Molecular Plant Breeding 2024, Vol.15, No.4, 167-177 http://genbreedpublisher.com/index.php/mpb 167 Research Insight Open Access Autotetraploid Rice Hybrids: Overcoming Sterility Barriers for Enhanced Heterosis QianZhu1,2,3, Xiaoling Zhang4, Hui Zhang1,3, JuanLi 1,2,3, Chunli Wang1,3, Dongsun Lee1,2,3, Lijuan Chen1,2,3 1 Rice Research Institute, Yunnan Agricultural University, Kunming, 650201, Yunnan, China 2 The Key Laboratory for Crop Production and Smart Agriculture of Yunnan Province, Yunnan Agricultural University, Kunming, 650201, Yunnan, China 3 State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, 650201, Yunnan, China 4 Kunming University, Kunming, 650214, Yunnan, China Corresponding email: chenlijuan@hotmail.com Molecular Plant Breeding, 2024, Vol.15, No.4 doi: 10.5376/mpb.2024.15.0017 Received: 10 Jun., 2024 Accepted: 15 Jul., 2024 Published: 26 Jul., 2024 Copyright © 2024 Zhu 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: Zhu Q., Zhang X.L., Zhang H., Li J., Wang C.L., Lee D.S., and Chen L.J., 2024, Autotetraploid rice hybrids: overcoming sterility barriers for enhanced heterosis, Molecular Plant Breeding, 15(4): 167-177 (doi: 10.5376/mpb.2024.15.0017) Abstract Autotetraploid rice, developed through whole genome duplication of diploid rice, offers potential advantages such as larger grains, higher nutrient content, and increased resistance. However, its low fertility has been a significant barrier to its commercial viability. Recent advancements have focused on understanding and overcoming the sterility issues in autotetraploid rice hybrids to harness their heterosis potential. The development of high-fertility tetraploid rice lines and the application of molecular breeding techniques have shown promise in improving hybrid performance. This study synthesizes the genetic mechanisms underlying the low fertility of autotetraploid rice and its F1 hybrids from both cytological and molecular biological perspectives. It introduces the main types of high-fertility tetraploid rice and the latest research progress. Lastly, the study proposes ideas for future research on exploiting the heterosis of high-fertility autotetraploid rice, aiming to provide insights for polyploid rice breeding. Keywords Autotetraploid rice; Hybrid sterility; Heterosis; Fertility restoration; Molecular breeding 1 Introduction Autotetraploid rice, characterized by having four sets of chromosomes (2n = 4x = 48, AA to AAAA), has emerged as a promising avenue in rice breeding due to its potential to overcome sterility barriers and enhance heterosis. The development of autotetraploid rice hybrids has been suggested as a novel method to exploit heterosis more effectively, as these hybrids can exhibit significant improvements in yield components such as productive panicles per plant, total kernels per panicle, and seed set (Tu et al., 2007). Moreover, autotetraploid rice hybrids have shown better chromosome pairing and genetic stability, which are crucial for maintaining high fertility and yield (Luan et al., 2007). Heterosis, or hybrid vigor, refers to the phenomenon where hybrid offspring exhibit superior biological and agricultural traits compared to their parents. In rice, heterosis is a critical factor for achieving high yields and improving crop performance. Traditional diploid rice hybrids, especially those resulting from intersubspecific crosses between indica and japonica varieties, often face challenges related to poor fertility, which significantly limits the practical utilization of heterosis due to hybrid sterility (Tu et al., 2007; Guo et al., 2017; Bei et al., 2019; Liu et al., 2023). Recent studies have highlighted the potential of autotetraploid rice hybrids to overcome these sterility barriers, thereby unlocking higher levels of heterosis. This suggests that polyploidy can be a viable strategy for enhancing rice breeding programs (Cai et al., 2007; Guo et al., 2017; Chen et al., 2020). The objective of this study is to provide a comprehensive analysis of the current state of research on autotetraploid rice hybrids, focusing on their ability to overcome sterility barriers and enhance heterosis. This study aims to summarize the key findings from recent studies on the production and performance of autotetraploid rice hybrids; explore the genetic and molecular mechanisms underlying the fertility and heterosis observed in these hybrids and discuss the potential applications and future directions for autotetraploid rice breeding. By synthesizing the available literature, this study expects to offer valuable insights into the advantages and challenges associated with autotetraploid rice hybrids, ultimately contributing to the development of more robust and high-yielding rice varieties.
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