Chromosome studies on some Asteraceae from South America

Abstract

Mitotic or meiotic chromosome numbers for 42 accessions belonging to 39 species of different genera of Asteraceae were determined. First chromosome counts are reported for one genus ( Gymnocoronis ), 14 species, and one variety. These are as follows: Solidago chilensis var. megapotamica (2 n = 2 x = 18), Chromolaena barbacensis (2 n = 3 x = 30), Chromolaena christieana (2 n = 3 x = 30), Chromolaena hirsuta (2 n = 4 x = 40), Chromolaena verbenacea ( n = 20 II, 2 n = 4 x = 40), Disynaphia multicrenulata (2 n = 2 x = 20), Gymnocoronis spilanthoides var. subcordata (2 n = 2 x = 20), Mikania thapsoides (2 n = 4 x = 68), Stevia commixta (2 n = 2 x = 22), Porophyllum brevifolium (2 n = 4 x = 44), Viguiera rojasii (2 n = 2 x = 34), Pterocaulon angustifolium (2 n = 2 x = 20), Gochnatia haumaniana (2 n = 4 x = 44), Senecio ostenii (2 n = 4 x = 40), Senecio pinnatus (2 n = 8 x = 80), and Lepidaploa amambaia (2 n = 2 x = 28). Chromosome numbers differing from those reported previously in the literature were found in Campuloclinium macrocephalum (2 n = 2 x = 20), Melanthera latifolia (2 n = 4 x = 60), Chrysolaena flexuosa (2 n = 2 x = 20), and Cyrtocymura cincta (2 n = 4 x = 40). The relevance of the results is discussed in relation to the available data for each of the analysed taxa.

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) from Northeast Paraguay

“…This number also has been found in the two species here analyzed, which is consistent with previous studies carried out in others Chrysolaena species (Dematteis 1997a, 1997b, 1998, 2002, 2009, Dematteis et al 2007, Angulo and Dematteis 2009a, 2009b, Via do Pico and Dematteis 2012a, 2012b). The only cytological record available for Chrysolaena sceptrum was reported by Dematteis (2002) for a population from Paraguay, which showed an octoploid cytotype with 2 n =8 x =80.…”

“…The review of chromosomal studies reveals that the tetraploid cytotype is the most common. From nine species in which chromosome number is known, seven had populations with tetraploid cytotypes (Dematteis 1997a, 1997b, 1998, 2002, 2009, Dematteis et al 2007, Angulo and Dematteis 2009b, Via do Pico and Dematteis 2012a, b). Ploidy differences are not restricted to comparisons between species, but also occur frequently within species (Miller 1978, Burton and Husband 1999, Weiss et al 2003).…”

Cytotaxonomy and geographic distribution of cytotypes of species of the South American genus Chrysolaena (Vernonieae, Asteraceae)

“…The present data document the most extensive polyploid series known for Chrysolaena to date, with six ploidy levels (2 x , 4 x , 5 x , 6 x , 7 x and 8 x ). These results are consistent with the basic number and some chromosome numbers reported for the genus in previous studies (Dematteis, , , , 2009; Dematteis et al, ; Angulo & Dematteis, , ; Via do Pico & Dematteis, , , , 2017). However, the results found in this study broaden the cytological information of the genus, since the first chromosome count of C. cordifolia is reported, as well as a new cytotype for C .…”

“…It is estimated that 25% of the South American entities are polyploid, mostly tetraploid and octoploid (Angulo & Dematteis, ). Lessingianthus is one of the genera with the highest proportion of polyploids, nearly 82.5% of a total of 39 taxa, and with ploidy levels up to 11x (Ruas et al, ; Dematteis, , , ; Dematteis et al, ; Oliveira et al, ; Angulo & Dematteis, , , ). The information provided in the present study, together with previously published chromosome numbers, reveals that the South American genus Chrysolaena is cytologically complex and that polyploidy has played a very important role in the evolution of the group.…”

Caryological analysis of South American species ofVernonia(Vernonieae, Asteraceae)

“…The latter populations are tetraploid, based on x ¼ 10, while the material analyzed by Hunziker et al (1990) could be an unstabilized hexaploid with this same basic number. The diploid cytotype has been previously found in plants of southern Paraguay (Dematteis et al 2007), while our count has been made on specimens of central Uruguay.…”