Maize Genomics and Genetics 2025, Vol.16, No.2, 80-88 http://cropscipublisher.com/index.php/mgg 80 Feature Review Open Access Advances in Haploid Breeding Techniques for Maize Improvement: Innovations and Applications Delong Wang, Pingping Yang, Jiong Fu Hainan Provincial Key Laboratory of Crop Molecular Breeding, Sanya, 572025, Hainan, China Corresponding author: jiong.fu@hitar.org Maize Genomics and Genetics, 2025, Vol.16, No.2 doi: 10.5376/mgg.2025.16.0008 Received: 30 Jan., 2025 Accepted: 16 Mar., 2025 Published: 31 Mar., 2025 Copyright © 2025 Wang et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Wang D.L., Yang P.P., and Fu J., 2025, Meta-analysis of genetic diversity in global fresh-eating maize germplasm resources, Maize Genomics and Genetics, 16(2): 80-88 (doi: 10.5376/mgg.2025.16.0008) Abstract The study provides a comprehensive overview of recent advances in haploid breeding techniques for maize, particularly the revolutionary role of doubled haploid (DH) technology in maize breeding. DH technology significantly enhances breeding efficiency and effectiveness by rapidly generating pure inbred lines, offering numerous economic, logistic, and genetic benefits compared to traditional methods, especially in commercial breeding programs. Key advancements include the development of efficient haploid inducers, the application of new marker systems, and enhanced chromosome doubling protocols. Additionally, the integration of DH technology with genome editing tools, such as CRISPR/Cas9, further accelerates the breeding of elite lines with desirable traits. Despite current challenges, including low induction rates, genomic stability, and technical and economic feasibility, DH technology holds immense potential to meet global food demands and address agricultural challenges. Its widespread adoption will contribute significantly to sustainable agriculture and food security. Keywords Haploid breeding; Doubled haploid (DH) technology; Maize breeding; Genome editing; Inducer lines 1 Introduction It goes without saying that corn (Zea mays L.) is an indispensable member in the fields of food, feed and fuel. Millions of people around the world rely on it as their staple food. It is one of the most important cereals for mankind, second only to rice and wheat (Gupta et al., 2022; Wang et al., 2022). But in many places, especially in tropical agricultural areas where people rely on the weather for food, it is not so easy to grow corn. Drought, heat, high humidity, and saline-alkali land are all long-standing problems that affect harvests (Prasanna et al., 2020; 2021). Can we use existing methods to combat these climate troubles? It is difficult. Therefore, we have to think of new ways, and the upgrading of breeding technology has become urgent. In this regard, haploid breeding is a method that has attracted much attention, especially the double haploid (DH) technology, which is considered a major breakthrough in the breeding process. Its principle is actually not complicated: first produce a haploid plant with only one set of chromosomes, and then use artificial means to double its chromosomes to become a homozygous DH line. Because there is no need for generation after generation of screening, this step directly increases the breeding speed, which is especially convenient when doing hybrid breeding (Dwivedi et al., 2015; Chaikam et al., 2019; Meng et al., 2021). Of course, this technology alone is not enough. In recent years, people have begun to use it in combination with molecular markers, genome editing and other technologies, which not only improves efficiency, but also broadens its application range in commercial breeding (Wang et al., 2019; Gupta et al., 2022; Zhou and Jiang, 2024). This review is intended to review the current progress in haploid maize breeding. The focus is not only on DH technology itself, such as how to improve the success rate of haploid induction, how to quickly identify haploids, and how to embed gene editing tools such as CRISPR/Cas9, etc. More importantly, we want to see whether these technologies can be used in actual stress-resistant breeding, especially under extreme conditions such as high temperature and drought. As for whether they can increase genetic gain and improve breeding efficiency, it depends on their performance in reality.
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