A novel strategy for creating a new system of third-generation hybrid rice technology using a cytoplasmic sterility gene and a genic male-sterile gene

Heterosis utilization is the most effective way to improve rice yields. The cytoplasmic male-sterility (CMS) and photoperiod/thermosensitive genic male-sterility (PTGMS) systems have been widely used in rice production. However, the rate of resource utilization for the CMS system hybrid rice is low, and the hybrid seed production for the PTGMS system is affected by the environment. The technical limitations of these two breeding methods restrict the rapid development of hybrid rice. The advantages of the genic male-sterility (GMS) rice, such as stable sterility and free combination, can fill the gaps of the first two generations of hybrid rice technology. At present, the third-generation hybrid rice breeding technology is being used to realize the application of GMS materials in hybrid rice. This study aimed to use an artificial CMS gene as a pollen killer to create a smart sterile line for hybrid rice production. The clustered regularly interspaced short palindromic repeats/CRISPR-associated 9 (CRISPR/Cas9) technology was used to successfully obtain aCYP703A3-deficient male-sterile mutant containing no genetically modified component in the genetic background of indica 9311. Through young ear callus transformation, this mutant was transformed with three sets of element-linked expression vectors, including pollen fertility restoration geneCYP703A3, pollen-lethality geneorfH79and selection marker geneDsRed2. The maintainer 9311-3B with stable inheritance was obtained, which could realize the batch breeding of GMS materials. Further, the sterile line 9311-3A and restorer lines were used for hybridization, and a batch of superior combinations of hybrid rice was obtained.

Automated summary

Heterosis utilization is an effective way to improve rice yields, but traditional CMS and PTGMS systems have limitations in resource utilization and are affected by the environment. The advantages of GMS technology can address the shortcomings of the first two generations of hybrid rice technology, and are now being applied in the third generation of hybrid rice breeding technology.