Quantitative Genetic Analyses of Crop Organ Shape based on Principal Components of Elliptic Fourier Descriptors

摘要

Crop organ shape as well as size is an important trait for the genetic improvement of crops because it directly or indirectly influences the values of agricultural products. In general, crop organ shape shows continuous variation. In order to clarify its genetic structure it is necessary to measure this genetic variation with a quantitative method. Principal component analysis (PCA) of a set of elliptic Fourier descriptors (EFDs) enables one to decompose the shape variation into statistically independent characteristics and to analyze these characteristics as ordinary quantitative traits. So far, crop organ shape has been analyzed with various quantitative genetic methods based on the principal components (PCs) of EFDs. Diallel analysis enabled the clarification of the mode of inheritance of commercially important shape characteristics in the radish root. Genome-wide association studies enabled the estimation of the positions and effects of quantitative trait loci (QTL) controlling rice grain shape variation observed in a germplasm collection. The results of these analyses were easy-to-understand because of the visualization of the results, and served as useful knowledge for plant breeding. In a series of analyses, different PCs of EFDs showed a different mode of inheritance or were controlled by different QTLs in general, indicating that PCA of EFDs unraveled the inheritance of shape controlled by a number of genes into simpler and more easily understood components. Recent advances in molecular biology technology allow one to utilize a more advanced method in quantitative genetics for the understanding of the biological processes controlling crop organ shape. For example, genomic selection may enable one to predict unobserved organ shapes of unknown genotypes and select desirable genotypes based on the predicted shape. Combining the PCA of EFDs with statistical genetic methods, may provide genetic improvement of crop organ shape. Moreover, this approach allowed for a more rapid and efficient procedure for the design of new and novel crop organ shapes.