Karyology and cytotaxonomy of the genus Passiflora L. (Pasifloraseae).

• Autor(a) principal: MELO, N. F. de
• Data de Publicação: 2001
• Outros Autores: CERVI, A. C., GUERRA, M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da EMBRAPA (Repository Open Access to Scientific Information from EMBRAPA - Alice)
• Texto Completo: http://www.alice.cnptia.embrapa.br/alice/handle/doc/134324
• topic: Cytotaxonomy; Citotaxonomia; Maracujá; Melhoramento Genético Vegetal; Passiflora; passion fruits

The chromosomes of 31 species of Pas- siflora, distributed throughout the subgenera As- trophea, Calopathanthus, Distephana, Dysosmia, Passiflora, Plectostemma and Tacsonia were ana1- ysed. Three different karyotypes were observed: 2n = 12, 24, 36; 2n = 18, 72 and 2n = 20. The karyotype of these species was a1most always constituted of metacentric and submetacentric chromosomes with variable karyotype symmetry. In the group with x = 6, represented by the subgenus Plectostemma, six diploid species with 2n = 12, one tetraploid with 2n = 24 (P. suberosa) and an intraspecific polyploid with 2n = 12, 36 (P. misera) were analysed. P. pentagona (subgenus Astrophea) may also be included in this karyolog- ical group since it presents 2n = 24 and may be of polyploid origin, with x = 6. The interphase nuclei in this group were areticulate, except those of P. morifolia and P. pentagona with semi-reticulate characteristics. Two small terminal heterochroma- tic blocks, positive for chromomycin A3, were identified in the largest chromosome pair of P. capsularis and P. rubra, species very closely related, while P. tricuspis displayed four chromo- somes with proximal blocks. In the group with x = 9, represented mainly by subgenus Passiflora, 20 species with 2n = 18 and one with 2n = 72 were studied. They presented chromosomes larger than those species with x = 6 and interphase nuclei of semi-reticulate type, except for P. mixta with areticulate nuclei. Four terminal CMA + block: were observed in P. edulis, six blocks in P. caerulel and P. racemosa, while five blocks were observed ir the single P. amethystina plant analysed. P. foetid\{ (subgenus Dysosmia), the only species witt 2n = 20, exhibited six chromosomes with CMA + blocks and interphase nuclei of the areticulate type The meiotic analysis of representatives of the three groups (P. foetida, P. suberosa, P. cincinnata and P. racemosa) always presented regular pairing and regular chromosome segregation, except in P.jilekil where a tetravalent was observed. The analysis of the chromosome variation within the genus and the family suggests that the base number of Passiflora may be xi = 6 or XI = 12, whereas X2 = 9 is only an important secondary base number.