HOUSEHOLD DETERMINANTS OF THE ADOPTION OF IMPROVED CASSAVA VARIETIES USING DNA FINGERPRINTING TO IDENTIFY VARIETIES IN FARMER FIELDS: A CASE STUDY IN COLOMBIA

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Abstract

We examine factors affecting the adoption of improved cassava varieties of 217 households in the Cauca Department in southwest Colombia. Using DNA fingerprinting through Single Nucleotide Polymorphisms (SNPs), we identified different cultivars in farmers fields. We also used this information to remove possible bias in the adoption model that could have resulted from a misclassification of improved varieties (IVs). As a result, we found that farmers substantially overestimate their use of IVs and there are important differences in the determinants of adoption between farmer self‐identification and DNA fingerprinting. This finding implies that the incorporation of DNA fingerprinting in IV adoption studies is important to ensure the accuracy of future agricultural economic research and the relevance of subsequent policy recommendations.

1 Introduction

Cassava (Manihot esculenta Crantz) is a key crop in tropical countries because it can be cultivated in marginal conditions, with principal traits including: tolerance to low or unpredictable rainfall; cultivability in acidic or nutrient‐deficient soils; easy and low‐cost propagation; ability to be grown all‐year round (Henry and Hershey, 2002; Howeler et al., 2013). In Colombia, smallholders have traditionally grown cassava but high demand for cassava starch has increased the number of large plantation style farmers. However, nearly all the pests and diseases known to affect cassava are present in the country (Henry and Hershey, 2002) making the adoption and studies on the adoption of improved varieties (IVs)1 critical.

Up to now, nearly all studies on the factors affecting adoption of IVs have relied on farmers’ self‐reported cultivar names to estimate varietal adoption (Labarta et al., 2015). Despite efforts by recent studies to engage crop experts with photographs and morphological descriptors, many studies have encountered difficulty in verifying crop varieties cultivated by farmers (Larochelle et al., 2015; Walker, 2015). These difficulties are particularly acute in cassava, which is exclusively maintained by vegetative propagation (stem cuts or in vitro culture). Vegetative propagation allows easy exchange of planting materials among farmers, but maintaining the full genetic integrity of these materials is challenging as farmers do not use uniform naming conventions or uniform cultivar arrangements on their farms.

In recent years, the incorporation of DNA fingerprinting in agricultural economic studies has been proposed to resolve IV identification issues. We use DNA fingerprinting and econometric analysis to compare the determinants of adoption of improved cassava varieties between farmer self‐reported identification and identification by geneticists in the Cauca department of Colombia.

2 Cassava Production and the Use of Improved Varieties in Cauca

In Colombia, cassava remains a staple food, retaining a special status in food and livelihoods of the poor, particularly for cassava starch making (Hershey et al., 2000; Howeler et al., 2013). In addition, cassava genetic diversity in the Americas provides numerous opportunities for improvement through research and development. In Colombia alone, there are hundreds of cassava landrace varieties and at least 15 IVs bred by the Centro Internacional de Agricultura Tropical (International Center for Tropical Agriculture, ‘CIAT’) and the Corporación Colombiana de Investigación Agropecuaria (Colombian Corporation for Agricultural Research, ‘CORPOICA’). Each of these IVs was developed over at least 8 years through selective crossing of landraces2 and older IVs for five key characteristics: fresh root yield, dry matter yield, dry matter content, plant type score (i.e. resistance to disease and pest tolerance),3 and harvest index4 (H. Ceballos, personal communication, 25 July 2016). Further, these IVs maintain the starch gelatinisation and pasting5 traits of landraces that millers/bakers prefer, while often having superior characteristics relative to landraces under either poor or good planting conditions (CORPOICA‐CIAT, 2014). For example, Table 1 shows the five characteristics of the improved variety SM 1495‐5 (released in 2014) against MCOL 1522 known as ‘Algodona’ by smallholder farmers in Cauca, which is the most commonly used landrace in the region.

HOUSEHOLD DETERMINANTS OF THE ADOPTION OF IMPROVED CASSAVA VARIETIES USING DNA FINGERPRINTING TO IDENTIFY VARIETIES IN FARMER FIELDS: A CASE STUDY IN COLOMBIA