Does cyclic water stress damage wheat yield more than a single stress?

Abstract

The occurrence of water stress during wheat growth is more frequent due to climate change. Three experiments (cyclic drought, cyclic waterlogging, and cyclic drought plus waterlogging) were conducted to investigate the effects of mild and severe cyclic/single water stress at elongation and heading stages on winter wheat (Triticum aestivum L.) yield. The effect of either mild drought at elongation or mild waterlogging at heading on wheat yield was not significant; however, significance did occur under other single water stresses. As the stress becomes more severe, the yield loss significantly increases. Extreme drought/waterlogging treatment at elongation caused a greater yield penalty than stress at heading stage. Except the combination of mild drought and mild waterlogging treatment, cyclic water stress significantly decreased wheat yields. The decrease in wheat yield under cyclic severe drought and waterlogging was significantly higher than any other treatment, with percentage decreases of 71.52 and 73.51%, respectively. In general, a yield reduction from mild cyclic water stress did not indicate more severe damage than single treatments; in contrast, grain yield suffered more when water stress occurred again after severe drought and waterlogging. Drought during elongation significantly decreased kernel number, whereas drought at heading/waterlogging during elongation and heading decreased the spike weight, which might be the main reason for the yield penalty. Furthermore, water stress caused variation in the decrease of total biomass and/or harvest index. The present study indicates comprehensive understanding of the types, degree, and stages of water stress are essential for assessing the impact of multiple water stresses on wheat yield.

Fig 1

Relative soil moisture content during cyclic drought (A), cyclic waterlogging (B), and cyclic drought with waterlogging (C) experiments.

Fig 2. Effects of drought stress during the stages of elongation and heading on grain yield and HI.

CK, MD and SD denote control, mild drought, and severe drought, respectively. Different letters indicate statistical significance among treatments at the P≤0.05 level.

Fig 3. Effects of waterlogging stress at the elongation and heading stages on grain yield, kernels per spike, 1000-kernel weight and total biomass.

CK, MW and SW denote control, mild waterlogging, and severe waterlogging, respectively. Different letters indicate statistical significance at the P≤0.05 level among different treatments.

Fig 4. Effects of drought and waterlogging stress at the stages of elongation/heading on grain yield.

CK, MD and MW denote control, mild drought and mild waterlogging, respectively. Different letters indicate statistical significance at the P≤0.05 level among different treatments.