Research shows that potato seed sold in local seed markets is often of unknown quality and health, and may have diseases that affect the quality and quantity of productivity, which can only be assessed through laboratory testing.16 Reportedly, more than 70 percent of potato seed planted in Tanzania is infected with bacteria wilt (BW),17 which can remain in the soil even without a host, sometimes for years.

Once the soil is contaminated, productivity can still be affected even when disease-free seeds are planted. For instance, 80 percent of farms producing certified seed were reportedly infected with potato cyst nematode (PCN).19 Late blight is another disease associated with poor quality seed potato, affecting some uncertified seed from local markets.