Biplot AMMI graphic representation of specific combining ability
João Batista Duarte and Rogério de Melo Costa Pinto
Specific combining ability (SCA) is a genetic property of great interest in breeding programs aiming at hybrid cultivars. It enables assessment of the genotype combinations most promising for hybridization. This study presents the foundations of biplot graphic display associated with AMMI (additive main effects and multiplicative interaction) analysis, and their application to genetic studies of this kind. The analysis allows the partition of the sum of squares of the elements of a diallel table (matrix), the SCA sum of squares, to capture a systematic portion and discard an additional noise to the experimental error. The systematic part or pattern is represented graphically by the biplot. The parental combinations with greatest potential for hybrid production may be identified in this graph, and the SCA divergence among the parents can also be assessed. A numerical example is presented with SAS (Statistical Analysis System) statements for its implementation.