Insights into drought tolerance in sugar beet (Beta vulgaris L.) focusing on adaptive mechanisms and mitigation approaches

Drought stress is a major environmental factor limiting global sugar beet production. Water deficit impairs photosynthesis, disrupts osmotic balance, induces oxidative stress, and disturbs source–sink relationships, ultimately leading to inhibited root growth, reduced sucrose accumulation, and decreased overall yield. In response to drought stress, sugar beet initiates a series of adaptive mechanisms. Morphologically, it develops deeper roots and reduces leaf area to optimize water uptake and conservation. Physiologically and biochemically, it accumulates osmoregulatory compounds such as proline and glycine betaine to maintain cellular turgor and enhances the activity of antioxidant enzymes to mitigate oxidative damage. At the molecular level, drought tolerance involves the induction of stress-responsive genes and transcription factors including DREB (dehydration-responsive element-binding) proteins, MYB (myeloblastosis) factors, NAC transcription factors (e.g., NAM (no apical meristem), ATAF (Arabidopsis transcription activation factor), and CUC (cup-shaped cotyledon)), and WRKY transcription factors, as well as signaling molecules such as abscisic acid and aquaporins. In addition to these inherent tolerance mechanisms, external management practices can enhance drought resistance. These include optimized irrigation scheduling, soil amendments such as biochar and vermicompost, foliar application of plant hormones (e.g., abscisic acid, gibberellic acid, and jasmonic acid), and the use of nanoparticles such as fullerenol and silicon. However, the efficacy of nanoparticles is strongly dose-dependent. This review synthesizes current knowledge on drought responses in sugar beet, identifies key research gaps, and proposes strategies to alleviate drought stress, with an emphasis on morpho-physiological, biochemical, and molecular adaptations. It aims to provide a theoretical foundation for developing drought-tolerant sugar beet cultivars and formulating sustainable production strategies under changing climatic conditions.