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 F1 and in early progenies. Recent development of mapped molecular markers provides the opportunity to rationalise and to monitor introgressions between the two cultivated rice species. Development of such introgressed lines through interspecific hybridisation and backcrossing represents high potential to create new genetic and transgressive variation. We are initiating an original marker-aided backcross program with the aim of producing a set of 100 ‘contig lines’, each one bearing an alien O. glaberrima chromosomal fragment of around 20 cM in the O. sativa genetic background. As a preliminary step, we are now developing a genetic linkage map based on STS and RAPD markers, using an interspecific backcross between O. sativa and O. glaberrima. BC1 plants will then be selected to expedite the production of ‘contig lines’ exhibiting only the target fragment. The interspecific polymorphism is anticipated to be large enough to make this methodology feasible. Many advantages are expected from this approach, such as: (i) systematic assessment of the useful genetic resources displayed by O. glaberrima, (ii) improved 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 development of the BC1 population is presented.