Loss of nucleolar-organizer regions during polyploid evolution in scilla autumnalis

Abstract

The organization and behaviour of nucleolar-organizer regions (NOR) of Scilla autumnalis were studied in two diploid races, their allotetraploid and autoallohexaploid derivatives and hybrids between them. The diploids of genome constitution AA and B7 B7 each have a pair of nucleolar- organizer chromosomes while the polyploids AAB7B7 and AAB7 B7 B7 B7 only carry visible organizers on the B7 chromosomes. In situ hybridization using ribosomal probe pTA7 was used to localize ribosomal cistrons. In polyploids the sites of hybridization are limited to the B7-derived nucleolar-organizer chromosomes and ribosomal cistrons have thus been deleted from the A genome. A NOR-associated C-band has also been deleted. © 1993 The Genetical Society of Great Britain.