Cassava is one of the crops powering the engine of agricultural development in Tanzania. In the latest breakthrough, ‘certified seed’ (= certified planting material) produced by smallholder seed producers has been shown to deliver huge yield benefits to farmers, helping them produce more food and increase their incomes.

In Tanzania, cassava is consumed daily in different forms, including roasted, fried, boiled, and porridge prepared from flour. Its leaves are highly popular as a green vegetable. Although the crop grows well in almost every part of the country, it is badly affected by two viral diseases – cassava brown streak disease (CBSD) and cassava mosaic disease (CMD). These diseases are spread by the whitefly (a tiny insect vector) and through infected planting materials that lead to yield reduction and crop damage.

To curb the effects of these diseases, the International Institute of Tropical Agriculture (IITA) in collaboration with Mennonite Economic Development Associates (MEDA), the Tanzania Agricultural Research Institute (TARI) and the Tanzania Official Seed Certification Institute (TOSCI) work closely with the Ministry of Agriculture to develop improved disease-resistant varieties and reinforce the development of an economically sustainable seed system. A key aim is to help farmers get high-quality, disease-free planting material of the best new varieties.

A recent study conducted by the cassava seed system team that explored the benefits of certified seed in the Eastern and Lake Zones found that farmers who used certified seed got substantially greater yields than farmers who used uncertified (recycled) seed. Certification is a process in which TOSCI inspects a seed producer’s field to check seed quality and ensure that pests and diseases are well managed.

The research team measured cassava yields in the selected fields of 36 farmers in the Eastern Zone (growing variety Kiroba) and 36 farmers in the Lake Zone (growing variety Mkombozi). In each zone, the study ensured half of the assessed farmers had used recycled seed (uncertified), and half had used certified seed so that the two could be compared.

“In the Eastern Zone, farmers who planted certified seeds got 34% greater yields than those who planted recycled seed of the same variety,” Rudolph Shirima, a Plant Virologist at IITA Tanzania, said. “In the Lake Zone, the difference was even greater, and yields of variety Mkombozi from certified seed were 42% more than those from recycled seed of the same variety”. Shirima, who is a member of the research team, explained that the yield increases translate to profit gains of TSh 1,030,600 (US$445) per hectare for Kiroba and TSh 678,600 (US$293) for Mkombozi.

The team pointed out that the findings are being validated through field experiments at several sites by measuring the yields that can be obtained from the seed of each of the four certified cassava seed classes currently recognized in Tanzania and comparing them with farmer-saved seed of the same improved varieties.

These studies demonstrate the importance of quality seed, the value of seed certification, and the necessity for farmers to purchase certified seed to avoid yield losses and the associated threats to food insecurity.

As healthy cassava seed flows through Tanzania’s steadily expanding modernized seed system, millions of smallholder farmers stand to benefit from improved yields and new income generation opportunities. This will have a vital positive impact on food security in the country and underline Tanzania’s efforts to transform its agricultural economy through the development of the cassava sub-sector.

The research was carried out under the “Building an Economically Sustainable Seed System for Cassava in Tanzania (BEST)”, which supported the country’s cassava seed system development initiative from 2017 to 2021. The work is now being supported by the “Building an Economically Sustainable Integrated Cassava Seed System, Phase 2 (BASICS-II)” project working in Nigeria and Tanzania.