Landraces persist where seed does not reach: genotype inventory, farmers’ perception and demand for improved versus landrace yam (Dioscorea spp.) genotypes in Oyo State, Nigeria
Despite the availability of improved yam varieties with higher yields in Oyo State, Nigeria, farmers predominantly cultivate landraces due to a critical lack of seed access rather than a reluctance to adopt new genotypes.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the humid, rolling landscapes of West Africa, the yam is more than just a crop; it is a cornerstone of culture, a marker of status, and a vital source of income for countless households. Unlike wheat or corn, which are grown from tiny seeds, yams are propagated from pieces of the tuber itself. A farmer cuts a section of a harvested yam, lets it heal, and plants it to grow the next crop. This method means that the health and quality of the planting material are everything. If the piece planted is diseased or weak, the entire harvest suffers. For decades, scientists have worked to create "improved" yam varieties—plants bred in research stations to be larger, more resistant to disease, and capable of producing far more food per acre than the traditional types farmers have grown for generations. These new varieties exist on paper and in test fields, promising to solve a long-standing gap between what yams could produce and what they actually do. Yet, despite years of effort to get these superior plants into the hands of farmers, they remain largely absent from the fields where they are needed most.
A team of researchers from the University of Ibadan and the International Institute of Tropical Agriculture set out to understand why this disconnect exists in Oyo State, a major yam-producing region in southwestern Nigeria. They wanted to know what farmers were actually growing, why they chose those specific plants, and whether the lack of adoption was due to farmers simply not wanting the new varieties or something else entirely. To find the answer, the researchers traveled to five different farming centers across the state, from the bustling outskirts of Ibadan to the quieter northern towns. They spoke with twenty-eight farmers, many of whom were part of local cooperatives, and walked through their fields to take a detailed inventory of the yams growing there. They recorded the names farmers used for their crops, measured the size of the tubers, and noted the physical characteristics of the leaves and skin to identify the species. They also asked the farmers directly why they chose the plants they did and what stopped them from trying the new, improved versions.
The picture that emerged from the fields was striking. The researchers found a rich diversity of thirty-five different yam types, mostly traditional varieties known as landraces that have been passed down through generations. These landraces were named with distinct local titles, each carrying a specific reputation for taste, storage life, or market value. In contrast, the improved varieties released by scientists over the last two decades were almost entirely missing. Out of all the farmers surveyed, none were growing an improved variety exclusively. Only one improved type, a water yam called VA Yam, was found at all, and it appeared in just a single location with very few plants. This single improved variety was actually the heaviest of all the yams measured, weighing an average of 3.9 kilograms per tuber, yet it had failed to spread beyond that small patch. The farmers who grew it alongside their traditional crops kept the traditional ones on the larger share of their land.
When the researchers asked the farmers why they stuck with the old varieties, the answer was not a rejection of the new ones. The farmers did not say the improved yams were bad or that they preferred the taste of the old ones. Instead, they said the improved seed simply was not available to them. They grew what they could find in the local markets at planting time. The study revealed that the barrier was not a lack of interest or a stubborn attachment to tradition, but a physical shortage of the planting material. The researchers noted that the informal system of farmers trading seeds with one another is actually very effective at spreading new plants when they are introduced. They pointed to a foreign yam variety called Côte d'Ivoire, which had no official release or government support, yet had spread widely across the region because farmers liked its taste and size and shared it with their neighbors. This proved that if the improved seed were available in the local market, the farmers would likely adopt it just as they had adopted the foreign variety.
The study also highlighted a quiet crisis of genetic loss. Some yam names that were once common in the fields and markets were reported by farmers to be disappearing, likely because the planting material had become diseased or weak over years of reuse. Other unique varieties were found only on the farms of the oldest growers, cultivated on small plots as those farmers reduced their work with age. These findings suggest that without intervention, these unique genetic treasures could vanish forever. The researchers concluded that the solution lies not in trying to convince farmers to change their minds, but in fixing the supply chain. They proposed that the existing networks of farmer cooperatives and local seed traders should be supported to multiply and distribute the improved seeds. By getting the high-performing seeds into the same informal markets where farmers already shop, the gap between scientific potential and farm reality could finally be closed, allowing the improved yams to take root where they have been waiting for years.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.