Rice Genomics and Genetics 2024, Vol.15, No.4, 190-202 http://cropscipublisher.com/index.php/rgg 195 Shanyou 63’s success can be attributed to its vigorous growth, high tillering capacity, and enhanced photosynthetic efficiency. Field trials demonstrated that Shanyou 63 could achieve yields up to 20% higher than conventional inbred varieties under optimal conditions. Its high yield potential made it a cornerstone of China's hybrid rice program, contributing significantly to national food security (Cheng et al., 2007). The International Rice Research Institute (IRRI) has also developed several high-yielding hybrid rice varieties. IRRI's super hybrids, such as Mestizo 1 and Mestizo 2, are notable examples. These hybrids were developed by crossing elite tropical rice lines with high yield potential and stress tolerance. Mestizo 1 and Mestizo 2 have shown yield advantages of 15%~20% over traditional inbred varieties. Their development involved extensive field testing across multiple environments to ensure adaptability and stability. These hybrids have been widely adopted in the Philippines and other Asian countries, contributing to increased rice production and farmer incomes (Khush, 2013). 4.2 Stress-resistant hybrids Sub1 hybrids, developed to withstand submergence stress, are a remarkable example of stress-resistant hybrid rice. These hybrids carry the Sub1 gene, which confers tolerance to prolonged flooding, a common challenge in many rice-growing regions. The Sub1 gene was incorporated into popular hybrid varieties through marker-assisted backcrossing (Xu et al., 2006). Sub1 hybrids, such as Swarna-Sub1 and Samba Mahsuri-Sub1, have demonstrated their resilience in flood-prone areas. These hybrids can survive complete submergence for up to two weeks, allowing farmers to achieve stable yields despite adverse weather conditions. The adoption of Sub1 hybrids has been particularly beneficial in South and Southeast Asia, where flooding is a recurrent problem (Ismail et al., 2013). Drought tolerance is another critical trait for improving rice resilience. Hybrid varieties such as Arize 6444 Gold, developed by Bayer CropScience, have been bred for enhanced drought tolerance. Arize 6444 Gold combines the traits of high yield potential and drought resilience, making it suitable for regions with erratic rainfall patterns. Field trials have shown that Arize 6444 Gold can maintain high yields under water-limited conditions, providing a reliable option for farmers facing drought stress. This hybrid's performance highlights the importance of integrating stress tolerance traits into hybrid breeding programs to ensure food security in the face of climate change. 4.3 Quality-enhanced hybrids In India, hybrid rice breeding has also focused on improving grain quality. Varieties such as Pusa RH10 and DRRH3, developed by the Indian Agricultural Research Institute (IARI), combine high yield potential with superior grain quality. These hybrids are characterized by long, slender grains, high amylose content, and good cooking quality, catering to consumer preferences (Singh et al., 2017). Pusa RH10 and DRRH3 have been well-received by both farmers and consumers. Their adoption has not only increased rice production but also enhanced market value due to their premium grain quality. These hybrids exemplify the successful integration of yield and quality traits in hybrid rice breeding. Vietnam has made significant strides in developing quality-enhanced hybrid rice varieties. Hybrids such as TH3-3 and PAC 807, developed by the Vietnam Academy of Agricultural Sciences (VAAS), are known for their high yield potential and excellent grain quality. These hybrids feature aromatic grains, desirable texture, and good cooking properties, meeting the high standards of both domestic and export markets. TH3-3 and PAC 807 have gained popularity among Vietnamese farmers, leading to increased adoption and improved livelihoods. The success of these hybrids underscores the importance of breeding programs that address both productivity and quality to meet consumer demands (Nguyen et al., 2015).
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