GENETIC-MAPPING IN EUCALYPTUS-UROPHYLLA AND EUCALYPTUS-GRANDIS USING RAPD MARKERS

Two single-tree linkage maps were constructed for Eucalyptus urophylla and Eucalyptus grandis, based on the segregation of 480 random amplif ied polymorphic DNA (RAPD) markers in a F-1 interspecific progeny. A m ixture of three types of single-locus segregations were observed: 244 1:1 female, 211 1:1 male, and 25 markers common to both, segregating 3 :1. Markers segregating in the 1:1 ratio (testcross loci) were used to establish separate maternal and paternal maps, while markers segregat ing in the 3:1 ratio were used to identify homology between linkage gr oups of the two species maps. An average of 2.8 polymorphic loci were mapped for each arbitrary decamer primer used in the polymerase chain reaction. The mean interval size between framework markers on the maps was 14 cM. The maps comprised 269 markers covering 1331 cM and 236 ma rkers covering 1415 cM, in 11 linkage groups, for E. urophylla (2n = 2 x = 22) and E. grandis (2n = 2x = 22), respectively. A comparative map ping analysis with two other E. urophylla and E. grandis linkage maps showed that RAPDs could be reliable markers for establishing a consens us species map. RAPD markers were automatically and quantitatively sco red with an imaging analyzer. They were classified into four categorie s based on their optical density. A fragment intensity threshold is pr oposed to optimize the selection of reliable RAPD markers for future m apping experiments.