Effective weed control can protect yields of cassava (Manihot esculenta)
storage roots from losses. Hence, a herbicide tolerant cultivar could
benefit farmers. The team of Aaron W. Hummel from the University of
Minnesota applied traditional transgenesis and gene editing to generate
glyphosate tolerance in cassava.

The team aimed to replace the native promoter of cassava's
5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene with a strong
constitutive promoter. To achieve this, the team prepared a CRISPR-Cas9
endonuclease that targets the promoter of the EPSPS locus.

Two repair templates were also combined with the guide RNA and the Cas9
nuclease to help initiate homologous recombination and assist in the
insertion of the new promoter. The team then introduced the best-performing
allele of the EPSPS locus into the cassava genome while also performing a
promoter swap. EPSPS-edited plants exhibited normal phenotypes and were
tolerant to high doses of glyphosate.

This study demonstrates a strategy for creating glyphosate tolerance in
crops as well as the potential of gene editing for further improvement of
cassava.

[onlinelibrary.wiley.com]