Maize smart-canopy architecture enhances yield at high densities.

Area of Science:

• Genetics and Plant Breeding
• Agricultural Science
• Molecular Biology

Background:

• Increasing planting density is crucial for enhancing maize yields.
• A 'smart canopy' with optimized leaf angles is needed for dense planting to maximize light interception and photosynthesis.
• Understanding the genetic basis of leaf angle architecture is key to developing high-density tolerant maize.

Purpose of the Study:

• To identify genetic factors controlling leaf angle architecture for improved maize performance under dense planting.
• To characterize the 'smart canopy 1' (lac1) mutant and its role in plant architecture and photosynthetic efficiency.
• To develop an accelerated strategy for introducing the lac1 trait into maize breeding programs.

Main Methods:

• Identification and characterization of the lac1 natural mutant with distinct leaf angle architecture.
• Molecular cloning of lac1 and investigation of its gene function, involving brassinosteroid regulation and light signaling pathways (Phytochrome A, RAVL1).
• Large-scale field trials to assess yield improvements and transformation of haploid inducers for rapid trait introgression.

Main Results:

• The lac1 mutant exhibits upright upper leaves, less erect middle leaves, and flatter lower leaves, forming a 'smart canopy'.
• lac1 enhances photosynthetic capacity and reduces shade response under dense planting.
• The lac1 gene encodes a brassinosteroid C-22 hydroxylase, regulated by light signaling pathways, controlling upper leaf angle.
• Field trials confirmed that lac1 significantly boosts maize yields at high planting densities.
• Accelerated breeding strategy using haploid inducers successfully introduced lac1 into diverse inbred lines, conferring smart-canopy architecture.

Conclusions:

• The lac1 mutant provides a valuable genetic resource for developing maize cultivars tolerant to high planting densities.
• Understanding the molecular mechanism of lac1 offers insights into plant architecture regulation and light optimization.
• lac1 serves as a genetic chassis for further engineering of smart canopies, paving the way for future maize yield improvements.