DNA fingerprinting shows high adoption of improved cassava varieties in Nigeria

DNA fingerprinting shows high adoption of improved cassava varieties in Nigeria

DNA fingerprinting has improved the accuracy of adoption studies and revealed that 66% of surveyed cassava farmers in Nigeria are cultivating improved varieties.

Improved cassava varieties can boost yields, helping rural African farm families to become food secure and overcome poverty. A study published in 2017 by the International Institute of Tropical Agriculture (IITA) and partners, with support from RTB, suggests that the adoption of improved cassava varieties is higher than was previously thought. DNA-fingerprinting of cassava leaves revealed that about 66% of surveyed Nigerian cassava growers have adopted improved varieties. Extrapolating these results suggests that around 3.1 million households nation-wide grow the new cassava varieties.

Since the early 1970s, the International Institute of Tropical Agriculture (IITA) has been breeding cassava varieties with resistance to major diseases such as cassava mosaic virus disease (CMD) and cassava bacterial blight (CBB). IITA and partners have developed and released more than 46 high-yielding, disease-resistant cassava varieties, working with the National Root Crop Research Institute of Nigeria (NRCRI), state governments and multiple agencies and projects to promote uptake.

The 2017 study used a large survey to determine the rate of adoption of improved cassava varieties on small farms in Nigeria. The survey covered 2,500 farming households in 16 states that contribute at least 80% of the total production of cassava in Nigeria. Each surveyed household self-reported the improved cassava varieties they had adopted. Besides collecting socio-economic data, the team also sampled cassava leaves for DNA-fingerprinting from each cassava variety in each farm plot of surveyed farmers. DNA-fingerprinting is an accurate way to identify varieties grown by farmers, allowing credible measurement of adoption of improved varieties.

About 60% of the cassava farmers reported planting improved varieties. However, DNA-fingerprinting showed that about 66% of the farmers had adopted improved cassava varieties. This may seem like a slight difference, but the misclassification rate is large. Misclassification happens when farmers who think they are growing improved varieties are actually growing local ones or vice versa.

“Farmers do not always know if they are growing improved cassava varieties or not. By comparing farmers’ responses with the DNA fingerprinting we were able to see that some farmers were growing improved cassava without realizing it and others were growing local varieties that they thought were improved,” said Dr. Abdoulaye Tahirou, impact economist at IITA.

IITA and partners have developed more than 46 improved cassava varieties, such as these pictured at IITA in Ibadan, Nigeria. Credit: H.Holmes/RTB

The surveyed farmers plant about 38% of their cassava area with improved varieties. Informal seed systems are important for sharing improved varieties, with over 70% of the farmers obtaining new varieties mainly from friends, relatives and neighbors. As cassava planting material is shared through local networks, farmers are often unsure if such varieties are improved or not. For example, in the village of Oke Dayo, in Kogi state in 2016, women farmers told researchers Tessy Madu of NRCRI and Olamide Olaosebikan of IITA, “most of us plant Oko Iyawo which we believe is an improved variety. Last year some women who went for immunization at the health center were given some cassava cuttings and we believe those are improved variety.” This uncertainty over varietal identity in seed provision is a strong justification for a more structured and integrated approach where trueness to type of seed can be guaranteed, such as is being promoted under the ‘Building a Sustainable, Integrated Seed System for Cassava in Nigeria’ (BASICS) project.

About 4.7 million households in Nigeria grow cassava on about 5.2 million ha. An adoption rate of 66% means that about 3.1 million households adopted improved cassava varieties on 2 million ha. Improved varieties are associated with productivity gain of 82% in farmers’ fields, so adoption has led to a 4.6% poverty reduction (using a poverty line of USD1.90 per person, per day), implying that 7.5% of the rural poor cassava producers escaped poverty by adopting improved cassava varieties.

Photo: Close to 4.7 million households in Nigeria grow cassava which is a major staple food. Credit: H.Holmes/RTB