Abstract

Traditional yellow maize though contains high kernel carotenoids, the concentration of provitamin A (proA) is quite low (<2 μg/g), compared to recommended level (15 μg/g). It also possesses poor endosperm protein quality due to low concentration of lysine and tryptophan. Natural variant of crtRB1 (β-carotene hydroxylase) and lcyE (lycopene-ε-cyclase) cause significant enhancement of proA concentration, while recessive allele, opaque2 (o2) enhances the level of these amino acids. Development of biofortified maize enriched in proA, lysine and tryptophan thus holds significance in alleviation of micronutrient malnutrition. In the present study, marker-assisted stacking of crtRB1, lcyE and o2 was undertaken in the genetic background of four maize hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) popularly grown in India. HP704-22 and HP704-23 were used as donors, while four elite QPM parents viz., HKI161, HKI163, HKI193-1, and HKI193-2 were used as recipients. CrtRB1 showed severe segregation distortion, while lcyE segregated as per the expectation. Recovery of recurrent parent genome (RPG) among selected backcross progenies ranged from 89 to 93%. Introgressed progenies possessed high concentration of proA (7.38–13.59 μg/g), compared to 1.65–2.04 μg/g in the recurrent parents. The reconstituted hybrids showed an average of 4.5-fold increase in proA with a range of 9.25–12.88 μg/g, compared to original hybrids (2.14–2.48 μg/g). Similar plant-, ear-, and grain- characteristics of improved versions of both inbreds and hybrids were observed when evaluated with their respective original versions. Mean lysine (0.334%) and tryptophan (0.080%) of the improved hybrids were at par with the original versions (lysine: 0.340%, tryptophan: 0.083%). Improved hybrids also possessed similar grain yield potential (6,301–8,545 kg/ha) with their original versions (6,135–8,479 kg/ha) evaluated at two locations. This is the first study of staking crtRB1-, lcyE-, and o2-, favorable alleles in single genetic background. The improved inbreds can be effectively used as potential donor for independent and/or simultaneous introgression of crtRB1, lcyE, and o2 in the future breeding programme. These biofortified maize hybrids, rich in proA, lysine and tryptophan will hold great promise for nutritional security.

Highlights

  • Micronutrient malnutrition popularly known as “hidden hunger” is a serious health problem worldwide, in the under-developed and developing countries (Bouis and Saltzman, 2017)

  • The number of polymorphic markers in each chromosome ranged 7–17. These polymorphic markers were used for background selection for recovering the recurrent parent genome (RPG) in the backcross-derived populations

  • We report here the development of four maize hybrids using marker-assisted stacking of o2, crtRB1, and lycopene ε-cyclase (lcyE)

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Summary

Introduction

Micronutrient malnutrition popularly known as “hidden hunger” is a serious health problem worldwide, in the under-developed and developing countries (Bouis and Saltzman, 2017). Two billion people suffer from deficiency of micronutrients, while 815 million people are under-nourished (Global Nutrition Report, 2017). Vitamin A plays, key role in human metabolism. This deficiency lead to visual blindness which may cause eye sight damage to millions preschool-age children. Unbalanced protein in the diet leads to protein energy malnutrition (PEM) that affects more than a billion people across the world (Bain et al, 2013). The adoption of quality protein maize (QPM) varieties possessing balanced protein due to higher lysine and tryptophan which has shown significant promise in solving problem of PEM across the world (Nyakurwa et al, 2017)

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