Flooding stress resilience and crop improvement

Promoting the long-term viability of agriculture in the face of climate change has spurred a rise in alternative approaches to enhance crop resilience. Universally, the significant risk of crop yield reduction in cereal crops due to flooding has become a prominent concern, and this threat is anticipated to intensify in various regions worldwide due to future climatic anomalies. Flooding stress induces oxygen (O₂) deficiency within the plant system, serving as a major restriction for plant growth during submerged and waterlogged environments. Plants experience fluctuating levels of O₂ contents, including normoxia, hypoxia, and anoxia, which can vary across both time and space. Gaining insight into how plants adapt to unexpected flooding is essential for the generation of novel crop cultivars having enhanced resilience to such conditions. Although several research studies on the flooding toxicity impact on plants are available, as well as different adaptive strategies to reduce these detrimental effects. However, many of them focussed on two adaptive mechanisms of the plants, or types of flooding and their toxicities in plants, or based on regulatory role of genes network involved in flooding stress, but we have attempted to include all these facts in one platform for better clarification of readers. In this context, we systematically outline the survival strategies employed by plants in response to flooding stress, addressing morphology, physiology, anatomy, and metabolic aspects. These strategies include anaerobic germination (AG), the development of adventitious roots (ARs), the formation of aerenchyma, radial O₂ loss (ROL) fences, photosynthetic activity, and engagement in fermentative metabolism. Furthermore, we delve into the molecular mechanisms that underlie these adaptive strategies, providing a summary of recognised efficient genes or proteins involved in flooding resilience. The regulatory roles of phytohormones, particularly ethylene and its related transcription factors (TFs) from the group VII Ethylene Response Factor (ERF-VII) family, are also discussed. We compile and analyse information on ERF-VIIs in major crops and those associated with plant flooding stress resilience mechanisms. The article also explores the potential contributions of nitric oxide (NO) and hyponasty in the context of flooding exposure. Finally, we highlight and discuss potential future research directions. As we strive to develop flooding-resistant crops with desired agronomical traits for sustainable agriculture in a growing world population, understanding the diverse mechanisms through which plants shield themselves from flooding stress becomes crucial. This article serves as a reference for future studies on plant flooding stress tolerance and the breeding of novel, resilient crop varieties.