Differential response of sugar beet to long-term mild to severe salinity in a soil–pot culture

Attempts to cultivate sugar beet (Beta vulgaris spp. vulgaris) in the sub-tropical saline soils are ongoing because of its excellent tolerance to salinity. However, the intrinsic adaptive physiology has not been discovered yet in the sub-tropical climatic conditions. In this study, we investigated morpho-physiological attributes, biochemical responses, and yield of sugar beet under a gradient of salinity in the soil–pot culture system to evaluate its adaptive mechanisms. Results exhibited that low and high salinity displayed a differential impact on growth, photosynthesis, and yield. Low to moderate salt stress (75 and 100 mM NaCl) showed no inhibition on growth and photosynthetic attributes. Accordingly, low salinity displayed simulative effect on chlorophyll and antioxidant enzymes activity which contributed to maintaining a balanced H₂O₂ accumulation and lipid peroxidation. Furthermore, relative water and proline content showed no alteration in low salinity. These factors contributed to improving the yield (tuber weight). On the contrary, 250 mM salinity showed a mostly inhibitory role on growth, photosynthesis, and yield. Collectively, our findings provide insights into the mild–moderate salt adaptation strategy in the soil culture test attributed to increased water content, elevation of photosynthetic pigment, better photosynthesis, and better management of oxidative stress. Therefore, cultivation of sugar beet in moderately saline-affected soils will ensure efficient utilization of lands.