Hybrid rice has achieved high grain yield and greatly contributes to food security, but the manual-labour-intensive hybrid seed production process limits fully mechanized hybrid rice breeding. For next-generation hybrid seed production, the use of small-grain male sterile lines to mechanically separate small hybrid seeds from mixed harvest is promising. However, it is difficult to find ideal grain-size genes for breeding ideal small-grain male sterile lines without penalties in the number of hybrid seeds and hybrid rice yield. Here we report that the use of small-grain alleles of the ideal grain-size gene GSE3 in male sterile lines enables fully mechanized hybrid seed production and dramatically increases hybrid seed number in three-line and two-line hybrid rice systems. The GSE3 gene encodes a histone acetyltransferase that binds histones and influences histone acetylation levels. GSE3 is recruited by the transcription factor GS2 to the promoters of their co-regulated grain-size genes and influences the histone acetylation status of their co-regulated genes. Field trials demonstrate that genome editing of GSE3 can be used to immediately improve current elite male sterile lines of hybrid rice for fully mechanized hybrid rice breeding, providing a new perspective for mechanized hybrid breeding in other crops.

杂交水稻实现了粮食高产，为粮食安全做出了巨大贡献，但杂交制种过程中的手工劳动密集型限制了杂交水稻育种的全机械化。对于下一代杂交种子生产，使用小粒雄性不育系从混合收获中机械分离小型杂交种子是有前途的。然而，很难找到理想的粒级基因来培育理想的小粒雄性不育系而不会对杂交种子的数量和杂交水稻产量造成影响。在这里，我们报告说，在雄性不育系中使用理想粒型基因GSE3的小粒等位基因可以实现全机械化杂交种子生产，并显着增加三系和两系杂交水稻系统中的杂交种子数量。 GSE3基因编码一种组蛋白乙酰转移酶，可结合组蛋白并影响组蛋白乙酰化水平。 GSE3 被转录因子 GS2 募集至其共同调节的颗粒大小基因的启动子，并影响其共同调节的基因的组蛋白乙酰化状态。田间试验表明， GSE3的基因组编辑可用于立即改良现有的杂交水稻优良雄性不育系，用于杂交水稻全程机械化育种，为其他作物的机械化杂交育种提供了新的前景。