With the ever-increasing human population and deteriorating environmental conditions, there is an urgent need to breed environmentally friendly and resource-conserving rice cultivars to achieve sustainable agricultural development and food security. However, conventional rice improvement strategies, such as hybrid breeding, are time-consuming and laborious processes and may not be able to keep pace with increasing food demand in the future. Targeted genome-editing technologies, especially clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (CRISPR/Cas), permit efficient targeted genome modification and offer great promise for the creation of desired plants with higher yield, improved grain quality, and resistance to herbicides, diseases, and insect pests. There is also great potential for tapping heterosis using the CRISPR/Cas technology. In this review, we focus on the most essential applications of CRISPR/Cas genome editing to rice genetic improvement, considering traits such as yield, quality, and herbicide, disease and insect-pest resistance. We discuss applications of CRISPR/Cas to the exploitation of heterosis. Finally, we outline perspectives for future rice breeding using genome-editing technologies.

CRISPR-Cas12a offers a convenient tool for multiplex genome editing in rice. However, the CRISPR-Cas12a system displays variable editing efficiency across genomic loci, with marked influence by CRISPR RNAs (crRNAs). To improve the efficiency of the CRISPR-Cas12a system for multiplex genome editing, we identified various architectures and expression strategies for crRNAs. Transformation of binary vectors loaded with engineered CRISPR-Cas12a systems into rice calli and subsequent sequencing revealed that a modified tRNA-crRNA array not only efficiently achieved rice multiplex genome editing, but also successfully edited target sites that were not edited by the crRNA array. This improvement contributes to the application of the CRISPR-Cas12a system in plant genome editing, especially for genomic loci that have hitherto been difficult to edit.