Maize Genomics and Genetics 2025, Vol.16, No.1, 45-59 http://cropscipublisher.com/index.php/mgg 53 7.2 Application of marker-assisted selection (MAS) in maize breeding Speaking of corn breeding, there is now an interesting technology called molecular marker-assisted selection (MAS). Simply put, it is to select good varieties through DNA markers, which is much more accurate than traditional methods. Ribaut and Ragot conducted an experiment in 2006, using the marker-assisted backcrossing (MABC) method to transfer some good genes related to yield and flowering traits into new varieties (Ribaut and Ragot, 2006). Guess what? The yield of these new varieties has indeed increased significantly under drought conditions. Of course, this method is not a panacea, but it is particularly useful for improving complex traits such as drought resistance. The most practical thing is that this technology can save a lot of time and shorten the breeding cycle. But then again, although the efficiency is high, field trials still need to be done, after all, actual performance is the hard truth. Sequencing technology is really helpful for corn breeding now. In particular, the GBS method combines genotyping and marker discovery in one package, which is very cost-effective (Elshire et al., 2011). In the past, genome-wide association studies (GWAS) were time-consuming and laborious, but now GBS is much faster. However, although NGS technology has made MAS more powerful, not all laboratories can afford it. The most practical thing is that GBS can not only be used for genetic diversity analysis, but also for genomic selection. Our project team used this technology to screen a batch of materials last year, and the breeding cycle was indeed shortened a lot. Of course, the field verification link cannot be saved. After all, no matter how good the technology is, it depends on the actual performance. 7.3 Potential of CRISPR and genome editing technology in genetic improvement of maize Now the corn breeding circle is discussing the new technology CRISPR. To be honest, it is really amazing. Unlike traditional methods that are time-consuming and labor-intensive, it is a direct operation on the gene (Yixin et al., 2015). For example, if you want corn to be disease-resistant or drought-tolerant, just find the relevant gene editing. However, the actual operation is not that simple, and sometimes the editing effect will go astray. But it is undeniable that CRISPR is much faster than previous methods. Our laboratory used it to improve a strain last year, and the drought resistance was significantly improved. Of course, in the end, it still depends on the field performance, after all, laboratory data and actual planting are two different things. When it comes to corn breeding, genome editing technology has indeed opened up a lot of new ideas. Traits that cannot be solved by traditional methods may be solved by CRISPR (Rice and Lipka, 2021). For example, those "brake genes" that affect yield may have an immediate effect if they are directly knocked out. However, in actual operation, it is still quite difficult to find the right editing site. Interestingly, this method can create new mutations that do not exist in nature at all, which was unimaginable before. Although the technology is still being improved, a lot of potential can be seen. You can see that recent research is all about how to make editing more accurate and efficient. Of course, whether it can be used in actual breeding in the end depends on field performance. 8 Conservation of Maize Diversity and Germplasm Innovation 8.1 Strategies for the conservation of maize germplasm resources When it comes to corn germplasm conservation, it's just like saving money - you can't put all your eggs in one basket. Nguyen and Norton emphasized in 2020 that off-site gene banks are a good idea (Nguyen and Norton, 2020). These gene banks can not only preserve existing varieties, but also collect some new alleles that naturally occur in the field. Although it is quite troublesome to manage, and regular seed regeneration and trait identification are required, it is particularly worthwhile in the long run. Think about it, the climate is becoming more and more unstable, and maybe one day you will need to use these preserved genetic diversity. And to be honest, without these basic materials, it is simply impossible to cultivate new varieties that are high-yielding and resistant to adversity. Gene bank management is not as simple as it used to be. It is not enough to just store the seeds. Advanced phenotyping techniques must be used to truly realize their value (Nguyen and Norton, 2020). These new technologies are indeed useful, especially when dealing with large quantities of germplasm, which is much more efficient. However, the most intuitive one is still molecular marker technology. Maize inbred lines were analyzed
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