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The traits that Mendel chose to study could be classified into clearly defined, discrete groups. Thus, by following the ratios from a cross between two distinct pure breeding lines in different generations, one could easily understand the genetics of such traits. However, there were a large number of traits where the variation was more of a continuous nature. To study inheritance of these so called quantitative traits, biometrical approaches were developed. Subsequently, mating designs were developed to estimate different genetic components of variation. Based on information generated through mating designs, methods were developed to predict performance of hybrids and populations, and identify breeding methods designed to utilize different types of gene actions. Molecular markers technologies have helped identifying QTLs (quantitative trait loci). Interval mapping, based on maximum likelihood methods and implemented in the software package MAPMAKER, is now widely used in QTL mapping experiments and information regarding the minimum number of genes, their additive/dominance effects, and the extent of variation explained by the involved QTLs can be obtained. This paper reviews the development and role of mating designs in elucidating the nature of quantitative variation for their use in plant breeding, during the past, and how is this being now integrated with the molecular techniques for more precision and efficiency in plant breeding. |
