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Journal articleIFPRI3; HarvestPlusHarvestPlusNon-P

The present study evaluated selected East African (EA) sweetpotato varieties for storage root dry matter and nutrient content and obtained information on the potential contributions of the varieties to alleviate vitamin A and mineral deficiencies. Roots obtained from 89 farmer (white- and orange-fleshed) varieties and one introduced variety (‘Resisto’) were analyzed for storage root quality using near-infrared reflectance spectroscopy technology. Location differences were only significant for starch content. The variance was significant (P < 0.01) for all the traits except sucrose content. Overall, the farmer varieties had higher dry matter, higher starch, and lower sucrose contents than the control clone, ‘Resisto’. It is these qualities that make sweetpotato attractive as a starchy staple in EA. A low population's mean β-carotene content (19.0 ppm) was observed. However, deep orange-fleshed farmer varieties, ‘Carrot_C’, ‘Ejumula’, ‘Carrot Dar’, ‘Mayai’, and ‘Zambezi’, had β-carotene content that can meet 350% or greater of recommended daily allowance (RDA) with 250-g serving to a 5- to 8–year-old child. More but light orange-fleshed farmer varieties ‘K-118’, ‘K-134’, ‘K-46’, ‘KMI61’, ‘MLE162 Nakahi’, ‘PAL161’, ‘Sowola6’, ‘Sponge’, ‘SRT34 Abuket2’, ‘SRT35 Anyumel’, ‘SRT52’, and ‘Sudan’ can provide 50% to 90% RDA of pro-vitamin A for the child. The root minerals’ content was generally low except for magnesium whose content can meet 50% or greater RDA in many farmer varieties. However, in areas with high sweetpotato consumption, varieties ‘Carrot_C’, ‘Carrot Dar’, ‘KRE nylon’, ‘MLE163 Kyebandula’, and ‘SRT49 Sanyuzameza’ can make good intakes of iron, zinc, calcium, and magnesium. In conclusion, some EA farmer varieties can contribute greatly to alleviation of vitamin A deficiency and substantial mineral intakes.

Key message β-Carotene content in sweetpotato is associated with the Orange and phytoene synthase genes; due to physical linkage of phytoene synthase with sucrose synthase, β-carotene and starch content are negatively correlated. Abstract In populations depending on sweetpotato for food security, starch is an important source of calories, while β-carotene is an important source of provitamin A. The negative association between the two traits contributes to the low nutritional quality of sweetpotato consumed, especially in sub-Saharan Africa. Using a biparental mapping population of 315 F 1 progeny generated from a cross between an orange-fleshed and a non-orange-fleshed sweetpotato variety, we identified two major quantitative trait loci (QTL) on linkage group (LG) three (LG3) and twelve (LG12) affecting starch, β-carotene, and their correlated traits, dry matter and flesh color. Analysis of parental haplotypes indicated that these two regions acted pleiotropically to reduce starch content and increase β-carotene in genotypes carrying the orange-fleshed parental haplotype at the LG3 locus. Phytoene synthase and sucrose synthase, the rate-limiting and linked genes located within the QTL on LG3 involved in the carotenoid and starch biosynthesis, respectively, were differentially expressed in Beauregard versus Tanzania storage roots. The Orange gene, the molecular switch for chromoplast biogenesis, located within the QTL on LG12 while not differentially expressed was expressed in developing roots of the parental genotypes. We conclude that these two QTL regions act together in a cis and trans manner to inhibit starch biosynthesis in amyloplasts and enhance chromoplast biogenesis, carotenoid biosynthesis, and accumulation in orange-fleshed sweetpotato. Understanding the genetic basis of this negative association between starch and β-carotene will inform future sweetpotato breeding strategies targeting sweetpotato for food and nutritional security.