Rice Genomics and Genetics 2024, Vol.15, No.6, 277-286 http://cropscipublisher.com/index.php/rgg 280 create superior hybrid varieties. The cumulative effects of these genetic components, including overdominance and epistatic interactions, are essential for achieving significant yield improvements in hybrid rice (Figure 2) (Luo et al., 2001; Zhou et al., 2022). Genetic engineering approaches, including CRISPR technologies, provide novel solutions to tackle fertility challenges in autotetraploid rice by targeting genes involved in meiosis and pollen development. Through CRISPR/Cas9-mediated knockout of genes like TMS9-1 and TMS5, researchers have observed significant effects on fertility and pollen formation (Zhu et al., 2024). Figure 1 Comparisons of F1 lines derived from PA64s/L54, PA64s/L53, PA64s/L55, PA64s/L90, and LYP9 lines. L54, L53, L55, and L90 were four CSSLs (Adopted from Liu et al., 2020) Image caption: a The physical map of the 9311 variety and the CSSLs harboring qHD8PA64s. b Comparison of 1000-grain weight of the four F1 lines and LYP9. c-g The seed length, width, length, width ratio, and level of chalkiness in LYP9 and PA64s/L90. h Image of the seeds of LYP9 and PA64s/L90 (Adopted from Liu et al., 2020) 5 Recent Advances in Hybrid Rice 5.1 Latest varieties and their characteristics Recent advancements in hybrid rice breeding have led to the development of several high-yielding varieties with improved traits. For instance, China has successfully developed new rice hybrids with super high-yielding potential by utilizing indica-inclined and japonica-inclined parental lines. These hybrids have been grown on a large scale, demonstrating significant improvements in yield and grain quality (Cheng et al., 2007). Another notable example is the development of intersubspecific hybrids such as ‘Liangyoupeijiu’ and ‘Liangyou E32’, which have exhibited grain yields higher than 10.5 t/ha and have been widely adopted due to their superior performance and adaptability. Additionally, the ideotype approach has been employed to create second-generation New Plant Type (NPT) lines that outperform first-generation lines and indica check varieties, further enhancing yield potential (Peng et al., 2008). 5.2 Breeding advances based on genomic selection (GS) Genomic selection (GS) has revolutionized hybrid rice breeding by enabling the identification and selection of superior alleles associated with high yield and other desirable traits. A comprehensive genomic analysis of 1 495 elite hybrid rice varieties and their parental lines revealed numerous superior alleles that contribute to heterosis. This study identified 130 loci associated with 38 agronomic traits, highlighting the importance of accumulating rare superior alleles with positive dominance effects to achieve high yields (Huang et al., 2015). Moreover, marker-assisted selection has been effectively used to develop restorer lines carrying disease resistance genes, thereby increasing breeding efficiency and enhancing the genetic diversity of hybrid rice (Cheng et al., 2007).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==