Cultivar variation in keeping quality of sweetpotatoes

Under marketing conditions in tropical developing countries sweetpotatoes have a shelf-life of only 1 to 2 weeks. Storage trials conducted under simulated tropical marketing conditions showed that root shrivelling due to weight loss and rotting are the two major forms of deterioration. Measurement of respiration rates indicated that under these conditions weight loss is primarily (86%) due to water loss. Under these environmental conditions rotting is promoted by water loss, which is therefore the driving force of deterioration. For the cultivars studied, a large range in rates of weight loss was found, which was consistent between seasons, suggesting that breeding for extended shelf-life is feasible. A range of root quality characteristics were assessed, including dry matter content, sugar content, surface area, initial weight, rough weevil ( Blosyrus spp.) damage, latex production, cortex thickness and hardness of the tissue. Multiple regression models for rates of weight loss indicated that dry matter content and root monosaccharide content were important controlling factors. Cultivars with low dry matter content and with high monosaccharide levels lose less weight. The two characteristics are related, and we do not know which more directly affects rates of weight loss. Other root characteristics were less important, although it was found that root size and pre-harvest rough weevil damage had significant effects.