Forage quality analysis in response to salt stress and plant maturity in Sorghum

In the present study, forty sorghum (Sorghum bicolor L. Moench) genotypes were evaluated for salt tolerance during autumn 2020 and among these, three salt-tolerant genotypes (SPSSV40, SCL3 and PV2068) were examined for forage quality under different salt concentrations and plant age (40, 50 and 60 days after sowing) at Punjab Agricultural University, Ludhiana, during autumn season 2021. The treatments included three salt concentrations (50 mM, 100 mM and 150 mM) which were compared with the control conditions (0 mM). The results showed that salt stress significantly decreased the forage quality assessed in terms of crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF), In-Vitro-dry matter digestibility (IVDMD) and hydrocyanic acid of all three sorghum genotypes. CP content and IVDMD declined from 10.57% to 63.99% under control conditions to 7.86 and 51.39% at 150 mM salt concentration, respectively. While, ADF and NDF content increased under increasing salt concentrations varying from 34.97% to 54.88% under control to 42.79% and 62.79% under 150 mM salt concentration. In contrast to this, HCN content increased significantly with 60.88% under control to 69.55% at highest salt concentration, i.e. 150 mM. However, with increase in plant maturity, CP, IVDMD and HCN content decreased significantly, while ADF and NDF content increased substantially. While there was a decrease in the forage quality of all three sorghum genotypes, it remained at an acceptable level and also supported robust plant growth. Consequently, these genotypes can be cultivated in environments with higher salinity levels and can be used to generate breeding material for salt-affected areas.