II. Cytogenetics

6. The construction of chromosome substitution lines of African rice (Oryza glaberrima Steud.) in the background of Japonica rice (O. sativa L.)

K. DOI. N. IWATA and A. YOSIMURA

Faculty of Agriculture. Kyushu University, Fukuoka. 812-81 Japan

African rice (Oryza glaberrima Steud.) is an endemic cultivar in West Africa. Although it has different characteristics from Asian rice, O. sativa L., such as morphology, reaction to drought, insect resistance and annual growth habit, it has hardly been exploited for breeding of O. sativa.

Development of molecular markers has made it possible to locate useful genes, or quantitative trait loci (QTLs). Some new concepts, such as advanced backcross QTL analysis (Tanksley and Nelson 1996) and introgression line analysis (Eshed and Zamir 1995), were proposed to seek and precisely locate QTLs using molecular markers. We have constructed a series of O. glaberrima (IRGC 104038) chromosome substitution lines (CSLs) in the background of Japonica rice, Taichung 65, to analyze the genetics of traits specific to O. glaberrima and to fully exploit the genetic potential of the species.

Using BC1F1, population, framework RFLP linkage map was constructed (Doi et al. 1996). Based on the RFLP map, plants with desired genotypes were selected from BC2F1, and BC3F1, generations using RFLP markers. For fixed CSLs, 907 plants from 45 BC3F2 lines were genotyped and 91 candidate plants for CSLs were selected to carry homozygous chromosome segments from the donor parent, O. glaberrima.

Fig. 1 gives a representation of introgressed chromosome segments in a sub-set (39 plants) of the candidates for CSLs. Except regions in chromosomes 7 and 10, most parts of the genome were covered. The regions in chromosomes 7 and 10 were related to pollen sterility (Doi et. al. 1997).

CSLs reported here provides a good material for more detailed genetic analysis on traits of (O. gluberrima, or characteristics of hybrid progenies.

References

Doi, K., A. Yoshimura and N. Iwata, 1996. RFLP mapping based on an interspecific BC1F1, population (Oryza sativa L. / O. glaberrima Steud. // O. sativa). Breed. Sci. 46 (Suppl. 2): 206. (in Japanese)

Doi, K., A. Yoshimura and N. Iwata, 1997. Production and evaluation of Oryza glaberrima Steud. chromosome substitution lines of rice. -QTL analysis for pollen fertility and days to heading in the BC2F1 population-Breed. Sci. 47 (Suppl. 1): 133. (in Japanese)

Eshed, Y. and D. Zamir, 1995. An introgression line population of Lycopersicon pennellii in the cultivated tomato enables the identification and fine mapping of yield-associated QTL. Genetics 141: 1147-1162.

Tanksley, S. D. and J. C. Nelson, 1996. Advanced backcross QTL analysis: a method for the simultaneous discovery and transfer of valuable QTLs from unadapted germplasm into elite breeding lines. Theor Appl Genet 92:191-203.