RAPD GENOME MAPS OF DOUGLAS-FIR

We present linkage maps and estimate genome length for two hybrid indi viduals of Douglas-fir [Pseudotsuga menziesii (Mirb.) France], a conif erous tree species of wide distribution in the western United States. The hybrids were produced by crosses between the coastal (var, menzies ii) and interior (var. glauca) varieties. Haploid megagametophytes fro m 80 seeds of each individual were analyzed using 81 10-bp random ampl ified polymorphic DNA (RAPD) primers selected for polymorphism, fragme nt strength, and repeatability in preliminary segregation analysis. Mo st (82-90%) of the segregating fragments followed the expected 1:1 Men delian segregation; however, 10-18% showed significant segregation dis tortion (P <.05) among megagametophytes of the two trees. In one tree, 201 of 221 segregating loci analyzed were combined into 16 major link age groups of 4 or more loci (plus 1 group of 3 loci, 3 groups with pa irs of loci, and 11 unlinked loci); in the other, 238 of 250 segregati ng loci were combined into 18 major groups (plus 2 groups of 3 loci ea ch and 6 unlinked loci). Analyses of the distribution of markers indic ated highly significant clustering in both trees (P <.001). Including flanking regions and unlinked loci, both trees had linkage maps of sim ilar length, 2600 cM and 3000 cM; expected total map size ranged from 2800 to 3500 cM based on method-of-moments estimation. When a common R APD protocol was used, more than one-third of the RAPD markers segrega ted in both hybrids. These maps of Douglas-fir are among the largest r eported for conifers, a possible consequence of its 13 haploid chromos omes.