Characterization of taro [#Colocasia esculenta# (L.) Schott] germplasm for improved flavonoid composition and content

The starchy corms of taro (Colocasia esculenta) are consumed throughout the tropics and are essential for food security in many developing countries. Taro corms are increasingly processed into fries, chips, flours or flakes in urban areas, and varieties with attractive corm flesh colours are now needed. The identification of flavonoids in taro corms would add value to this crop. The present study developed a high-performance thin layer chromatography (HPTLC) protocol for the high-throughput screening of flavonoids in taro germplasm. Overall, 350 different accessions were analysed including 259 varieties from Vanuatu, one from Vietnam, eight from Thailand, eight from the Philippines, six from Malaysia, two from Japan and 18 from Indonesia. Forty-eight breeding lines (hybrids) including 21 from Vanuatu, 21 from Samoa, four from Hawaii and two from Papua New Guinea were also analysed. Ten flavones, namely luteolin-6-C-hexoside-8-C-pentoside, schaftoside, luteolin-3?,7-di-O-glucoside, homoorientin, isovitexin, orientin, luteolin-4?-O-glucoside, luteolin-7-O-glucoside, vitexin and apigenin-7-O-glucoside, were successfully detected in the corm and are responsible for the attractive yellow colour of the flesh and fibres. Quantitatively, luteolin-6-C-hexoside-8-C-pentoside and schaftoside were the most important of all the detected flavonoids. However, only 18% of the varieties analysed presented these two compounds and 80% presented poor flavonoid composition. No geographical structure of the variation was detected and the most flavone-rich varieties originated from Vanuatu, Thailand, the Philippines, Malaysia and Indonesia. The compounds detected in the present study were significantly and positively correlated, suggesting that there is potential for fast improvement through controlled crosses, subsequent evaluation of full-sib progenies and cloning of elite individuals. (Résumé d'auteur)