Mapping of the Dioscorea tokoro genome: AFLP markers linked to sex

Two framework linkage maps were constructed for the genome of the dioecious wild yam species Dioscorea tokoro. The pseudo-testcross strategy was emplo yed, using 271 amplified fragment length polymorphisms (AFLPs), five sequen ce-tagged microsatellite sites, one isozyme, and one morphological marker. For the two parents DT7 and DT5 used in the cross, 13 and 12 linkage groups , respectively, were identified. The total map lengths were 669 and 613 cM, respectively, for DT7 and DT5, which cover more than 75% of the D. tokoro genome. Ten AFLP markers heterozygous only in the male parent showed tight linkages with the sex of its progeny, which suggests that male is the heter ogametic sex (XY) and the female is the homogametic sex (XX).