A Molecular Genetic Linkage Map For Hybrid Population Of Populus Adenopoda×P. Alba And A Comparative Map In Populus

We report a molecular genetic linkage map for an inter-specific F1 ,hybrid population between Populus adenopoda×P. alba by means of two-way pseudo-test cross mapping strategy. A total 122 markers were available for mapping on the maternal tree Populus adenopoda, including 116 SSRs and 6 SRAP markers. Thirty one linkage groups were constructed, map length between 2.1 cM¹53.7 cM, which 59.90 cM was average group length. The average interval was 15.22cM between adjacent markers .A total of 1857 cM was observed for P. adenopoda map. A total 153 markers were available for mapping on the paternal tree P. alba, including 143 SSRs and 10 SRAP markers. Thirty five linkage groups were constructed, map length between1 4.2cM²57.4cM, which 64.95 cM was average group length. The average interval was 14.86 cM between adjacent markers. A total of 2273.1 cM was observed for the P. alba map.The comparison of the P. trichocarpa reference map and the 2 parental maps revealed 181 homologous markers, 107 of them were common to the female map and 127 to the male map. Sixteen and seventeen homological linkage groups were aligned respectively in P.adenopoda and P. alba maps. And the orthologous markers showed the higher synteny and co-linearity between the three maps. 71 of 107 homologous markers(66.36%) between P.adenopoda map and P. trichocarpa reference map and 90 of 127 homologous markers(70.87%) between P. alba map and P. trichocarpa reference map were at higher synteny. 63 of 71 (88.73%)and 78 of 90 (88.63%) respectively in P. adenopoda and P. alba maps were at higher co-linearity.The P. deltoides (clone `I-69' )and P. euramericana (clone '1-45' ) maps of this comparative analysis were gently provided by doctor Zhang Bo. They were constructed in our laboratory with the same strategy. The comparison of these 4 maps revealed 42 SSR common markers. Finally, we aligned P.adenopoda and P.alba maps with the P. deltoides (clone `I-69' )and P. euramericana (clone '1-45' ) maps and the P. trichocarpa reference map. The co-alignment of these 5 maps revealed 345 common markers. Only three markers G₂900,G₃269-1and P₂536 was present on the 5 maps. 19 markers were common to 4 maps, 93 markers were common to 3 maps, 178 markers were common to 2 maps and 52 markers which were mapped on different linkage groups. The marker order was conserved in most of the cases. The linkage group I was one of the largest group in all the maps and had the most number of homologous markers 28. The linkage group ADâ…¨,ADâ…«and ADâ…©â…§in P.adenopoda map, ALâ…«and ALâ…©â…¨in P.alba map and E17 in P. euramericana (clone '1-45' ) map were not identified. 16 QTLs controlling tree height and 2 QTLs affecting spring bud flush were mapped. Our result also indicated the dynamics of height QTLs efect. The phenotypic variance explained by each height QTL ranged from5.83% to 36.78%. The total phenotypic variance explained by 2 QTLs affecting spring bud flush was 17.64%.