Maize Genomics and Genetics 2025, Vol.16, No.5, 251-257 http://cropscipublisher.com/index.php/mgg 251 Review Article Open Access Fine Mapping of a Major QTL for Stay-Green Trait in Maize Using Near-Isogenic Lines Pingping Yang, Jin Zhou, Minli Xu Hainan Provincial Key Laboratory of Crop Molecular Breeding, Sanya, 572025, Hainan, China Corresponding author: minli.xu@hitar.org Maize Genomics and Genetics, 2025, Vol.16, No.5 doi: 10.5376/mgg.2025.16.0022 Received: 18 Jul., 2025 Accepted: 03 Sep., 2025 Published: 23 Sep., 2025 Copyright © 2025 Yang 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: Yang P.P., Zhou J., and Xu M.L., 2025, Fine mapping of a major QTL for stay-green trait in maize using near-isogenic lines, Maize Genomics and Genetics, 16(5): 251-257 (doi: 10.5376/mgg.2025.16.0022) Abstract The greenness retention trait is one of the key agronomic traits determining the stress resistance and high-yield potential of maize (Zea mays L.), especially showing significant value under stress conditions such as drought and late maturity. In this study, Near-Isogenic Lines (NILs) were used as research materials to precisely locate a major QTL in corn that was significantly associated with greenness holding traits, reveal its genetic basis and explore candidate gene resources. Through the construction of a high-density molecular marker map and precise phenotypic evaluation, The fine localization region of this QTL on chromosome 9 was identified under multi-environment experiments. Further, through recombinant single-plant analysis, candidate gene expression profiling and functional annotation, multiple key genes that may be involved in regulating chlorophyll degradation, photosynthesis maintenance and antioxidant pathways were preliminarily identified. This study also verified the expression and explored the biological significance of typical candidate genes such as Stay-Green1 (SGR1) and SAG12, providing an important basis for the molecular breeding of green-holding traits in maize and potential targets for the improvement of complex traits such as drought resistance and delayed senescence. Keywords Corn; Green-holding property; QTL fine positioning; Near-isogenic line; Candidate gene 1 Introduction The high yield of corn does not only depend on the number of kernels, but also on whether the leaves can remain in a "green state" during the filling period. The greenness retention trait refers to the fact that when leaf senescence is delayed, photosynthesis can still continue for a period of time. Especially in abiotic stress environments such as drought and high temperature, once photosynthesis stops too early, the yield often declines accordingly (Wang et al., 2012). Therefore, genotypes that can "preserve greenness" tend to be more stable and more resilient (Belicuas et al., 2014; Zhang et al., 2019). However, it is no easy task to figure out which group of genes are at work behind this trait. Researchers have identified many regions related to green conservation on corn by using QTL mapping technology. Some major QTLS can even explain a large proportion of the phenotypic differences (Yang et al., 2017). The problem is that the resolution of traditional QTL mapping is often insufficient, and the mapped intervals are too wide, which may contain hundreds of genes - this is not very friendly for gene cloning and subsequent breeding selection (Wang et al., 2018). To solve this "too vague" problem, precise positioning becomes very important. Among them, the near-isogenic line (NIL) is particularly suitable for doing this. Their genetic backgrounds are relatively uniform, with only differences in the target QTL regions. As a result, some background noise can be avoided and the evaluation effect becomes clearer (Eichten et al., 2011). In addition, NIL is also very useful in QTL validation and functional research, which can significantly accelerate the breeding speed of key traits (Zhong et al., 2025). This study utilized near-isogenic lines (NIL) to precisely locate the major QTL of green retention traits in maize, narrowed the QTL interval to identify candidate genes, and verified the impact of this QTL on green retention traits and yield-related traits, providing genetic resources and molecular markers for breeding projects. This study aims to enhance the efficiency of marker-assisted selection and contribute to the cultivation of high-yield and stress-resistant corn varieties, ultimately ensuring food security in the context of climate change.
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