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The 82 genera recognized for Bignoniaceae are organized in eight major tribes, Jacarandeae, Tourrettieae, Tecomeae, Coleeae, Crescentiae, Oroxyleae, Catalpeae and Bignonieae. In addition, a monophyletic group, Crescentiina, including the Tabebuia alliance and the Paleotropical clade is recognized. The Tabebuia alliance, endemic to the Neotropics, includes c. 14 genera of trees and shrubs and is comprised of c. 147 species mainly of the genera Tabebuia and Handroanthus. We measured the nuclear DNA contents of 19 Bignoniaceae species to address genome size and chromosome number evolution of the Tabebuia alliance. Nuclear DNA content was estimated using flow cytometry and chromosome counts were performed using propidium iodide-stained metaphase cells. We also obtained data for three different Bignoniaceae species from the Royal Botanical Garden, Kew Plant DNA C-values database. We obtained the phylogenetic tree of analysed species from published data and used independent phylogenetic contrast to correlate chromosome number and 1C DNA content. An almost threefold range of variation in nuclear DNA content was observed among the 22 Bignoniaceae species that could only partially be explained by the occurrence of polyploidy. We found no significant correlation between chromosome number and DNA content among the analysed species. Our results suggest that both increases and decreases of genome size occurred in the evolution of the analysed Bignoniaceae Juss. species, with a large variation among Tabebuia alliance species. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the chromosome number and DNA amount of accessions of Psidium sp. (araça tree, used as rootstocks) and accessions of P. guajava (guava tree) resistant/susceptible to M. enterolobii, which holds some morphophysiological affinity and which could enable their use as rootstocks compatible with commercial varieties of guava. Metaphase chromosomes were obtained by the squash technique and stained with 2 % Giemsa. The determination of DNA amount was done by flow cytometry using Mary buffer. The intraspecific variation in DNA amount (2C) was of the order of 9x, with 2 n = 22 observed in only one species of P. guajava. The other species presented variations in the ploidy level in relation to the basic chromosome number x = 11, including the occurrence of polyploidy, cytotypes and disploidy. In some species, the interspecific variation of 2C showed a direct relationship with the ploidy level. Our data confirm that variations in the number of chromosome and in ploidy level are important events to Psidium and can support the understanding of the incompatibility of the graft on rootstocks of guava and araça trees resistant to the nematode M. enterolobii. [ABSTRACT FROM AUTHOR]

Silene ciliata Poiret is a small perennial that presents several ploidy levels and inhabits the mountain ranges of the European Mediterranean basin. Recent studies have shown evidence of local adaptation in populations located across an altitudinal gradient in Sierra de Guadarrama (Central Spain) at the species' southernmost distribution limit. In this study, we assessed whether the existence of local adaptation in these populations was related to differences in karyological features (ploidy level or chromosome number modification) or in nuclear DNA amount. Optical microscope (phase contrast and epifluorescence after DAPI staining) and flow cytometry were used to estimate the ploidy level and genome size of several family lines in three populations across the altitude gradient. With a sampling three times higher than usual in genome size assessments, all individuals showed a constant diploid set (2 n = 24), so that polyploidy or other chromosome number modifications were discarded. The small genome size found (mean ± SD; 2C = 1.76 ± 0.06 pg) was within the range of those found in other Silene species. Significant differences in genome size were found when the three populations of S. ciliata were compared. The largest genome size found at the intermediate population may be associated to lower environmental stress at the mid elevation, in line with the recent studies in this area. [ABSTRACT FROM AUTHOR]