Development of cytoplasmic male sterile female parents for heat-and drought-resilient maize (Zea mays L.) hybrids through marker-assisted breeding

Abstract

Efficient hybrid seed production in maize (Zea mays L.) relies on cytoplasmic male sterility (CMS) systems that eliminate the need for detasseling, thereby reducing labor and cost while ensuring genetic purity. The present study aimed to develop cytoplasmic male sterile (CMS-C) versions of elite female inbred parents of two heat- and drought-resilient maize hybrids, RCRMH-2 and RCRMH-3, using Marker-Assisted Backcross Breeding (MABC). The CMS-C donor line VL192114 was identified through SSR-based cytoplasmic typing, producing a specific 398 bp amplicon. Genome-wide polymorphism analysis using 3,305 DArTag-SNP markers revealed 72.82% and 71.73% polymorphism between the donor and recurrent parents CAL1514 and ZL153493, respectively. Foreground selection for the CMS trait was performed phenotypically based on tassel sterility, while background selection across backcross generations employed high-throughput SNP genotyping. The Recurrent Parent Genome Recovery (RPGR) increased from ~70% in BC₁F₁ to over 90% in BC₃F₁, confirming near-isogenic recovery of the recurrent genome. The developed BC₃F₁ CMS lines were completely male sterile, genetically stable, and comparable to their fertile counterparts. These novel CMS-based A-lines eliminate detasseling, reduce hybrid seed production costs by up to 20%, and enable efficient large-scale hybrid seed production under heat- and drought-prone environments. This study represents the first successful report of CMS introgression through MABC in Indian maize hybrids, providing a robust model for accelerating CMS-based hybrid breeding programs.