Maize Genomics and Genetics 2025, Vol.16, No.2, 60-69 http://cropscipublisher.com/index.php/mgg 62 3 Collection and Conservation of Fresh Corn Germplasm Resources 3.1 Germplasm collection methods There are many ways to collect corn germplasm resources. The most direct way is to go to the fields to collect, especially those local varieties that farmers keep for themselves (Figure 1) (Vidal et al., 2020). The study shows how to determine the best collection strategy through diversity surveys. However, field collection alone is not enough. It is also important to talk to farmers, so that you can learn a lot of local planting tips and variety characteristics. Of course, the collected seeds must be well preserved, and this is what gene banks do - Nass and others emphasized the value of long-term preservation in 2000 (Nass and Paterniani, 2000). Although technology is advanced now, these basic work is still indispensable. After all, no one knows when the unique genes of an old variety will be needed. Figure 1 In situ/on farm Base Collection, subgroups and sampling strategies for maize landraces (Adopted from Vidal et al., 2020) 3.2 Germplasm preservation techniques When it comes to preserving corn germplasm resources, there are quite a few methods. The most commonly used method is freezing in gene banks, and large warehouses like CIMMYT are quite reliable (Guzzon et al., 2021). Interestingly, the basic bank at minus 15 degrees Celsius has a better preservation effect than the active bank at minus 3 degrees Celsius, and the seeds can survive longer. However, it is not enough to just store them, and the vitality of the seeds must be checked regularly, and arrangements must be made when it is time to re-breed. A study in 2021 mentioned that field preservation is also a good method (Stagnati et al., 2021), especially for those local varieties, directly planting them in their place of origin can maintain their characteristics. Of course, each method has its advantages and disadvantages, and the key depends on what specific materials are to be preserved. 3.3 Phenotypic and genetic diversity assessment The evaluation of corn germplasm resources must be approached from multiple angles. In a study conducted in Italy, by measuring appearance traits such as plant height and ear type, it was found that different local varieties were quite different (Stagnati et al., 2021). However, looking at the appearance alone is not enough, molecular marker analysis can better explain the problem. For example, the national corn inbred seed bank in the United States used SNP markers to detect and found more than 680 000 variant sites (Romay et al., 2013). Although SSR markers were used early, SNPs are more popular now because the data is more detailed. Interestingly, some varieties look similar, but they are very different at the genetic level. Of course, in actual operations, these two methods must be combined to fully evaluate genetic diversity.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==