JXB Advance Access originally published online on July 25, 2006
Journal of Experimental Botany 2006 57(11):2815-2824; doi:10.1093/jxb/erl046
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RESEARCH PAPER |
Heavy genetic load associated with the subspecific differentiation of japonica rice (Oryza sativa ssp. japonica L.)

1Institute of Crop Sciences/The National Key Facility for Gene Resources and Genetic Improvement, Chinese Academy of Agricultural Sciences, 12 South Zhong-Guan-Cun Street, Beijing 100081, PR China
2Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
3Harbin Institute of Technology, Harbin 150001, PR China
4International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines
To whom correspondence should be sent. E-mail: z.li{at}cgiar.org or lizhk{at}caas.net.cn
Genetic load in the genome of the model species, rice, was genetically dissected by mapping quantitative trait loci (QTLs) affecting the radiosensitivity of 226 recombinant inbred lines (RILs) to
-ray- and spaceflight-induced radiation. The parents and RILs varied considerably in their radiosensitivity to
-ray irradiation. A total of 28 QTLs affecting the two index traits, seedling height (SH) and seed fertility (SF), of radiosensitivity were identified. The japonica parent, Lemont, was much more sensitive to
-ray irradiation than the indica parent, Teqing, and its alleles at almost all QTLs were associated with increased radiosensitivity, suggesting a much higher genetic load in the japonica genome of rice. Six QTLs (QSh2a, QSh2b, QSh5a, QSh7, QSf3b, and QSf10b) were located in the genomic regions particularly sensitive to radiation and thus might represent possible mutation hot spots in the japonica genome. Detailed characterization of these genomic regions may shed light on the evolution and subspecific differentiation of rice.
Key words:
Genetic load, mutagenesis,
-rays, radiation damage, radiosensitivity, spaceflight