iBridges


The genetic model of gamete elimination described above predicts that interspecific lines –like the O. sativa x O. glaberrima CSSLs– generally carry the O. glaberrima S1g allele, making their use in breeding difficult as this allele will be almost always transmitted to their progeny. In order to facilitate the use of O. glaberrima in breeding schemes, we conceived of and developed in collaboration with IRD (Montpellier, France) the concept of interspecific bridges, or iBridges. Basically, iBridges are derived by marker-assisted selection of homozygous S1s/S1s interspecific BC1F1 individuals, followed by several steps of selfing for fixation. This results in a much-increased proportion of fertile BC1 individuals in the first backcross generation. More importantly, these lines are compatible with O. sativa, as they do not carry the S1g allele, so breeders can use them just as regular O. sativa progenitors. Supported by the Generation Challenge Programme, several combinations of iBridges were produced at CIAT, AfricaRice and PhilRice (Philippines) from a selection of crosses involving twenty-five O. glaberrima and three O. sativa accessions.