Heterosis for yield and yield contributing characters in inter sub-specific crosses of rice

Forty two inter and intra sub-specific hybrids were studied utilising seven wide compatible varieties (WCVs) including two indicas (Dular and ASD 16) and five tropical japonicas (WCR 6, IR 65600-32-4-6-1, IR 65601-120-3-5, IR 66158-38-3-2-1 and IR 67323-46-2-1) for nine biometrical characters including grain yield. For most of the characters, the mean heterosis per cent are in the order of indica/japonica F₁ tropical japonica/indica F₁indica/indica F₁> tropical japonica/japonica F₁. The combinations with significant standard heterosis over local variety MDU 5 for grain yield along with important yield components recommended for heterosis breeding were Dular x IET 16114 (indica/japonica); IR 65601-120-3-5 x ADT 43, IR 67323-46-2-1 x ADT 43 (tropical japonica/indica) and IR 66158-38-3-2-1 x Odaebayeo (tropical japonica/japonica).