The Institute of Forest Genetics and the Weyerhaeuser Company have developed two immortalized loblolly pine reference mapping populations that are available to the international forest tree genome community. The two mapping populations, known as the BASE and QTL pedigrees (Devey et al. 1994; Groover et al. 1994), are three-generation pedigrees with four grandparents, two parents, and 96 progeny. Over 600 genetic markers have been mapped in these pedigrees and the constituent maps have been merged to form a consensus map (Sewell et al. 1999).