Maize leaf angle dynamics: Genetic architecture, hormonal regulation and phenomics approach

Maize (Zea mays L.), a key staple crop, supports human consumption, animal nutrition and diverse industrial uses. High-density planting (HDP) is an important strategy to improve crop yield per unit land area. Leaf angle (LA) is a key factor in determining maize plant architecture, photosynthetic efficiency and suitability for HDP. An urgent need exists to elucidate the genetic basis of these complex, polygenic traits, such as LA, to address the remaining information gaps in optimising canopy architecture. This review offers comprehensive insights into the molecular basis of regulatory networks involved in LA morphogenesis. It revisits advances in mutant and quantitative genetics research, identifying quantitative trait locus (QTL) across all 10 chromosomes and candidate genes through diverse studies employing genome-wide association studies (GWAS), genotyping by sequencing and linkage analysis. Leaf angle regulation is mediated by phytohormones and their crosstalk, as well as agronomic and environmental factors. Future progress depends on integrating advanced phenomics tools, such as 3D LiDAR, UAV-based hyperspectral imaging and deep learning, with CRISPR/Cas9-assisted breeding to precisely tune LA without undesirable pleiotropy. A standardised, ideotype-driven framework targeting upper-erect and lower-horizontal leaves will enable the development of climate-resilient, high-yielding maize varieties optimised for dense canopies.