New way to grow rice plant clones from seeds

Scientists, including those of Indian origin, have discovered a way to grow rice plant clones from seeds, an advance that could lead to high-yielding and disease-resistant crops. The ability to produce a clone, an exact replica, of a plant from its seeds would be a major breakthrough for world agriculture, said researchers at the University of California, Davis in the US. Instead of purchasing expensive hybrid seeds each year, which is often beyond the means of farmers in developing countries, farmers could replant seeds from their own hybrid plants and derive the benefits of high yields year after year.

"It's a very desirable goal that could change agriculture," said Venkatesan Sundaresan, a professor at UC Davis. Sundaresan and postdoctoral researcher Imtiyaz Khanday discovered that the rice gene BBM1, belonging to a family of plant genes called "Baby Boom" or BBM, is expressed in sperm cells but not in eggs. After fertilisation, BBM1 is expressed in the fertilised cell but -- at least initially -- this expression comes from the male contribution to the genome.

BBM1 switches on the ability of a fertilised egg to form an embryo, according to the study published in the journal Nature. Researchers first used gene editing to remove the ability of the plants to go through meiosis (cell division), so that the egg cells formed instead by mitosis, inheriting a full set of chromosomes from the mother. Then they caused these egg cells to express BBM1, which they would not normally do without fertilisation.

"So we have a diploid egg cell with the ability to make an embryo, and that grows into a clonal seed," Sundaresan said. So far the process has an efficiency of about 30 per cent, but the researchers hope that can be increased with more research. The approach should work in other cereal crops, which have equivalent BBM1 genes, and in other crop plants as well, Sundaresan said.