Comparative evaluation of physiological post-harvest root deterioration of 25 cassava (Manihot esculenta) accessions: visual vs. hydroxycoumarins fluorescent accumulation analysis

Cassava (Manihot esculenta) is the most important root crop in the tropics and due to its drought tolerance, ability to grow in poor soils, and resistance to herbivore, cassava is well suited for cultivation by subsistence farmers. However, its use and expansion is constrained by rapid physiological post harvest deterioration (PPD), which often starts within 24 hours after harvest. PPD is a complex process that involves changes in the metabolic process and accumulation of secondary metabolites, such as hydroxycoumarins. The quantification of the fluorescence emitted by these hydroxycoumarins has been proposed as a quantifiable tool to evaluate PPD. Traditionally, the evaluation of PPD has been performed by more subjective methods based on the visual analysis of deterioration. Presented here is the use of a standard subjective rating in comparison to the accumulation of hydroxycoumarin fluorescence during PPD. PPD evaluation of ten month old tuberous roots from 25 accessions of cassava after five days of storage at room temperature shows that there was no correlation between the florescent accumulation of hydroxycoumarins and the visual symptoms. This suggests that the accumulation of hydroxycoumarins is not a reliable marker for evaluation of PPD response in different cassava accessions.