Diallel analysis of root shape of Japanese radish (Raphanus sativus L.) based on elliptic Fourier descriptors

Abstract

A set of 6 x 6 diallel crosses was made using the inbred lines from the Miyashige group of Japanese radish varieties. The root shape contours were delineated by elliptic Fourier descriptors, and information contained in the coefficients of the descriptors was summarized as the score of principal component analysis. The coefficients related to symmetrical (group A) and asymmetrical variations (group B) were handled separately. It was shown that the 1st and 2nd components of group A were associated with the aspect ratio and bluntness of the distal part of the root, respectively. The 1st component of group B was related to the degree of curvature of the root. The 1st and 2nd components of group A showed high broad and narrow sense heritabilities, and incomplete dominance. The 1st component of group B was also heritable, and showed incomplete dominance. Correlation between the proportion of dominant alleles of the parents (Vr + Wr) and the parental values showed that most alleles of the genes related either to thin shape or to straight shape were dominant. The size of the roots as expressed by their projection area was analyzed in a similar fashion. The size showed a high broad sense heritability but a low narrow sense heritability, and overdominance. The alleles producing larger root sizes were mostly dominant. Thus, symmetrical and asymmetrical variations and, also, shape and size showed different modes of inheritance.