Grade: The second prize
Winners: Wan Jianming, Zhao Zhigang, Jiang Ling, Cheng Zhijun, Chen Mingliang and Liu Shijia.
Collaborators：Nanjing Agricultural University, Crop Science Institute of China Academy of Agricultural Sciences
There have strong heterosis between indica and japonica rice with a high yield increasing by 15% to 30%, compared with hybridization between sub-varieties within indica rice. However, there have several problems of semi-infertility, late maturity, and tall stalk when using indica-japonica heterosis, which prevent application of this heterosis. In this program, the researchers have spent over 20 years in studies, such as identifying rice genes of wide compatibility, early maturity and dominant short stalk, developing close linkage molecular marker and breeding technologies, successfully improving new high-yield rice varieties byindica-japonica hybridized.
(1) Identifying 17 infertility sites and wide compatibility genes. The researchers have identified nine female-infertility sites, such as S8 and S9, and six male-infertility sites, such as S19 and S33, controlled fertility of indica-japonica hybrid, and map-based cloned two gene related fertility. One is the pollensemi-infertile genepssland other is the reproduction-development-related gene DAO, its functional mechanisms were illustrated. They invented the related molecular breeding technology, integrated the widely compatible genes, developed the widely compatible and restorable line andindica-as-background japonica-type infertile line. They have obtained over 85% of setting rate of the indica-japonica new varieties. The hard problem of hybrid infertility was effectively solved.
(2) Identifying early-mature genes. The researchers have determined light-sensitive genes at the heading stage in all the rice production regions in the country and map-based cloned the gene Dth8 (contribute to light-insensitive), the key gene Ehd4 (contribute to heading under long or short period of sun light), and the slightly effectivedth2( enhances heading under long daylight). Then they have proposed molecular designing method based on light-sensitive and light-insensitive genes, designed the optimal breeding programs, obtained indica-japonica hybridized varieties with ideal maturing periods and solved the problem of indica-japonica hybrid transgressive late heading.
(3) Identifying key genes of dominant short stalk and ideal plant type. The researchers have cloned the dominant short stalked gene Epi-df, which determined the epigenetic mechanism causing dwarfism of rice plant; the semi-dominant stalked gene D53, which controlled the rice plant type by the pathway of strigolactone signaling; the key plant-type controlling gene APC/CTE. They deep analysed the functional mechanism for these genes; developed related molecular markers, and lay a foundation for cultivating indica-japonica hybridized ideal plant type.
(4) They have constructed a technological system of molecular marker pyramid breeding of rice, and bred five new indica-japonica hybridized varieties. They have created a pyramid breeding system by integrating multiple hybridization and molecular-marked selection, aggregated wide compatible and partly dominant short stalk genes, employed the heterosis between indica and japonica and selectively bred from their progenies. Three japonica varieties have been developed including Ningjing No. 3 and Ningjing No. 4, both of which have been determined by the Ministry of Agriculture as a super-grade new rice variety and a super-grade dominant rice variety, respectively. They also have aggregated the wide-compatible genes S5n, S7n and S17n and the early mature gene Dth8, cultivated the restorer line W107 with strong wide adaptability, and assembled two hybrid varieties Xieyou 107 and IIyou 107, which passed the state and Anhui Province examinations respectively. In 2006, Xieyou 107 had a yield of 1287kg/mu on the 1.13mu of experimental field. The new varieties have been extended to 31.07 million mu with an economic benefit of 4. 4.059 billion RMB. In 2011 to 2013, the new varieties were grown in 19.61 million mu more of farmland with a benefit of 2.647 billion RMB. The indica- as-background japonica-type infertile line 509S has been offered to 18 institutes in rice breeding with eight assembled varieties, which having in national-level and provincial-level regional tests.
Overall, in this program, the researchers have obtained seven patents, and eight new plant variety rights, and published 71 papers, including 41 papers in authoritative international SCI journals of Nature, PNAS, Plant Cell, and so on,with 220 citations by other authors. This program has effectively solved the problems of semi-infertility, late maturity, and tall stalk when using indica-japonica heterosis and produced a series of new varieties, which is a significant contribution to guarantee of national food safety and to increase income of farmers in China.
