Two Genome-Edited Trees Are Approved

Two non-transgenic genome-edited orange plants — a Hamlin and a Valencia that may resist HLB — have been federally approved and are ready for Florida growers. Nian Wang, University of Florida Institute of Food and Agricultural Sciences eminent scholar endowed chair in biotechnology, reported this news in a June 17 virtual presentation.

The plants, which Wang termed “Eds1-edited,” have received regulatory approvals from the U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) and the Environmental Protection Agency (EPA). He reported that the Hamlin and Valencia plants are ready for planting by growers but need propagation by nurseries.

BACKGROUND

Before providing the advantages of and cautions relating to the new plants, Wang provided some background information. He noted HLB is a pathogen-triggered immune disease. Candidatus Liberibacter asiaticus (CLas), the bacterium that causes HLB, triggers systemic and chronic immune responses, including reactive oxygen species (ROS) production and callose deposition, leading to phloem cell death and HLB symptoms. Wang said that manipulation of either ROS or phloem callose deposition can partially reduce HLB damage.

ADVANTAGES

Wang gave several reasons to consider using the Eds1-edited plants in the fight against HLB in Florida groves:

• Editing of Eds1 abolishes CLas induction of ROS production, phloem callose deposition and phloem cell death. Thus, the plants are likely HLB tolerant.
• The plants have received APHIS and EPA approvals.
• There are no effects on citrus growth and fruit quality.

CAUTIONS

Wang provided what he termed “cautions to adopt the non-transgenic Eds1-edited sweet orange against HLB and how to address them.” This includes the following points:

• Mutation of Eds1 likely reduces accumulation of salicylic acid (SA), thus reducing disease resistance against several biotrophic pathogens such as the citrus canker pathogen but increases resistance against phytophthora.
• This compromise is partially alleviated by rootstocks. Most commercial rootstocks are resistant or tolerant against most biotrophic pathogens.
• The compromise mainly results from reduced accumulation of SA. Foliar spray with SA can prevent this issue related to Eds1-edited plants.
• The benefit of improving disease tolerance against HLB using this approach likely outweighs the cost because most scion diseases, except HLB, have effective control approaches.  

Wang provided more information about the plants, HLB and his work on other non-transgenic plants in his virtual presentation.