Interaction between genetic effects and soil type in diallel analysis of root shape and size of Japanese radish (Raphanus sativus L.)

We conducted diallel analyses of root shape and size in Japanese radish to determine the interaction between genetic effects and soil type in the selection for these traits in a breeding program. A set of diallel crosses of six inbred lines was grown in an andosol, a clayey soil and a sandy soil. The major shape characteristics accounted for by the principal components of elliptic Fourier descriptors were the ratio of length to width, the bluntness of the distal part, the curvature of the central part, and the curvature of the proximal and distal parts. Analysis of variance of diallel tables showed that the genetic effects were highly significant for all the characteristics. In contrast, the influence of the soil type was markedly different among the characteristics. Soil type effect was significant for size characteristics and the bluntness of the distal part. In the bluntness of the distal part, the interaction between genetic effects and soil type was significant, and the heritability and the degree of dominance varied between the soil types. The results indicated that the differences in the soil types did not influence the selection for the root size or shape in most characteristics. However, the interaction between genetic effects and soil type should be taken into account in the selection for the bluntness of the distal part.