Combining ability and heterosis for aluminium stress tolerance of soybean roots and shoots grown in acid sand culture

A six parent F2 diallel of soybeans was evaluated in potted acid sand culture with the objective of estimating combining ability and heterosis for aluminium stress tolerance. Highly significant differences were observed among the genotypes, crosses (F2/R), Parents, F2, Reciprocals (R) and Parents Vs (F2/R) for the root dry weight, shoot dry weight and relative root surface area. Both general combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant for the three traits, except the root dry weight, where the SCA was not significant. The result also showed the presence of both additive and dominance gene action and the preponderance of the former compared to the later, indicating the possibility of selection of pure lines from the genotypes studied. Selection from TGX 1896-3F and TGX 1844-18E and crosses involving these two genotypes on acid soil would enhance a rapid progress in the breeding of aluminium tolerant genotypes of soybeans.   Key words: Glycine max, diallel analysis, general combining ability, specific combining ability, additive effect, dominance effect.