Rick, C. M.
Three and possibly four new trisomic identifications of li@cage groups have been made. The data are summarized in the following table. All progenies were F2 from trisomic F1's with one dose of the recessive marker.
Chromosome gene 2N 2N+l Total
3 wf^+ 101 20 121
wf 11 0 11
6 c^+ 68 11 79
c 11 0 11
7 tf^+ 56 41 97
tf 8 0 8
The first test places linkage group II (r - wf) on chromosome 3. Normal
segregations were obtained for wf in F2 tests with all the remaining trisomics
except triplo-1, which has not yet been tested.The second test gives a home to linkage group IV (c, B, sp, Mi, yv, Cf\2, and ri) in chromosome 6. Normal segregations were obtained for c in F2 tests with all the remaining trisomics.
The third test places tf in chromosome 7 with genes from MacArthur's groups X and XII (wt, mc, N, and Fw). The total seedling population segregated 23O:23tf. A linkage between tf and a wilty gene was reported by Robinson and Rick, but considering other evidence they concluded that the wilty gene concerned was not wt. On the basis of this trisomic test and other data presented in my review of chromosome 7 in this Peport this conclusion is contradicted and it now appears likely that the wilty gene was allelic or identical with wt. Normal segregations were obtained for tf in F2 tests with triplo-2, 4, 6, 8, 9, & 10.
With this new data four trisomics remain unidentified genetically, triplo-4, 5. 11, and 12. A small F2 in which both e and c were segregatng from a triplo-4 hybrid gave a suggestion that e might be located on chromosome 4, but seeds have now been obtained for a larger family without the complicating segregation of c. Present efforts in the trisomic work are being concentrated on the unlocated genes and trisomics. The findings reported here are incorporated in the linkage summary in the first part of this Report.