Characterization and utilisation of Oryza glaberrima Steud. in upland rice breeding

Oryza glaberrima Steud. is a potential source of useful genes for a range of econornically important characters. During the 1992 and 1993 growing seasons, 1130 accessions of 0. glaberrima and 591 accessions of 0. sativa L. were characterized at the West Africa Rice Development Association (WARDA) at M'bé, Côte d'lvoire for 43 morphological traits. A number of accessions with desirable morphological traits and resistance to stresses such as drought and blast have been identified and are now being utilized in the breeding program. Progenies from interspecific hybridization of 0. sativa and 0. glaberrima are showing high sterility in the F1 hybrids and early generations. However, fertility was obtained (5-95%) and retained after two to four backcrossings in some populations. Although true intermediates between 0. glaberrima and 0. sativa were generally rare, their occurrence in some populations was as high as 30%. Desirable morphological traits introgressed frorn 0. glaberrima into segregating BC2 F3 populations included early maturity (75-100 days), rapid seedling growth and high tillering. To exploit the potential of 0. glaberrima in interspecific breeding, it is necessary to better understand its physiology and ecology. It will also be necessary to characterize alien gene introgression through isozyme analysis and molecular markers to examine the crossability, genetic homoeology and nuclear stability of hybrid progenies. (Résumé d'auteur