Waterlogging Effects on Root Morphology, Yield, and Stress Tolerance in Cowpea (Vigna unguiculata L. Walp) Grown on Semi-Arid Vertisols

Abstract

Waterlogging, a global environmental stress, jeopardises food security, causing an economic loss of US$ 74 billion. This could intensify by 14%–35% due to climate change, particularly affecting leguminous crops by altering root morphology and yields. Therefore, studies on the crops root systems and yield reduction to waterlogging stress are required to ensure global food security (sustainable development goals; SDG 2) and an adaptation strategy against climate threats (SDG 13). Hence, studies were conducted for 2 years (2022 and 2023) to understand the effect of varied durations of waterlogging (1–25 days) at three growth stages (15 DAE; Days After Emergence, 25 DAE and at 50% flowering) of cowpea. Results revealed that the highest reduction in root length density (17.97%), surface density (17.31%), weight density (17.63%) and volume density (19.60%) was observed at early growth stages of cowpea (15 DAE) over control. As a result, the maximum reduction in crop growth and grain yield (62.90%) with the lowest yield stability index (YSI ~0.62) and stress tolerance index (STI ~0.78) were recorded. Waterlogging for 17 to 25 days significantly reduced root morphological features and growth, resulting in highest reduction in grain yield (71.32%–81.64%), and the lowest YSI and STI. Notably, plants at early growth stages produced a greater number of lengthier aerial roots with increasing waterlogging durations after 7 days. Whereas, the interaction of 1 day waterlogging at 25 DAE reported minimal yield reduction (~0.36%) with greater YSI (~0.99) and STI (~1.52). Therefore, the sensitivity of cowpea roots to waterlogging explained the reduction in grain yield and stress tolerance. In conclusion, cowpea was found to be highly sensitive at early growth stages (15 DAE) after 3 days of waterlogging stress on vertisols of semi-arid tropics.