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

The chromosomes of 31 species of Passiflora, distributed throughout the sub genera Astrophea, Calopathanthus, Distephana, Dysosmia, Passiflora, Plectos temma and Tacsonia were analysed. Three different karyotypes were observed: 2n = 12, 24, 36, 2n = 18, 72 and 2n = 20. The karyotype of these species w as almost always constituted of metacentric and submetacentric chromosomes with variable karyotype symmetry. in the group with x = 61 represented by t he 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 inc luded in this karyological group since it presents 2n = 24 and may be of po lyploid origin, with x = 6. The interphase nuclei in this group were aretic ulate, except those of P. morifolia and P. pentagona with semi-reticulate c haracteristics. Two small terminal heterochromatic blocks, positive for chr omomycin A(3), were identified in the largest chromosome pair of P. capsula ris and P. rubra, species very closely related, while P. tricuspis displaye d four chromosomes with proximal blocks. In the group with x = 9, represent ed 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 w ith areticulate nuclei. Four terminal CMA(+) blocks were observed in P. edu lis. six blocks in P. caerulea and P. racemosa, while five blocks were obse rved in the single P. amethystina plant analysed. P. foetida (subgenus Dyso smia), the only species with 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. cincin nata and P. racemosa) always presented regular pairing and regular chromoso me segregation, except in P. jilekii where a tetravalent was observed. The analysis of the chromosome variation within the genus and the family sugges ts that the base number of Passiflora may be x(1) = 6 or x(1) = 12, whereas x(2) = 9 is only an important secondary base number.