Genome editing of MeSWEET10A for cassava bacterial blight resistance

Overview

Cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xam), is one of the most destructive diseases of cassava, threatening food security across sub-Saharan Africa. This program targets the MeSWEET10A susceptibility gene, whose promoter contains an Effector Binding Element (EBE) recognized by the Xam TAL20 effector. By using CRISPR-based editing to disrupt or remove the EBE, the host gene can no longer be hijacked by the pathogen, suppressing disease establishment. Early proof-of-concept lines have shown loss of MeSWEET10A expression alongside reduced bacterial growth and milder symptoms, indicating strong potential for durable CBB resistance.

Technical specifications

• Pathogen target: Xam TAL20 effector and its interaction with the EBE in the MeSWEET10A promoter
• Editing approach: CRISPR/Cas-mediated knockout of the EBE region using Agrobacterium-mediated transformation of cassava friable embryogenic callus (FEC)
• Validation pipeline: Targeted sequencing of recovered lines to confirm mutation extent, reverse transcription analysis to verify gene repression, and Xam infection assays to measure symptom severity and bacterial colonization
• Current results: Two edited lines showed complete loss of MeSWEET10A expression and significant reduction in disease symptoms and bacterial growth
• Next steps: Design an expanded gRNA repertoire to delete larger portions or the entire EBE, scale up transformation to recover larger populations, and conduct multi-season field validation for durability

Technology readiness level

The technology is at an early-to-mid stage of development (TRL 4–5). Proof-of-concept has been demonstrated in controlled laboratory and greenhouse assays, with edited cassava lines showing measurable disease resistance. Further work is needed to expand editing scope, scale up line production, and validate resistance durability under field conditions across multiple agro-ecologies. The two-year validation plan includes expanded gRNA design, construct development, cassava transformation, and field assessment of candidate lines.