Maize Genomics and Genetics 2025, Vol.16, No.1, 45-59 http://cropscipublisher.com/index.php/mgg 54 using SNP markers, and it was found that the genetic differences between different breeding materials were greater than expected (Lu et al., 2009). This discovery is very important. After all, only by understanding the genetic background of germplasm resources can we better protect and utilize them. Of course, there are always some problems in actual operations, such as some rare alleles are particularly difficult to find. But in general, these methods do help us understand our assets, and we have a better idea when breeding. 8.2 Utilization strategies for genetic diversity to enhance maize breeding When it comes to corn breeding, local varieties are really a treasure trove. Especially those local varieties in Africa, which are particularly interesting (Nelimor et al., 2020). The varieties in the Sahel region and the coastal areas of West Africa are quite different. Some are drought-resistant and some are disease-resistant. They are simply natural gene banks. However, it is not easy to make good use of these resources. A lot of phenotypic identification work must be done first. Nelimo et al. (2020) found that the diversity of these local varieties is beyond imagination and can indeed provide a lot of new genes for modern breeding. Of course, finding a good genotype is only the first step, and it will take a long screening and breeding process. But in any case, these traditional varieties do bring new hope for improving corn. In corn hybrid breeding, the combination of tropical and temperate germplasm often brings surprises. Studies have found that tropical corn germplasm is particularly suitable for increasing the yield of temperate varieties (Yu et al., 2020). However, in actual operation, it is not enough to look at the performance of the parents. The key is to look at the specific combining ability (SCA)-this indicator is particularly useful for predicting hybrid vigor. Although the temperate varieties themselves perform well, the hybrid offspring are often better after the addition of tropical germplasm. Of course, this combination is not random and must go through a lot of screening. But it is undeniable that doing so can indeed broaden the genetic base, but the process will be more laborious. 8.3 The significance of creating new germplasm in maize breeding Corn breeding is becoming more and more difficult now, with pests and diseases changing year by year and the climate being unstable. However, an interesting method has recently been discovered - using local varieties to make double haploids (Mayer et al., 2020). There are many good things hidden in these traditional varieties, especially the diversity of some early developmental traits, which have not been well utilized before. Although the process is a bit troublesome, you can really dig up treasures. For example, some haplotype variations are particularly useful for improving complex traits such as yield. In 2020, a study showed that this method can indeed breed better-performing strains (Mayer et al., 2020). Of course, not all local varieties are suitable for this, so you have to choose carefully. But anyway, this provides new ideas for breeding work, which is better than sticking to old materials. When it comes to corn breeding, the GEM project has done a lot of practical work over the years. They hybridized temperate varieties with exotic materials and specifically selected those offspring with high yield potential (Rogers et al., 2022). Although some people doubted whether this method would work at first, it turned out to be quite effective - hundreds of breeding lines have been released, broadening the genetic basis of American corn a lot. Interestingly, they later added genomic selection, and the speed of genetic improvement was significantly faster. Of course, not all hybrid combinations can produce good materials, and they have to be screened repeatedly. But research in 2022 showed that this innovative method has indeed brought new breakthroughs to modern corn breeding (Rogers et al., 2022). To put it bluntly, to meet the current planting challenges, it is not enough to rely on old varieties alone, and we have to find a way to create new germplasm. 9 Research Challenges and Future Directions 9.1 Challenges in integrating phenotypic and genotypic data The most troublesome thing about corn research is to match phenotypic and genotypic data together. Take ear traits for example. They seem to be closely related to yield, but once combined with genotypic analysis, it becomes very complicated (Tucker et al., 2019). The same is true for root traits and phenological traits. There are too many influencing factors. Even more troublesome is the metabolite level. The data measured in different environments often do not match (Ding, 2024). To be honest, to sort out these relationships, data alone is not
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