Seed fertility of F1 hybrids between upland rice NERICA cultivars and Oryza sativa L. or O. glaberrima Steud.

NERICA (New Rice for Africa) cultivars were crossed with Oryza sativa L. and O. glaberrima Steud. All the F1 hybrids between NERICA and two strains of O. glaberrima were highly sterile, while the F1 hybrids of NERICA with two cultivars of O. sativa showed differing levels of fertility depending on the cross combinations. NERICA cultivars were classified into three groups: (1) those compatible with both ssp. indica and ssp. japonica of O. sativa (i.e. NERICA12, NERICA15, NERICA16, NERICA17 and NERICA18); (2) those compatible with japonica but incompatible with indica (NERICA3, NERICA4, NERICA7, NERICA8, NERICA9, NERICA11, NERICA13 and NERICA14); and (3) incompatible with both types (NERICA1). In the first group of NERICA cultivars, four cultivars from NERICA15 to NERICA18 are derived from the same cross of CG 14/3*WAB 181-18, and they have the cytoplasm of CG 14, from an O. glaberrima strain. No ‘bridging cultivar’ between both cultigens was found in NERICA cultivars, but some NERICA cultivars were compatible with both japonica and indica. This finding is very useful for improvement of NERICA cultivars through hybridization.