Farmer preference, utilization and biochemical composition of improved cassava (Manihot esculenta Crantz) varieties in Southeastern Africa

Abstract

Cassava (Manihot esculenta Crantz) varieties are ethnobotanically classified by farmers into two distinct classes—“sweet” or “bitter”—based on their taste, most often reflecting the inherent cyanogenic glucoside potential and intended end use. Varietal preference based on general utilization as well as more targeted end use for preferred local and improved varieties is poorly understood and not well documented. The objectives of this study were to investigate prevailing varietal preferences based on utilization and the biochemical composition of local and recently improved cassava varieties. Interviews were conducted with farmers to document the existing varieties, their origin and taste classification, and processing in relation to end use. Biochemical composition was determined for flour samples with particular emphasis on color and perceived dryness. Of the nine varieties identified, four were classified as local, while the rest were classified as improved varieties. Two varieties were classified as bitter, and the rest were classified as sweet based on end use. The classification dichotomy based on taste is an important factor in determining potential toxicity. Labile varieties that are easily affected by microenvironmental factors were classified as bitter. Reasons for preference and utilization focus as much on the leaves for use as vegetables as on the roots. The taste classification of the roots determines how and whether they are to be processed. The varieties “Mweulu” and “Tanganyika” were perceived by farmers as having excellent characteristics for making the staple dish “nshima,” reflected by their high carbohydrate contents. The variety “Bangweulu” was identified as having “bigger and starchier” roots in interviews, and the biochemical assay verified these observations. The flour sample analysis revealed crude protein content ranged from 4.86% to 7.09%. Cluster and principal component analyses showed four groupings, with the single Malawian variety exhibiting the greatest differences from the Zambian clones, while the improved varieties bred from a single mother line displayed the closest similarities. The high energy and carbohydrate values of the nine varieties provide a good basis for acceptance; however, factors such as shelf life, storage, and other postharvest qualities such as susceptibility to weevil attacks also play a determining role in the acceptance of improved cassava varieties