Screening and evaluation of sorghum germplasm for salinity tolerance using physiological indices in hydroponic culture

Abstract

Salinity is a major abiotic stress limiting crop productivity globally, particularly in coastal and deltaic regions prone to saltwater intrusion. This study aimed to screen and evaluate eighteen Sorghum bicolor L. germplasm for salinity tolerance using physiological and biochemical indices under controlled hydroponic conditions. The experiment was conducted in a completely  randomized design with two salinity treatments (0 and 12 dS m^-¹), replicated thrice, in the physiology laboratory of Bangladesh Agricultural University. Morphological (shoot/root length, leaf number), physiological (SPAD value, Fv/Fm, proline content), and biochemical traits (Na⁺, K⁺, and K⁺/Na⁺ ratio) were assessed to quantify salinity responses. Significant genotypic differences (p ≤ 0.001) were found in key indices: shoot length stress tolerance index ranged from 74.16% (BD-738) to 92.10% (BD-713), while root-shoot ratio reached a maximum of 135.34 in Safal 999. The highest K⁺/Na⁺ ratio was observed in sorghum BD-731 (10.44), whereas sorghum BD-701 showed the lowest (2.16), indicating high susceptibility. Proline accumulation increased under stress, notably in sorghum BD-713 and Hybrid Sorgo, suggesting osmotic adjustment mechanisms. Based on visual SES scoring, five genotypes (Sorghum BD-703, Sorghum BD-706, sorghum BD-713, sorghum BD-730, sorghum BD-737) were classified as tolerant, and seven as moderately tolerant. Hydroponic screening coupled with physiological indices provided a robust and reproducible method to identify salinity-tolerant sorghum lines. These findings highlight sorghum BD-703, Sorghum BD-713, Sorghum BD-706, and Hybrid Sorgo as promising candidates for further field evaluation in salt-affected environments.