Biochemical basis of hybrid vigour. The genetics of grain weight of Oryza sativa.

Four cathodal bands (C1, C2, C3 and C4) of esterase (E1, C1. 3.1) were correlated with the grain weight of rice (Oryza sativa L.). Zymogram patterns indicated intensity differences among these bands infinegrain and coarse-grain varieties. Bands C1. and C2 were dark in fine grain varieties whereas C3 and C4 were dark in coarse grain varieties. These bands were specific to endosperm. Observations on fine-grain (Kalanamak), coarse grain (SR(26)B) varieties and their reciprocal hybrids indicated the presence of 4 esterase loci G1, G2, G3 and G4, corresponding to bands C1, C2, C3 and C4, respectively. A possible model for heterosis in grain weight of rice was proposed which supports the dominance theory of heterosis. In hybrid vigour the 4 esterase loci appear to be associated with grain weight and they complemented each other in an additive manner.