Advances in wheat breeding techniques

The breeder’s equation (Lush, 1937) is a statistical summation of the evolution of quantitative traits. It measures the change in the mean of a population over a single generation as a function of the selection differential (a measure of the difference in mean trait values between selected individuals and the entire population; Falconer and Mackay, 1996). The complexity of multi-locus inheritance (quantitative variation involving many genes) is distilled into the narrow sense heritability h2, the proportion of variation attributed to additive genetic effects. Breeding is targeted at increasing the rate of genetic gain via the components of the equation. This encompasses increasing the selection intensity (the number of individuals selected), the selection accuracy (the precision by which individuals are selected), genetic variation and reducing the years per breeding cycle. All methods of wheat breeding operate within the parameters of the breeder’s equation and new technology must be assessed within the context of increasing the rate of genetic gain.