Identification and Characterization of Carotenoids, Vitamin E and Minerals of Biofortified Sorghum

Abstract

Sorghum is a critical staple crop in Sub-Saharan Africa and has been included in biofortification efforts to enhance shortfall micronutrient content including provitamin A carotenoids (pVA), zinc and iron. The purpose of this study was to evaluate progress in enhancement of pVA, tocochromanol (vitamin E), iron and zinc content as well as improvements in stability from a new generation of transgenic biofortified sorghum events in order to prioritize selection for translation to food systems.Transgenic sorghum events (n = 16) from three different genotypic backgrounds developed to increase provitamin A biosynthesis (PSY1 + CRTI genes, +/− CRTB gene) and increase tocochromanol accumulation (HGGT gene) for vitamin A stability were characterized for carotenoid and tocochromanol profile using liquid chromatography coupled with diode array detection. Events were compared against their respective null segregants and wild type (WT) sorghum. Mineral content of sorghum lines and those developed to increase iron and zinc accumulation (YSL2 + NAS2 genes) was assessed by inductively coupled plasma - optical emission spectrometry. Storage stability of carotenoids and tocochromanols was assessed under controlled conditions (25°C; 57%RH) over 3 months.Total pVA content from transgenic sorghum (5.9 ± 0.1 – 28.6 ± 0.6 mg/gFW) was significantly different (P < 0.05) from null (0.4 ± 0 – 1.2 ± 0 mg/gFW) or WT (0.73 ± 0.2 mg/gFW). A general increase in total tocochromanol accumulation was observed in transgenic sorghum events (14.9 ± 0.8 – 36.2 ± 1.3 mg/gFW) compared to null/WT (14.2 ± 0.5 – 32.4 ± 4.4 mg/gFW) with significant differences observed among transgenic events across different sorghum genotypes (P < 0.05). Mineral accumulation varied among sorghum events with levels ranging from 28.44 ± 1.9 – 48.85 ± 4.9 mg/g and 27.65 ± 4.5 – 63.59 ± 13.4 mg/g FW for zinc and iron respectively. Highest level of zinc and iron was observed in Tx430 sorghum event.Findings from this study highlight progress in pVA levels of transgenic biofortified sorghum and the potential for increased vitamin E levels to improve pVA stability over storage. Studies are underway to characterize the bioaccessibility of pVA carotenoids, Fe and Zn from these events.Pioneer Foundation.