A GENETIC-LINKAGE MAP OF PINYON PINE (PINUS-EDULIS) BASED ON AMPLIFIED FRAGMENT LENGTH POLYMORPHISMS

Amplified fragment length polymorphisms (AFLP) were used to rapidly ge nerate a dense linkage map for pinyon pine (Pinus edulis). The map pop ulation consisted of 40 megagametophytes derived from one tree at Suns et Crater, Arizona. A total of 78 primer combinations, each with three to five selective nucleotides, amplified 542 polymorphic markers. Of these, 33 markers showed significant deviation from the expected Mende lian genotypic segregation ratio of 1:1, and 164 showed complete linka ge with another marker. This resulted in 338 unique markers mapping to 25 linkage groups, each of which ranged from 2 to 22 markers, averagi ng 80 centiMorgans (cM) in size and covering 2,012cM (2,200cM with the inclusion of 25 cM for each of 7 unlinked markers). Pairwise linkage values gave a genome size estimate of 2,390 cM, suggesting comprehensi ve coverage of the genome. A search for subsets of primer combinations giving the best map coverage found 10 primer combinations which toget her marked 72% of the linkage map to within 10 cM; an additional 10 pr imer combinations increased this percentage to 85%. Our map represents an initial step towards the identification of quantitative trait loci associated with pest resistance and water stress in pinyons and will further allow us to examine introgression rates between P. edulis and P. californiarum.