ASHS 2025 Conference

Citrus, a globally significant fruit crop, is rich in nutrients and vitamins but is adversely affected by environmental stresses, particularly drought. Drought stress hinders plant growth and reduces crop yields. This study focused on sour orange (SO) and trifoliate orange (TO) rootstocks to evaluate their performance under control and drought conditions. Transcriptomic results showed that the control vs drought TO have 3620 differentially expressed genes (DEGs) were down-regulated and 2440 genes were upregulated while the control vs drought SO group showed 3625 genes were down-regulated and 2290 genes were upregulated. Most of the DEGs were associated with different molecular functions and biological processes including metabolic pathways, flavonoids biosynthesis, photosynthesis, and glutathione metabolism in both rootstocks under drought; however, the gene expression analysis showed that the expression of flavonoids and glutathione metabolism genes were higher in SO than TO after 12 days of drought stress (12DS). Moreover, the antioxidative enzymes, free radical scavenging activities, and total flavonoids contents were increased in both rootstocks, but the increase was higher in SO than TO, after 12DS. After 12DS, the TO has significantly higher levels of reactive oxygen species, hydrogen peroxide, electrolytic leakage, and malondialdehyde contents than SO. Our study concluded that SO rootstock enhances genes linked to metabolic pathways, flavonoid biosynthesis, photosynthesis, and glutathione metabolism. It also, boosts antioxidant enzyme activities, antioxidant capacity, and flavonoid levels, while effectively neutralizing the reactive oxygen species. Hence, after 12 days of drought stress, sour orange performs better than trifoliate orange in maintaining these protective mechanisms.