Waterlogging tolerance of winter crops: Root mass density and canopy dynamics

Waterlogging has become an increasingly important abiotic stress. To develop strategies for mitigating its effects, it is crucial to identify traits that confer tolerance. Root mass density (RMD) is a pivotal trait for waterlogging tolerance; however, the behavior of this trait during waterlogging is not well understood. Therefore, two experimental years were conducted to study the effects of early- and late-waterlogging at the canopy level on wheat (Triticum aestivum L., barley (Hordeum vulgare L.), oilseed rape (Brassica napus L.), and pea (Pisum sativum L.) crops in 1 m(3) containers. The results showed that early-waterlogging reduced RMD, green leaf, and stem dry weights (DWs) in wheat and barley. Nevertheless, they were able to recover without yield penalties. Late-waterlogging had little impact on RMD in wheat and barley; however, it lowered the tiller number and caused accelerated leaf senescence, resulting in a 65% yield reduction in barley. Early-waterlogged oilseed rape and pea also exhibited reduced RMD, with oilseed rape recovering with a 17% yield reduction, whereas pea was the most sensitive crop, showing no recovery and a 90% yield reduction. Overall, early- waterlogging generally reduces RMD, particularly in the shallow soil layer, but with recovery potential. In contrast, late- waterlogging affects yield by reducing tillers/branches and accelerating senescence, with little impact on RMD. Identifying these traits and their responses to waterlogging stress can aid in the development of strategies to mitigate the negative impacts of waterlogging on crops.