Enrichment of Vitamin A and Vitamin E in Sweet Corn Kernels Through Genomics-Assisted Introgression of Mutant Version of crtRB1 and vte4 Genes

Abstract

Recessive shrunken2 (sh2)-based sweet corn is preferred worldwide as it possesses higher sugar and extended shelf life. However, traditional sh2-based sweet corn is poor in vitamin A and vitamin E. Here, parental lines of two sh2-based sweet corn hybrids, viz. PSSC-2 and ASKH-2, were targeted for introgression of β-carotene hydroxylase 1 (crtRB1) and γ-tocopherol methyltransferase (vte4) genes through marker-assisted backcross breeding. Seeds with sh2sh2sh2 genotype in the endosperm were selected based on the shrunken phenotype in BC₁F₁, BC₂F₁ and BC₂F₂ generations. Gene-based markers, viz. 3'-TE-InDel and 118-InDel specific for crtRB1 and vte4, respectively, were successfully utilized for foreground selection in BC₁F₁, BC₂F₁ and BC₂F₂. Reconstituted hybrids showed high provitamin A (proA: 19.52 ± 0.52 µg/g) with a maximum of 7.8-fold increase over original hybrids (ASKH-2 and PSSC-2: 3.33 ± 0.28 µg/g). High α-tocopherol (20.75 ± 0.44 µg/g) and α/γ-tocopherol ratio (0.55 ± 0.02) with an average enhancement of 2.3- and 1.7-fold, respectively, was recorded among reconstituted hybrids over original versions (α-tocopherol: 9.21 ± 0.33 µg/g, α/γ-tocopherol ratio: 0.31 ± 0.01). The average yield of reconstituted hybrids (11.40 ± 0.22 t/ha) was at par with the original sweetcorn hybrids (11.60 ± 0.20 t/ha). This is the first report of stacking sh2, crtRB1 and vte4 genes to improve nutritional quality in sweet corn. These biofortified sweet corn hybrids hold immense significance to alleviate micronutrient malnutrition.

Keywords: Biofortification; Maize; Malnutrition; Marker; Molecular breeding; Sweetness.