Fig. 2

The third-generation hybrid rice technology. (1) Male-sterile lines are obtained by mutant screening or CRISPR/Cas9 technology. (2) The fertility-restoration gene, pollen-inactivation gene, and seed-sorting gene are connected in one T-DNA and transformed into the male-sterile plant to obtain a maintainer line. (3) The maintainer line self-pollinates and produces 50% male-sterile seeds and 50% maintainer seeds that are separated based on the seed-sorting marker. (4) Cross-pollination the male-sterile line by the maintainer generates 100% male-sterile seeds, because transgenic pollen is killed by the pollen-inactivation gene. (5) Any normal rice germplasm can be used as the paternal line to cross with a genic male sterility (GMS) line to breed hybrid rice