Framework linkage maps of Pinus radiata D. Don based on Pseudotestcross markers

Abstract

Using a double pseudotestcross strategy, we have constructed framework linkage maps of two Pinus radiata D. Don trees (850.055 and 850.096) with RAPD, AFLP and SSR markers. These maps consist of 235 and 194 markers respectively, which mapped to 20 and 21 groups with three or more markers. Maps were constructed using a support-for-order criterion of LOD 3.0 for final order of framework markers, and covered 1413.7 and 1144.0 (Kosambi) cM each, equating to an estimated 85 and 77% of genome covered within 10cM of a marker. Depending upon threshold LOD for declaring linkage, estimates of total map length for 850.055 ranged between 1927.2 and 2068.1 cM (Kosambi), and 1902.8 to 1998.1 cM for 850.096. These map lengths were not significantly different, indicating no differences in recombination rates between male and female gametophytes. These estimates of total map length were similar to other Pinus species, providing further evidence of an overall conservation in recombination rate in this genus. These framework maps will serve as a basis for adding new codominant markers, which in turn should further applications such as QTL detection, molecular breeding, and candidate gene mapping.