WASHINGTON, Feb. 12 (Xinhua) -- Japanese scientists have identified the gene that causes hybrid sterility in rice, a major reproductive barrier between species.

The findings, published on Monday in Proceedings of the National Academy of Sciences, are important not only for understanding the evolutionary biology of speciation, but also for improving crops for food production.

There are only two cultured rice species in the world: an Asian one and an African one. The African species is tolerant of various abiotic and biotic stresses such as high temperature, providing a valuable source of genes that could be useful in rice production.

However, the interspecific reproductive barrier stands in the way of using the African species in breeding programs with the Asian species. Plants obtained from hybridizing the two species yield almost no seeds when they are cultivated. This is known as hybrid sterility.

A Japanese team found that a peptidase-coding gene called SSP causes the hybrid sterility.

The team then studied the evolutionary pathways of SSP and found that the gene is present only in the African species and some other wild species, not in the Asian one, hence leading to the interspecific boundaries.

"Our study shows the interspecific reproductive barrier can be overcome by a disruption of a single gene. Further research could help improve breeding programs and enhance rice yields to address food shortages in growing populations," said Yohei Koide, assistant professor of Hokkaido University and the paper's lead author.