Genomics-assisted stacking of waxy1, opaque2, and crtRB1 genes for enhancing amylopectin in biofortified maize for industrial utilization and nutritional security

Abstract

Waxy maize is highly preferred diet in developing countries due to its high amylopectin content. Enriching amylopectin in biofortified maize meets food security and fulfils the demand of rising industrial applications, especially bioethanol. The mutant waxy1 (wx1) gene is responsible for increased amylopectin in maize starch, with a wide range of food and industrial applications. Conventional maize has a modest amount of amylopectin (70–75% of starch), but waxy maize, with favourable wx1 allele, has ~ 95–100% amylopectin. In this study, the wx1 allele was introgressed into the multi-nutrient-rich maize parental inbreds (PMI-PV9 and PMI-PV5) of APQH8, a multi-nutrient rich maize hybrid having high lysine, tryptophan, and provitamin-A nutritionally superior over the traditional hybrids. Gene-specific markers specific for o2 and crtRB1 were employed to select desirable gene segregants from BC₁F₁, BC₂F₁, and BC₂F₂. Background selection was employed with > 90 SSR markers. Selected backcross progenies showed high recovery of recurrent parent genomes (RPG: 94.8–96.8%). The reconstituted waxy hybrids exhibited an increase in amylopectin (mean: 98.4%) compared to the original hybrid (mean: 72.7%). The reconstituted hybrids also recorded enhanced lysine (mean: 0.382%), tryptophan (mean: 0.092%), and provitamin-A (mean: 10.36 ppm), respectively, than normal maize, however similar to the original hybrid with high lysine: 0.330%, tryptophan: 0.079% and provitamin-A: 10.42 ppm. Furthermore, MAS-derived genotypes showed similar agro-morphological traits and grain yield. These biofortified waxy maize hybrids, rich in provitamin-A, lysine, and tryptophan with enhanced amylopectin hold great potential in diverse industrial applications and nutritional security.