Kerr, E. A. Yellow-green-2 (yg-2) may be on chromosome 12.
Since 1959, yg-2 has been assigned to chromosome 6. I believe this was on the basis of 45.63 ± 3.81%a
C.O. reported between yg-2 (yg282) and m-2 (md) (Burdick TGC 9:21). Burdick (TGC 9:19) also suggested 41.58 ±
4.37% C.O. between nd on chromosome 10 and yg-2. Mutations with low chlorophyll content or speckled leaves are
sometimes difficult to distinguish in the seedling stage.
Beginning in 1963 I have periodically used yg-2 in tests for linkage. No indication of linkage within 45 units
has been found with y, d, wf, ls, at, sp-c-m-2, gf, marm, u-h-t, ne-2-f-a, Gr, fu, rvt. Suggestions of linkage were
obtained with e, mc, Mi, gs, alb, and hp. A summation of the data for chromosomes 4, 5, 6, 7 and 12 is given in the
table.
Obviously some of these suggested linkages must be fallacious. If yg-2 is on chromosome 6 it must be near
pds
on the distal end of the short arm. The suggestions of linkage with mc on chromosome 5 and with gs on
chromosome 7 are based on consistent data from 6 different populations each. However, they were in repulsion
phase and the suggested linkages are not close. The data for e are based on 3 populations only one of which
suggested linkage.
The data for yg-2-alb and yg-2-hp are from different populations grown in 1978. In both there is an excess of
yg-2 plants. Possibly there was some selection for yg-2 when the seedlings were pricked off at the cotyledon stage.
Also the proportion of hp plants in the yg-2+ plants is very close to a 3:1 ratio. This population was scored for hp in
the field where hp is not always easily distinguished. In view of the probable linkage of hp and alb which is reported
in a separate note, I think yg-2 is on chromosome 12.
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