The exploitation of heterosis to integrate parental advantages is one of the fastest and most efficient ways of rice breeding. The genomic architecture of heterosis suggests that the grain yield is strongly correlated with the accumulation of numerous rare superior alleles with positive dominance. However, the improvements in yield of hybrid rice have shown a slowdown or even plateaued due to the limited availability of complementary superior alleles. In this study, we achieved a considerable increase in grain yield of restorer lines by inducing an alternative splicing event in a heterosis gene OsMADS1 through CRISPR-Cas9, which accounted for approximately 34.1%–47.5% of yield advantage over their corresponding inbred rice cultivars. To achieve a higher yield in hybrid rice, we crossed the gene-edited restorer parents harbouring OsMADS1^GW3p6 with the sterile lines to develop new rice hybrids. In two-line hybrid rice Guang-liang-you 676 (GLY676), the yield of modified hybrids carrying the homozygous heterosis gene OsMADS1^GW3p6 significantly exceeded that of the original hybrids with heterozygous OsMADS1. Similarly, the gene-modified F₁ hybrids with heterozygous OsMADS1^GW3p6 increased grain yield by over 3.4% compared to the three-line hybrid rice Quan-you-si-miao (QYSM) with the homozygous genotype of OsMADS1. Our study highlighted the great potential in increasing the grain yield of hybrid rice by pyramiding a single heterosis gene via CRISPR-Cas9. Furthermore, these results demonstrated that the incomplete dominance of heterosis genes played a major role in yield-related heterosis and provided a promising strategy for breeding higher-yielding rice varieties above what is currently achievable.

中文翻译：

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通过同化近交亲本中的显性杂种优势基因获得高产杂交水稻


利用杂种优势整合亲本优势是水稻育种最快、最有效的途径之一。杂种优势的基因组结构表明，谷物产量与大量具有正显性的稀有优势等位基因的积累密切相关。然而，由于互补性优良等位基因的可用性有限，杂交水稻产量的提高已经放缓甚至停滞不前。在本研究中，我们通过CRISPR-Cas9在杂种优势基因OsMADS1中诱导选择性剪接事件，实现了恢复系籽粒产量的大幅提高，与相应的自交水稻品种相比，其产量优势约占34.1%–47.5%。为了获得更高的杂交水稻产量，我们将携带 OsMADS1 ^GW3p6 的基因编辑恢复亲本与不育系杂交，开发出新的水稻杂交种。在两系杂交水稻广两优676（GLY676）中，携带纯合杂种优势基因OsMADS1 ^GW3p6 的改良杂种的产量显着超过携带杂合OsMADS1的原杂种的产量。同样，与OsMADS1 ^GW3p6 杂合体杂交的基因修饰F ₁ 与三系杂交水稻全优四苗（QYSM）相比，籽粒产量提高了3.4%以上具有 OsMADS1 纯合基因型。我们的研究强调了通过 CRISPR-Cas9 聚合单个杂种优势基因在提高杂交水稻产量方面的巨大潜力。此外，这些结果表明，杂种优势基因的不完全显性在产量相关杂种优势中发挥着重要作用，并为培育高于目前可实现水平的高产水稻品种提供了一种有前景的策略。