The potential for extending the shelf-life of sweetpotato in East Africa through cultivar selection

The potential of sweetpotato is limited by the perishable nature of the sto rage tubers. An extension of storage-life could be by improving the storage environment and by breeding for extended shelf-life. The latter has the ad vantage in that it would result in an increased storage-life, both under co nditions designed for long-term storage and under normal marketing conditio ns without incurring additional costs for producers and traders. To determi ne the feasibility of selecting cultivars for extended shelf-life, it is im portant to determine the genetic range in perishability among existing germ plasm and the effect of the growth environment. In addition, a practical me thodology for selection should be established. If possible, physiological c haracteristics associated with perishability should be identified to allow the development of indirect selection techniques. The progress of collabora tive work conducted in Tanzania to address these issues is presented. Twent y-nine sweetpotato varieties, representative of the wide genetic variabilit y of germplasm available in Tanzania, were assessed for their perishability . Under simulated Tanzanian marketing conditions, the major forms of deteri oration observed were weight loss (primarily due to water loss) and rotting . Varieties varied considerably in both their rates of weight loss and of r otting, and these two characteristics were significantly correlated. Market observations have indicated that roots are subjected to considerable mecha nical damage during normal transport and marketing. Thus, a range of variet ies were tested for their rate of deterioration following simulated damage. In initial trials the ranking of varieties was not affected by the damage treatment, indicating that simulated damage need not be used during the sel ection procedure. These results suggest that indirect selection on the basi s of physiological parameters may form part of the breeding programme in Ta nzania.