This invention provides a novel means of predicting plant phenotypes that incorporates previously unusable dense marker data derived from historical pedigrees. The method operates by collecting information from a population pertaining to one or more loci, which is used to build one or more matrices by calculating, for the alleles present at the measured loci, the probability that the alleles are identical by descent. These matrices are then used to develop a second set of one or more matrices in which each value represents the probability that a certain individual in the population descended from a certain ancestral (founder) genotype. This set of second matrices can then be used as part of a breeding program for selecting and breeding individuals from the population or can be used to better classify the individuals in the population, leading to improved plant phenotypes.