Abstract:

Maize is the crop with the largest planting area in China, playing a crucial role in safeguarding national food security. Dwarfing breeding is a core approach to break the bottleneck of maize yield per unit area by optimizing plant architecture and increasing planting density. This paper systematically reviews the research progress on maize dwarf genes, with a focus on clarifying the biological significance of maize plant height traits, the practices of dwarf genetic breeding, and the regulatory mechanisms of plant hormones on plant height, while proposing future research directions. The results show that: (1) maize plant height is co-regulated by the number of internodes and internode length. Dwarf plants can reduce lodging risk by shortening internode length, optimize canopy structure, and improve light energy use efficiency and adaptability to dense planting, but it is necessary to coordinate the relationship between dwarfing and yield traits. (2) Maize dwarf genetics is divided into two major systems: single-gene and multi-gene. In the single-gene system, the br2 gene has the clearest molecular mechanism—it inhibits the elongation of stem cells, reducing stem length by 40% to 50% compared with the wild type, with a more significant effect on internodes below the ear position—and it is the most widely used major gene at present. The multi-gene system can avoid the defect of pleiotropy by accumulating minor-effect genes, and varieties such as 'Aidan 268' that balance dwarfing and high yield have been bred. (3) Gibberellin (GA), brassinosteroid (BR), and auxin (IAA) are the core hormones regulating plant height: mutations in GA synthesis-related genes (d1, an1) or signal genes (d8, d9) lead to dwarfing, loss of function of BR synthesis genes (brd1, na2) or signal genes (ZmBRI1a) causes stunted plants, and abnormal function of the IAA polar transport gene (br2) results in dwarfing of lower stem nodes. Currently, maize dwarf breeding has problems such as a relatively small number of applicable genes (more than 60 dwarf genes have been discovered, and about 40 have been cloned), genetic linkage drag restricting the coordination of traits, and insufficient functional verification of novel dwarf genes (such as the mapped genes K718d and d8227). In the future, it is necessary to explore medium dwarf genes suitable for dense planting, use genome-wide selection technology to aggregate multiple genes, and integrate phenomics with artificial intelligence to screen for ideal plant architecture, so as to breed maize varieties with the characters of dwarf stalks for lodging resistance, dense planting for high yield, wide adaptability and easy mechanical harvesting, and provide support for the sustainable development of the maize industry.

Key words: maize, plant height, dwarf gene, genetic breeding, plant hormone, plant height regulation, br2 gene