CRISPR/Cas9 and Modern Breeding Tools for Genetic Improvement of Maize Seeds

Abstract

Maize (Zea mays) is a cornerstone of global food security, yet its production faces intensifying pressures from climate variability, biotic stresses, and rising nutritional demands. Traditional breeding methodologies, while historically successful, now face stagnation due to long generational cycles and linkage drag, rendering them insufficient to meet the 2030 zero hunger goals. This review explores the paradigm shift toward genomics-assisted precision breeding, highlighting the integration of Genomic Selection (GS) and CRISPR/Cas9 genome editing. We examine the evolution of breeding tools, detailing how GS utilizes whole-genome prediction to accelerate polygenic trait improvement, while CRISPR/Cas9 offers unprecedented precision for creating novel alleles to address monogenic deficiencies, such as Provitamin A availability and drought tolerance. The review further analyzes technical bottlenecks, including genotype-dependent transformation and off-target effects, and proposes a synergistic "Triple-A" framework combining Allele Creation (CRISPR), Assessment (GS), and Acceleration (Speed Breeding) to maximize genetic gain. Finally, we discuss the divergent global regulatory landscapes, contrasting process-based restrictions with product-based "regulatory escape" pathways, and their implications for the commercial deployment of climate-resilient maize.