DEVELOPMENT AND APPLICATION OF MOLECULAR MARKER LINKAGE MAPS IN WOODYFRUIT CROPS

Extensive linkage maps, consisting primarily of molecular markers, are being developed for apple, pear, and grape varieties. The intrinsical ly high heterozygosity of outcrossing perennial species is utilized to produce segregating populations directly from a cross between varieti es. Nearly complete linkage maps have been generated for the apple var ieties 'Rome Beauty' and 'White Angel'. The map for 'Rome Beauty' cont ains 161 molecular markers, while that for 'White Angel' has 251 marke rs. Maps for the pear varieties, 'Bartlett' and NY10353, also are bein g developed. Linkages conserved between the pear and apple genomes hav e been identified. In grapes, maps for four varieties are available, t he most extensive being those for 'Cayuga White' and 'Aurore'. The app le maps have been used to investigate the genetic basis of morphologic al and physiological characters. A gene controlling the presence of an thocyanins in the skin of the fruit is located on linkage group 3. Gen es controlling early bud break, branching habit, and production of roo t suckers have also been identified and mapped.