Chinese scientists have completed sequencing a "working draft" of the genome of the nation's F1 super hybrid rice.

The genome map will be published for free use by the world's scientists, said Chen Zhu, vice president of the Chinese Academy of Science (CAS), and China's leading gene researcher.

Mapping the hybrid rice genome will make China the second country, after the United States, to complete a genome sequencing of a rice plant. The breakthrough was made by the CAS Genome Research Center, along with the Beijing Huada Gene Research Center and its southern base in Hangzhou, in eastern China's Zhejiang Province

China's super hybrid rice set a new world yield record of 17.072 tons per hectare, PlanetRice reported in November 2000.

One purpose of the genome mapping is to discover what makes the super hybrid rice so productive, according to Zhu Lihuang, director of the CAS Laboratory of Biological Engineering.

The rice genome has about 430 million base pairs, a seventh of that of the human genome, the China Daily reported. The genome sequencing and its analysis will help people understand the genetic mechanism of rice, which could be used to improve future rice varieties.

Deciphering the genetics of an F1, or first-generation hybrid rice, marks a still-newer phase in the revolutionary field of plant genome mapping, PlanetRice reported in May. Other rice gene mappings are underway, but using conventional varieties. This is the world's first attempt to decipher what makes an F1 hybrid rice tick.

The working draft covers more than 90 percent of the total DNA sequences of the ultra high-yielding hybrid rice, which was developed by rice breeder Yuan Longping.

Yuan, who developed the world's first F1 hybrid rice, is known worldwide as "the father of hybrid rice."

Yang Huanming, a CAS leader of the sequencing project, said that unraveling the rice genome will also help in the study of crops such as wheat and corn.

The database, set up after completion of the rice genome sequencing, covers all 12 rice chromosomes, and more than 95 percent of the rice genome.

The accuracy of sequencing data, on 90 percent of the genome, was more than 99 percent, Yang said. The Chinese researchers also developed a unique mathematic system that overcomes enormous difficulties that were encountered in analyzing the human genome sequencing, the gene specialist said.

The researchers' software can be run in both state-of-the-art SUN and China-made Dawn 3000 supercomputers.

The working draft and database of the rice genome are the first stage of China's hybrid rice genome project, launched in May 2000. The complete hybrid rice genome map should be finished in 2002. The researchers plan to identify specific genes that determine traits like rice yield and maturity, plus disease and insect resistance.

China's hybrid rice

F1 hybrid varieties, of any crop, are developed for heterosis or hybrid vigor--the phenomenon in which the progeny of two distinctly different parents grow faster, yield more, or resist stresses better than either parent.

China has only 7 percent of the world's arable land, but feeds 22 percent of the world's total population, Xinhua reported last year. Feeding that population is possible partly because F1 hybrids are planted on about 16 million hectares, or about half of China's rice land.

Rice accounts for more than 40 percent of China's total grain output. From 50 to 60 percent of China's rice land is planted to F1 hybrids.

(China Radio International 10/17/2001)