Kevin V. Pixley

Biofortified orange maize is as efficacious as a vitamin A supplement in Zambian children even in the presence of high liver reserves of vitamin A: a community-based, randomized placebo-controlled trial

Background: Biofortification is a strategy to relieve vitamin A (VA) deficiency. Biofortified maize contains enhanced provitamin A concentrations and has been bioefficacious in animal and small human studies. Objective: The study sought to determine changes in total body reserves (TBRs) of vitamin A with consumption of biofortified maize. Design: A randomized, placebo-controlled biofortified maize efficacy trial was conducted in 140 rural Zambian children. The paired 13C-retinol isotope dilution test, a sensitive biomarker for VA status, was used to measure TBRs before and after a 90-d intervention. Treatments were white maize with placebo oil (VA−), orange maize with placebo (orange), and white maize with VA in oil [400 μg retinol activity equivalents (RAEs) in 214 μL daily] (VA+). Results: In total, 133 children completed the trial and were analyzed for TBRs (n = 44 or 45/group). Change in TBR residuals were not normally distributed (P < 0.0001); median changes (95% CI) were as follows: VA−, 13 (−19, 44) μmol; orange, 84 (21, 146) μmol; and VA+, 98 (24, 171) μmol. Nonparametric analysis showed no statistical difference between VA+ and orange (P = 0.34); both were higher than VA− (P = 0.0034). Median (95% CI) calculated liver reserves at baseline were 1.04 (0.97, 1.12) μmol/g liver, with 59% >1 μmol/g, the subtoxicity cutoff; none were <0.1 μmol/g, the deficiency cutoff. The calculated bioconversion factor was 10.4 μg β-carotene equivalents/1 μg retinol by using the middle 3 quintiles of change in TBRs from each group. Serum retinol did not change in response to intervention (P = 0.16) but was reduced with elevated C-reactive protein (P = 0.0029) and α-1-acid glycoprotein (P = 0.0023) at baseline. Conclusions: β-Carotene from maize was efficacious when consumed as a staple food in this population and could avoid the potential for hypervitaminosis A that was observed with the use of preformed VA from supplementation and fortification. Use of more sensitive methods other than serum retinol alone, such as isotope dilution, is required to accurately assess VA status, evaluate interventions, and investigate the interaction of VA status and infection. This trial was registered at clinicaltrials.gov as NCT01814891.

Reliable and inexpensive colorimetric method for determining protein-bound tryptophan in maize kernels.

Biofortification programs in maize have led to the development of quality protein maize (QPM) with increased contents of the essential amino acids lysine and tryptophan, and increased nutritional value for protein deficient populations where maize is a staple food. Because multiple genetic systems control and modify the protein quality of QPM, tryptophan or lysine monitoring is required to maximize genetic gain in breeding programs. The objective of this work was to develop an accurate, reliable, and inexpensive method for tryptophan analysis in whole-grain maize flour to support QPM research efforts around the world. Tryptophan reacts with glyoxylic acid in the presence of sulfuric acid and ferric chloride, producing a colored compound that absorbs at 560 nm. A series of experiments varying the reagent concentrations, hydrolysis time, and length of the colorimetric reaction resulted in an optimized protocol which uses 0.1 M glyoxylic acid in 7 N sulfuric acid and 1.8 mM ferric chloride, and 30 min reaction time. This method produced stable and reproducible results for tryptophan concentration in whole-grain maize flour and was validated by comparison with data obtained using an acetic acid-based colorimetric procedure (r(2) = 0.80) and high pressure liquid chromatography (HPLC) (r(2) = 0.71). We describe adaptations that permit high throughput application of this tryptophan analysis method using a microplate platform.

Comparative Intake of White- versus Orange-Colored Maize by Zambian Children in the Context of Promotion of Biofortified Maize

Background Vitamin A deficiency is associated with poor health outcomes related to reproduction, growth, vision, and immunity. Biofortification of staple crops is a novel strategy for combating vitamin A deficiency in high-risk populations where staple food intakes are high. African populations are proposed beneficiaries of maize (Zea mays) biofortified with provitamin A carotenoids, often called “orange maize” because of its distinctive deep yellow-orange kernels. The color facilitates ready recognition but presents a cultural challenge to maize-consuming populations, including those in much of Africa, who traditionally eat white varieties. Objective This study explores the intake patterns of, as well as adaptation to, traditional foods made with provitamin A–biofortified maize compared with white maize in rural Zambian children 3 to 5 years of age (n = 189) during a 3-month feeding trial. Methods The subjects were fed a breakfast of maize porridge (sweet mush), a lunch of maize nshima (stiff mush) with various side dishes, and an afternoon snack based on a 6-day rotating menu. The trial was conducted in 2010. The orange maize used in the trial came from three different sources. O1 maize was from the 2009 harvest and was stored in a freezer until use in 2010. O2 maize was also from the 2009 harvest and was stored in a cold room until 2010. O3 (“fresh”) maize was from the 2010 harvest and was fed immediately after harvest in week 9 of the study and then stored in a freezer until milling for the final four weeks. Results Consumption of menu items, except snacks, was influenced by week (p < .0084). The intakes of porridge and nshima made with orange maize equaled those of porridge and nshima made with white maize from week 2 onward. The intakes of porridge and nshima prepared from O1 and O2 did not differ, but intakes became significantly higher when meals made from O3 were introduced (p < .014 for porridge and p ≤ .013 for nshima). Conclusions These results demonstrate quick adaptation to orange maize, a preference for recently harvested maize, and an optimistic outlook for similar adaptation patterns in other biofortified-maize target countries.

Maize genotype and food matrix affect the provitamin a carotenoid bioefficacy from staple and carrot-fortified feeds in Mongolian gerbils (Meriones unguiculatus)

Biofortification to increase provitamin A carotenoids is an agronomic approach to alleviate vitamin A deficiency. Two studies compared biofortified foods using in vitro and in vivo methods. Study 1 screened maize genotypes (n = 44) using in vitro analysis, which demonstrated decreasing micellarization with increasing provitamin A. Thereafter, seven 50% biofortified maize feeds that hypothesized a one-to-one equivalency between β-cryptoxanthin and β-carotene were fed to Mongolian gerbils. Total liver retinol differed among the maize groups (P = 0.0043). Study 2 assessed provitamin A bioefficacy from 0.5% high-carotene carrots added to 60% staple-food feeds, followed by in vitro screening. Liver retinol was highest in the potato and banana groups, maize group retinol did not differ from baseline, and all treatments differed from control (P < 0.0001). In conclusion, β-cryptoxanthin and β-carotene have similar bioefficacy; meal matrix effects influence provitamin A absorption from carrot; and in vitro micellarization does not predict bioefficacy.

The research and implementation continuum of biofortified sweet potato and maize in Africa

The enhancement of sweet potato and maize with provitamin A carotenoids has been part of HarvestPluss research continuum since the formation of the biofortification project. This review includes case studies of biofortification strategies used for sweet potato in Uganda and orange maize in Zambia. The current status of the science and release of biofortified varieties was reviewed by three scientists who were part of the HarvestPlus program for more than a decade with input from a scientist who experienced orange maize dissemination in Zambia. High β‐carotene varieties of sweet potato were introduced into South Africa and Mozambique, and efficacy and effectiveness studies, respectively, showed promise to improve vitamin A status, followed by dissemination efforts in Uganda. A randomized, controlled effectiveness trial tested extension models to promote sweet potato and assessed vitamin A intake among Ugandans. Orange maize breeding was initially a challenge, but considering that the carotenoid biosynthetic pathway was present in maize germplasm, breeders quickly bred higher amounts of provitamin A into the maize that was ultimately released in Zambia. Initial resistance occurred because orange maize was associated with yellow maize, which had negative connotations associated with food aid and animal feed, and consumers preferred white maize. Currently, both orange crops are available on the market.

Genetic interrelations among grain quality indicators and agronomic traits for oat

SummaryTest weight, seed weight, and groat percentage are three common measures of grain quality for oat (Avena sativa L.). There is considerable disagreement, however, about the utility of each of these traits as measures of grain quality, so it is important to understand the genetic interrelations among them and between them and other agronomic traits. In this study, 50 random F2-derived F3 lines from each of 13 biparental oat crosses were evaluated. Genotypic variances, heritabilities, and genotypic correlations for test weight (TW), seed weight (SW), groat percentage (GP), grain yield (GY), harvest index (HI), plant height (PH), and date of heading (DH) were used to predict and compare direct and indirect gains from single-trait selection. Direct selection was always the most effective method for improving single traits; average predicted improvement of population means was 4% for TW, 10% for SW, 1% for GP, and 14% for GY when 10% selection intensity was applied. Genotypic correlation coefficients, averaged for all crosses, were 0.04 for TW with SW, 0.37 for TW with GP, -0.09 for SW with GP, and 0.29, 0.36, and 0.30 for GY with TW, SW, and GP, respectively. Thus, direct selection for TW, SW, or GP should not greatly affect the other two grain quality indicators. For the seven traits considered, there seemed to be no large advantage or disadvantage, in terms of correlated responses, associated with selection for any of the grain quality indicators.

CIMMYT's Seeds of Discovery Initiative: Harnessing Biodiversity for Food Security and Sustainable Development

A visionary investment by Mexicos Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA) has enabled the Seeds of Discovery (SeeD) initiative to assemble a platform of technologies to facilitate the effective use of genetic resources in breeding to address challenges of climate change and evolving consumer demands to ensuring universal food security. The platform consists of 1) high-density genotypic data and extensive phenotypic data characterizing maize and wheat germplasm bank accessions, 2) software tools to enable bioinformatics analyses of these and relevant germplasm bank data, and 3) maize and wheat lines incorporating novel diversity for priority traits from exotic germplasm into breeder-preferred, elite genetic backgrounds. Each of these platform components was co-developed with partners bringing unique expertise and resources to the project. Sustained impact, and equitable access to the platform and the maize and wheat genetic resources it describes, are pursued via multi-pronged capacity development and proactive intellectual property strategies described herein. After describing the SeeD initiative and some of its products, we conclude by sharing comments and insights from eminent scientists and partners who attended a special session on ‘Harnessing Biodiversity for Food Security and Sustainable Development’ during the 1st International Agrobiodiversity Congress (IAC), in New Delhi, November 2016.

Elevating the conversation about GE crops

VOLUME 35 NUMBER 4 APRIL 2017 NATURE BIOTECHNOLOGY issues of most importance to the public as well as directly involved individuals and groups. The majority of our work involved carefully combing through the literature, focusing more on primary research studies than on reviews. Just for the three report chapters concerning currently commercialized GE crops, our report includes over 900 references. Once our committee developed a full draft of the report, it was sent to 26 reviewers with diverse expertise and perspectives (these reviewers were anonymous to the committee, until they were acknowledged in the final report). Each of the 918 comments and criticisms in the reviews had to be specifically addressed by the committee to the satisfaction of a US National Academies’ independent review board before the report could move forward for the Academies’ approval. Clearly, the report represented more than the opinions of the 20 committee members. Giddings and Miller’s statement that the report’s “unwillingness to overtly back GE crops, and the report’s efforts to give credence to alternative viewpoints —rather like the media’s obsession with giving two sides of an argument equal play, irrespective of which view is supported by the evidence” is, in effect, an uninformed indictment of the US National Academies’ process. Giddings and Miller also charge that we understate how much GE crops have contributed to yield increases, commenting that the report “muddies the debate about yields of GE crops compared with ‘conventionally’ bred crops, [and] gives undue credence and prominence to views backed by paltry peer-reviewed evidence.” In fact, our report carefully states, based on all evidence available to us, that when there was substantial pest pressure, insect-resistance traits did have higher yields compared with conventionally bred crops. However, we also report that many of the early studies purporting to show yield increases due to GE herbicide-resistance and insect-resistance traits were not designed rigorously. Furthermore, we point out that there is less evidence of herbicide-resistance traits increasing yield. So why were these GE Elevating the conversation about GE crops

Harnessing genetic potential of wheat germplasm banks through impact-oriented-prebreeding for future food and nutritional security

The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the ‘T’ allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes were also identified on chromosomes 1A, 6A and 2B effective against abiotic/biotic stresses. Results demonstrate positive contributions of exotic germplasm to PBLs derived from crosses of exotics with CIMMYT’s best elite lines. This is a major impact-oriented pre-breeding effort at CIMMYT, resulting in large-scale development of PBLs for deployment in breeding programs addressing food security under climate change scenarios.

Carotenoid and Tocochromanol Profiles during Kernel Development Make Consumption of Biofortified “Fresh” Maize an Option to Improve Micronutrient Nutrition

Biofortification is a strategy to reduce micronutrient malnutrition. The aim of this study was to investigate whether consumption of biofortified fresh maize can supply nutritionally meaningful amounts of provitamin A carotenoids (PVA), zinc, lysine, and tryptophan. The accumulation patterns for PVA and tocochromanol compounds in developing grain of 23 PVA hybrids was studied, and nutritionally meaningful amounts of those compounds were found in grain by milk stage, when fresh maize is eaten. The highest PVA and tocochromanol accumulation occurred by physiological maturity. The percent apparent retention in boiled fresh maize was 92%, 117%, 99%, and 66% for PVA, zinc, lysine, and tryptophan, respectively. Consumption of 0.5 to 2 ears of fresh maize daily could supply 33-62.2%, 11-24% and more than 85% of the estimated average requirement of PVA, tryptophan, and zinc, respectively. The results indicate that eating biofortified fresh maize can contribute to improved micronutrient nutrition.