Karyomorphological analysis and distribution of GC-rich heterochromatin in wild species of Passiflora L.

The chromosomal characterization of five Passiflora L. species was performed through karyomorphometric analysis and the localization of GC-rich heterochromatin. The species P. cerradensis, P. eichleriana, P. elegans, and P. trintae from the subgenus Passiflora exhibited a diploid chromosome number of 2n=18, whereas P. misera from the subgenus Decaloba showed 2n=12, consistent with the chromosome numbers reported for species in these subgenera. A significant difference was observed in mean chromosome length among the species, with P. misera and P. trintae exhibiting the shortest and longest chromosome lengths, respectively. The smallest haploid chromosome complement was observed in P. misera, suggesting that this species is more derived relative to the others, with chromosomal modifications present. Karyotypic symmetry was inferred based on the TF% (karyotype asymmetry index), which was lower in P. misera (36%) and higher in species of the subgenus Passiflora (39 to 40%). Most species showed a lower number of satellites with conventional staining compared to the CMA3+/DAPI− blocks observed. Two pairs of satellited chromosomes were observed in P. misera, including one pair with an interstitial satellite (CMA3+/DAPI− block). On the other hand, variations were observed in the number and position of satellites among species of the subgenus Passiflora. The results corroborate the cytogenetic events involved in the karyotypic evolution of the species and are important for the planning of crosses to obtain interspecific hybrids in Passiflora breeding programs.