Abstract

GIANINI AQUINO, Analía C.; RODRIGUEZ MATA, Orlando A.; HONFI, Ana I.  and  DAVINA, Julio R.. Cytogenetic studies in the polyploid complex Zephyranthes mesochloa (Amaryllidaceae). Bol. Soc. Argent. Bot. [online]. 2023, vol.58, n.3, pp.5-5. ISSN 1851-2372.  http://dx.doi.org/10.31055/1851.2372.v58.n3.40181.

Background and aims: Zephyranthes mesochloa, is a bulbous species with white flowers that inhabits the subtropical región of South America and presents different chromosome numbers. The aim of this work is to carry out the chromosome analysis of Z. mesochloa from northern Argentina, to contribute to the cytogenetic knowledge of the genus.

M&M: Ploidy levels and somatic chromosome numbers were determined in individuals from 8 populations in northern Argentina using conventional staining. In addition, meiotic preparations with acetic carmine were performed on individuals from one population.

Results: Seventy-five percent of the populations were diploid, with 2n = 2x = 12 and presented a karyotypic formula of 4m + 4sm + 4st. In two of the diploid populations, individuals with 2n = 13 were observed, with the presence of an additional metacentric chromosome, possibly a B chromosome. Microsporogenesis analysis, in diakinesis and metaphase I, of aneuploid cytotype (2n = 13), showed six bivalents and one univalent in all pollen mother cells analyzed. The remaining populations (25%) were tetraploids with 2n = 4x = 24 and karyotypic formula 8m + 8sm + 8st. Geographically, the distribution of cytotypes in Z. mesochloa is discontinuous.

Conclusions: The duplicate karyotype formula in tetraploids regarding its con-specific diploids may indicate the origin of an autopolyploid cytotype. The available data allows us to consider the group of cytotypes as part of a polyploid complex with a basic number of x = 6.

Keywords : Autopolyploidy; B chromosome; chromosomes; karyotype; meiosis; ornamental bulb plant.

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