SEGREGATION DISTORTION AT ISOZYME LOCUS LAP-1 IN SCHLUMBERGERA (CACTACEAE) IS CAUSED BY LINKAGE WITH THE GAMETOPHYTIC SELF-INCOMPATIBILITY (S) LOCUS

The inheritance of leucine aminopeptidase (LAP), phosphoglucomutase (P GM), and shikimate dehydrogenase (SKD) isozymes was studied in Schlumb ergera truncata and S. x buckleyi (Cactaceae). Isozymes were extracted from phylloclades and separated using polyacrylamide-gel electrophore sis. F-1, F-2, and BC1 populations were examined to determine the mode of inheritance. Relatively few families exhibited disturbed segregati on ratios at Pgm-1 or Skd-1. In contrast, segregation ratios at Lap-1 were distorted in 14 of the 22 families that were examined. Disturbed segregation at Lap-1 was attributed to linkage with the gametophytic s elf-incompatibility (S) locus (recombination frequency = 7% +/- 1%). L ap-1, Pgm-1, and Skd-1 assorted independently of each other. Lap-1 and S may be useful for assessing linkage conservation among self-incompa tible taxa In the Cactaceae.