IV. 11. Coordinator's report: Translocations and balanced tertiary trisomics.
R.T. Ramage, Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721 U.S.A.
No new translocations were added to the collection during 1978. Dr. L.C. Lehmann, The Swedish Seed Association, Svalöv, Sweden, sent seed stocks of eight balanced tertiary trisomics and of two balanced telotrisomics to be added to the collection. The BTT's are: 56b msgl, 56e msgl, 56v msgl, 56G3 msgl, 64p msg,,bk, 65a msg6 and 65m msg6. The two balanced telotrisomics both involve the long arm of chromosome 3 and are balanced for the msg5 allele. One is derived from the translocation T3-6j and the other is derived from the BTT 37c msg5.
We have started a program designed to assign break-positions to appropriate arms of the T1-2, T1-3, T1-4, and T3-4 translocations by the intercross method. Based on Metaphase I configurations exhibited by intercrosses within translocation groups, we can separate the translocations into two groups: LL or SS and LS and SL. We can then separate each group into LL and SS or LS and SL based on either spore abortion or linkage tests. While examining the intercrosses, we have found several errors in translocation designations. T1-2e and T2-4b give rings of 6 when intercrossed with other T1-2 and T2-4 translocations. This indicates that one of the chromosomes is identified correctly and the other is not. T1-2f and T1-3m give two rings of 4 when intercrossed with other T1-2 and T1-3 translocations. This indicates that neither chromosome is correctly identified in these two translocations. T1-4c, T3-4c, and T3-4k appear to have the normal chromosome arrangement (they are not translocations) as they always give a ring of 4 when intercrossed with other T1-4 and T3-4 translocations. As we find errors in designations, we are crossing the lines involved onto tester sets so as to correctly identify them.