Molecular cytogenetics of the genus Artemisia (Asteraceae, Anthemideae):: fluorochrome banding and fluorescence in situ hybridization.: I.: Subgenus Seriphidium and related taxa

The distributional pattern of AT- and GC-rich regions and the physical mapping of ribosomal DNA (location of 18S-5.8S-26S and 5S rDNA) in the chromosomes of seven Artemisia species have been established by means of fluorochrome banding and fluorescence in situ hybridization (FISH). This is the first study in the large genus Artemisia using FISH. Five species (A. barrelieri, A. caerulescens subsp. gallica, A. fragrans, A. herba-alba subsp. valentina, A. herbaalba subsp. herba-alba) belong to the subgenus Seriphidium, one of the most homogeneous in the genus; one (A. tridentata susbp. spiciformis) belongs to the small subgenus Tridentatae, classically included in Seriphidium; and one (A. annua) belongs to the subgenus Artemisia, but shows some affinities with Seriphidium. Genome organization is relatively constant in all the species studied. AT- and GC-rich DNA is predominantly terminal, but some intercalary and centromeric bands also exist. The rDNA loci are also most often terminal and usually located in GC-rich regions. 5S rDNA sites are present in a lower number than 18S-5.8S-26S sites, and are always colocated with some of them. In the light of these cytogenetic features, subgenus Seriphidium is clearly placed within the genus Artemisia, so that it does not make sense to segregate it as a genus; on the other hand, subgenus Tridentatae must not be classified within Seriphidium, but kept as an independent subgenus.