In Tanzania's Southern Highlands, better seed is tripling potato yields

Tanzania's potato heartland sits in the Southern Highlands — the Njombe, Iringa and Mbeya districts — which together account for an estimated 70 to 80% of national output, helped by a bimodal rainfall pattern that allows two harvests a year.

Where clean seed has reached farmers, the gains have been dramatic. Under a seed-development programme run by the SAGCOT initiative with the Alliance for a Green Revolution in Africa, yields in parts of Iringa rose from under 5.2 tonnes per hectare to about 18 — still short of the 30 tonnes the crop can achieve, but a tripling that, sustained across the region's roughly 50,000 hectares, would exceed national consumption.

The certified-seed supply behind those gains is thin but professionalising. Mtanga Farm, in the Southern Highlands, is the country's main commercial certified-seed producer, raising over 1,200 tonnes of seed a year from tissue-culture minitubers and supplying the Njombe, Iringa and Mbeya zones. A CIP-led project with the University of Helsinki and Tanzanian agencies, including the seed-certification body TOSCI, has rehabilitated laboratories and built greenhouses to expand minituber production across five highland districts.

The hard ceiling is variety choice. Tanzania has only about three legally registered potato varieties, despite the crop's importance — a constraint SAGCOT and AGRA have been working to lift. With more registered varieties, expanded irrigation and value addition, the region boosters call "Africa's potato paradise" could supply far beyond its borders. For now, the gap between 18 and 30 tonnes is mostly a seed-and-variety problem.