Marker-assisted selection with spatial analysis of unreplicated field trials

Many studies have shown that molecular markers can improve the efficiency o f the selection of quantitative traits in plant breeding provided that larg e population sizes are used. As a way to limit experimental costs it appear s that the use of unreplicated trials may be more valuable than the use of replicated plots in one trial. In this particular context of unreplicated l arge trials, spatial heterogeneity within the field may reduce the efficien cy of the selection. The problem of controlling spatial heterogeneity was s eldom considered in the case of marker-assisted selection (MAS). Here, we p ropose an integrated method to predict genetic values considering simultane ously marker information and possible spatial heterogeneity. This method wa s applied to a population of 300 F-3 lines of maize evaluated in ii unrepli cated trials for grain yield. We show that when spatial field heterogeneity is considered through appropriate statistical models the accuracy of genet ic value predictions is improved and the same genetic gain can be achieved with a reduced number of trials.