Field Crop 2025, Vol.8, No.6, 265-273 http://cropscipublisher.com/index.php/fc 268 3.2 Intra-population competition and nutrient distribution patterns The denser the density, the more intense the competition for nutrients. This is a fundamental rule. Water, light and nutrients have all become scarce resources. The opportunities for individual plants to obtain them have decreased, and the distribution of nutrients will also become more skewed (Li et al., 2018). Especially in plots where soil supply is uneven, the root systems compete more fiercely with each other, and in the end, it may even lower the overall yield. In contrast, medium density is more stable, with a more uniform distribution of canopy nutrients and higher nitrogen utilization efficiency. However, if the density continues to increase, the space and nutrients allocated to each plant will be less, the photosynthetic nitrogen efficiency of the lower leaves will be limited, and the nutrient deficiency phenomenon will be more prominent (Wang et al., 2019; Tang, 2024). 3.3 Growth period regulation and plant uniformity under high-density conditions High-density planting seems to grow fast and the canopy takes shape quickly, but this is not always a good thing. The leaves age too early, especially when they are too dense, compressing the entire rapid growth period (Wu et al., 2024). Not all varieties can adapt so well. Some dense-resistant materials can maintain a relatively stable canopy and photosynthetic state even in high-density environments, with small yield fluctuations (Ye et al., 2025). However, the issue of uniformity is not solely dependent on variety; it is also related to management. For instance, how nitrogen fertilizer is used and whether the variety is compact can both affect the consistency of the plants and the duration of their growth. Only by properly matching these management measures can the dense planting system perform more stably. 4 Breeding Strategies for Lodging Resistance under High-Density Conditions 4.1 Evaluation and utilization of lodging-resistant germplasm resources Not all corn varieties can stand firm in high-density environments. Screening good germplasm resources is the first step in breeding varieties resistant to lodging. In recent years, the screening work has covered hundreds and thousands of inbred lines and hybrids. Among them, bending strength, stem thickness, pericarp hardness, spike height, and stem cellulose content have become several recurring core indicators. However, some traits do not alone indicate the issue. For instance, a high spike position does not necessarily mean that it will definitely fall over. It is necessary to consider them comprehensively. The results of clustering and principal component analysis did provide quite a few clues - for instance, among 220 inbred lines, in groups like Luda Hongsui, some key alleles were particularly prominent (Zheng et al., 2023). Improved varieties like J133A, JM25, JM115, and JM1895 have performed exceptionally well. They are not only less prone to collapse but also have decent yields, making them suitable for mechanization (Yang et al., 2024). However, it should be noted that environmental impacts cannot be ignored. Lodging resistance is not just about performing well in one plot; it is best to verify it in multiple sites over many years. 4.2 Genetic improvement of target traits and marker-assisted selection When it comes to breeding, relying on experience to "guess" is no longer sufficient. One has to rely on molecular means to do things meticulously. Traits related to lodging resistance, such as stem thickness, stem bending resistance, and pericarp hardness, have now identified many candidate genes and loci through GWAS and QTL mapping. However, many of these superior alleles have not yet been truly introduced into mainstream varieties. That is to say, there is still much room for improvement. Techniques such as molecular marker-assisted selection (MAS) offer breeders a shortcut - they can specifically introduce fragments related to stem strength, plant type, and cell wall structure directly into the high-yield background. For instance, through transcriptome analysis, it was found that genes of those cell wall biosynthesis pathways were frequently upregulated in anti-inversion lines, which precisely supports the application of such molecular markers (Guo et al., 2021). However, relying solely on molecules is not enough. It is still necessary to combine on-site performance, taking a two-pronged approach of phenotyping and molecules, in order to improve efficiency. 4.3 Integrated breeding approaches for compact plant architecture and lodging resistance To carry out high-density planting and ensure that the varieties can withstand the "crowding", efforts must be made simultaneously in terms of plant shape and resistance to lodging. The current approach is quite different. It's
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