Differential trade-offs between morpho-physiological, antioxidant profile and nutritional qualities of proso millet seedlings under elevated UV-B radiation

Amid numerous climate-crisis, elevated UV-B (eUV-B) influences the productivity and quality of common crops; however, its impact is unexplored in nutritionally enriched millet. The present study demonstrates the impact of eUV-B radiation on seedlings of two Proso millet cultivars (TNAU 145 and TNAU 202). We investigated detailed morpho-physiological characteristics, nutritional qualities and biochemical parameters in these cultivars under eUV-B. Our result indicated eUV-B induced germination and biomass accumulation with substantial decrease in chlorophyll and carotenoid and photosynthetic efficiency (F_v/F_m) in both the cultivars. TNAU 145 showed significantly higher membrane lipid peroxidation and solute leakage than TNAU 202, indicating greater UV-B susceptibility. Total phenolic content was increased by 81.5% and 73.2% in TNAU 202 and TNAU 145 respectively, although flavonoid content was exclusively increased in TNAU 145 by 31.5%. Significant increase for ROS was recorded in TNAU 202 (H₂O₂ by 23% and, .O₂^- by 25.3%) contrary to TNAU 145 (H₂O₂ by 29.7% and .O₂^- by 29.5%) whereas antioxidants were increased by 12.5% (SOD), 21.1% (CAT) and 37.5% (APX) in TNAU 202. Moreover, significant increase was observed for total soluble sugar (34%), reducing sugar (13.7%), starch content (16.7%), total protein (3.4%) content and total free amino acid (11.8%) in TNAU 202 reflecting the germination-induced biochemical changes in combination with UV-B radiation. The present study indicated that enhanced antioxidants and bioactive compounds in TNAU 202 attributed to its better performance under eUV-B leading to improved nutritional qualities and biomass accumulation relative to TNAU 145.