10. Tests for analyzing gene differences between inbreds.

A number of translocations marked with endosperm genes have been crossed recurrently to the inbred lines R4 and WF9. These conversions have been carried on chiefly by Dr. M. T. Jenkins at Beltsville and by Dr. Anderson at Cal Tech. In addition to the translocation lines, normal sugary and waxy lines have also been converted to R4 and WF9 backgrounds for use in testing.

To test for genes which differentiate the two inbred lines, many of the R4‑converted translocations were crossed to WF9, and the WF9‑converted translocations, to R4. The F₁'s involving wx were test crossed to wx R4 and to wx WF9. those involving sugary, to su R4 and to su WF9. In the waxy series 45 test‑crosses involving 18 translocatioms have been made; in the sugary series 28 test crosses, involving 13 translocations. By growing the normal and waxy seeds of each test cross in adjacent cultures, one should detect as consistent differences between the two cultures any linked genes which differentiate the two inbred lines.

The testing or observation of these test crosses is being done as a cooperative effort to locate genes for the characteristic differences between these two inbreds. One set will be grown at Johnston, Iowa by Dr. Wm. L. Brown of the Pioneer Hi‑Bred Corn Company. A duplicate set will be subjected to corn borer resistance tests at Toledo, Ohio by Mr. F. F. Dicke of the European Corn Borer Laboratory of the Bureau of Entomology and Plant Quarantine. A set will also be grown at Lincoln, Nebraska by Drs. E. F. Frolik and Rosalind Morris and another here at Cal Tech.

A number of similar crosses and test crosses have been made involving KYS, with emphasis on the analysis of genes located in the distal part of the long arm of chromosome 10. Several have also been made with L 289 in an attempt to locate genes responsible for the failure of this line to tolerate the climate of southern California.

These tests are the initial application of this technique for the analysis of gene differences between inbred lines. Further work is under way to extend the analyses to other inbreds.

E. G. Anderson and Earl B. Patterson