FIRST STEPS TOWARDS A RATIONAL USE OF AFRICAN RICE, ORYZA-GLABERRIMA,IN RICE BREEDING THROUGH A CONTIG LINE CONCEPT

In the past, utilisation of African cultivated rice, Oryza glaberrima, in O. sativa breeding was hampered by high sterility in interspecific F-1 and in early progenies. Recent development of mapped molecular ma rkers provides the opportunity to rationalise and to monitor introgres sions between the two cultivated rice species. Development of such int rogressed lines through interspecific hybridisation and backcrossing r epresents high potential to create new genetic and transgressive varia tion. We are initiating an original marker-aided backcross program wit h the aim of producing a set of 100 'contig lines', each one bearing a n alien O. glaberrima chromosomal fragment of around 20 cM in the O. s ativa genetic background. As a preliminary step, we are now developing a genetic linkage map based on STS and RAPD markers, using an intersp ecific backcross between O. sativa and O. glaberrima. BC1 plants will then be selected to expedite the production of 'contig lines' exhibiti ng only the target fragment. The interspecific polymorphism is anticip ated to be large enough to make this methodology feasible. Many advant ages are expected from this approach, such as: (i) systematic assessme nt of the useful genetic resources displayed by O. glaberrima, (ii) im proved and simplified detection of QTLs and (iii) comparative analysis of genomic organisation of O. glaberrima vs. O. sativa. Current work on evaluation of STS and RAPD polymorphism between parents and develop ment of the BC1 population is presented.