Maize Genomics and Genetics 2025, Vol.16, No.1, 45-59 http://cropscipublisher.com/index.php/mgg 52 2022). In fact, it's not just yield. Simple traits like plant height also change when the environment changes. Interestingly, sometimes the impact of the environment is more obvious than the genotype difference. Of course, the degree of environmental influence varies for each trait, and this requires specific analysis of specific issues. Corn is quite magical. The same variety grown in different places may not look like "real brothers" at all. This is the so-called phenotypic plasticity - to put it bluntly, the genes have not changed, but the phenotype changes with the environment (Westhues et al., 2021; Li et al., 2022). For example, in the case of phosphorus fertilizer, some plots have less application, but the yield is not necessarily bad. This is the effect of phosphorus utilization efficiency. But then again, the impact of climatic conditions may be greater, especially in recent years. The weather has become more and more unstable. In fact, this plasticity is a good thing for corn, at least it allows them to adapt to all kinds of strange planting environments. Of course, not all traits are so "changeable", and some key characteristics are still quite stable. 6.3 Impact of gene-environment interactions on trait stability in fresh-eating maize Anyone who is engaged in fresh corn breeding knows that the most troublesome thing is the unstable performance of the varieties. What grows well in this field today may be completely different in another field. This is the gene-environment interaction (GEI) at work (Singamsetti et al., 2022; Azrai et al., 2023). In theory, stable yield and quality are basic requirements, but GEI makes trait expression particularly "changeable". However, some methods are still quite useful now, such as AMMI and GGE double plots, which can at least help us see which hybrids are more "reliable". Of course, it still takes a lot of effort to find a truly stable genotype, after all, environmental factors are too complicated. Corn growers know that the same variety may produce high yields this year but fail to produce the same yields next year. This cannot be entirely blamed on the seeds. Environmental factors such as soil moisture and nitrogen fertilizer levels have a great impact (Bozovic et al., 2022; Ljubičić et al., 2023). Some genotypes are stable in dry land, but may not adapt to an environment with sufficient water and fertilizer. To be honest, if these gene-environment interactions (GEIs) are not considered in breeding, the selected varieties may be good-looking but not practical. However, the good news is that combining genetic data with environmental factors can indeed help us select more "reliable" varieties. Although the process is a bit troublesome, it is worth the effort to cultivate fresh corn that is both high-yielding and stable. 7 Maize Breeding Applications 7.1 Hybrid breeding through phenotypic and genotypic diversity in maize Those who are engaged in corn hybrid breeding know that the key is to find the right parent combination. This is easier said than done. The inbred lines of CIMMYT are quite interesting. Using SSR markers, it was found that their genetic variation is quite rich (Xia et al., 2005). However, variation alone is not enough. The key is to find out which combinations can produce strong hybrid vigor. Some parents don't look very good, but they work particularly well when paired together. Of course, breeding is much more convenient now than before, at least you can do a first round of screening through genotyping analysis. But in the final analysis, it all depends on the performance in the field, after all, agronomic traits are the hard truth. When it comes to corn hybridization, the choice of parents is actually very particular. Some recent studies have found that the effect of combining temperate and tropical corn germplasm is surprisingly good (Yu et al., 2020). For example, key traits such as ear length and number of grains per row are particularly outstanding after hybridization. Of course, there is a trick here, which is to understand the difference between general combining ability and specific combining ability - some parents are good with anyone, while others depend on the specific combination. But then again, although laboratory analysis can be of great help, it ultimately depends on the performance in the field. After all, the selected hybrids must be able to adapt to different environments, and it is not enough to perform well under specific conditions.
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