Maize Genomics and Genetics 2025, Vol.16, No.2, 80-88 http://cropscipublisher.com/index.php/mgg 86 7 Case studies and Field Applications 7.1 Commercial case studies Double haploid (DH) technology is now a key tool in commercial corn breeding, mainly because it can quickly and efficiently obtain homozygous lines. Compared with traditional inbred line breeding, this technology has obvious advantages in economic cost, operation process and genetic stability. However, the popularization of DH technology is not achieved overnight. For example, the development of induced lines with high haploid induction rate and the adaptation of these lines to different environments, especially tropical regions, have greatly promoted its application (Chaikam et al., 2019). It is also worth noting that the introduction of new marker systems, such as red root markers and high oil content markers, has made DH technology more efficient in dealing with diverse germplasm resources. The germplasm covers flint corn, local varieties and even tropical materials, and the utilization rate of these diverse gene pools has been improved (Chaikam et al., 2019). In addition, DH technology has also performed well in the development of hybrids. Through in situ parthenogenesis, DH lines can be generated in large quantities and quickly, and these inbred lines become the basis of hybrid parents. This method is not only low-cost but also highly efficient, which accelerates the pace of hybrid breeding. More importantly, the genetic progress obtained through DH-RS has been able to match the traditional methods, showing the important value of DH technology in commercial breeding (Gallais and Bordes, 2007). 7.2 Field trials and performance Field trials are the key link to test the effect of DH technology in different environments. For example, a study in Uganda tested 44 newly developed DH test cross hybrids in five locations, focusing on their grain yield and other agronomic traits. The results showed that environmental factors, genotypes and their interactions all significantly affected yield, with the environment explaining nearly half (46.5%) of the variation. It is worth mentioning that the average yield of these DH hybrids was nearly half (49.2%) higher than that of commercial control varieties, showing strong stability and superiority in multiple environments (Sserumaga et al., 2015). This shows that even in complex and changing environments, DH lines still maintain good adaptability. 7.3 Major breeding programs Globally, several large maize breeding programs have adopted DH technology because it can effectively shorten the breeding cycle and increase the speed of genetic improvement. Rapidly obtaining homozygous lines is very important for these programs, allowing genetic progress to be manifested in a shorter time (Trentin et al., 2020). However, it is worth noting that it is not only large-scale projects that have begun to use DH technology, but also small and medium-scale breeding programs are slowly following suit. Although the promotion speed is relatively slow, in order to adapt to specific environments, especially the needs of tropical regions, these projects are also working hard to cultivate haploid induced lines suitable for local areas. The goal is to make DH technology more accessible and more able to help small breeding operations improve efficiency and genetic benefits (Trentin et al., 2020). 8 Future Prospects and Research Directions The application of haploid induction technology in corn breeding has achieved a lot of results, but it still has a lot of room for improvement. One important direction is to improve the haploid induction rate (HIR), which is related to the efficiency and cost of the technology. Recently, it has been found that the maternal HIR can be increased to 16.3% by genetically improving the induced line, such as overexpressing CENH3 in the Stock6 derivative line (Meng et al., 2022). In addition, mutations in the ZmDMP gene can also significantly increase the haploid production rate, sometimes doubling or tripling it (Zhong et al., 2019). Although these advances are promising, there are still many technical details that need to be solved in practical applications. Although haploid breeding technology has made significant progress, there are still several difficulties that cannot be ignored. For example, how to combine genome editing technology (CRISPR/Cas9) with haploid induction is
RkJQdWJsaXNoZXIy MjQ4ODYzNA==