EVIDENCE FOR INDUCTION OF A B-A TRANSLOCATION INVOLVING THE LONG AND SHORT ARMS OF CHROMOSOME-10 IN MAIZE

To add to a collection of B-A translocations that are marked by R-scm3 (an allele which allows distinction of various doses of the transloca ted segments), an X-irradiation experiment was conducted. The procedur e involved irradiating immature tassels of plants carrying the translo cation, TB-10L18, and selecting newly induced aberrations that uncover markers on both arms of 10. TB-10L18 has breakpoints in the long arm of chromosome 10 and the minute short arm of the B chromosome. Previou s work utilized this translocation to mark other regions of the genome by recovering recombinants between the B-10 chromosome and the B-A of other B-A translocations. Because the B-10 is translocated in the B s hort arm and other B-A's are translocated in the B long arm, recombina tion is possible. It would be very difficult to recover a T10S-B-10L c hromosome by the recombination method, because two exchange events, on e in the B chromosome and one in chromosome 10, would have to be recov ered simultaneously. Therefore, irradiation was used to induce a T10S- B-10L chromosome. An isolate was recovered that uncovers markers in bo th arms.