The maps are aligned using common markers in Figs. 1-7. The maps appear to be collinear. The only switching of gene order occurs with very close linkages, for example ABC254 and ABC308, CDO537 and MWG557, ABC153 and ABC165, and ABC166 and Prx1B (all in SM,HT). These are all within the experimental error of the population size used. The recombination distances between individual markers do vary in the different maps. However, more noteworthy is the remarkable similarity in the recombination distances between markers in the SM and HM maps, a 6-rowed by 6-rowed versus 2-rowed by 6-rowed cross. The recombination distances in the HT map are somewhat expanded compared to the SM map. Taken at face value, the T (TR306) parent in the HT cross appears to contribute to increased recombination, but some of the differences might be due to the fact that the HT map was not checked as rigorously for errors as the SM map. Note the Amy1 and Nir markers that show cosegregation in SM, but are 15 cM apart in HT. Examination of the DCO table for HT showed a number of questionable cross-overs between these markers, suggesting that the real difference in the distances between these two markers in the SM and HT maps is considerably less.
In summary, the three NABGMP maps appear to be very robust and reassure us that there are no major chromosome rearrangements among the parents not even between the 2- and 6-rowed parents. The common markers (still a bit deficient for some of the chromosomes), can be used to identify all available markers in any chromosome region of interest.
Figure 1-7 legend. All maps are drawn to the same scale for easy comparison. The markers common to all three maps are in 12pt. bold type, the markers common to two maps are in 1Opt. bold type and other markers used to "glue" the chromosomes together are in 9pt. plain type. Chromosomes 1-7 were aligned with the VAtp57A and MWG2031, CDO537, ABC166, ABG472, MWG912, ABC175, and mSrh markers, respectively.
Table 1. Distribution of markers mapped to the SM, HT and HM crosses.
____________________________________________________ Chr. SM HT HM All SM,HT SM,HM HT,HM ____________________________________________________ 1 97 55 22 7 15 5 1 2 82 34 19 3 11 4 3 3 69 25 21 7 2 7 1 4 50 16 10 2 2 3 1 5 64 18 12 1 8 6 1 6 60 35 20 6 11 2 3 7 78 46 17 6 12 4 3 ___________________________________________________ Total 500 229 121 32 61 31 13 ____________________________________________________
