Maize Genomics and Genetics 2025, Vol.16, No.2, 70-79 http://cropscipublisher.com/index.php/mgg 71 we can expand its genetic diversity. But the problem is that there are not many genetic changes in fresh corn itself, and the genetic laws of many traits are very complex, and the issue of environmentally friendly planting must also be considered, all of which make research particularly difficult. Interestingly, as the variety is introduced in various places, people have found that different climatic conditions have a great impact on it (Jompuk et al., 2020), which brings up new questions: Can these corns adapt to various environments? Will the performance be compromised? Our main purpose in this study is to clarify the genetic diversity of fresh corn varieties around the world. To be honest, although molecular marker technology is very advanced now, comprehensive analysis specifically for fresh corn is rare. The research team plans to use the latest genotyping methods to focus on which key genes determine the quality characteristics of corn. For example, why are some varieties particularly disease-resistant and some have particularly high yields? It is important to understand these. Of course, knowing the genes is not enough, we also have to look at the relationship between these genes and actual planting performance. The significance of this work is that it can not only help us better understand the genetic characteristics of fresh corn, but more importantly, it can provide a basis for breeding better new varieties - those with higher yields, better disease resistance, and richer nutrition. In the final analysis, only by continuously improving varieties can fresh corn continue to maintain its market competitiveness, which is also critical to the development of global agriculture. 2 Data and Methods 2.1 Data sources and selection criteria The data used in this analysis are actually quite interesting. They mainly come from reports from around the world that use molecular markers to study maize genetic diversity. You may have heard of technologies such as SNP and SSR, right? They are methods that can accurately detect genetic differences (Njeri et al., 2017). However, we were very strict when screening the data, and only selected studies published after 2015. Why? Because the newer the research technology, the more reliable it is. There is also a hard requirement, that is, these studies must record the molecular marker data in detail, and the maize samples collected must be comprehensive enough - they cannot come from just one region. After all, what we want to know is the true situation of maize genes worldwide. If the samples are too single, they will have no reference value. 2.2 Selection of genetic diversity evaluation indices When it comes to assessing genetic diversity, researchers actually use several "rulers" to measure it. For example, they will count how many variants there are at each gene locus (Yang et al., 2022), look at the richness of the gene, and calculate the indicator called PIC, which reflects the amount of information about polymorphism. Interestingly, they pay special attention to those unique genetic variants because these often tell the story. Of course, just looking at these numbers is not intuitive enough, so methods such as cluster analysis and PCA are usually used. You may think these terms are a bit professional. To put it bluntly, it is to classify similar varieties and see how they are related. In this way, we can have a more comprehensive understanding of the genetic differences between different corn varieties, both within and between groups. 2.3 Meta-analysis methods and model construction We chose a random effects model for this analysis, mainly considering the differences between studies - after all, there will always be discrepancies in the data produced by different laboratories. In terms of specific operations, we first converted the genetic diversity indicators reported in each paper into effect sizes, and then used the I² statistical method to look at the degree of difference in these research results (Shu et al., 2021). Interestingly, through the weighted average method, we finally obtained the overall level of genetic diversity of global maize germplasm. However, it is not enough to just look at the overall picture. We also made special group comparisons, such as looking at the differences in maize in different regions, or comparing different types of genetic diversity such as local old varieties, inbred lines and open-pollinated varieties. After this analysis, the results are much more comprehensive.
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