Submitted to: American Journal of Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/28/2008
Publication Date: 7/3/2008
Citation: Iovene, M., Grzebelus, E., Carputo, D., Jiang, J., Simon, P.W. 2008. Major Cytogenetic Landmarks and Karyotype analysis in Carrot and Other Apiaceace. American Journal of Botany. 95:793-804. Interpretive Summary: Carrot, celery, and their relatives are members of the Apiaceae family. Chromosome studies within the family have been based primarily on chromosome counts and chromosome morphology. Preliminary chromosome studies of carrot, celery and coriander have been published. This research reports the first chromosome studies of carrot and its wild relatives to identify major chromosome landmarks. We used new fluorescent stains to evaluate chromosomes for two major chromosome landmarks referred to as 5S and the 18S-25S rDNA. We examined the distribution of rDNA regions in 21 species including carrot and celery. Using these methods approximately 20 to 40% of the chromosomes could be unequivocally identified and results suggested one major change in chromosome structure occurred as these species evolved. This research is of interest to botanists and plant researchers working on carrot and its relatives to help synthesize models of crop evolution. It is also of interest to the seed industry as a tool to categorize and classify samples in large seed collections.
Technical Abstract: Chromosome localization of the rDNA gene clusters was determined for the first time in several Apiaceae using double-color fluorescence in situ hybridization (FISH). Twenty-one Apioideae species including taxa of economic importance (e.g. Apium graveolens, Coriandrum sativum, Cumin cyminum, Daucus carota, Petroselinum crispum, Pimpinella anisum) and some wild Daucus relatives were investigated. Interestingly, Daucus species did not vary in the number of the rDNA loci despite their variation in chromosome number (2n=18, 20, 22 and 44). Indeed, they all had one single locus for both the 5S and 18S-25S rDNA, located on two different chromosome pairs. However, the 5S rDNA was on the short arm of a metacentric chromosome pair in D. crinitus (2n=22) and D. glochidiatus (2n=44) and on the long arm of a metacentric pair in the other Daucus species. This suggested a possible rearrangement of the chromosome bearing the 5S rDNA in the Daucus genus. As for the other Apiaceae, the number of chromosomes bearing the 18S-25S rDNA site varied from two (e.g. Apium graveolens), to three (Orlaya grandiflora), and to four (e.g. Cuminum cyminum). Variability for number (from one to four loci) and position of the 5S rDNA was also observed. Linkage association between the 5S rDNA and the NOR sites was observed in Carum carvi. Depending on the species, the FISH signals enabled the identification of ~ 20-40% of the chromosome complement. Based on chromosome arm ratio and FISH landmarks, tentative karyotypes were obtained for several species.