Open AccessChromosome numbers and meiotic studies in species of Senecio (Asteraceae) from Argentina
Author(s) -
LÓPEZ MARIANA G.,
WULFF ARTURO F.,
POGGIO LIDIA,
XIFREDA CECILIA C.
Publication year - 2005
Publication title -
botanical journal of the linnean society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.872
H-Index - 68
eISSN - 1095-8339
pISSN - 0024-4074
DOI - 10.1111/j.1095-8339.2005.00415.x
Subject(s) - chiasma , bivalent (engine) , biology , meiosis , senecio , asteraceae , botany , chromosome , karyotype , taxon , homologous chromosome , evolutionary biology , genetics , gene , chemistry , organic chemistry , metal
Meiotic chromosome counts, chromosomal behaviour and meiotic configurations of ten taxa of Senecio from Argentina were examined. Most counts are original: S. crepidifolius DC., S. francisci Phil. and S. octolepis Griseb. var. saltensis (Hicken) Cabrera & Zardini have 2 n = 40, and S. chrysolepis Phil., 2 n = 80 + 8B. We confirmed previous reports for S. deferens Griseb. (2 n = 40 + 4B), S. filaginoides DC. var. filaginoides (2 n = 40), S. hieronymi Griseb. (2 n = 40 + 7B), S. pampeanus Cabrera (2 n = 40) and S. rudbeckiifolius Meyen & Walp. (2 n = 40 + 7B). In S. bracteolatus Hook. & Arn. var. bracteolatus , we found a new number (2 n = 40) that differs from the one cited previously. In four species, numerical polymorphisms for B‐chromosomes were observed. Several of the analysed species presented secondary bivalent association. This phenomenon, together with other evidence, supports x = 5 as the basic chromosome number. The number of chiasmata and their positions were also surveyed, with the finding that open bivalents were the most frequent meiotic figures and terminal chiasmata the preferential position. These features are related to recombination rate, and the success and persistence of these polyploids. We discuss some systematic and evolutionary aspects in the light of cytogenetic data and conclude that polyploidy is the major force modelling the chromosome evolution within this genus. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 465–474.