Rick, C.M. and L. Butler.
As part of a review article that we recently completed on tomato genetics for Advances in Genetics, we attempted to size all available data on the tomato linkage groups. This summary has again been amended to include new data submitted for this TGC Report. In their present form the maps include the loci of 47 genes, and 12 additional genes have been assigned to their respective groups by trisomic or two-point tests, but additional segregations must be tested before their approximate position will be known.
For many reasons the present linkage situation in tomatoes cannot be considered good, satisfactory, or even fair. In the first place, of the many known genes less than half have been assigned to their groups. Secondly, 6 of the groups are still populated by only one or two genes apiece, and a number of additional genes like rv, yv, and Gs are floating around as additional independent groups because they also have not shown linkage in the many tests thus far made; an important job remains to be done in joining together these loose ends and in conclusively establishing the 12 groups.
Discrepancies between the results of various workers present other serious problems. Linkage values for the same interval may differ very significantly; thus a range from 3 to 17 has been reported for c-sp and from 1-12 for m-d. As to chromosome 2 (I), the map we present is admittedly only a rough compromise between many contradictory figures; future work will no doubt necessitate many changes. Attention should also be called to the uncertainty regarding the independence of groups V and X as brought out by Research Notes by Burdick and Rick in this issue.
We are confident that the tomato linkage picture will be cleared up fairly rapidly if the efforts of the many interested parties are coordinated. The Coordinating Committee presents a scheme for this purpose at the beginning of this Report.