Molecular Plant Breeding 2024, Vol.15, No.4, 198-208 http://genbreedpublisher.com/index.php/mpb 198 Research Report Open Access The Contribution of Exotic Varieties to Maize Genetic Improvement Junfeng Hou1, Junmei Zhang2, Fei Bao1, Ping Zhang1, Hailiang Han1, Heping Tan1, BinChen1, Fucheng Zhao1 1 Institute of Maize and Featured Upland Crops, Zhejiang Academy of Agricultural Sciences, Dongyang, 322100, Zhejiang, China 2 Agricultural Industry Service Center of Qingyuan County, Lishui, 323899, Zhejiang, China Corresponding email: zhaofc@zaas.ac.cn Molecular Plant Breeding, 2024, Vol.15, No.4 doi: 10.5376/mpb.2024.15.0020 Received: 10 Jul., 2024 Accepted: 15 Aug., 2024 Published: 30 Aug., 2024 Copyright © 2024 Hou 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: Hou J., Zhang J., Bao F., Zhang P., Han H., Tan H., Chen B., and Zhao F., 2024, The contribution of exotic varieties to maize genetic improvement, Molecular Plant Breeding, 15(4): 198-208 (doi: 10.5376/mpb.2024.15.0020) Abstract Maize (Zeamays L.) is one of the most important staple crops globally, providing essential food and energy resources for millions of people. The genetic improvement of maize has been a focal point of agricultural research, aiming to enhance yield, resilience, and adaptability to various environmental conditions. The introduction of exotic maize lines into adapted germplasm has shown significant potential in increasing genetic variability and improving agronomic traits. For instance, testcrosses of backcross-derived lines exhibited substantial yield improvements, with some lines producing up to 1 056 kg/ha more grain than the control. RNA-sequencing of diverse maize lines revealed extensive genetic and transcriptomic diversity, identifying novel transcripts that contribute to heterosis. Screening of elite exotic inbreds demonstrated that certain tropical lines performed well in temperate environments, suggesting their utility in broadening the genetic base of U.S. maize. Additionally, molecular marker studies confirmed high levels of polymorphism and genetic diversity in tropical maize germplasm. Adaptation efforts have successfully integrated tropical germplasm into temperate breeding programs, enhancing genetic gains. The findings underscore the value of exotic germplasm in maize breeding programs. The integration of exotic alleles has not only expanded the genetic base but also led to the development of high-yielding hybrids with improved agronomic traits. These results highlight the importance of utilizing diverse genetic resources to achieve sustainable genetic improvement in maize. Keywords Maize (Zeamays L.); Genetic diversity; Exotic germplasm; Yield improvement; Tropical maize; Temperate breeding 1 Introduction Genetic diversity is crucial for the sustainability and improvement of crop species. In maize, genetic diversity allows for the development of varieties that can withstand biotic and abiotic stresses, thereby ensuring food security and agricultural productivity. The iterative selection process during domestication has often restricted the genetic diversity available in modern maize varieties, making it imperative to explore alternative sources of genetic variation (Hake and Richardson, 2019). Wild relatives of maize, such as teosinte (Zea mays ssp. parviglumis), offer a rich reservoir of genetic traits that have been lost during domestication but can be reintroduced to enhance modern maize varieties (Hake and Richardson, 2019; Kong et al., 2020). Exotic varieties refer to maize strains that originate from different geographical regions or wild relatives that have not been subjected to the same selection pressures as domesticated varieties. These exotic varieties possess unique genetic traits that can be harnessed to improve modern maize. For instance, the genetic diversity found in teosinte has been shown to contain sequences that can directly increase maize yields under field conditions (Hake and Richardson, 2019). By incorporating these exotic genetic traits, breeders can develop maize varieties with improved yield, disease resistance, and adaptability to high-density planting (Kong et al., 2020; Cai et al., 2024). This study aims to evaluate the contribution of exotic maize varieties to the genetic improvement of maize. This involves identifying and integrating beneficial genetic traits from exotic varieties into modern maize breeding programs. The study also aims to assess the genetic diversity present in exotic maize varieties and their wild relatives, identify specific genetic sequences from exotic varieties that can enhance yield and other agronomic traits in maize, and develop breeding strategies that effectively incorporate these exotic traits into modern maize varieties to improve overall performance and sustainability. By achieving these objectives, the research hopes to
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