Location of Bif, Clt*-985 and pro on chromosome 8

During the past two years we have attempted to establish the order and map distances on chromosome 8 for two dominant mutants, Bif (barren inflorescence) and Clt*-985 (clumped tassel, short plants) and also the recessive mutant pro (proline requiring). Bif and Clt had been located on chromosome 8 by use of the T wx series. The backcrosses showed no linkage with 16 of the 17 translocations used but the following data for wx T8-9d (breakpoints 8L.09 9S.16) show good linkage:
  Wx Dom. Wx + wx Dom. WX + T % co
Bif 18 2 0 20 40 5
Clt 120 43 65 83 311  35

This evidence, along with some preliminary indication of linkage between Clt and ms8, suggests that Bif is near the T8-9d breakpoint on chromosome 8 and that Clt is some distance away on the long arm.

We attempted to set up the F1 Bif Clt . . . . /+ + pro v16 ms j to be crossed on + + + v16 ms8 j. Because the crosses involving combinations of Bif and Clt were difficult to make and because pro is a recessive lethal requiring selfing (impossible for ms8 plants) to establish genotypes of the backcross progeny, our results have been fragmentary. For these reasons no reliable 3-point data were obtained. It is possible, however, to take fragmentary data and combine it in groups of 2-point tests that will establish working distances for the genes involved.

The following are our data from these tests arranged as 2-point tests following the format of Emerson, Beadle and Fraser:


The map distances for v16, ms8 and j agree with the published map and are in harmony with the listed 3-point data obtained for these markers. Our tentative map is Bif ( pro Clt) v16 ms8 j. The parentheses indicate that there is still some doubt about the relative order of pro and Clt.

M. G. Neuffer and Dan J. England

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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