In our two earlier studies on bread wheat, we identified three molecular marker loci - one (Xwmc41) associated with grain protein content (GPC) was located on 2DL and the other two (Xwmc104 and Xmst101) associated with pre-harvest sprouting tolerance (PHST) were located one each on 6BS and 7DL. These studies were extended using additional marker loci already known to be located on these arms. Seven STMS marker loci, that were already mapped on 2DL (Roder et al., 1998a), and 13 STMS marker loci that were already mapped on 6BS and 7DL were tested for possible genetic association with GPC/ PHST. Although, some of these markers did show polymorphism between the contrasting parents, none of them showed linkage with GPC/ PHST or with the markers associated with them. This encouraged us to undertake physical mapping of all the loci known to be located on 2DL, 6BS and 7DL. The marker loci and the regions to which they were mapped included the following: (i) Xwmc41 (an STMS locus), that was associated with a QTL for GPC, was assigned to the terminal 0.24 fraction of 2DL; (ii) from among two molecular marker loci associated with PHST, Xwmc104 (an STMS locus) was assigned to terminal 0.76 fraction of the 6BS satellite and Xmst101 (an STS locus) was assigned to proximal centromeric 0.10 fraction of 7DL; (iii) 13 STMS marker loci, earlier genetically mapped on 6BS and 7DL, were also assigned to specific physical regions of these two arms. The marker loci that were physically mapped during the present study were integrated with those earlier mapped in a similar way, and integrated physical maps with 27 marker loci on 2DL, 42 marker loci on 6BS and 54 marker loci on 7DL were prepared. We believe that these integrated physical maps should prove useful for a variety of studies in future.
