Wild rice, a closely related species of cultivated rice, share the same ancestors of cultivated rice but have experienced different evolutionary pathways.

About 10,000 years ago, ancient Chinese lived in the southern China domesticated primitive common wild rice (Oryza rufipogon) into Asian cultivated rice (Oryza sativa).

Due to the founder effect and the genetic bottleneck, the genetic diversity in cultivated rice is greatly reduced, which limits further improvement of rice yield and quality. In addition, wild rice has long been in the wild environment, undergoing harsh natural selection, thus accumulated a large number of resistant genes for stress that are lacking in cultivated rice varieties.

In order to utilize wild rice resources efficiently, researchers in Institute of Subtropical Agriculture (ISA) of Chinese Academy of Sciences, in cooperation with the Biotechnology Research Institute, the Chinese Academy of Agricultural Sciences, constructed a genetic population of wild rice and cultivated rice.

The donor parent, LSWR (LingShui Wild Rice), was a common wild rice (O. rufipogon) collected from Lingshui City, Hainan Province, China (18°52′N, 110°02′E) and the recurrent parent was an elite Indica cultivar 9311 (O.sativa ssp. indica cv. 9311).

156 Indel markers evenly distributed on 12 chromosomes were developed to get a physical map with high resolution, providing an efficient tool for molecular marker assisted selection (MAS). Crossing was carried out between LSWR and 9311, during which 9311 was regarded as “female” and LSWR as “male.” After obtaining hybrid seed successfully, continuous backcrossing as well as MAS and selfing was applied to get an introgression population with high generation (6th generation) finally.

The introgression lines (ILs) contained 77 lines including 1.286 introgressed fragments with an average length of 6.511 Mb, covering 93.59% of the donor parent’s chromosomes. The agricultural traits of 77 lines were investigated. Many old quantitative trait loci (QTLs) involved in plant height, awn length, seed traits and other characteristics reappeared in ILs, proving that the system was reliable.

Further, many new QTLs were identified. A QTL related to drought tolerance located on chromosome 4 was thoroughly elaborated. ILs with special fine traits such as large grain size and high tolerance to drought were screened out and would provide important germplasm resource materials for green super rice breeding. This set of ILs provides a new insight and resource for utilizing the excellent features of wild rice.

The study has been published in Theoretical and Applied Genetics and details could be found at https://doi.org/10.1007/s00122-018-3241-0.

Funding was provided by CAAS Innovation Project (Grant No. CAAS-XTCX2016002) and Fundamental Research Funds for central Non-profit scientific Institution (Grant No.1610392018004).

Contact: Qin Guannan

E-mail:qinguannan13@mails.ucas.edu.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences