No abstract

In this work, the cytotaxonomic implications of the chromosomal characterization of cultivated and native Zephyranthes species described in northeastern Brazil were studied. All individuals had karyotype formed by a set of metacentric chromosomes, in addition to submetacentric and acrocentric chromosomes. In Zephyranthes robusta, 2n = 12 was observed and karyotype with formula 4M ? 2SM in somatic cells, representing the most symmetric karyotype among the investigated species. Z. sylvatica showed three different chromosome complement numbers: 2n = 12 with formula 1M ? 5SM, 2n = 12 ? 1B with 1M ? 5SM ? (1B), and 2n = 18 formed by cracks. The cultivated species Z. rosea Lindl. presented 2n = 24 with 4M ? 7SM ? 1A, however Z. grandiflora Lindl. showed the same chromosome number with 2M ? 5SM ? 5A. Zephyranthes aff. rosea Lindl. presented 2n = 25 with one small metacentric forming a crack in the fourth metacentric pair. Z. brachyandra has 2n = 24 ? (1B) and formula 4M ? 3SM ? 5A ? (1B). Z. candida Herb. presented 2n = 38 and karyotype formula 9M ? 10SM. In Habranthus itaobinus numerical variation was observed, with the majority of populations showing a chromosome complement composed of 2n = 44 ? 1B with 5M ? 12SM ? 5A ? (1B), or 2n = 44 ? 3B in a single population. Mechanisms involved in the formation of these karyotypes from chromosomal imbalance data are discussed. Taken together, data from this study only partially confirm previous counts for epithets and further enhance the cytological variability data previously reported for the genus.

-(Intrapopulational chromosome number variation in Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) from Northeast Brazil). Zephyranthes Herb. is a taxonomically complex and cytologically variable group, with about 65 species of Neotropical distribution. Chromosome number variability in 32 individuals of a Zephyranthes sylvatica population from Northeast Brazil was investigated. Three cytotypes were found: 2n = 12 (one metacentric, four submetacentric and one acrocentric pairs), in 24 individuals; 2n = 12 + 1B, in five and three individuals with 2n = 18, a triploid cytotype. All diploid individuals showed chromosomes with polymorphism in pair one and two, while in triploids this polymorphism was observed in all chromosome triplets, generally with two homomorphic chromosomes and a higher or lower heteromorphic chromosome. All individuals had reticulated interfasic nucleus and a slightly asymmetric chromosome complement, with one metacentric chromosome pair and the others more submetacentric to acrocentric. These data confirm the cytological variability previously registered for the genus. Mechanisms involved in karyotypic evolution in this population are discussed.Key words -Amaryllidaceae, B chromosomes, chromosome variability, triploid, Zephyranthes RESUMO -(Variação cromossômica numérica intrapopulacional em Zephyranthes sylvatica Baker (Amaryllidaceae: Hippeastreae) no Nordeste do Brasil). O gênero Zephyranthes Herb. é um grupo taxonômicamente complexo e cariologicamente variável, compreende cerca de 65 espécies de distribuição predominantemente neotropical. O presente trabalho aborda a variabilidade cariológica em um total de 32 indivíduos de Z. sylvatica obtidas em uma única população do Nordeste do Brasil. Todos os indivíduos apresentaram núcleo interfásico reticulado e complemento cromossômico bimodal, pela ocorrência de um par cromossômico metacêntrico e os demais submetacêntricos. Foram observados três citotipos: 2n = 12 (um par metacêntrico, quatro submetacêntricos e um acrocêntricos) em 24 indivíduos; 2n = 12 + 1B, em cinco, além de um citotipo triplóide com 2n = 18 em três indivíduos. Todos os citotipos diplóides exibiram polimorfismo cromossômico para os pares um e dois, enquanto nos triplóides esse mesmo polimorfismo foi observado nas trincas correspondente aos pares cromossômicos diplóides, geralmente com dois cromossomos homórficos e um cromossomo heteromórfico maior que os dois anteriores. Esses dados confirmam a variabilidade cariológica anteriormente registrada para o gênero. São discutidos os mecanismos de evolução cariotípica envolvidos nessa variabilidade.