PRELIMINARY MOLECULAR MARKER MAPS CONSTRUCTED BY USING AN INTERSPECIFIC CROSS BETWEEN PYRUS COMMUNIS AND P. USSURIENSIS

Abstract

Here we report for the first time on a preliminary linkage map of Chinese pear Pyrus ussuriensis. A segregating F 1 progeny originating from cross 'Doyenne du Comice' and P. ussuriensis was used to construct maps based on AFLPs, AFLP-RGAs and SSRs developed from pear and apple. The map of the 'Doyenne du Comice' consisted of 38 loci including 21 AFLPs, 17 SSRs on 11 linkage groups over a total length of 573 cM, while that for P. ussuriensis contained 43 loci including 27 AFLPs, 16 SSRs on 12 linkage groups encompassing a genetic distance of 797 cM. These maps were partially aligned using 7 codominant markers which showed segregating alleles in both parents. The position of 10 SSRs originating from apple could be successfully determined in pear maps, which enabled us to compare the two maps. The alignment among the two maps supports the colinearity of the two genomes with respect both to identification and to orientation of the linkage groups. Among tested SSRs just 39% are transferable to the progeny, 14% have a dominant segregation in 'Doyenne du Comice' and only 9% in P. ussuriensis. Despite the low percentage of SSR transferability in this progeny, presumably due to phylogenetic divergence of P. ussuriensis genome, it was possible to construct a frame of map with SSR and AFLP markers.