Design and construction of recombinant inbred lines

Recombinant inbred lines (RILs) are a collection of strains that can be used to map quantitative trait loci. Parent strains are crossed to create recombinants that are then inbred to isogenicity, resulting in a permanent resource for trait mapping and analysis. Here I describe the process of designing and constructing RILs. This consists of the following steps. Parent strains are selected based on phenotype, marker availability, and compatibility, and they may be genetically engineered to remove unwanted variation or to introduce reporters. A construction design scheme is determined, including the target population size, if and how advanced intercrossing will be done, and the number of generations of inbreeding. Parent crosses and F1 crosses are performed to create an F2 population. Depending on design, advanced intercrossing may be implemented to increase mapping resolution through the accumulation of additional meiotic crossover events. Finally, lines are inbred to create genetically stable recombinant lines. I discuss tips and techniques for maximizing mapping power and resolution and minimizing resource investment for each stage of the process.