Comparison of mating designs for establishing nested association mapping populations in maize and Arabidopsis thaliana.

The nested association mapping (NAM) strategy promises to combine the advantages of linkage mapping and association mapping. The objectives of my research were to (i) investigate by computer simulations the power and type I error rate for detecting quantitative trait loci (QTL) with additive effects using recombinant inbred line (RIL) populations of maize derived from various mating designs, (ii) compare these estimates to those obtained for RIL populations of Arabidopsis thaliana, (iii) examine for both species the optimum number of inbreds used as parents of the NAM populations, and (iv) provide on the basis of the results of these two model species a general guideline for the design of NAM populations in other plant species. The computer simulations were based on empirical data of a set of 26 diverse maize inbred lines and a set of 20 A. thaliana inbreds both representing a large part of the genetic diversity of the corresponding species. I observed considerable differences in the power for QTL detection between NAM populations of the same size but created on the basis of different crossing schemes. This finding illustrated the potential to improve the power for QTL detection without increasing the total resources necessary for a QTL mapping experiment. Furthermore, my results clearly indicated that it is advantageous to create NAM populations from a large number of parental inbreds.