Reassessing Drought Tolerance in Citrus Tetraploid Rootstocks: Myth or Reality?

Polyploidy, particularly tetraploidy, has emerged as a promising tool in citrus rootstock breeding due to its potential to enhance drought tolerance. This review examines the role of tetraploid rootstocks in drought resilience, focusing on molecular and physiological adaptations observed in controlled environments and field conditions. Tetraploids display traits such as increased abscisic acid (ABA) production, antioxidant defenses, and osmotic adjustments. However, these advantages often fail to translate into superior drought tolerance in field conditions, where competition for resources and environmental complexities significantly influence plant responses. Recent evidence suggests that methodological limitations in earlier studies, particularly in pots, may have overstated the benefits of tetraploids. Field studies indicate that diploids, with more extensive root systems and greater water extraction capacity, often outperform tetraploids under water stress. To advance citrus breeding, it is essential to standardize experimental approaches, control soil matric potential, and prioritize long-term studies. Identifying key genes and metabolic pathways associated with drought tolerance, along with the application of advanced tools such as CRISPR/Cas9, will enable the development of resilient rootstocks, ensuring sustainable citrus production amidst increasing water scarcity and climate change.