A field experiment was conducted during the years 2022 and 2023 to evaluate eight sorghum varieties for salinity tolerance based on their photosynthetic efficiency under saline conditions. The salinity under the field conditions varied between 8 to 10 dS m-1 in each subplot. Exogenous application of melatonin (0, 50, and 100 µM L-1) was given at 35 and 50 DAS to mitigate the adverse effect of salinity stress. Among all the varieties, a significantly higher chlorophyll a and b content was observed in HJ 513 (3.9 and 0.91 mg g-1 FW) and HC 308 (3.6 and 0.81 mg g-1 FW) compared to other genotypes under study, respectively. Maximum chlorophyll stability index (CSI) was observed in HC 308 (96.9) followed by CSV 32F (96.0) with application of 100 µM L-1 melatonin. Melatonin concentration 100 µM L-1 was found most effective in mitigating the adverse effect of salinity and varieties HC 308, HJ 513 and HJ 541 performed relatively superior to other varieties which can be used in crop breeding programs aimed to improve salt tolerance in sorghum.

Sorghum bicolor, salinity, melatonin, chlorophyll content, photosynthesis

Based on the current investigation, it can be concluded that salinity stress adversely affected the photosynthetic efficiency of all the sorghum varieties. However, foliar application of both concentrations of melatonin (50 and 100 µM L-1) significantly mitigated the adverse effect of salinity stress. All the varieties performed differently due to their difference in their genetic potential. Forage sorghum varieties HC 308, HJ 513, HJ 541 and CSV 35F performed relatively better compared to other varieties in terms of higher chlorophyll content, higher CSI and lower TMD (%) while varieties CSV 32F and HC 260 performed relatively poor compared to other varieties. Application of 100 µM L-1 melatonin was found most effective in mitigating the adverse effects of salinity compared to 50 µM L-1 and control. Conclusively, HJ 513, HJ 541 and HC 308 varieties have significant potential for higher forage production under saline areas and can be used in crop breeding programs for salt tolerance while foliar application of melatonin can also be potentially exploited for mitigating the adverse effect of salinity in various crops

Gayatri Kumari, Sarita Devi, Satpal, Charan Singh, Pankaj, Bhupnesh and Ankisha (2025). Exogenous Application of Melatonin Mitigates Salinity Stress by Modulating the Photosynthetic Efficiency of Sorghum bicolor (L.). Biological Forum, 17(6): 14-19.