Progress in Improving Citrus Resistance Against Huanglongbing via CRISPR Genome Editing
Posted August 2025
Researchers: Nian Wang, Jude Grosser, Ahmad Omar
Contact: Nian Wang, UF/IFAS CREC nianwang@ufl.edu
Summary:
In a recent study, we have identified multiple genes that are required for Candidatus Liberibacter (CLas) triggered immune disease development. CRISPR genome editing technology has been employed to generate over 200 genome edited lines by targeting those genes. Importantly, the non-transgenic genome edited lines for the two top target genes (Eds1 and Dmr6) have received regulatory approvals by both USDA-APHIS and EPA. The non-transgenic genome edited Eds1 (Valencia Super UF W1 and Hamlin Super UF W3) and Dmr6 (Valencia Super UF W2 and Hamlin Super UF W4) citrus trees were provided to the DPI New Budwood Program on July 15, 2025. The non-transgenic Eds1 edited ‘Valencia’ and ‘Hamlin’ are likely tolerant to HLB. Using the HLB pathogen relative which infects tomato, we have found that huanglongbing (HLB) pathogen relative triggers induction of ROS production, and phloem callose deposition through the Eds1 pathway. Knockout of Eds1 abolished the disease symptoms of tomato caused by the HLB pathogen relative. The non-transgenic Dmr6 edited ‘Valencia’ and ‘Hamlin’ are likely resistant to HLB by enhancing the killing of the HLB pathogen. Knockout of Dmr6 is known to increase the level of salicylic acid in response to pathogen infection and increase disease resistance against bacterial, fungal, and oomycete pathogens in many tested crops. It is one of the broadest disease susceptibility gene required for pathogen growth. The Eds1 and Dmr6 edited plants were inoculated with CLas for disease resistance evaluation. Further evaluation of those non-transgenic genome edited lines in field trials are needed.
Take Home Message:
- We have found the genetic evidence for HLB being Candidatus Liberibacter triggered immune disease and those genes are suitable targets for genome editing to improve citrus resistance/ tolerance against HLB.
- The non-transgenic Eds1 and Dmr6 edited lines have received regulatory approvals.
