CHROMOSOME STUDIES IN ORCHIDACEAE FROM ARGENTINA, III

GRABIELE, M.; CERUTTI, J. C.; HOJSGAARD, D. H.; ALMADA, R. D.; DAVIÑA J. R.; HONFI, A. I.

TAXON

INT ASSOC PLANT TAXONOMY

Lugar: Viena; Año: 2011 vol. 60 p. 24 - 27

0040-0262

Twelve species of eleven genera of orchids from NE Argentina were chromosomally studied at meiotic stage for the first time. Aspidogyne kuczynskii (Porsh) Garay (n = 21), Brassavola tuberculata Hook. (n = 20), Campylocentrum neglectum (Rchb. f. & Warm.) Cogn. (n = 19), Capanemia micromera Barb. Rodr. (n = 12), Cyclopogon calophyllus (Barb. Rodr.) Barb. Rodr. (n = 14), C. oliganthus (Hoehne) Hoehne & Schltr. (n = 32), Cyrtopodium hatschbachii Pabst (n = 23), Galeandra beyrichii Rchb. f. (n = 27), Mesadenella cuspidata (Lindl.) Garay (n = 23), Oeceoclades maculata (Lindl.) Lindl. (n = 28), Pelexia bonariensis (Lindl.) Schltr. (n = 23) and Sarcoglottis fasciculata (Vell.) Schltr. (n = 23 + 3B) share main traits related to meiosis. In all the cases, diakinesis/metaphase I chromosomes associate as bivalents exclusively, typically rings (83.5%) with distal chiasmata (89.3%) averaging a high number of chiasmata per bivalent (1.89). In general the Recombination Index (RI) and Excess Chiasmata Frequency (EC) values are high, existing a positive correlation with the gametic number and the total chiasmata per cell, evidences which added to the high amount of chiasmata per bivalent reveal an elevated intra and interchromosomal meiotic recombination for each taxa, a major fact taken into account the widespread sexual reproduction in the family. Meanwhile, the gametic number alone confines the total meiotic recombination of those taxa with low RI and EC values, i.e. C. micromera and C. callophyllus. In all the analyzed taxa the meiotic behavior is regular and the pollen grain viability is high, suggesting reduced, balanced and fertile gamets. Furthermore, even though the phylogenetically distance between the studied taxa, the common diploidized meiotic behaviour and the high gametic number suggest derived basic numbers and in turns the status of ancient polyploid orchids.