DNA content, Fundamental Number and Karyotype changes in Tribe Leucocoryneae (Amaryllidaceae, Alliodeae)

SASSONE, AGOSTINA B.; LOPEZ, ALICIA; GIUSSANI, LILIANA

texas

Congreso; Botany 2017 - Botanical Crossroads; 2017

ASPT

The tribe Leucocoryneae (Amaryllidaceae, Alliodeae) is monophyletic and composed by 6 genera, with ca. 100 species exclusively distributed in South America, except for Nothoscordum, which is widespread in South America with one species extended to North America. Tribe Leucocoryneae includes the monophyletic genera: Ipheion (x= 5, 6, 7), Latace (x= 12), Leucocoryne (x= 5), and Tristagma (x= 4), and ?Notoscordum + Beauverdia?. Only Nothoscordum sect. Inodorum (x= 5) is monophyletic and Beauverdia (x= 5) is nested within N. sect. Nothoscordum (x= 4, 5). A wide variation in cytogenetic parameters has been accumulated during evolution; for instance, the ploidy level ranges from diploid to hexaploid, the fundamental number ranges from 14 to 48, and the karyotype formula shows metacentric, submetacentric and acrocentric chromosomes. Here, we elucidate the evolution of tribe Leucocoryneae from a cytogenetic approach with the following aims: (1) to estimate the genome size of species of Leucocoryneae; (2) to analyze the patterns of genome size variation; and (3) to investigate the impact of karyotype evolution on the distribution of total DNA content. Nuclear DNA content was assessed in 18 species using fresh young leaves from cultivated material or silica gel dried leaves by propidium iodide (PI) flow cytometry assay. For each species, the mean value of 2C was obtained from measurements of at least three specimens. Nuclei of Ipheion uniflorum (2n=2x=12, 2C=19.3 pg) were used as internal standards. Monoploid genome sizes (1Cx) were calculated from 2C, and ploidy level (reported in previous literature). As a result, total DNA content in genera of Leucocoryneae range from 19 to 77 pg., being 15 folds of the average in Angiosperms; Cx content varies among genera and species: Beauverdia ranges from 13.05 to 17.9 pg; Ipheion ranges from 9.07 to 9.65 pg.; Latace andina 18.6 pg.; Nothoscordum varied from 11.8 pg to 23.7 pg.; and Tristagma from 15.3 to 17.7 pg. Moreover, total DNA content was analyzed in a phylogenetic context, and it is inferred that conservation or reduction of genome size is a product of poliploidization and/or robertsonian traslocations.