Heterosis and Combining Ability of Amylose Content and Amylographic Breakdown Viscosity in Milled Rice (Oryza sativa L.)

Abstract

Heterosis and combining ability for two quality paramenters, amylose content and amylographic breakdown viscosity, of rice grain were studied in 30 cross combinations involving six entries of rice (Oryza sativa L.). Data indicated that heteroses over their midparent (MP) or higher-parent (HP) were observed. The extent of heteroses over their MP or HP varied from cross to cross for these two evaluated quality parameters. As to amylose content, heterosis over their MP almost appeared to be in positive direction, however, heterosis over their HP were almost in negative direction. In contrast, heteroses over their either MP or HP almost were in negative directions for amylographic breakdown viscosity. High significant differences were observed for mean squares of general combining ability (GCA) and specific combining ability (SCA) of these two evaluated quality parameters. Futhermore, the mean square of GCA was very larger than that of SCA. The ranking of the parents according to GCA effects closely corresponded to their ranking according to parents means. It minght conclude that despite of issues indicated in discussion in this paper, gene action for amylose content and amylographic breakdown viscosity was similar and mainly additive, although dominance effect was also involved; reciprocal effect upon two evaluated quality parameters could be ignored; and parent choice based upon GCA effects would be similar to selection based upon parent means.