45. Development of Oryza glumaepatula introgression lines in rice, 0. sativa L.
Sobrizal1, K. IKEDA1, P.L. SANCHEZí, K. Doií, E.R. ANGELES2, G.S. Khush2 and A. Yoshimura1
1) Plant Breeding Laboratory, Faculty of Agriculture, Kyushu University, Fukuoka, 812-8581 Japan.
2) International Rice Research Institute, Manila, Philippines

 
     The wild species Oryza glumaepatula Steud. is distributed in central and south America and Caribbean (Vaughan 1983). This species is distributed widely in the Amazon basin, Brazil and is adapted to flooded conditions (Akimoto et a!. 1998). Like other common wild rice 0. rufipogon, 0. glumaepatula differs from cultivated rice, 0. sativa L. in morphology, environmental adaptability and growth habit. To analyze the genetics of traits specific to 0. g!umaepatula and to exploit the genetic potential of this species, we attempted to develop series of 0. glumaepatu!a introgression lines (glumlLs) with 0. sativa L. cv.Taichung 65 and 0. glumaepatu!a cytoplasms in the genetic background of 0. sativa L. cv. Taichung 65.
     For developing glumlLs, F, seeds were obtained through the reciprocal crosses between 0. glumaepatula (Acc. IRGC 105668) and Taichung 65. The resultant F, plants served as female parents and were continuously backcrossed with Taichung 65 to generate the BC4FI populations. To select the plants having desired genotypes, whole genome survey was conducted in BC3F1 generation by using 106 RFLP markers scattered in 12 chromosomes. Selections in BC4F, generation were made on the basis of observation of genotypes of the target regions only.
     Out of 103 BC3F, plants having 0. glumaepatula cytoplasm, 27 were selected based on the introgressed segment in the target regions. Out of 167 BC4FI plants derived from 27 selected BC3F, progenies, 63 promising plants canying both cytoplasm and entire chromosome segments of 0. glumaepatula were selected as candidates for glumlLs with 0. glumaepatula cytoplasm. In the same manner, out of 83 BC3F1 plants having Taichung 65 cytoplasm, 36 plants were selected. Out of 184 BC4F1 plants derived from 36 selected BC3F1 progenies, 84 promising plants carrying Taichung 65 cytoplasm and entire chromosome segments of 0. glumaepatu!a were selected as candidates for glumlLs with Taichung 65 cytoplasm.
     The representation of introgressed chromosome segments in sub-sets (34 plants having Taichung 65 cytoplasm and 25 plants having 0. glumaepatula cytoplasm) are shown in Fig. 1. Most part of the 0. glumaepatula genome was covered, except the regions marked with arrows. In the region around RFLP marker C1115, 0. glumaepatula genotypes were observed in almost all promising plants having 0. glumaepatula cytoplasm. This region involved hybrid weakness restoration locus (Rhw) reported by Ikeda et a!. (1999).
     These glumlLs are a good source of genetic materials for detailed analysis of special traits of 0. glumaepatula and for evaluating various morpho-agronomic characters of hybrid progenies. Selfing of BC4F,s and further selections are underway to fix and obtain a complete set of glumlLs.
     This study was supported in part by Bio-oriented Technology Research Advancement Institution (BRAIN), Japan. Sobrizal and K. Ikeda were supported by postdoctoral fellowships from BRAIN, Japan.


 
 

References
Akimoto, M., Y. Shimamoto and H. Morishima, 1998. Population genetic structure of wild rice Oryza glumaepatula distributed in the Amazon flood area influenced by its life-history traits. Molecular Ecology7: 1371-1381.
Ikeda, K., Sobrizal, P. L. Sanchez, H. Yasui and A. Yoshimura, 1999. Hybrid weakness restoration gene (Rhw) for Oryza glumaepatula cytoplasm. Rice Genetic Newsletter 16 (in press).
Vaughan, D., 1989. The genus Oryza L. current status of taxonomy. IRRI research paper series No. 138. The International Rice Research Institute, Manila, Philippines