Effect of Scopoletin and Carotenoids on Postharvest Physiological Deterioration (PPD) of Transgenic High Beta Carotene Cassava

Abstract

Cassava tubers suffer from postharvest physiological deterioration (PPD) which normally sets in within 72 hours of harvest. This study examines the role of scopoletin and carotenoids in the onset or delay in PPD in two transgenic varieties EC20-7 and EC20-8 compared to a wild variety TME-7. Scopoletin and carotenoids were quantified by liquid chromatography-mass spectrometry. The scopoletin content (0.10 – 0.20 nmol/g) in the fresh varieties was not significantly (P>0.05) different from the amount in stored cassava roots (12.58 – 14.90 nmol/g). The carotenoid content values in EC20-7 variety were 6.66 µg/g (α-carotene), 80.45 µg/g (β-carotene) and 5.98 µg/g (lutein). As for EC20-8, α-carotene, β-carotene and lutein values were 6.19 µg/g, 69.11 µg/g and 3.12 µg/g, respectively. There was no significant (P>0.05) difference between the varieties in α-carotene content but in their lutein content. The results indicate that carotenoids are more relevant in the delay of PPD and scopoletin content is not a major factor in PPD vascular streaking or discolouration. Hence scopoletin content of cassava varieties may not be considered as a chemical marker for determining the potential of PPD in cassava tubers.