Engineering vascular potassium transport increases yield and drought resilience of cassava

Cassava (Manihot esculenta) is an important crop for food security in the tropics, particularly for smallholder farmers in sub-Saharan Africa, where yields are often severely limited by pathogen pressure, nutrient deficiency and water scarcity. We expressed a non-rectifying Arabidopsis thaliana potassium (K⁺) channel gene version, AKT2_var, in the vascular tissue of cassava plants. The transgenic cassava plants had higher electron transport and CO₂ assimilation rates, a higher bulk flow velocity and increased source-sink carbohydrate transport, as demonstrated by comparative ¹¹C-positron emission tomography and tissue-specific metabolite profiling. Cassava storage root yield was significantly increased in greenhouse experiments and in a multi-year field trial conducted under subtropical conditions. AKT2_var plants were also more tolerant of drought stress and had higher storage root yield. Targeted alteration of K⁺ transport is therefore a promising strategy to improve cassava productivity without additional fertilizer input and in climate-adverse growing conditions.