The study comprised of a set of 56 F1s and F2s which were developed at the Teaching and Research farm of the Federal University of Technology, Owerri, Nigeria, during the early season of 2007. The parental lines consisting of eight genotypes of rice were grouped into low, medium and high protein parents and crosses were made in all possible combinations. The laboratory analysis for the protein content determination was done at the Analytical Laboratory of International Institute for Tropical Agriculture (IITA, Ibadan), in 2008. Positive heterosis was observed in all the hybrids in the F1 and 37 hybrids for the F2 over their MP indicating dominance in the positive direction. On the other hand, negative heterosis was recorded in 14 hybrids in the F1 over the HP. About 19 hybrids showed negative heterosis over the MP in the F2 while the others were positive. Only two crosses, CT 7127-49 x WITA 4(2.33) in the medium x low combination and NERICA 1 x Fofifa 16(0.76) in the high x high combination showed positive heterosis over the HP in the F2 generation while the rest of the hybrids were observed to have shown negative HP. The mean square due to GCA, SCA and reciprocal effects were highly significant for percentage protein content for the Diallel analysis, implying the presence of genetic diversity among the genotypes. About 50% of the parents showed desirable positive GCA effects and included: CT7127- 49, EMPASC 105, WAB 96-1-1 and Max. 20 crosses showed positive SCA effects.
Key words: Heterosis, combining ability, mid- parent, high parent, hybrid, rice, gene effect.
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