Summary: This review of the literature on varietal change in sub‐Saharan Africa looks in detail at adoption of new varieties of bananas in Uganda, cassava in Nigeria, potato in Kenya, sweetpotato in Uganda and yams in Côte d’Ivoire. The review explored three hypotheses about drivers of varietal change. There was a strong confirmation for the hypothesis that insufficient priority given to consumer‐preferred traits by breeding programmes contributes to the limited uptake of modern varieties (MVs) and low varietal turnover. Lack of evidence meant the second hypothesis of insufficient attention to understanding and responding to gender differences in consumer preferences for quality and post‐harvest traits was unresolved. The evidence on the third hypothesis about the informal seed system contributing to slow uptake of MVs was mixed. In some cases, the informal system has contributed to rapid uptake of MVs, but often it appears to be a barrier with inconsistent varietal naming a major challenge.

Cassava, originally from South America, is the fourth most important source of calories in the developing world after the cereal crops wheat, maize, and rice. Worldwide, it feeds an estimated 700 million people directly or indirectly. Cassava production has increased steadily for the last 50 years, with 242 MT harvested in 2012. The increase is likely to continue as farmers in more than 105 countries come to recognize the crop’s advantages. A semi-perennial root crop, cassava can stay in the ground for up to 3 years. This makes it an excellent food security crop: when all other crops have been exhausted, cassava roots can still be harvested. It is naturally drought resistant and resilient to climatic changes, high temperatures, and poor soils, and in addition, cassava responds extremely well to high CO₂ concentrations, making it a very important crop for the 21st century. Africa alone accounts for more than 55 % o ...

Value chains linked to urban markets and agro-industry present new opportunities for adding value and raising rural incomes. Small farmers, who produce small volumes, struggle to enter these markets. A lack of trust among value chain actors increases transaction costs and short-circuits innovation. This paper explores how multi-stakeholder platforms have been used to address these problems in potato-based value chains in Bolivia, Peru and Ecuador. It uses the Institutional Analysis and Development (IAD) framework to understand how platforms work. Differences in characteristics of the value chains, the participating actors and institutional arrangements have led to the emergence of two types of platforms. The first type brings traders, processors, supermarkets and others together with farmer associations and research and development (R&D) organizations to foster the development of new market opportunities through commercial, institutional and technological innovation. The second type is structured around geographically delimited supply areas, meshing farmers and service providers to address market governance issues in assuring volumes, meeting quality and timeliness constraints and empowering farmers. Evidence from these cases indicates that platforms that bring stakeholders together around value chains can result in new products, processes, norms and behaviours that benefit poor farmers, which could not have been achieved otherwise.

The development and scaling of orange-fleshed sweetpotato (OFSP) during the past 25 years is a case study of a disruptive innovation to address a pressing need – the high levels of vitamin A deficiency among children under five years of age in sub-Saharan Africa. When the innovation was introduced consumers strongly preferred white or yellow-fleshed sweetpotato, so it was necessary to create a demand to respond to that need. This was at odds with the breeding strategy of responding to consumers’ demands. Additional elements of the innovation package include seed systems and nutrition education to create the awareness amongst consumers of the significant health benefits of OFSP. Complementary innovation is required in promotion and advocacy to ensure a supportive institutional environment.

Vegetatively propagated crop (VPC) seed tends to remain true to varietal type but is bulky, often carries disease, and is slow to produce. So VPC seed needs to be handled differently than that of other crops, e.g., it tends to be sourced locally, often must be fresh, and it is less often sold on the market. Hence, a framework was adapted to describe and support interventions in such seed systems. The framework was used with 13 case studies to understand VPC seed systems for roots, tubers, and bananas, including differing roles and sometimes conflicting goals of stakeholders, and to identify potential coordination breakdowns when actors fail to develop a shared understanding and vision. In this article, we review those case studies. The framework is a critical tool to (a) document VPC seed systems and build evidence; (b) diagnose and treat coordination breakdown and (c) guide decision-makers and donors on the design of more sustainable seed system interventions for VPCs. The framework can be used to analyze past interventions and will be useful for planning future VPC seed programs.