Gold struck on chromosome 6.

Rick, C. M. and W. H. Dempsey

Old gold (og) was first described in Amer. Nat. 87:366-367 (1953). The source of this gene was traced to a plant of L. chilense from the F2 with L. esculentum. Since the time of its discovery, og has been transferred to the latter species by nine successive backcrosses. In either species it behaves as a normal, complete recessive. The intensity of coppery or tawny color of the corolla has diminished with backcrossing. The most rapid change occurred in earlier backcrosses, the phenotype remaining little changed from BC\4 to BC\9. Under conditions of high light intensity the difference in corolla pigmentation is not great, but og can be recognized by the darker flush of orange on the stamens, reminiscent of t, and by a strong tendency of the corollas of aged flowers to fade to white.

Our progenies this year gave double indication of the presence of og on chromosome 6. The following test was observed in F2 for triplo-6:

Family   Gene  2N  Triplo-6  Total

60L584   og+   81      4      85
         og     8      0       8
In segregations with other trisomics a total segregation of 166+ : 44og was observed.

Confirmation of this situation came from some small F2 families segregating simultaneously for og and sp. The pooled values for these familes are: 60+ +: 22 + og: 30sp + : 0 sp og. These figures suggest the possibility that another gene is involved in the knot of B-c-sp, although they are too meagre to rule out longer distances from this group.