--William D. Beavis and David Grant

Several genetic maps using RFLP and other molecular markers and based on data from one or more F2 populations have recently been reported in this Newsletter
(Helentjaris et al. 1986; Murray et al. 1988; Working Map 1988 and 1989). Unfortunately, because the mapping was done using different populations and often with different markers, it has been difficult to define a single genetic map which includes all of the information available. As a first step in the construction of such a composite map, we have developed a method for combining data from different populations prior to generating an RFLP map. Specifically, we utilize the log likelihood statistic to test for homogeneity of recombination among populations and to genetically map partially overlapping sets of markers. A more detailed description of the methods can be found in Beavis and Grant (Theor. Appl. Genet. 1991, in press).

In this report we present a composite map composed of 209 markers and based on data from four F2 populations (B73/Mo17, B73/G35, K05/W65 and J40/v94). Population sizes were 112, 112, 144 and 144 individuals, respectively. The probes used came from Ben Burr (bnl), Univ. of Missouri (umc) and Pioneer Hi-Bred (pio). All molecular biology steps were done using standard conditions. Genetic maps were constructed using MAPMAKER (Lander et al. 1987).

Figure 1.  Maize RFLP likage map (1-5 & 6-10)

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