POCA exhibited greater solute leakage, malondialdehyde, and ascorbic acid, indicating higher sensitivity to salinity.
- Key traits like proline accumulation and K+/Na+ ratio are proposed as potential markers for salinity tolerance.

## Abstract

Salinity stress is a major abiotic constraint limiting soybean (Glycine max L.) productivity in saline–alkali soils; however, the physiological and biochemical mechanisms underlying genotypic tolerance remain poorly understood. This study aimed to identify key traits that underpin salinity tolerance and can inform breeding and agronomic strategies to enhance soybean performance under saline conditions. Two contrasting soybean genotypes, YAKARTA and POCA, were exposed to 25, 50, 75, and 100 mM NaCl from the first to the fourth trifoliate stage (V1–V4) under controlled conditions for 30 days. YAKARTA maintained higher relative water content (75.51% vs. 66.97%), stomatal conductance (342 vs. 286 mmol H2O m−2 s−1), proline (6.15 vs. 4.36 µmol g−1 fresh weight), K+/Na+ ratio (61.8 vs. 32.2), and H2O2 (833.8 vs. 720.2 µmol g−1 fresh weight) compared with POCA, whereas POCA exhibited elevated solute leakage (87.1% vs. 79.21%), malondialdehyde (122 vs. 112 µg g−1), and ascorbic acid (334 vs. 293 µg g−1), indicating greater sensitivity. At 100 mM NaCl, relative water content, stomatal conductance, K+/Na+ ratio, and H2O2 declined by 44.5%, 81.9%, 99.8%, and 49.5%, respectively, while proline, solute leakage, malondialdehyde, and ascorbic acid increased by 56-, 1.27-, 11.6-, and 1.68-fold, respectively. The contrasting physiological and biochemical responses between these genotypes highlight key traits, such as relative water content, stomatal conductance, proline accumulation, malondialdehyde content, and the K+/Na+ ratio, as promising potential markers associated with salinity tolerance in soybean. These findings provide a foundational understanding that can guide future research to validate these markers across a wider genetic pool and under field conditions.